4 492+?(7LOS AL AMOS NAT ION AL LAB ORATOR Y

DO NOTCIRCULATEiiELE=

PERMANENT RETENTION E

1~.~- - ..—-..‘.”.::. .,—-L.+:.AZ.=. ~+. T. .... -;;--+>.-:: . .. . . . . . . - ..- .: -

——---- --2= . ..-..:..- . .--zuke&d <>,::—- . . . .

COVER

Eric Vigil of Information Services Division created the aerial viewdrawing of TA-55, using Alias software on a Silicon Graphicswork station.

i Nuclear Materials Technology Divk.lon Annual Review

N U C LEAR MATE RIALS

TECH NO LOGY

W EAPONS COMPLEX 21

R E C O N F I G U RAT I O N

Annual Report1992

LALP-92-41issued: June 1992

Nuclear Materials Technology DivisionMail Stop E500Los Alamos, New Mexico 87545

LosAlamosNATIONAL LABORATORY

ii

...U1 Nuclear h4ateriaLsTechnology Division Annual Rdcw

CONTENTS

Contents

Foreword .....................................................................................................4

PrefaceWeapons Complex Reconfiguration:The Future of PlutoniumTechnology ..................................................8

Overviews:Site-ReturnDisassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Automationand IntegrationofSite-ReturnProcessing ....................18Advanced CIeaningTechnologies . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Plasma Chemical Processing . . . . . . . . . . . . . . . . . . . . . . . . ...............26

Overviews: Advanced ManufacturingTectiolo~ . . . . . . . . . . . . . . . .34PlutoniumCastingand Forrning ........................................................38PlutoniumDryMachining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....42

Overviews:NitrateRecovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....44Prm=shdyticdCheti~ . . . . . . . ........................49Process MeasurementandControl . . . . . . . . . . . . . . . . . . . . . . . . . . .52ProcessChemishy ................................................................................56SystemsIntegration..............................................................................61

Overviews:ChlorideRecovery . . . . . . . . . . . . . . . . . . . . . . . . . . . ..........63lnSitu ChlorinationofPlutonium Metal ......................67OpportunitiesforMagnetic SeparationApplicationsin Complex21 .......................................................................................69OWgenSpar@g.ti........m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74MaterialsDevelopmentforPyrochemical Applicationsin the Weapons Complex Reconfiguration ........................................78PyrochemicalINtegratedActinideChlorideLine (PINACL) ...........82

Overviews:Waste Management..............................................................85DestructionofHazardousWastesby SuperCriticalWaterOxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................87Waste StreamMonitoring.. . . . . . . . . . . . . . . . . . . . . . . . . ..................99WasteTreatmentiChelatingPolymers forRemovalofHeavy Metals fromAqueous WasteS&em . . . . . . . . . . . . . . .......101

contentscontinuedonnext page

1

CONTENTS

Group Profiles .........................................................................................107Nuclear MaterialsTechnologyDivisionOrgtition Chart .........108NuclearMaterialsTechnologyDivision ...........................................109Nuclear Fuels Technology .................................................................110Nuclear MaterialsProcessing:NitrateSystems................................112NuclearMaterialsProcessing:ChlorideSystems.............................114Nuclear MaterialsMeasurementand Accountability......................116PlutoniumMetallurgy .......................................................................117ActinideMaterialsChemistry ...........................................................119Nuclear MaterialsManagement........................................................120TA-55 FacilitiesManagement ............................................................121Heat SourceTechnology ....................................................................122

Awards, Honors, and Patents ................................................................123

Publications .............................................................................................127NuclearFuels Technology ................................................................128Nuclear MaterialsProcessing:NitrateSystems................................129Nuclear MaterialsProcessing:ChlorideSystems............................. 130Nuclear MaterialsMeasurementand Accountability......................134PlutoniumMetallurgy .......................................................................134Actinide MaterialsChemistry ...........................................................136NuclearMaterialsManagement........................................................140Heat SourceTechnology ....................................................................141

Credits......................................................................................................143

2 Nuclear h4aterialsTdnology Divtslon Annual RAw

Fo R E w o R D

FOREWORD

by Delbert R. Harbur

Most of the nuclear materi-als activities at the Los AlamosNational Laboratory are donein the Nuclear Materials Tech-nology Division. The Divisionis responsible for the PlutoniumFacility located at TechnicalArea 55 (TA-55). With ourexpert research and develop-ment in the fields of metallurgy,chemistry, engineering, andsolid state physics, we examinethe complex chemistry associ-ated with plutonium and otheractinides in various physicalstates.

+

--.‘?..-—.+-“\l s

~ ~ ‘).*Y. . “+J s

1 Division Leader. Delbert R. Harbur

To remain at the forefrontof important areas of actinidechemistry and materials science,we maintain a strong and vitalbase of scientific research. Ourmaterials research is directedat understanding the relation-ships among processing, compo-sition, structure and propertiesof materials and ultimately atdiscovering how these materialsrespond to external environ-ments. Our chemical processingresearch is aimed at understand-ing the basic chemistry involvedtogether with the complexinteractions found in realsystems.

In the national defense arena,we support nuclear weapondesign, development, and test-ing programs by developingsafe, efficient, and environmen-tally acceptable technologies formanufacturing and processingof plutonium in the nation’sproduction complex. In addition,the division’s energy programsfocus on nuclear reactors forspace power and radioisotopeheat sources.

The Laboratory’s technologyleadership role for the nation’splutonium production complexhas been well established overthe last decade. Rapid, signifi-cant changes in world eventsand within the nation’s weaponsproduction complex indicate astrengthening of this role. Thenation’s nuclear materials pro-duction complex is widelyperceived as at the end of itsuseful life and as no longer sizednor technologicallymeet future needs.

equipped to

4 Nuclear Materials Technology Division hnuai Rdcw

“Technologiesthat we researchedand demonstratedasprototypesat TA-55willmakeup thebasetechnologiesfor thefuturePlutoniumManufacturingPlant in the WmponsComplexReconfiguration(Complex21).”

For the last decade, we havebeen upgrading the manufactur-ing and processing technologiesdeveloped at TA-55 to meet theproessing need to decommissionand decontaminate older facili-ties and to reconfigure theweapons complex into properlyequipped facilities for theirfuture missions. Using theLaboratory’s strong research anddevelopment base, we initiatedthese upgrades to address prob-lems inherent in the inability ofthe older technologies to prop-erly deal with the growth ofregulatory, compliance, andwaste issues confronting theDepartment of Energy.

Technologies that we re-searched and demonstrated asprototypes at TA-55 will makeup the base technologies for thefuture Plutonium ManufacturingPlant in the Weapons ComplexReconfiguration (Complex 21).Fortunately, many of thesetechnologies will also be theones required to decommissionolder facilities and to stabilizeresidues.

This year focuses on theprocessing technologies that wehave developed for Complex 21.Most of these technologies arequite mature, and the associatedmetallurgy and chemistry arewell understood. We are nowemphasizing process integration,real-time sensors, and process-control systems. Automation isapplied only to mature, fully-integrated, and optimizedprocess systems.

This publication provides abrief review of the scientific andtechnical activities in each of ouroperating groups, as well as acompilation of our accomplish-ments during the past 18months, including awards,patents, and publications. +

Fomwod 5

6 Nuclear Materials Technology Division Annual Rcvlew

PREFACE

Weapons Complex Reconfiguration:The Future of Plutonium Technology

by Dana C. Christensen

Weapons ComplexReconfiguration Concerns

Recent unforeseen changes inthe global balance of power haveprompted a reevaluation of theentire nuclear weapons complex,including research and develop-ment in the area of nuclearmaterials technology. Nationaldefense concerns related specifi-cally to plutonium processinginclude

s stockpile security andsurety,

● existing production andsupply infrastructure, and

● future production andsupply infrastmcture.

In the area of stockpile secu-rity and surety, we must main-tain a safe but robust arsenal ofnuclear weapons while reducingthe numbers of various types ofweapons. Constant surveillanceof stockpile components andmaterials is essential to ensurethat devices will work whencalled upon and that they willremain in a safe and securecondition until that time.

As to the existing productionand supply infrastructure, thenation currently owns a signifi-cant quantity of plutonium; itexists in the form of weaponcomponents, oxides and metals,miscellaneous lean residues, andcontaminated equipment. How-ever, most of the productionfacilities are more than 35 yearsold and have reached the end oftheir useful lives.

Of utmost concern is manag-ing the plutonium supply so as toavoid environmental contamina-tion and to prevent loss of mate-rial to a proliferant group. Wemust have available safe, securefacilities in which to store thematerial returned from stockpiledisassembly activities as well asthe material recovered fromresidues. The mandated shrink-ing stockpile and the reducedreliance on the nuclear deterrentas a key to national defense meanthat our excess and aging facili-ties must be decontaminated anddecommissioned. Existing envi-ronmental damage resultingfrom the activities conducted inthese facilities must also beameliorated.

Deputy Division LeaderDana C. Christensen

Finally, the future productionand supply infrastructure re-quires technical support for thestockpile (at whatever level itfinally reaches), the capability tofabricate improved componentsand upgrades of the stockpile,and the means to survey thestored inventory of material toensure accountability and safety.The primary concern will con-tinue to be the minimization ofhazardous waste and the manage-ment of necessary waste so as topreclude release to the environ-ment. Future facilities mustformalize operations in compli-ance with increasingly stringentfederal requirements, therebyproviding a high degree of safetyto employees, the public, and theenvironment.

The Los Alamos PlutoniumFacility

The successful reconfigurationof the nuclear weapons complexrequires that the above key areasbe addressed. Although sometechnical developments at LosAlamos uniquely address onlyone area, many others contribute

8 Nuclear Materials Technology DivMon Annual Rcvlcw

‘i’e+=)-(==k’r:::ctReturns

@-@

to all three areas. The perva-sively multidisciplinary natureof the Laboratory makes ituniquely suited to addressthe entire spectrum of con-cerns associated with thereconfiguration of the nuclearweapons complex. TheLaboratory’s formula forcontinued success comprisesan educated and experiencedstaff possessing detailed knowl-edge of the important issuesand specially designed equip-ment and facilities unparalleledthroughout the world.

IDisposal

For more than a decade, themission of plutonium operationsat Los Alamos has included

● conduct of fundamentalandapplied research,

● development of advancedprocesses,

● full-scale demonstration ofthose processes in aplutonium environment,and

● exchange of technologywith other DOE contractorsand industry.

Fig. 1. Baseline flow sheet for thePlutonium Processing Facility for thereconfigured weapons complex.

This emphasis on advancedtechnology, including the suc-cessful demonstration of pluto-nium production, ensures thatthe Los Alamos PlutoniumFacility will continue to refinethe technologies of the 1990s asit plans the developments ofthe 2000s.

Baseline Flow Sheet forPlutonium Processing

Pivotal to selecting the appro-priate development activities isthe effective charting of a direc-tion that ensures progress bysetting a defined goal. All of ouractivities focus on the plutoniumprocessing facility of the future.Fig. 1, a baseline flow sheet forthat facility, highlights the keytechnical areas of emphasis forprocessing and, in addition,identifies technology develop-ments needed for the enthecomplex reconfiguration.

Weapons Complex Reconfiguration:The Future of Plutonium Technology (continued)

Improvements designated asapplicable to the future pluto-nium complex will assist inmeeting existing cleanup re-quirements as well as facilitatethe management of futurematerial inventories. The fivechapters in this section providedetailed attributes of projects asthey apply to the Fig. 1 flowsheet.

Site Return ProcessingThe chapter on site return

processing provides details ofthe problems being addressedand of a new suite of technolo-gies being implemented assolutions. The processing ap-proach is elegantly simple butinvolves the integration of anumber of processing steps,each of which uses unique anddifferent chemistries. The goalof this work is to demonstratethat complex site-return process-ing operations can be integratedinto a flow loop in which safety,accountability, and processingcomplement each other.

Because no acceptable technologyfor performing this task presentlyexists, the successful integrationof site-return operations at LosAlamos will be a landmarkachievement. Further, the wastegenerated in this fully integratedapproach is near zero. Develop-ments in this area will applydirectly to needs in stockpilesecurity and surety and futureproduction and supply infra-structure.

Advanced ManufacturingTechnology

The chapter on advancedmanufacturing technologyaddresses significant changesin techniques for fabricatingweapon components whileminimizing waste and promotingsafety. Plutonium manufacturingprocesses, which require the useof chlorinated and fluorinatedhydrocarbons, has historicallybeen responsible for the produc-tion of mixed waste; however,new operations now underdevelopment will eliminate theproblem of mixed waste.

Improvements in this areawill also significantly reducethe amount of residues and thequantity of plutonium in resi-dues, thereby reducing the needfor aqueous recovery. The majorgoals in the manufacturing areacenter on maximizing the utili-zation efficiency of plutoniummetal and on minimizing thegeneration of residues andwaste. Developments in n~anu-facturing will directly impactstockpile surety and futureproduction and supply infra-structure.

Nitrate Recovery and ChlorideRecovery

The chapters on nitraterecovery and chloride recoveryaddress the aqueous recovery ofresidues resulting from the site-return- processing and manufac-turing functions. The recoveryoperations generally involve thedissolution of residues in acids,the separation and purificationof plutonium, and the conver-sion of the plutonium intofoundry-acceptable metal.

10 Nuclear Materials Techrwlogy Division Annual Review

“The overall goal of Complex 21 is ‘zero discharge, ’ thatis, no release of plutonium to the environmerit.”

The bane of aqueous systems hasbeen the volume of waste liquidsand sludges generated. The goalof recent developments in theprocess control area is to operatethe process chemistries as closelyas possible to the stoichiometriclimits, thereby minimizing theneed for excess reagents andultimately reducing the volumeof waste. Scientists are alsodeveloping element- or non-selective systems capable ofplucking plutonium out of ascrap matrix without the helpof reagents. Finally, a key goalof nitrate and chloride reco~eryoperations is to demonstrateprocess integration in an envi-ronment where the synergism ofunit operations can be measured.The work described in these twochapters will have a profoundimpact on all aspects of futureplutonium processing.

In particular, the existing residueand waste inventory is not nowcapable of being packaged forlong-term storage. Technologiesin nitrate and chloride recoverywill provide the basis for devel-oping processing and packagingtechniques for long-term storageof residues.

Waste ManagementThe final chapter covers waste

management. The essentialfocus of all nuclear materialsprocessing is the minimizationor elimination of waste whereverpossible. Although not all wastecan be eliminated, the goal inwaste management is either toremove all activity before dis-charge or to immobilize thewaste so as to preclude anyuncontrolled release. To theextent possible, reagents as wellas any recovered plutonium willbe reconstituted and recycled.

The important types of wastethat must be managed includeliquids, sludges from liquidtreatment, combustibles, plastics(especially polyvinyl chlorides),stack gases, and various solids,such as tools, glove boxes, andprocess equipment.

The overall goal of Complex21 is “zero discharge,” that is,no release of plutonium to theenvironment. The extent towhich that goal can be met isa measure of our success inthis key area of operations.Los Alamos has addressed thisgoal by consistently subscribingto a very direct and logicalapproach to waste processing:

1. Identify the problem anddevelop an approach for solvingit that begins at the initial stagesof all related processes.

2. Identify and understandthe related fundamental chemis-try and metallurgy.

3. Develop process controlmechanisms such as sensors.

Preface 11

4. Engineer processing equip-ment to meet process and pro-cess control requirements andconstraints.

5. Adapt engineered equip-ment to facility operating con-straints, or, in the case of a newfacility, engineer the facilityaround processing requirementsand constraints.

Experience shows that whenprocess engineering precedes aclear understanding of theproblem or of the process chem-istry involved, failure is certain.Projects can be successfullybrought to fruition only whenknowledge precedes action.A unique strength of research,development, and demonstra-tion activities at the Los AlamosPlutonium Facility is that theyfollow the five-step logicalapproach in a healthy rangeof activities.

12

The Role of the Nuclear Materi-als Technology Division

In conclusion, the Los AlamosPlutonium Facility is an un-equaled national resource be-cause it is the only site that hoststechnologies covering the entirespectrum of plutonium needs.The Nuclear Materials Technol-ogy Division is responsible forapplying this capability to meetweapon complex reconfigurationrequirements and to respond tochanging needs in a manner thatadheres to the premise of safeconduct of operations and fullcompliance with regulatoryrequirements. +

Weapons Complex Reconfiguration:The Future of Plutonium Technology (continued)

Nuclear Matdals Technology Dwision Annual Rmlew

SITE-RETURN

PROCESSING

Site-Return Processing Overview

by John HaschkePlutonium Metallurgy Group

Scope and OptionsBecause nuclear reactors are

unlikely to be operated for thepurpose of producing additionalsupplies of plutonium, the onlyremaining somce of plutoniummetal for future weapons fabri-cation is site-return components.Consequently, site-return pro-cessing is the key element of theflow sheet for the plutoniumprocessing facility for Complex21 (see the introductory article)because all metal entering thefacility will be subject to suchprocessing. The objective of site-return processing is to producerequired quantities of WarReserve metal from site-returnfeed materials while minimizingwaste generation and workerradiation exposures and maxi-mizing safety and efficiency.

Site-return processing incor-porates both mechanical andchemical operations. The initialmechanical operation is disas-sembly of site-return units intobasic components; subsequent

mechanical operations areconcerned with convertingplutonium-containing compo-nents into a form suitable forchemical reprocessing. Thechemical operations include asequence of process steps thatproduce purified metal for usein fabricating new components.

Selection of the best processtechnologies is of utmost impor-tance. All baseline technologiesshould be adequately demon-strated and should reflect state-of-the-art technology. In contrastto the well-established processfor mechanical operations,several process alternatives areproposed for chemical opera-tions. The selection of baselinemethods for chemical processingof plutonium-bearing materialsisa somewhat controversialissue, complicated by the factthat the initial chemical opera-tion fol-lowing mechanicaloperations largely determinesthe structure of the entire flowsheet.

Only two chemical processingoptions, aqueous recovery andpyrochemical purification, aresufficiently developed to meritserious consideration as baselineflow sheet technologies forplutonium recovery. Alternativepurification methods, such asfractional distillation of thehalides, are viewed as competingoptions that must be adequatelydemonstrated and evaluatedwith regard to flow sheet impactbefore serious consideration asan alternative to the two provenprocesses.

Aqueous and pyrochemicalmethods represent substantiallydifferent purification options.Aqueous processing, the moretraditional approach, requiresseveral steps. The plutonium-bearing metal is first dissolvedin aqueous nitric acid, and theplutonium is then separatedfrom impurities by ion exchangeor solvent extraction methods.

Site Return Processing 13

—

Site-Return Processing Overview (continued)

Plutonium is removed from thepurified solution by precipita-tion, and metal is regeneratedby calcium reduction of theoxide or fluoride. All residuesare redissolved for recyclethrough the process.

In contrast, pyrochemicalpurification is a two-step ap-proach in which the plutoniumretains its metallic form through-out the process. Molten saltextraction to remove americiumis followed by electrorefining toeliminate other impurities.Because both of thesepyrochemical processes usemolten metal chlorides as sol-vents, the reprocessing of theirresidues requires that an aque-ous chloride facility be providedin addition to the aqueousnitrate facility used for repro-cessing oxide residues.

Pyrochemical purification hasbeen adopted as the baselinerecovery process because thecombination of purification andsupport technologies is consid-ered superior to the technologiesfor aqueous nitrate recovery.Important considerations in theselection of the baseline processincIude the quantity of wastegenerated, the level of radiationexposure, the complexity andcost of equipment, and theprocess efficiency. Althoughsuch issues are best addressedfor the respective flow-sheetoptions using available data andprocess modeling, certain keyissues merit brief consideration.The main disadvantage of theaqueous process is the genera-tion of large amounts of waste.The use of aqueous nitrate andchloride facilities to supportpyrochemical operations wouldbean unnecessary duplication ofcapability.

The advantages of thepyrochemical method are real-ized in reduced waste generationand in a high single-pass processefficiency. A comparable single-pass efficiency is realized inaqueous nitrate recovery, butthat operation requires severalsteps and is significantly lesscost-effective and energy effi-cient than pyrochemistry be-cause a chemical reduction stepis required to regenerate themetal. Incorporation of aqueouschloride and nitrate facilitieswith pyrochemical methods canbe viewed as advantageousbecause it provides a balancedcapability for handling the manytypes of residues stored forrecovery and accommodates theflexibility needed to exploit thewaste-stream polishing potentialof aqueous methods.

14 Nuclear MatddsTcchnolagy Dividon Annual Rdew

“The baseline flow sheet provides a basis forformulating relevant research and developmentstrategies and for effectively directing resourcesto support the most promising options.”

The baseline flow sheetprovides a basis for formulatingrelevant research and develop-ment strategies and for effec-tively directing resources tosupport the most promisingoptions. As implied in thepreceding discussion, twocategories of effort are recog-nized: efforts to modify thebaseline process and efforts toprovide alternatives to it.A decision to pursue an activityfalling in the second categorymust weigh the potentialpayback from the alternativemethod against its complexityand development time andagainst its impact (positive ornegative) on the flow sheet andon facility design. Althoughpursuit of promising alternativesis necessary, allocation of limitedresources to enhancing baselinetechnologies seems most pru-dent because modification of abaseline technology neither

changes the facility footprint norsignificantly alters equipmentdesign. Baseline improvementscan be accommodated at a pointwell beyond the date for finalprocess definition and theyguarantee that a usable processwill always be available forimplementation.

Baseline ProcessesDisassembly

The baseline process forcomponent disassembly incorpo-rates standard precision machin-ing techniques. The need forresidue reprocessing is avoidedbecause precision methods arecapable of selectively removingmaterials without includingturnings from adjacent compo-nents. Further development isnot needed.

The decontamination of en-riched uranium components isan ancillary disassembly process.Plutonium-containing particlesmust be removed from a compo-nent before it can be returned tothe uranium reprocessing facility.

The baseline decontaminationprocess is a demonstratedmanual operation in which dilutenitric acid solution and abrasionare used to remove plutoniumoxide particles from uraniumsurfaces. The process generateslarge volumes of liquid wastethat must be treated by a cur-rently undefined method.

ConsolidationA baseline method for con-

solidating plutonium compo-nents also remains undefined.Demonstrated alternativesinclude compaction, casting,and in-process fusion ofcomponent fragments.

Molten Salt ExtractionMolten salt extraction is the

baseline process for removingamericium-241 from aged pluto-nium metal. Ingrowth of theamericium isotope from betadecay of plutonium-241 (half-lifeof 13.2 years) present in theoriginal metal presents a signifi-cant radiation hazard for workershandling aged metal.

Site Return Processing 15

Site-Return Processing Overview (continued)

Americium-241 (half-life of 458years) undergoes alpha decay,but a large fraction of the processforms an excited-state nep-tunium-237 daughter that emitsa penetrating 60-kiloelectron-volt gamma ray. The maximumactivity of aged metal is reachedafter approximately 75 years.Immediate separation of ameri-cium is essential for reducingradiation exposures.

Americium is extracted into amolten salt phase that is physi-cally separated from the ameri-cium-free metal in a subsequentbreakout step. When plutoniumtrichloride is added to a moltencalcium dichloride phase that isin contact with molten pluto-nium, americium in the metal isexchanged for plutonium in thesalt by an ensuing redox reac-tion. Although molten saltextraction is an establishedproduction method, significantupgrades are possible.

The production of plutoniumtrichloride reagent for molten saltextraction and electrorefining isan essential support operation ofthe site-return flow sheet. Thebaseline process is a demon-strated technology that involvespreparation of plutonium hy-dride. The hydride is subse-quently converted to plutoniumtrichlondeby reaction withgaseous hydrogen chloride atelevated temperatures.

ElectrorefiningElectrorefining is the baseline

process for producing high-purity plutonium. The techniqueuses molten calcium dichloriderich in plutonium trichloride asa transport medium for an elec-trolysis process that removesplutonium from an impureplutonium anode and depositspure metal at a second electrode.The anode residues constitute amajor portion of the reprocessing

load for the aqueous chloridefacility. However, only a portionof the site-return metal must bepurified by electrorefining; WarReserve metal is obtained byblending the high-purity productwith americium-free metal frommolten salt extraction.

BaseIine Modifications andAlternatives

The baseline site-returnprocesses provide severalopportunities for modificationand substitution. Such effortsinclude the development ofreusable crucibIes for variouspyrochemical applications andseveral larger developmentactivities that have potentialfor significantly upgradingprocesses.

16 Nuclear MaMialsTechnology D1vMon Annual Re\5ew

“’’s-o-e-p’:;”Fi!&6iz!z!i!iE’’’’;’J0nsPlutonium Processing Facility

I + I

\I

DlsPosai

An in situ chlorinationprocess for use in molten saltextraction and electrorefiningis one of the larger activitiesbeing pursued. Plutoniumtrichloride is generated withinthe pyrochemical apparatusby bubbJ.inga stoichiometricamount of chlorine gas intothe molten metal. The potentialpayback is large because processoperations are simplified andthe need for a facility to prepareplutonium dihydnde andplutonium trichlorideis elimi-nated. Application of the tech-nique has been demonstratedfor molten salt extraction. Adetailed description of the effortis included in the chapter onchloride recovery operations.

The use of a fluorine-richplasma as an alternative methodfor decontaminating uraniumcomponents is also being investi-gated. Fluorine atoms generatedfrom inert fluorocarbons in aradio-frequency field react withparticles contaminated withplutonium oxide to form gaseousplutonium hexafluoride that iscollected in a downstream trap.The technology will replace theacid decontamination processwith a method that producesminimal solid residue. Thisreplacement will eliminate theneed for a Ieachate treatmentfacility and will not negativelyaffect the flow sheet becausedecontamination is a terminalflow-sheet process. The condi-tions and kinetics for etchingplutonium oxide have alreadybeen defined.” A detailed reporton plasma processing is includedin this chapter.

*J. C. Martz, D. W. Hess,J. M. Haschke, J. W. Ward, and B. F.Flamm, “Demonstration of PlutoniumEtching in a CFd/OzRF Glow Dis-charge,” ]. NucZ.Mater. 182,277 (1991).

AutomationAn important and unifying

initiative of site-return activitiesis their automation and integra-tion, as detailed here in a sepa-rate article. Although this con-cept is not indicated on thebaseline flow sheet, consolidat-ing operations are expected toreduce radiation exposures,enhance safety, and increaseefficiency. Negative impact onthe flow sheet is not introducedbecause the approach beingdeveloped does not alter thefundamental chemistry of thebaseline process; the effortattempts only to exploit op-portunities that currently exist.In addition to accomplishingimprovements cited above,the automation and integrationprogram will provide a uniqueand necessary opportunity forunifying individual technologiesand demonstrating their chemi-cal and process compatibilitybefore final flow sheetdefinition. +

Site Return Processing 17

SITE-RETURN

PROCESSING

Automation and Integration of Site-ReturnProcessing

Joseph C. Martz and John M. HaschkePlutonium Metallurgy Group

Tony J. Beugelsdjik and Lawrence E. BroniszMechanical and Electronic Instrumentation Group

Thenext-generaticm nuclearmaterials processing complexwill require new technologiesto dismantle site-return compo-nents and recover the nuclearmaterials. By integratingbaseline technologies withproven techniques in roboticsand automation, we can createa safe, environmentally friendlyoperation that will eliminatemixed wastes, reduce wastegeneration to theoretical mini-mums, reduce personnel radia-tion exposure to as low as rea-sonably achievable, and placeprocess safety above all otheroperational concerns. A second-ary objective of this technologydevelopment is to maximizeprocess efficiency.

The three key processes inthe site-return operation aredisassembly of the weaponcomponent, recovery of itsnuclear material, and purifica-tion of the recovered metal tomeet War Reserve specifications.

The component forms the inputto the process. Exit streamsinclude nonnuclear componentmaterials, salt from the purifica-tion step, and nuclear materialin a form suitable for long-termstorage or immediate reuse.Added reagents include stoichio-rnetric quantities of oxidant forremoval of americium andcalcium dichloride forpyrochemical operations.

The high radiation levelsresulting from americium build-up in the weapons stockpilemake remote handling highlydesirable for site-return material.Specifically, the high-radiation-exposure operation of saltbreakout after molten salt extrac-tion can be automated to reduceworker exposures. In addition,the pyrochemical methodsenvisioned for site-return pro-cessing are amenable to automa-tion. Increases in process safetyand efficiency are an addedbenefit of system integration.

Reconfiguration of thenuclear weapons complexprovides a unique opportunityto apply the concepts of concur-rent engineering to site-returndisassembly. In the past, auto-mation technologies—usuallyinvolving the application ofcommercial equipment in aglove-box enviornment—havebeen applied to preexistingprocesses and process equip-ment with mixed results.Los Alamos has been involvedin developing automated tech-nologies for almost a decade.This extensive experience hasled to the identification of theimportant issues that influenceglove-box automation. Thus,Los Alamos expertise, combinedwith knowledge of the importantprocess chemistries, has led tothe development of a systemrequirements document thatoutIines the key issues andtechnologies involved in thesuccessful implementation of anautomated site-return processingsystem. Engineering analysis

18 Nuclear MakvialsTcdmology Division Annual Review

“ By integratingbaselinetechnologieswithproventechniquesin roboticsandautomation,we can createa safe, environmentallyfriendlyoperationthatwill eliminatemixedwastes,reducewastegenerationto theoreticalminimums,reducepersonnelradiationexposuretoas lowas reasonablyachievableand placeprocesssafetyaboveall otheroperationalconcerns.”

and design are currently inprogress. Individual processtechnologies have matured overthe past several years so thatthey are now amenable to inte-gration and process automation.

Separation of site-returncomponents is accomplishedthrough the use of intelligentmodules optimized to performthis task. A specially designedparting system consisting of aparting lathe and custom toolingreceives the intact pit. Designof the parting system addressessuch typical glove-box opera-tional issues as maintenancewithin the inert atmosphere,reliability of components, acces-sibility for routine service, andoptimum use of glove-box space.Important features of the systeminclude modular x- and y-axes,a telescoping z-axis, externallymounted electronics, and dust-proof construction. The intentof this effort is to develop aflexible, modular handlingsystem in partnership withprivate industry.

Certain assemblies requireconsolidation before materialpurification. An intelligentstation is used to perform thistask. This modular approachfollows closely the developmentof automated chemical analysistechnologies for the Departmentof Energy’s Office of Environ-mental Restoration and WasteManagement. Software architec-ture and control structuresalready in place allow a facileand rapid development effort.

In the purification stages ofthe site-return system, intelligentstations perform the requisiteprocess chemistry. Fixed auto-mation stations provide repeat-able process control that enablesautomation of highly repetitiveprocess operations. The automa-tion system provides a means oftransport between these stations.Individual processes are coordi-nated to the extent that theproduct from one operationprovides the feed for the next.In addition, each chemicaloperation will be optimizedsuch that its by-products willnot negatively impact subse-quent process operations.

A single glove box accommo-dates all process operations. Acentrally located parting systemseparates intact assemblies intohemishells. The automatedmaterial-handling system trans-ports individual hemishells tothe chemical recovery andpurification operations. A singleparting and material transportsystem serves two separaterecovery stations.

The changing culture in theDepartment of Energy withrespect to environmental andsafety awareness demands thatall new operations generateminimal wastes, avoid mixingdifferent types of waste, mini-mize personnel radiation expo-sure, and operate to the higheststandards of safety and security.The automated site-returnprocessing system describedhere meets these requirementswhile ensuring high processefficiency. +

Site Return Processing 19

SITE-RETURN

PROCESSING

Advanced Cleaning Technologies

by John M. HaschkePlutonium Metallurgy Group

IntroductionPlutonium components are

exposed to a variety of organiccompounds during fabrication.In normal production practice, aprotective flow of hydrocarbonoil is directed over a part duringmachining. Residual oil must beremoved by an in-process clean-ing procedure to facilitate han-dling and inspection of a part.During these operations acomponent is exposed to otherorganics that are removed bya final cleaning procedureimmediately before assembly.Hydrocarbon residues remain-ing on plutonium surfaces areradiolytically decomposedduring stockpile storage ofweapon assemblies,and causedetrimental corrosion of nuclearcomponents.

As in many other establishedmanufacturing processes,chlorocarbon solvents are usedto degrease plutonium compo-nents. The in-process operationuses a carbon tetrachloride sprayrinse, and an ultrasonic clean-ing/vapor decreasing method.A 111-trichloroethane (TCA)soIvent is used for finaI cleaning.

These chlorocarbon solvents(which deplete ozone, pose acarcinogenic hazard, and gener-ate mixed waste) are subject toregulation limiting their contin-ued use and availability. Duringrecent production cycles, thecombined annual usage of thesechlorocarbons has approached100,000 liters, a large part ofwhich is released as atmosphericemissions.

Although anticipateddecreases in weapons produc-tion wilI result in substantialreductions in solvent usage,chlorocarbon-based processesmust be eliminated. The use ofdry machining techniquesprecludes the need for in-processcleaning. However, final clean-ing is necessary because compo-nents are exposed to oils andother hydrocarbons duringsubsequent manufacturingoperations. Advanced cleaningtechniques are being investi-gated to identify and developenvironmentally acceptablealternatives to chlorocarbon-based methods. In addition tosatisfying all environmental,

safety, and health requirements,suitable alternative technologiesmust not generate mixed waste,must be economically feasibIeand process compatible, andmust satisfy requirements forcomponent cleanliness. Al-though the levels of cleanlinessachieved by the existing TCA-based process are unknown, themaximum allowable level ofhydrocarbon residue calculatedfrom evaluation of data fromstockpile systems is 5 micro-grams per square centimeter ofcomponent surface area.

Results of joint developmentefforts with collaborators fromEG&G Rocky Flats are presentedhere. Technologies based onsupercritical fluid (SCF) carbondioxide and on aqueous mediaare described along with effortsto establish analytical methodsfor defining surface cleanliness.A third cleaning alternativebased on plasma processing isdescribed in the article titled“Plasma Chemical Processing.”

Nuclear h4aterials TcchnoIogy Oividon Annual Review20

“Advanced cleaning techniques are being investigatedto identify and develop environmentally acceptablealternatives to chlorocarbon-based methods.”

Baseline Cleaning ProcessUnlike most baseline tech-

nologies in the flow sheet for theComplex 21 Plutonium Process-ing Facility, the process for finalcleaning of plutonium compo-nents has not been demonstratedfor production. Use of SCFcarbon dioxide is recommendedbecause of its potential cleaningcapability and its anticipatedprocess compatibility. However,because pursuit of a singlealternative technology forreplacing the chlorocarboncleaning method is imprudent,the cleaning potential of aqueousmedia is also being investigated.

Supercritical Fluid CleaningBackground

Supercritical carbon dioxideis the primary candidate forreplacing TCA in the finalcleaning of plutonium compo-nents. A recycle SCF carbondioxide process satisfies boththe Ietter and the spirit ofenvironmental regulation.

Carbon dioxide occurs naturally,is nontoxic and unreactive, andposes minimaI risk to the envi-ronment and to the health andsafety of employees and thepublic. Supercritical conditionsare attained at modest conditions(above 31°C and 74 bar pres-sure), and the high volatility ofcarbon dioxide facilitates theseparation of solvent and solute.SCF carbon dioxide technologyis well developed and widelyused for extracting organics inthe food, polymer, pharmaceuti-cal, and synthetic-fuel industries.Large SCF systems are commer-cially available.

Prior work suggests that SCFcarbon dioxide is an effectivecleaning medium. Results ofinitial studies of SCF cleaningconducted at Rocky Flats showthat comparable levels of carbon-containing residues remain on

steel and uranium surfaces aftercleaning with carbon dioxideand with TCA.1 Tests conductedat a vendor laboratory show that20-centimeter-diameter steelhemispheres are cleaned tolevels well below the limit forplutonium at reasonable tem-peratures, pressures, flow rates,and times.2 These studies, whichare consistent with earlier extrac-tion work showing that thesolvent properties of SCF carbondioxide are strongly dependenton solvent density, establishtentative conditions for cleaning(temperature of 35°C to 400C andpressure of 150 to 200 bars). Atthese conditions, the fluid den-sity is in the range of 0.80 to 0.85grams per cubic centimeter.Cleaning times for hemispheresare less than 20 minutes at afluid flow of 1.0 Iiter per minute.

Site Return Processing 21

Advanced Cleaning Technologies (continued)

Fig. 1. Dirzgrmnof n closed-loop SCFcleaning system.

GloveBox~re~~ureTemperaturem

ConceptThe concept of an SCF

carbon dioxide cleaningapparatus is illustrated inFig. 1. The part is containedin a heated cleaning cham-ber with a clearance of 2 to 3millimeters on each side ofthe part to minimize fluidvolume and to direct flowover the part surface. Liquid

II L, 1

IF?!!tC02supply

HeatedExpansion

Valve((~)]

Residue- C02

Collection CollectorVessel

.

u JI

carbon dioxide is drawn fromthe supply, pumped to thedesired pressure, and heated tothe desired temperature in thesupercritical range before flow-ing over the part at a controlledrate. Organic residues dissolvein the solvent phase and arecarried out of the chamber andthrough a heated expansionvalve. The decrease in densityaccompanying expansion forcesdissolved organics to precipitatein a collection trap. The carbondioxide is condensed and re-cycled to the supply vessel.Important cleaning parameterssuch as temperature, pressure,flow rate, and time are readiIycontrolled.

+——MechanicalorThermalCompression_

Several advantages of theconcept are evident. In additionto using a solvent posing mini-mal risk, the process concen-trates all cleaning residues fordisposal or processing. If in-linefilters do not remove plutonium-containing particles entrained bythe fluid stream, they also willcollect with the residue. Therecycle potential of the process isparticularly attractive; no wastesor emissions are produced otherthan the concentrated organicresidue.

Stcitzls

A laboratory-scale SCFsystem has been constructed andinstalled. In this system, an air-driven pump delivers 18 millili-ters of solvent per minute at adensity of 0.85 grams per cubiccentimeter through a 20-cubic-centimeter cleaning chamber.Parallel chambers are installedinside a glove box for plutoniumstudies and outside the glovebox for nonnuclear samples.Sample surface areas up to 50square centimeters are accom-modated by these chambers.

22 Nuclear Materials Technology Cividon Annual Rdcw

“The recycle potential of the process is particularlyattractive; no wastes or emissions are produced other thanthe concentrated organic residue.”

Important compatibilityissues are resolved by initialstudies with plutonium. Al-though the reaction of pluto-nium with carbon dioxide toform plutonium dioxide isthermodynamically favorableand highly exothermic, reactionis not anticipated because ofslow kinetics.3 Numerouschemical compatibility testsconducted within the projectedcleaning range show that bur-nished plutonium remainsuntarnished after exposure toSCF carbon dioxide for severalhours. The metal also shows noevidence of reaction with thesolvent after one hour at extremeconditions of 100”Cand a pres-sure of 310 bars.

The effects of water contami-nation in the solvent are alsoestablished. The volubility limitof water in SCF carbon dioxideat 40”C is approximately 0.5mass percent. Although com-mercial carbon dioxide containswater at ppm levels, the flowprocedure exposes the pluto-nium surface to large amounts

of water whose chemical natureis unknown. If it exists as car-bonic acid, plutonium maydissolve and cause dimensionalchanges in the component andcontamination of the equipment.Visual observation of the surface,mass gain data, and downstreamcontamination surveys show thata l-hour exposure of clean metalto static SCF carbon dioxidecontaining 0.13 mass percentwater resulted in formation ofa passive surface film.

Cleaning studies with SCFcarbon dioxide are in progress.Attempts to use gravimetricmethods for quantifying residuallevels of hydrocarbon oil oncleaned samples show that suchtechniques are not sufficientlysensitive. An infrared spectro-scopic method of analysis isnecessary to establish cleaningefficacy. Future experiments willinvestigate effects of such param-eters as temperature, pressure,flow rate, time, and residue typein order to identify the optimalcondition for cleaning.

The results will be used to definespecifications for a pilot-scaleSCF system. The effects of thecleaning process on the chemis-try and storage behavior of themetal must also be determined.

A pilot system will establishthe cleaning parameters for aproduction process. Procure-ment and installation of com-mercial equipment is planned.Experiments will be conductedto define cleaning parameters forfull-sized parts, develop solventrecycle methods, and addresssafety issues.

Aqueous CleaningBackground

Aqueous cleaning methodsprovide an alternative to thebaseline SCF carbon dioxideprocess. The environmental,safety, and health risk is low, butthe compatibility of an aqueoussystem with the plutoniumrecovery process is uncertain.

23Site Return Processing

Advanced Cleaning Technologies (continued)

A major concern is the chemicalcompatibility of plutonium metalwith aqueous media. The corro-sion of plutonium by water anddilute salt solutions is a rapidreaction that produces hydrogenand a series of oxide hydridesand oxides.4 The possibility ofusing aqueous cleaning mediaarises because plutonium appar-ently does not corrode if the pHis greater than 8.s

Concept

The concept of an aqueouscleaning process closely parallelsthat of the SCF carbon dioxidesytem. Although the use of abasic detergent solution in anultrasonic bath is an attractiveoption, the potential for corro-sion from release of water vaporinto the process faciIity is unac-ceptable. Use of a closed-loopcleaning system is preferred.The apparatus resembles thatshown for SCF carbon dioxide inFig. 1. After being placed in asmall-volume cleaning chamber,a component is subjected to athree-step cleaning procedure.

in the first step, a high-pHdetergent solution is heated andpumped over the part to removeorganic residues from the sur-face. The cleaned component isthen rinsed with distilled wateror a selected buffer solutionbefore being vacuum driedduring the final step.

Several advantages of theprocess are recognized. Thesystem operates at low pressure,and the equipment requirementsand the safety concerns are lessthan with carbon dioxide clean-ing. However, although theprocess is likely to generate onlylow levels of waste, a processingfacility will still be required toconcentrate organic and deter-gent residues, to purify water,and to prepare fresh detergentsolutions.

statusInitial experiments designed

to determine the feasibility of anaqueous cleaning process willestablish the chemical compat-ibility of plutonium with waterand high-pH detergent solu-tions. Measurements are com-plete for a test matrix designed

to assess the effects of pH,temperature, detergent type, andtime on the aqueous corrosion ofplutonium. Burnished samplesof plutonium were weighed andplaced on the desired aqueousmedia for extended periods oftime. Periodic visual inspectionswere made, and mass changeswere measured after approxi-mately 2 weeks.

Results of the compatibilitytests are consistent with earIierreports indicating that corrosionis negligible in high-pH solu-tions. Tests at 22°C show thatthe metal remains untarnishedafter more than 24 hours inbuffered solutions having pHvalues of 7.0, 10.0, and 10.2 andin high-pH commercial deter-gents. Tests with the samesolutions at 49°C show that themetal surface becomes onlyIightIy tarnished during thattime period. Although distiIledwater produced localized areasof extensive reaction after 24hours, the surface was untar-nished after 1 hour at 220C.

24 Nudcar Materials Technology Division Annual Revkw

“The success ofefforfs to define advanced cleaningmethods hinges on the ability to determine the cleanlinesslevels attained by different procedures.”

These findings show that pluto-nium is compatible with warmcleaning solutions and thatcleaned components can berinsed with distilled water atroom temperature.

Construction and installationof a laboratory-scale systemmust be completed beforecleaning studies can be initiated.Cleaning efficacy will be evalu-ated using infrared spectroscopicmethods, and optimal cleaningconditions will be defined. Thedecision to construct a pilotfacility is contingent on theresults of studies of SCF carbondioxide cleaning.

Analytical ProceduresThe success of efforts to

define advanced cleaning meth-ods hinges on the ability todetermine the cleanliness levelsattained by different procedures.Fourier transform infrared(FTIR) spectroscopy is beingdeveloped for indirect and directmeasurement of the organicresidue remaining on a surfaceafter cleaning. Indirect measure-ment follows a standard proce-dure in which a solvent rinse of

Site Return Processing

the cleaned surface is followedby infrared analysis of thesolution. Although easily ac-complished, this technique isbased on the assumption that thesolvent is ideal and removes allresidues. Reflectance and dif-fuse-reflectance IWIR techniquesare being investigated as pos-sible means for directly quantify-ing hydrocarbon residues onsurfaces.

Development of a rinsemethod using Freon 113 solventis complete. The techniqueanalyzes for the total carbonhydrogen concentration from allorganic species by integratingthe 2800- to 3000-cm-’ spectralrange and defines hydrocarbonlevels as low as 0.3 ppm. Withsamples from laboratory-scalecleaning studies, the method candetermine residue levels of 0.1microgram of hydrocarbon persquare centimeter. The appara-tus and procedures for transfer-ring rinse samples from theglove box to the spectrometer aredemonstrated with nonnuclearsamples. Reflectance equipmentfor directly analyzing residues isnow in design and fabrication. +

Cited References1.K.M. Motyl,“CleaningMetal

SubstratesUsingLiquid/SupercriticalFluidCarbonDioxide;’RockwellInternationalreportRFP-4150(January1988).

2. J. M.HaschkeandC E. C. Rense,“SupercriticalCarbonDioxideforCleaningPlutonium,”presentationat theNuclearMaterialsTechnologyDivisionReview, LosAlamosNationalLaboratory(February1991).

3. J. M.HaschkeandS. J. Hale,“Altern-ativeSolventsforCleaningPlutonium:ThermodynamicandKineticConsider-ations,”LosAlamosNationalLaboratoryreportLA-12255-MS(March1992).

4. J. M.Haschke,A. E. Hodges,III,G. E.Bixby,andR. L. Lucas,“TheReactionofPlutoniumwithWater:KineticandEquilib-riumBehaviorof Phasesin thePu+O+HSystem,”RockwellInternationalreportRFP-3416(February1983).

5. J. M. Haschke,“HydrolysisofPlutonium:ThePlutoniumOxygenPhaseDiagram,”in Transuranium Elements: A HalfCentury (AmericanChemicalSociety,Washington,DC,inpress1992).

25

SITE-RETURN

PROCESSING

Plasma Chemical Processing II

by Joseph C. MartzPlutonium Metallurgy Group

BackgroundOver the past 20 years,

plasma processing has becomeincreasingly important in thefabrication of microelectronicdevices. Since the late 1960s,semiconductor manufacturershave exploited the characteristicsof plasmas to create increasinglycomplex circuits. Application ofplasma processing to othermanufacturing operations hasincreased in recent years. Di-verse operations such as toolhardening, industrial and cos-metic coating, medical instru-ment sterilization, componentcleaning, solar cell manufacture,analytical determination, andarchaeological restoration havebenefited from advanced plasmaprocessing techniques. Plasmasoffer a unique chemical environ-ment in which to deposit, alter,and pattern a wide variety ofmaterials. The plasma environ-ment offers an otherwise unat-tainable combination of reactivechemical species and energeticparticle bombardment, all atroom or near-room temperatures(300 to 600 K).

Extension of plasma process-ing techniques to plutoniumproduction operations offersmany advantages. Plasmaprocessing consists primarily ofgas/surface reactions conductedat low pressure (1 to 1000millitorr). For this reason, by-product formation is minimized(minimizing waste generation),feed chemical use is reduced,remote operation is readilyaccommodated, and processautomation is easily imple-mented. Specific application ofplasma processing to plutoniumproduction includes decontami-nation of items exposed toplutonium and other actinides,plasma-based cleaning of pluto-nium and nonplutonium compo-nents, selective removal ofplutonium compounds (such asthe selective etching of pluto-nium dioxide from plutonium),and the growth of novel chemi-cal layers on plutonium surfaces.

Plasma FundamentalsPlasmas may be generated

by a wide variety of excitationsources. Radio-frequency (rf)excitation is the most commonsource, and plasmas created inthis manner are often called rfglow discharges. Energy iscoupled into the gas by ioniza-tion of gas species, and transferof energy is accomplished byelectron impact. Because elec-trons are accelerated in theplasma by the presence ofelectrical fields, they have con-siderable kinetic energy. Subse-quent collision of these energeticelectrons with other gas-phasespecies results in substantialenergy transfer.

Examination of the collisionprocess reveals that electronicstates of atoms and moleculesare selectively excited. If thecollision is entirely elastic andoccurs without a change ininternal energy of the species,the electron will simply reboundfrom the massive neutral specieswith little transfer of energy.

26 Nuclear MatwialsTcchnology Division Annual Reiiew

“The plasma environment offers an otherwiseunattainable combination of reactive chemical speciesand energetic particle bombardment, all at room ornear-room temperatures (300 to 600 K).

Thus, elastic collisions areincapable of imparting a signifi-cant translation energy to neutralspecies. Because the averagetranslation energy of a neutralspecies is a measure of its tem-perature, electron impact resultsin little or no temperature rise.Conversely, if the collision isinelastic and occurs with achange in internal energy, theefficiency of energy transferincreases remarkably. A changein internal energy of an atom ormolecule is equivalent to anexcitation of the electronic statesof that species. Thus, the effi-cient transfer of energy to theneutral species from electronimpact results in an excitationof the electronic states of themolecule or atom.

Electron-impact excitationis sufficient to completelyremove one or more electronsfrom the outer electronic shellsof these species, thereby result-ing in ionization. The degreeof ionization in the plasma issmall, however—rarely occur-ring for more than 0.001‘%0ofall species in the plasma.

A more prevalent result of elec-tron impact is dissociation ofmolecular species caused byexcitation of electrons in bond-ing orbitals to higher-energyantibonding orbitals, resultingin species dissociation. In somediatomic plasmas, the degreeof dissociation can reach 6070.In addition, most free-radicalrecombination occurs as athree-body process, nearlyall of which occurs heteroge-neously at interfaces. Therefore,free radicals have a long gas-phase half-life, and most sur-faces exposed to the plasma aresubjected to a significant free-radical flux.

The free radicals resultingfrom molecular dissociationsdefine the unique chemicalenvironment of the plasma.Theyare often highly reactive species,such as free-radical halogens,that provide a powerful chemicalreagent in which to process awide variety of materials.

Translational, vibrational, androtational temperatures havebeen measured at or near roomtemperature in most plasmasystems. However, thermallyequilibrated systems with tem-peratures of several thousandkelvins would be required toachieve dissociation fractionscomparable with those of theplasma. Thus, the plasma is anonequilibrium thermal environ-ment.

Though the concentration ofions is low compared with theconcentration of neutrals,charged species play an impor-tant role in many reactions bybreaking surface bonds, creatingreaction sites, and enhancingproduct resorption. Ion bom-bardment provides a directionalcomponent to many plasmareactions, allowing anisotropicpattern transfer. Heating effectsarising from ion bombardmentcan play an important role in thekinetics of many importantchemical reactions.

Site Relurn Processing 27

Plasma Chemical Processing (continued)

Fig. 1. Scheuuzficof reaction pathwayswithin the carbon fetra/7uorideplasma.Circled species indicate stable reactionend products. Arrows indicate reactionof carbon-containing species. Note thatmost renctions produceatomic fi’uorine.

Despite the widespread use ofplasma processing in the manu-facture of solid-state devices,many fundamental aspects of theprocesses are poorly understood.Simple two-component mixturesof reactant gases in the plasmacan give rise to complex chemis-tries involving dozens of differ-ent reactions.]~Optimization ofthe plasma environment oftenstarts with enhancement of theactive reactant concentration.Plasma parameters, such aspressure, applied plasma power,and system residence time, canhave a dramatic effect on theproduction of desired atomicand molecular radicals.

The classic example ofgas-phase optimization is theaddition of oxygen to carbontetrafluoride discharges toenhance fluorine production.3For more than 20 years,semiconductor manufacturershave known that the additionof small amounts of oxygen(-10%) to carbon tetrafluoridecan result in a significant in-crease in fluorine production.

28

w+’I

<

\

CF3+F ‘ e-

MCFqe

40CO+Fe- 4

e- 7 CnF2n+2 92

CF2+F o\O fj 4P

5vo 0co ‘2F co“-<G

CFX F

12a

> COF2

13

+F

o+COFZ

&.- 0‘ co +2F

\

COF2 o+(x-l)F CO +(x+1 )F

Figure 1 is a schematic of theimportant chemical reactionswithin the carbon tetrafluoride/oxygen discharge.4 Major prod-ucts from these reactions includecarbon dioxide, carbon monox-ide, carbonyl fluoride, and largequantities of atomic and molecu-lar fluorine.

The efficient generation ofuseful quantities of fluorinegives rise to a whole class ofetching reactions based on theformation of volatile metalfluorides. In principle, anymaterial that forms a volatilecompound on reaction withfluorine may be etched. Tung-sten, tantalum, niobium, carbon,germanium, titanium, molybde-num, boron, sulfur, uranium,plutonium, and, of course,silicon are all candidates forfluorine-based plasma etching.

Nuclear Materials Technology Di\.isionAnnual Re$iew

“In principle, any material that forms a volatilecompound on reaction with fluorine may be etched.”

Other etching chemistries arepossible. The most importantof these is the chlorine-basedetching of aluminum and gal-lium arsenide. Although alumi-num and gallium do not formvolatile fluorides, they do formvolatile chlorides. Oxygen-basedetching of organic materials(plasma ashing) representsanother important class ofetching reactions.5

Plasma chemistry can beused to selectively etch certainmaterials in preference to others.For example, numerous oxides(such as silicon dioxide) arereadily etched in perfluoro-propane plasmas, whereas thecorresponding metals (such assilicon) do not etch appreciablyin these environrnentsb’7(because of the tendency forcarbon-rich discharges to formpolymeric films on surfaces).

If the ratio of carbon to fluorinein the feed gas is within a certaincritical range, only the polymericfilm created by the discharge isetched. In such an equilibriumcondition, the net result is neitheretching nor deposition. If thisprocess occurs on an oxidesurface, the oxygen present inthe surface helps to volatilize thecarbon-rich polymeric film,yielding an excess of fluorineatoms. This excess fluorine isavailable to etch the underlyingsubstrate material. Thus, theoxide is etched, but the metal isnot. This process yields selectivi-ties as high as 200 to 1 for silicondioxide-to-silicon etching.Application of this technologyto the selective cleaning andrestoration of actinide surfacesappears promising.

Uxygen- and water-basedplasmas are often used as clean-ing agents. The strong oxidizingpotential of these dischargesserves to ash nearly all organicmaterials to carbon dioxide andwater. Materials traditionallyresistant to solvent-based tech-niques, such as radiolyticallycross-linked polymers, arereadily removed by these plas-mas. This feature is particularlyimportant in plutonium process-ing because of the radiolyticreactions occurring at plutoniumsurfaces. Plutonium partsexposed to machining and otheroils (for longer than a few days)are usually difficult to clean.Plasma cleaning offers thebenefit of cleaning these compo-nents while generating onlyminimal quantities of additionalwaste.

Site Return Processing

—

29

Plasma Chemical Processing (continued)

Fig. 2. Plutonium etch rate versusreactor pressure in carbon fefraffuoride/10% oxygen discharge. Power is 50wn~ts,system residence time is 10seconds, and temperature is 298keluins.

Plasma DecontaminationThe potential advantage of

applying carbon tetrafluoride/oxygen plasma technology togenerate volatile plutoniumhexafluoride is clear. Efficientgeneration of fluorine by theplasma, in addition to the en-hanced reaction rates availablein the glow discharge, offerssignificant potentiaI for actinideprocessing and decontamination.The application of plasmaprocessing to plutonium volatil-ization has been describedelsewhere.8 Figure 2 shows theetch rate of plutonium versusreactor pressure in a carbontetrafluoride/10’%oxygendischarge. Fluorine atom con-centration increases linearly withreactor pressure across the rangeshown in Fig. 2. Thus, the etchrate appears to increase withincreasing fluorine concentration(possibly showing first-orderkinetics).

3

o

1

z!

++

I i. ....................... .................................................. ......................... ...............................................2j

A! :

A jj

A] 1. ......................~........................~.........................:........................i.........................;......................

4 ii1

:I I I i i

o 100 200 300 400 500 600Pressure (mtorr)

Figure 3 compares the etchrate of plutonium with that ofplutonium dioxide for severalsamples processed at a pressureof 200 millitorr. The etch rate ofplutonium dioxide is typically 5to 10 times higher than thatmeasured for plutonium metal.Several factors may account forthe high etch rate of the oxide.

Plutonium dioxide has a highsurface area when prepared ateither room or elevated tenlpera-tures. Stakebake and DringmanQreport a surface area of 16.9square meters per gram and acrystallite size of 9.7 nanometersfor low-temperature, unsinteredplutonium dioxide, whereas thesintered oxide is reported tohave a surface area of 3.48 squaremeters per gram and a crystallitesize of 68.2 nanometers. A largesurface area provides a largeetch area for the heterogeneousreaction of fluorine with pluto-nium dioxide, leading to en-hanced reaction rates.

30 Nuclear Materials Technology Ois,isionAnnual Rdcw

6 1

i

4

2

0PU02

............... .......................................................................4

Further, it is possible that anoxyfluoride of plutonium mayexhibit a higher vapor pressurethan pure plutonium hexafluo-ride, which would account forthe increased reaction rate forplutonium dioxide. This isunlikely, however, as the vaporpressures of all knownoxyfluorides of plutonium areseveral orders of magnitudebelow the vapor pressure ofhighly volatile plutoniumhexafluoride, for which thevapor pressure is 43.35kilopascals at 52°C.*0’”

A third possibility to accountfor the increased oxide etch rateinvolves the fluorocarbon filmmodel described previously.

* , ,{

Pu

Because of the high fluorinecontent of plutonium hexafluo-ride, the fluorine-to-carbon ratiofor plutonium dioxide etchingshould be larger than that forsilicon dioxide; the equilibriumfluorine-to-carbon ratio forselectively etching plutoniumdioxide in preference to pluto-nium should be nearer 4:1 (as forcarbon tetrafluoride feed gas).This effect may also contribute tothe observed increase in the etchrate for plutonium dioxide.

The observed plasma etchrate of plutonium dioxide com-pares favorably with that re-ported for purely chemicalsources of fluorine; plasma

Fig. 3. Comparison of etch rates ofplutonium and plutonium dioxide forseveral etch runs. Pressure is 200millitorr, power is 50 watts, andresidence time is 10 seconds.

volatilization of plutoniumhexafluoride proceeds consider-ably faster than the purelychemical reaction betweenfluorine and plutonium.12’*3Several reasons exist for thesedifferences in the etch rate.Chemical sources of fluorinetypically rely on surface disso-ciation of a parent molecule andsubsequent surface diffusionbefore reaction with plutoniumcan proceed. Conversely, theplasma produces fluorine in thegas phase. A flux of fluorineatoms impinges on all surfacesexposed to the plasma, resultingin a high reaction probabilitywithout the need for surfacediffusion. In addition, ionbombardment plays an import-ant role in the plasma by creat-ing adsorption sites, promotingreaction and surface activation,and enhancing plutoniumhexafluoride resorption. All ofthese factors may contribute tothe high etch rate for plutoniumdioxide observed in the plasma(as compared with the etch ratewith chemical sources).

Site Return Processing

—

31

Plasma Chemical Processing (continued)

Fig. 4. Schematic ofplasnm decontamination renctor. Main reactor body is2.25-i)l.-thick glnss. Radio-frequency power at up to 300 zuattsis inductivelycoupled into the plasma by external copper electrodes.

AutomaticVariable Conductance

13.56 M1-izGenerator

Unloading(from “Cold” side)

(from “Hot” side)

Fig. 4 is a schematic of aplutonium decontaminationreactor currently in operation atTA-55. Radiolytically contami-nated items are placed in thereactor at one end and, afterdecontamination, are removedat the other end. This procedureis used to avoid cross-contami-nation of plutonium during theoperation. The plasma reactor isself-cleaning. Established oper-ating conditions ensure that allinterior surfaces of the reactorare exposed to the discharge.

Demonstration of the abilityto decontaminate “real-world”items is proceeding with thisequipment, and initial resultsare expected in early spring1992. Plutonium contaminationtypically consists of small par-ticulate of plutonium dioxide.Further, the quantity of pluto-nium dioxide present on acontaminated item is often lessthan a few nanograms. Themeasured etch rate of plutoniumdioxide and the surface areasand particle sizes reported forlow-temperature oxidel’ indicate

that processing times of onlyseveral seconds are likely to beneeded to remove and recoverplutonium at typical levels ofcontamination. Well-establishedprocedures are followed toreadily recover and contain off-gas from this operation.

Plasma decontamination hasan immediate application in theflow sheet for the Complex 21Plutonium Processing Facility.Plutonium must be removedfrom enriched uranium compo-nents before they are returnedfor reprocessing.

32 Nuclear Matmial$Technolcgy Divishm Annual ReVICW

“Plasma decontamination of uranium in weaponsdisassembly should result in substantial waste elimination,a reduction in process times, and near elimination ofradiation exposure.”

The acid-wash process currentlyused generates many liters ofmixed waste, requires severalhours of manual scrubbing withan abrasive pad, and results inconsiderable personnel radiationexposure. Plasma decontamina-tion of uranium in weaponsdisassembly should result insubstantial waste elimination, areduction in process times, andnear elimination of radiationexposure. The advantages ofplasma processing in this appli-cation are numerous.

Other Applications of PlasmaProcessing

The use of plasmas for finalcleaning operations in weaponsmanufacture offers considerablepromise. Oxygen-based plasmascould easily remove the machin-ing oils used during productionof weapon components. Further,the ability to remove evenradiolytically polymerized oilsis a distinct advantage of theplasma. An added benefit ofoxygen-plasma-based finalcleaning is the potential tomodify the plutonium surfaceto a corrosion-resistant state.

Evidence exists that a uniformplutonium dioxide film willpassivate the metal to furtheroxidation. Previous work hasshown that dioxide plasmas cangrow uniform, adherent oxideson many metals. Therefore, itmay be possible to both cleanthe plutonium surface and growa well-characterized, uniformoxide film that passivates theplutonium to further oxidation.This process may be of benefitfor long-term storage ofplutonium.

Other novel compounds suchas oxychlorides and oxyfluorideshave been produced by plasmaexposure. Uniform layers ofplutonium oxydifluoride andplutonium oxydichloride areof interest for use in numerousreaction studies. Previous workat Los Alamos has shown thattantalum surfaces exposed firstto carbon tetrafluoride dis-charges and then to dioxideplasmas grow a uniform, adher-ent tantalum oxyfluoride film.This technique may be extendedto plutonium. +

Cited References1. I. C. PlumbandK, R. Ryan,Plasm.

Chem. Plasm. Proc. 6,205 (1986).

2. A.PicardandG. Turban,Plasm. Chem.Plasm. Proc. 5,333 (1985).

3. G. SmolinskyandD.L. Flamm,J. App/.Phys. 50,4982 (1979).

4. J. C. Martz,D.W. Hess,andW. E.Anderson,Plasm. Chem.Plasm.Proc. 10,261

(1990).

5. R. W. Kirk,inTechniques and Applica-tions of Plasma Chemistry, J. R. HollahanandA.T. Bell,Eds.(Wiley-Interscience,NewYork,1974),p. 347.

6. J. W.CoburnandH.F. Winters,j. Vac.Sci. Technol.16,391 (1979).

7. J. W.CoburnandE. Kay,IBM J. Res.Develop. 23,33 (1979).

8. J. C. Martz,D.W. Hess,J. M.Haschke,J. W.Ward,andB.F. Flamrn,). Nucl.Mater. 182,277 (1991).

9. J. L.StakebakeandM.R. Dnngman,J. Nucl. Mater. 23,349 (1967).

10. J. M.Cleveland,inPhitotriumHandbook, 2ndcd.,O.J. Wick,Ed. (AmericanNuclearSociety,LaGrangePark,Illinois,1985),p. 355.

11. B. Weinstock,E. E.Weaver,andJ. G. Maim,). hrorg.Nucl.Chem. 11,104(1959).

12. G. CampbellandB.A. Dye,InternalCommunication,LosAlamosNationalLaboratory(1988).

13. J. G. Mahn,P. G. Eller,andL. B.Asprey,J. Am.Chem.Soc.106,2726(1984).

Site Return Proces.shg 33

AD VANC E D MAN U FACTU RI N G

TEC H N O LOGY

Advanced Manufacturing Technology Overview

by Mike StevensP1utoniumMetallurgy Group

The manufacturing of pluto-nium components for nuclearweapons has traditionally used awrought processing schemewherein plutonium is cast in aform suitable for subsequentrolling and hydroforming to anear-net shape. These shapes arethen further processed by preci-sion machining to reliablyproduce a part with tightly helddimensional tolerances and ahigh degree of reproducibility.This processing scheme waschosen because of the wideindustrial familiarity withwrought processing and somelimited processing conveniences.

At the time wrought process-ing of plutonium componentswas implemented, capitalinvestment and maintenance,radiation exposure to personnel,and waste streams and residuesgenerated were not importantconsiderations. Recently, how-ever, a reexamination of themanufacturing scheme, usingprototype production experiencefrom Los Alamos and LawrenceLivermore national laboratories

and process development experi-ence from the Rocky Flats Plant,has Ied to a baseIine manufactur-ing scheme that addresses thesewider health, environmental,and capital-intensity issues.

The principal guiding phi-losophy in this effort has beento substitute modern near-net-shape casting for the traditionalwrought processing scheme.In near-net-shape casting, apremeasured and alloyed chargeof molten plutonium is direct-gravity cast into a reusable metalor graphite mold. This techniquehas been in use at both weapondesign laboratories for thefabrication of components forNevada Test Site experimentsand other development projects.Additionally, the Rocky FlatsPlant used shape casting forseveral production projects forwhich wrought processing wasunsuitable.

At Los Alamos, we use acustom-designed inductioncasting process featuring sepa-rate coils for both an uppercrucible and the lower mold. Inoperation, a manually operatedstopper rod and stirring paddlehold the melt in the crucible.When ready for casting, theoperator puIls the stopper andthe metal pours onto a metalrunner tray that feeds the moltenmetal into the mold gatingsystem. We have traditionallyused graphite molds in nestedconfiguration with calciumdifluorideas a mold coating toprotect against reaction betweenthe plutonium and the graphite.

Current development workfocuses primarily on improvingthe customized casting furnaceby adapting a design beguncollaboratively between RockyFlats Plant and Retech, Inc., aspecialty furnace manufacturer.

34 Nuclear Materials Technology Oivision Annual Reticw

“The principle guiding philosophy in this efiorf hasbeen to substitute modern near-net-shape casfing for fhetraditional wrought processing scheme.”

During 1992 we will be installinga new version of an induction-heated tilt-pour furnace that willallow us to conduct castingexperiments under high-vacuumconditions. The new design willeliminate operator radiationexposures by allowing forremote operational control of thefurnace during melting.

Ongoing experiments focuson development of a split molddesign that will facilitate easyremoval of the part and reuse ofthe mold. We have also begundevelopment of special fixturesfor “creep” annealing of pluto-nium parts following casting.Such a process will allow thepart to more closely assume thenecessary final dimensionalcontours before machining.These and other details of ourcasting development work arecovered in more detail in thearticle “Plutonium Casting andForming.”

Advanced Manufactwing Teclmology

Immediately following partcasting and heat treatment, thepart is moved directly to pre-liminary inspection stations forvisual, radiographic, density,and dimensional examinationand then to machining. There,another subtle but very impor-tant difference in technique isemployed. In the past, machin-ing of plutonium parts includedflood cooling and lubrication ofthe part/tool interface with alight oil. These processes neces-sitate cleanup with organicssuch as carbon tetrachloride,a suspected carcinogen, and1,1,1-trichloroethane, a chlorof-luorocarbon slated for elimina-tion. The Los Alamos PlutoniumFacility (TA-55) has long prac-ticed “dry” machining of pluto-nium, which requires no organiccutting aids or solvents. Thelathes used to dry machineplutonium are enclosed inwell-engineered and isolatedinert glove boxes not only topre- serve the metallic finish offreshly machined parts but alsoto prevent combustion of thefinely divided and pyrophoricplutonium turnings.

To further reduce residues(that k, to prevent plutoniumoxide accumulation) and controlfire hazards, we have also beeninvestigating machine chipmanagement methods. Theessential idea is to collect themachine chips in real time usinga vacuum-generating device,such as a venturi tube, and thenpackage the chips for rapiddelivery to a pyrochemicalprocessing station where theyare molten processed undercalcium chloride with calciummetal, resulting in a recoveryof more than 99.9’70of theplutonium metal. This metalis then directly returned forfoundry feed, with minimalresidue stream generation.

Another important aspectof successful plutonium ma-chining is rapid turnaroundto the machinist of accurategauging information so thatthe control software can becorrected to compensate fortool wear, temperature instabili-ties, and machine inaccuracies.

35

Advanced Manufacturing Technology Overview(continued)

Today, this information is gath-ered by removing the part andgauging it at a separate station.Plutonium metallurgy person-nel at Los Alamos have exploredthe use of on-machine gauging,a technique in which anoncontacting transducermounted to the tool post wouldprovide, without part removal,gauging information of equiva-lent quality. Ultimately, withthe proper signal processing andinterfacing to the tool positioner,this technique may allow forreal-time compensation andcontrol of the machining process,guaranteeing true part contourstime after time. The detailsbehind successful dry machin-ing of plutonium are discussedat greater length in the article“Plutonium Dry Machining.”

Joining technology used inlater stages of nuclear primaryfabrication has been basedprincipally upon electron-beamwelding methods, the state-of-the-art technology when RockyFlats began production, and itsapplication has been largelysuccessful. In recent years,however, powerful, compactlaser systems capable of deliver-ing focused energy depositionsuitable for welding or machin-ing applications have maturedto the point where obviousadvantages are available. As aresult, the Los Alamos l?luto-nium Facility has purchased al-kW, pulsed Nd:YAG laser formultipurpose joining applica-tions in nuclear weaponsresearch.

In the past, the use of largeelectron-beam welding facilitiesrequired special handlingprocedures and the mainte-nance of associated vacuumsystems. Duplicate welderswere required for plutoniumand nonplutonium applications,and secondary joining andbrazing apparatus was requiredto finish unit fabrication. Thelaser welding facility at TA-55will feature an enclosed roomcontaining three glove boxes inwhich all joining operations forprototype fabrication can beaccomplished. These gloveboxeswill require only inert gas envi-ronments, as opposed to expen-sive vacuum chambers, and asingle laser will service each boxthrough fiber-optic cablesswitched through a multiplexerstation.

36 Nuclear Materials Technology Division Annual Rm.iew

“For more than 40 years, as it manufactured prototypetest components, Los Alamos has been continuouslyinvestigating manufacturing improvements.”

Previous development workat Lawrence Livermore NationalLaboratory has shown that thisclass of laser couples well toplutonium and other materials ofinterest and can accommodatefiller metal feed, consumableshims, or autogenous joiningapplications. Additionally, thetuning of such a laser can bealtered for special drilling and/or machining applications,perhaps further minimizing thenumber of work stations neces-sary for manufacturing.

Researchers at the LosAlamos Plutonium Facility (TA-55) have also been investigatinga new method for accuratelymeasuring the density of pluto-nium components, termed gaspycnometry. Traditionally,plutonium component densitymust be determined by immers-ing the part in a compatible fluidof known density and by thenweighing it. By comparing theweight in air with the weight inthe fluid, we can ascertain thedensity of the component.

Unfortunately, the preferredfluids include Freon andmonobromobenzene, organicsslated to be discontinued forvarious reasons. In gaspycnometry, helium gas ischarged into a space with theplutonium and then evacuatedinto a calibrated volume. Thedisplaced volume of the part isthus accurately measured, andthis volume combined with theweight reveals the density.Preliminary tests with smallmetal samples have been suc-cessful thus far.

For more than 40 years, as itmanufactured prototype testcomponents, Los Alamos hasbeen continuously investigatingmanufacturing improvements.

While helping to define abaseline manufacturing schemefor the modern nuclear weaponscomplex, we are developingmany of the new technologiesthat will result in lower capitalequipment expenditures, re-duced radiation exposure topersonnel, smaller waste-streamvolumes, and actual eliminationof waste in some cases. Impor-tantly, Los Alamos does this ina pilot-scale manufacturing

environment using weapons-grade plutonium, therebyensuring that many factorsrelated to implementation andutility are addressed in a suitableenvironment. +

Advanced Manufacturing Teclmology 37

AD VAN C E D MAN U FACTU RI N G

TE C H N O LOGY

Plutonium Casting and Forming

S. Dale Soderquist and Jesus D. OlivasPlutonium Metallurgy Group

IntroductionPlutonium fabrication

processes incorporate a widevariety of complex and precisetechniques. Most of these tech-niques were established duringthe 1950s and 1960s and nowrequire upgrades to meet thetechnology needs of the 1990s.Of particular concern are effortsto simplify processes and mini-mize waste while maintainingproduct quality. Current re-search, design, and developmentactivities in the areas of near-net-shape gravity casting and finalforming of plutonium seek toreduce by half or more personnelradiation exposure, generation ofplutonium scrap and secondarywaste, production floor-spacerequirements, and environmen-tal pollution.

BackgroundCasting is a necessary and

versatile part of all plutoniumfabrication schemes. The castingmethods of the future will meetrequirements for minimizationof waste as well as for efficiencyof plutonium use.

To meet the challenge of envi-ronmental, safety, and healthconsiderations, Los Alamosscientists have been rethinkingplutonium casting procedures todevelop techniques that simplifythe wrought fabrication processcharacteristic of operations at theRocky Flats Plant. The wroughtprocess typically requiredmultiple steps as follows:

1. Cast plate2. Heat treat3. Roll4. Shear circle5. Heat treat6. Form shape7. Heat treat8. Machine

The wrought-fabricationmethod at Rocky Flats wastailored to produce flat parts forrolling, forming, and machiningprocesses developed decadesago. Although a die-castingprogram was initiated about 10years ago to improve efficiencyand minimize waste, the result-ing die-casting machine wascomplex, cumbersome, anddifficult to maintain.

Efforts to die cast near-net-shapehemishell parts contributed tomachine and mold complexity;therefore, die casting neverreached production status atRocky Flats.

A proposed new process,based on die-casting experienceat Rocky Flats and gravity-casting experience at Los Alamos,involves shaped gravity castingand final forming during heattreatment with reusable metalmolds and heat-treatment fix-tures. The process comprisesonly three steps:

1. Near-net-shape gravity cast2. Simultaneous homogenize

and creep form3. Dry machine

The creep-forming step(step 2) will increase flexibilityand reduce tolerance require-ments of the initial shaped cast-ing. Such a casting process issimple and relatively free ofproblems; the casting equipmentrequires only minimal nlainte-nance, and the simplified molddesign will improve mold life.

38 Nuclear Materials Technology DivMon Annual Review

“The casting methods of the future will meetrequirementsfor minimization of waste as well as forefficiency of plutonium use.”

Implications for environmen-tal issues are also favorable, asthe near-net-shape processrequires less plutonium alloythan does the wrought process.Therefore, it should generate lessprimary plutonium waste in theform of plutonium-bearingresidues. Reuse of molds andhardware will result in lowerquantities of secondary waste.Also, better casting-furnacedesign and improved glove-boxatmospheres will significantlydecrease plutonium oxideformation. At Rocky Flats mostplutonium waste was generatedduring recovery of plutoniummetal from plutonium oxide,and the plutonium foundry wasthe single largest generator ofplutonium oxide.

ApproachLos Alamos scientists are

undertaking a number of techni-cal activities in parallel to de-velop a process using graphitemolds and fixtures now butintegrating reusable metal moldsand fixtures later. These activi-ties include

1. Development of a subscaleplutonium casting and formingprocess using graphite molds andfixtures.

2. Development of metalmolds by saturable carburizing ornitriding and by coating withceramics.

3. Finite-element modeling tooptimize casting parameters andmold and fixture design.

4. Conduct of casting experi-ments using nonradioactivesurrogate alloys to shortendevelopment time.

5. Process flow modeling ofcasting and forming to quantifypredictions of total waste genera-tion and to identify areas needingimprovement; incorporation ofresults into larger process modelsfor the Complex 21 PlutoniumFacility to follow.

6. Full-scale plutonium castingand forming to verify all workdefined in 1 through 5 above.

Recent ResultsCasting, heat treating, and

final forming of a subscale parthave been completed. Gravity-casting equipment similar tothat already proved in a produc-tion environment was used.

The results of the subscalework are:

1. Calculations predictedcorrectly that the decrease indensity during heat treatmentwould significantly change thedimension of the plutoniumpart. The calculated dimen-sional change values were usedto design the mold and the heat-treatment fixtures.

2. A split-mold design al-lowed easy removal of the castplutonium part, thereby increas-ing mold life, decreasing dam-age of the part during break out,and reducing waste.

3. Inspection on a coordinate-measunng machine showed thatthe contour of the heat-treatedpart closely follows the contourof the heat-treatment fixture.

Advanced Manufacturing Technology 39

Plutonium Casting and Forming continued)

Fig.1. Expansion o} plutonium tocon~onnto contour of heat-treatment

Radial Increaseat EquatorSignificant

ThicknessIncreaseat PoleSmall

CASTING MOLD CORE

Load as cast part inhomogenization fixture.(At this stage, part is still , ‘-adhered to casting mold core).

HOMOGENIZATION FIXTURE ~

The split-mold design allowseasy release of the plutoniumcast part from the outer case.Figure 1 shows how expansionduring the phase change result-ing from heat treatment causesthe part to move out radiallyand closely conform to thecontour of the heat-treatmentfixture. Figure 2 shows how thecore of the plutonium castingmold is positioned in the heat-treatment fixture and how thepIutonium casting releases fromthe mold core during heattreatment and settles into theheat-treatment fixture.

Fig. 2. Simplified depiction of densityexpansion and creep fornling duringhenf treatment.

Apply heat. Part expansion :* .;{begins. Part releases from ._ .-,mold core and settles intohomogenizationfixture.

—. ——

Continue heating. Partcunforms to homogenizationfixture. (Density expansionand creep result in close-tolerance part).

40 Nuclear MaterialsTechnology Division Annual Review

2.145

2.140

2135

2.130

2.125

2.120

Heat-Treatment FixNrO

1

2.115 1! 1 1 1 1 I [ t 1 1 1 1 I 1 IPole Equator

Position on Part

The creep of the plutonium partcaused by gravitational forcecontributes to this hot formingprocess. In the future we wil lbetesting a low-thermal-expansionmetal fixture.

Figure 3 summarizes theinspection data recorded atvarious stages of the subscaleprocess. The contour of theplutonium part after heat treat-ment closely follows the contourof the heat-treatment fixture.

Fig. 3. Inspectiondata at various stagesoj the subscale casting process.

Summary By using bottom-pour and tilt-Los Alamos scientists are pour plutonium casting fur-

developing a production process naces, the process applies exist-for near-net-shape gravity ing technology rather thancasting, heat treatment, and developing major new equip-forrning of plutonium parts. ment, as would be required in aKey elements in the process are die-casting process. +gravity casting to shape, split-mold design for easy part re-lease, and use of phase changeand creep during heat treatment(homogenization) to expand theplutonium part into a close-tolerance heat-treatment fixture.

Advanced Manufacturing Technology 41

AD VAN C E D MAN U FACTU RI NG —TEC H N OLOGY

Plutonium Dry Machining

by Rueben L. GutierrezPlutonium Metallurgy Group

IntroductionThe machining of plutonium

parts to exact specifications iscrucial in the development ofnuclear weapon designs. Be-cause plutonium metal is pyro-phoric and the cutting operationperformed during machiningproduces heat from friction, themetal is susceptible to ignitionand combustion when exposedto air during the process. Before1986, machining of plutoniumparts for weapons research anddevelopment at Los Alamosrequired the use of freon forcooling during machining.Also, the Rocky Flats process formachining production quantitiesof plutonium parts required thatplutonium parts be flood cooledwith oil. The oil added to coolthe part during productionmachining not only preventscombustion of the plutoniummetal but also minimizesexpansion of the part.

However, in 1986, the Pluto-nium Metallurgy Group, devel-oped a dry machining techniquethat eliminates the need forsolvents and oils during glove-box operations involving ma-chining of plutonium metal.Implementation of the drymachining process at Rocky Flatswould have significantly re-duced the waste streams beinggenerated during the productionoperations for the manufactureof nuclear weapons. Use of drymachining rather than floodcooling with oil would haveeliminated the need for 2,500gallons of cutting oil and 15,000gallons of trichloroethylene,which is used as a cleaningsolvent, annually.

Combustion during drymachining of plutonium partsis prevented by performing theoperation in an inert glove-boxatmosphere in which the n~axi-mum upper limit for oxygen is3000 ppm. By using a low-oxygen atmosphere, machineturnings do not undergo surfaceoxidation.

Machining Support OperationsTwo other areas presently

under development will enhancethe dry machining operation.One is application of a vacuumtechnique for collecting chipsproduced during machining, andthe other is an in-process tech-nique for gauging the contoursof produced parts.

42 Nuclear Materials Technology DivMon Annual Review

Plutonium Dry Machining (continued)

Before production operationsat Rocky Flats stopped, person-nel there had initiated a tech-nique for removing plutoniumchips as the part was beingmachined. Called Vortex, thetechnique involves using avacuum to suck the metal chipsaway and siphon them into acanister. Before this methodwas introduced, machinistspulled the chips away with apair of tweezers and droppedthem into a canister. The Vortexsystem minimizes radiationexposure by allowing personnelto withdraw from the glove box.This technique is being refinedand will be incorporated intothe TA-55 plutonium machiningoperations.

An in-process method forgauging machine performancewill provide precise gauginginformation of the part beingmachined. The technique in-volves the use of a variableimpedance transducer (VIT) tomeasure the machined surfaceof the part. The VIT works inunison with the tool bit and thelathe’s preprogrammed control-ler. Once this technique is fullydeveloped and implemented,we will no longer need to re-move parts from the lathe toconfirm accuracy. This willminimize the number of timesa part must be handled, therebyreducing the potential risks ofdamage to the part and of per-sonnel radiation exposure.

Current and Future Develop-ments

Although dry machining isready for production operation,a few enhancements are beingaddressed. For instance, we areinvestigating thermal cooling ofthe pot chucks, which hold thepart, and the tool bit. The tech-nology for vacuum collectionof machine chips is nearingcompletion. However, in-process gauging of machinedparts is in the seminal stage ofdevelopment and will be readyfor production operation inabout 2 years. It is fully expectedthat dry machining, chip collec-tion and management, and in-process gauging will be fullydeveloped as a cohesive opera-tion within the next 2 to 4years. +

Advanced Manufacturing Technology 43

NITRATE

R E C O V E R Y ““

Nitrate Recovery Overview

by Bill McKerleyNuclearMaterialsProcessingGroup:NitrateSystems

The Plutonium Facility of theFuture, commonly referred to as“Complex 21,” will include thedisassembly of site-return pits,purification of site-return metal,assembly of product pits, recov-ery of plutonium from residuesgenerated in the production andrecovery operations, and pro-cessing and packaging of thewastes for shipment and dis-posal. This overview focuseson the nitrate recovery baselineflow sheet, which is an integralpart of the overall baselineplutonium faciIity flow sheetoutlined on page 9. The currentnitrate recovery operations atTA-55 provide the basis forthe nitrate recovery baselineflow sheet envisioned forComplex 21.

The nitrate recovery baselineflow sheet consists of the follow-ing unit operations:

● Pyrolysis and Calcination● Pretreatment● Acid Decontamination,

Leachate Treatment● Leaching● Cascade Dissolution● Anion Exchange● Precipitation● Calcination● Evaporation

At the Los Alamos PlutoniumFacility as well as Complex 21,the primary feed source will beplutonium process residues fromthe recovery, manufacturing, andanalytical laboratory operations.

A large quantity of bulk materi-als generated from other opera-tions will also require someprocessing. The goal of thenitrate recovery baseline flowsheet is to recover the pluto-nium, to produce a pure oxidefor conversion to metal, and toensure that the resulting resi-dues are in a form that meets allwaste acceptance criteria.

The pyrolysis and calcinationoperations will support severalflowsheets. As currently envi-sioned, these operations willproduce an ash from combus-tible materials for further chemi-cal recovery of the residualplutonium. An incineration-typecapability is a critical step in theflowsheet but presently is @considered to be a licensable/permittable process. Conse-quently, we are investigatingseveral alternatives, such as athermal decomposition unit thatis performed in an inert atmo-sphere, molten-salt thermaldecomposition, and supercriticalwater oxidation.

44 Nuclear M, NerialsTechnology Division Anntml Reki.w

‘The F%4torziwn Facility of the Fuh.-we,commonly rejerred

to as ‘Complex 21, ’ will include the disassembly of site returnpits, purification of site return metal, assembly of product pits,recovery of plutonium from residues generated in theproduction and recovery operations, and processing andpackaging of the wastes for shipment and disposal.”

Pretreatment operationsinclude sorting, milling andgrinding operations, that areused to segregate and size-reduce residues, as needed,before dissolution. Also, weare collaborating with research-ers in NMT-3 to develop anddemonstrate (on a productionscale) magnetic separationtechniques such as magnetic-roll or drum-type separatorsand high-gradient magneticseparation. This physicalseparation technique supportswaste minimization efforts byallowing only plutonium-richresidues to be sent for aqueousrecovery. The plutonium-leanportion is suitable for transferto waste management for dis-posal. Other physical processingmethods may be necessary, andwe continue to investigate newapproaches.

The acid decontaminationand Ieachate treatment opera-tions chemically remove pluto-nium surface contaminationfrom Oralloy parts. These partsare leached with nitric acid toremove residual plutoniumcontamination. The clean,nonplutonium metal will thenbe acceptable for return to theuranium handling facility.The solution (leachate) will betransferred to ion exchange orwaste treatment for furtherprocessing, depending on theplutonium content.

Nitrate leaching/dissolutionprocesses produce plutoniumnitrate solution by dissolvingand/or leaching plutoniumoxide from plutonium-contain-ing materials using nitric acidand fluoride ion. Dissolutiontakes place in dissolver pots orcascade dissolution systemswhere the flow rate of feed andreagents differs with the differ-ent feed materials.

Process analytical chemistrydevelopments will allow the real-time determination of key pa-rameters, such as acid concentra-tion, fluoride ion concentration,and plutonium concentration.This will allow better processcontrol, which directly affects theability to reduce waste, providesbetter materials control andaccountability, and greatlyincreases process efficiency.

The nitrate solution is filtered,and the undissolved solids arecollected and dried. The undis-solved solids are either recycledor disposed of as waste, depend-ing upon plutonium content.Dissolution techniques such asthe catalyzed electrochemicalplutonium oxide dissolver arebeing evaluated to determinetheir application on hard-to-dissolve residues. The filteredsolution is stored in tanks andanalyzed for subsequent process-ing in the anion exchange system.

Nitrate Recovery 45

Nitrate Recovery Overview (continued)

The purpose of the anionexchange process is to concen-trate and purify plutonium innitrate solution. The nitratesolutions are first analyzed foracid concentration, plutoniumvalence, and plutonium concen-tration. The acid concentrationis adjusted to 7 ~ by addingeither concentrated or dilutenitric acid (HNO~)as required.The Plutonium is stabilized inthe (IV) valence by the additionof reagents such as hydrogenperoxide. In 7N_lnitric acid,plutonium forms an anioniccomplex that will adsorb onanion exchange resin. The anionexchange operation is essentiallya four-step process— loading,washing, eluting, andreconditioning.

In the loading cycle, pluto-nium is adsorbed on the anionexchange resin. The effluentfrom a load cycle contains theelemental impurities and istransferred to the acid recyclesystem after being analyzed forplutonium.

If the plutonium content is abovethe discard limit, the effluent isrecycled. The nitric acid washcycle removes residual impuri-ties from the columns. The washsolution is also analyzed beforetransfer to the acid recyclesystem.

During the elution cycle theplutonium is removed from theion exchange resin by the addi-tion of a reducing agent such ashydroxylamine nitrate or withthe use of dilute nitric acid.The eluate, containing the puri-fied plutonium, is sent to theprecipitation step. After elution,the resin is returned to a nitratedstate by reconditioning thecoIumns with 7 ~ nitric acid.The ion exchange columns arenow ready to repeat the entirecycle. Current R&D activities inresin development, processanalytical chemistry, processchemistry, and process controland instrumentation are yieldingresults that are directly appli-cable to the needs of today’splutonium recovery operationsas well as the requirements forComplex 21.

The addition of solid oxalicacid to a plutonium nitratesolution results in the formationof an insoluble complex thatprecipitates from solution. Thissolid plutonium oxalate complexis colIected by filtration and istransferred to the calcinationoperation where excess nitricacid and water are removedand the plutonium oxalate isconverted to plutonium dioxide.The thermal decomposition ofthe oxalate ion takes place atapproximately 600°C or above.

Enhanced precipitationtechniques such as homogeneousoxalate and hydroxide precipita-tions are being investigated.These precipitation techniqueshold the potential for easierfiltration and lower actinidelevels in the filtrates.

The product from this pro-cess, the dry plutonium dioxide,would then be transferred to thechloride recovery area for con-version to metal using multicycledirect oxide reduction (MCDOR).

46 NucIcar MatwialsTechnology Civis{on Annual Review

“Tlzeseadvances in process control will not only allowan enhanced capability to manage our recovery operations,but will also support a superior materials control andaccountability program.”

The nitric acid recycle portionof the nitrate recovery baselineflow sheet incorporates evapora-tion, oxalate ion destruction,nitric acid fractionation, andnitrate destruction unit opera-tions. Solutions such as ion-exchange effluents and oxalatefiltrates are transferred to anevaporator in preparation fornitric acid recycle. This requiresseveral process steps:

1) oxidation of oxalic acid toC02 and I+O;

2) recovery of HNO~fromevaporator bottoms;

3) fractionation of recoverednitric acid to form a dilutenitric acid waste streamand a concentrated andpurified nitric acid streamfor recycle;

4) catalytic conversion ofexcess HNO~to benignNzgas; and

5) disposal of the dilute acidevaporator bottoms towaste.

The product from this process(pure, reusable 12 M HN03) willbe used, as required, throughoutthe nitric acid recovery system.The waste streams from thisprocess are CO, and N, off-gasses, evaporator bottomscontaining concentrated impuri-ties, and a dilute nitric acidstream from the fractionator.

Reagent recycle is obviouslyan important component of ourwaste minimization efforts.We are currently demonstratingnitric acid recycle on the Ad-vanced Testing Line for ActinideSeparations (ATLAS). Thisadvanced line will be the sitewhere many of the developmentand demonstration activities willtake place.

In many of the operationsdescribed above, there is a needfor real time information regard-ing acid concentration, anionconcentrations, plutoniumvalence, impurity concentra-tions, etc. By providing thisimportant information to theprocess engineer in real time ornear real time, decisions can bemade to tailor the processingparameters to the appropriateconditions. In addition, thisprocess information is beingcombined with a modern com-puter-based process monitoringand control system that willallow processes to be operatedfor reduced waste, decreasedpersonnel exposure, and purerproduct.

Nitrate Recovery 47

Nitrate Recovery Overview (continued)

These advances in processcontrol will not only allow anenhanced capability to manageour recovery operations, but willaIso support a superior materialscontrol and accountabilityprogram. These factors are vitalfor the plutonium facility oftoday and are even more import-ant for the plutonium facility ofthe future, which will most likelybe required in a much morerestrictive environment.

43

This overview of the nitraterecovery baseline flow sheet hassummarized the unit operationsthat will support Complex 21.In addition, a brief glimpse hasbeen provided into the researchdevelopment and demonstrationactivities that are ongoing atLos Alamos to ensure that the

plutonium facility of the futurewilI have the capability to re-spond to a wide range of pro-cessing requirements. +

Nuclear Materials Technology Division Annual Review

NIT R AT E

R E C O V ER Y

Process Analytical Chemistry

by Rick DayNuclearMaterialsProcessingGroup:NitrateSystems

The waste challenge forfacilities in the DOE complexengaged in the aqueous recoveryof plutonium from residues islargely a chemical processingissue. In fact, one important wayto minimize or eliminate waste isto address the problem at itssource: in the process. The closemonitoring of process param-eters and the early identificationof process upsets are key fea-tures of any system that seeks tominimize waste generation andreduce cost, both in dollars andworker exposure. Laboratorystudies indicate that many of theparameters that govern processoperation can be measuredsuccessfully using the on-lineand at-line techniques of processanalytical chemistry. Processinginformation thus acquired can

● lower reagent consumption,thereby reducing the amount ofwaste generated,

● reveal levels of actinides inwaste streams, thereby facilitat-ing more efficient recoveryoperations based on real-timeprocessing information,

● eliminate the need to repro-cess out-of-specification mate-rial,

● identify process inefficien-cies, and

. better characterize andmonitor waste stream composi-tions.

The Advanced Testing Linefor Actinide Separations (AT-LAS) provides the means fortesting, evaluating, and incorpo-rating into residue recoveryprocessing those process analyti-cal chemistry technologies thathave been proved in principle.ATLAS emphasizes the integra-tion of analytical methods into asingle system for supplying real-time chemical information andapplying that information toprocessing refinements. Theformulation of developmentalstrategies for all processingmodules requires that analyticalmethods be combined withstatistical process control andexperimental design.

The following baseline tech-nologies are now being demon-strated on ATLAS:

. an ion chromatographyformonitoring anion impurities,

. an automated titrationsystem for measuring free acid,

● a visible, near-infrared, fast-scanning spectrophotometer foron-line measurements of pluto-nium oxidation state, nitrateconcentration, and interferinganions,

● an on-line x-ray fluores-cence spectrometer for impuritymetal analysis, and

. specific chemical sensors,including a chloride sensor andthe R&D IOO-award-winninghigh-acidity sensor developed bythe Nuclear Materials Process—Nitrate Systems Group, NMT-2;the Materials Technology Poly-mers and Coatings Group, MST-7; and the Analytical ChemistryGroup, CLS-1.

49Nitrate Recovery

Process Analytical Chemistry (continued)

Instrumentation of threetypes is applied during thedevelopment of process ana-lytical chemistry technologies:specially modified instrumenta-tion for at-Iine use in a gloveboxenvironment, commerciallyavailable instrumentation foron-line use for real-time moni-toring, and chemistry-specificsensors developed at LosAlamos for on-line use duringplutonium processing.

At-line technologies suchas the ion chromatographyandautomated titration consistof standard laboratory instru-ments modified to work in aglove-box environment. At-lineinstruments in glove boxes arelocated adjacent to the process-ing Iocations and supply near-real-time information. Theanalysis they provide alsoserves as a “reference method”to guide the development ofmore advanced on-line andsensor methodologies.

Current on-line technologiesuse advanced data analysistechniques, including partial-Ieast-squares analysis, funda-mental-parameter analysis, andcommercially available instru-mentation. A fast-scanningspectrometer multiplexed byfiber-optic cables to remotesampling locations performsvisible spectroscopy duringanion exchange feed treatment,column wash make-up, oxalateprecipitation, and waste streammonitoring. Chemometricmethods are used to analyzespectral scans that measure totalplutonium, plutonium oxidationstate, nitrate concentration, andinterfering anions. An x-rayfluorescence spectrometer notonly operates at the line tocategorize various feed materialsbut also monitors the ion ex-change effluent on-line to opti-mize wash volumes and trackthe actinide concentrationscoming off the ion exchangecolumn.

Several compact chemistry-specific sensors are either al-ready in use or close to comple-tion. The recently developedhigh-acid sensor consists of aHammond indicator bound in apolymer coating and an opticalflow cell monitored by the fiber-optic spectrophotorneter. A newchloride sensor applies a com-mercial ion-selective electrode toconcentrations outside its nor-mal operating range; a similarfluoride sensor is under develop-ment. An electrochemical sensoris being designed for use insolutions containing mixtures ofuranium and plutonium.

The continuing developmentand use of process analyticalchemistry technologies and theresulting knowledge of processparameters and analytic rangeswill remain evolutionary, as newmethods and sensors continueto be explored and evaluated.

50 Nuclear MalcvialsTethnology Divkkm Annual Reticw

“The waste challenge for facilities in the DOE complexengaged in the aqueous recovery of plutonium fromresidues is largely a chemical processing issue.”

An inductively coupledplasma mass spectrometerbeing acquired to aid in themonitoring of waste streamswill also be used in near-linefashion to analyze solutionsbefore a concentration stepsuch as precipitation is per-formed. Detection of out-of-specification material at thispoint can substantially reducewaste by eliminating the needto rework out-of-specificationoxide.

Research in the area of sen-sors and related techniques, suchas flow injection analysis, willcontinue. As industrial processanalytical chemistry continues togrow as a field, the resultingnew instrumentation will beevaluated for application to thespecial requirements of actinideprocess stream analysis withinthe confines of the glove-boxenvironment.

Process Analytical ChemistryApplications to Complex 21.

The instrumentation andmethods being developed onATLAS are designed to supplynear real-time chemical analysison virtually all of the aqueousunit operations found in theComplex 21 flow sheet fornitrate recovery of plutoniumscrap. The measurements beingdeveloped on ATLAS supplyinformation on importantprocessing parameters includingplutonium oxidation states, free-acid concentration, interferinganions and trace metal impuri-ties. These process analyticaltechniques can also be appliedto the Complex 21 flow sheetsfor chloride recovery and aque-ous waste streams, which sharemany of the same parametersthat need monitoring.

Process Analytical ChemistryBenefits to Complex 21.

Closer monitoring of processparameters and early identifica-tion of process upsets in Com-plex 21 will ensure that productquality and waste minimizationgoals are met. Additional ben-efits include better understand-ing of the chemistry involved inthe processing, characterizationof process and waste streams,and minimizing the need torework out-of-spec products. +

Nitrate Recovery 51

NITRATE

R E C O V ER Y

Process Measurement and Control

by Noah G. PopeNuclearMaterialsProcessingGroup:NitrateSystems

.l?or many years, aqueousprocessing at TA-55 and othernuclear materials facilities hasbeen conducted with a hands-on,operator-based approach. Re-centIy, however, an effort toincorporate modern industrialcomputer-based process monitor-ing and control systems has beeninitiated. Complex 21 plays a vitalrole in this program. Most, if notall, of the processes planned forComplex 21 will require someform of computer-aided processcontrol or automation. Clearly,a strong control and automationprogram is essential to accom-plish these technical challenges.Modern control technologieswill strengthen Co~plex 21 byreducing operator radiationexposures to levels as low asreasonably achievable, minimiz-ing the generation of waste byoptimizing operations, increasingthe understanding of the chemi-cal processes by applying itera-tive techniques of data acquisi-tion and modeling, and increas-ing overall safety by incorporat-ing computer-supervised systemsof alarms and monitors.

A strong control effort isrequired for administrativereasons as well. At TA-55, theseissues include the increase inauditing requirements that hasresuIted from new DOE ordersrelated to conduct of operationsand quality assurance. Theavailability of computers along-side the processes also allowstechnical reports to be compiledin a more convenient and timelymanner.

It is vital that NMT Divisionmaintain a viable industrialcontrol and automation capabil-ity. Towards this end, we haveselected proven reliable andcommercially available technolo-gies that are common through-out other, more mainstreamchemical process industries.At TA-55 these capabilities arebeing introduced incrementallyto increase the overall safety,reliability, and efficiency of theoperating environment.

By emphasizing process controlas well as automation, we relyon the experience of the processoperators and plant environmenttesting to constitute the founda-tion on which automatic controlmay be successfully instituted. Inanticipation of the requirementsof the Complex 21 control envi-ronment, we have instituted aprogram that covers the majorityof processes within the nitrateflowsheet. The effort began byapplying industrial controltechniques to the nitrate evapo-ration unit operation. Using theexperience gained there, theprogram was recently expandedto include other unit operationscommon to bothTA-55 and Complex 21. Inaddition to evaporation, the unitoperation control systems underdevelopment include dissolu-tion, ion exchange, feed prepa-ration, acid recycle, eluate andoxalate precipitation, andcalcination.

52 Nuclear Materials Technology Oivkion Annual Review

“By emphasizing process control as well as automation,we rely on the experience of the process operators and plantenvironment testing to constitute the foundation on whichautomation control may be successfully instituted.”

From the experiences gainedon these projects and on a funda-mental understanding of currentcontrol technologies, a numberof important developmentprinciples have been established.These principles and the projectsto which they have been appliedare outlined as follows:

Information Flow. Informa-tion should be shared betweenunit operations for the totaloperation to flow smoothly fromstart to finish. Thus, a commoninformation data base should beaccessible from a variety ofprocessors and software lan-guages. Because process param-eters derived during one opera-tion may be of value in a subse-quent process, such informationshould by readily available.For example, during plutoniumprocessing, the amount of oxalicacid added by a technician tocomplete the precipitation stepdirectly affects the performanceof the downstream waste evapo-rator, a system operated bydifferent technicians.

A multitasking environment thatallows on-line, real-time accessto such information would beideal.

Hardware Selection andConfiguration. Hardwareshould be decentralized to avoidreliability problems common tolarge single-processor systems.A network of several smallcomputers, which are consider-ably less expensive and easier toreplace than a single largecomputer, provides severallayers of back-up processorpower should power fluctua-tions, contamination, or otherfacility problems cause a com-puter to fail. Although smallcomputers lack the speed com-mon to large systems, personalcomputers with 80386- and80486-type processors haveproved to be fast enough tohandle most industrial process-ing situations.

Software Selection. Commer-cial software should be used sothat scientists, engineers, andoperators spend their timeconfiguring the system ratherthan writing custom softwareand drivers. Their expertise liesin process operations, not in theinner workings of a computer.Therefore, operators and linesupervisors should be able tocustomize and modify theirprocess screens without in-depthknowledge of computer pro-gramming.

Control System Concept.Because process operatorspossess by far the greater controlintelligence, the control systemshould serve as an extension of,rather than a replacement for,their capabilities. Operatorsstabilize the environment byexerting an intelligence andflexibility that far exceed thequalities of even the most ad-vanced computers. Thus, thecontrol system’s function wouldbe to increase the operators’ability to interact with a process.

Nibate Recovery 53

Process Measurement and Control (continued)

However, the control systemshould be sufficiently flexibleto accommodate unforeseencircumstances because mostprocesses have a finite lifeexpectancy, and modificationsmay be required to meet newprocessing needs. The controlsystem should be layered so thatit has at least two back-up modesof operation, one of whichwould be a manual overridecapability to ensure that alloperations continue even with-out computer control. Preserva-tion of the excellent manualcontrol operations at TA-55 isessential because of their proventrack record and their contribu-tion to the training effort.

Current DevelopmentProjects. NMT-2 presently hasunder way several processcontrol and measurementprojects that embody the fea-tures specified above: theenhanced evaporator process,the metal preparation line, theAdvanced Testing Line forActinide Separations (ATLAS),and the multipurpose cascadedissolvers. These projects usesimilar computer hardware andsoftware and similar input/output hardware.

The enhanced evaporatorprocess, which is a technologycommon to both TA-55 andComplex 21, has more than twodozen inputs and has operatedsuccessfully for more than 2years. The system throughput isnearly double that previouslyachieved, and the number ofoperators required has beenreduced by half. The data-Iogging capability has provedvaluable for the diagnosis ofprocess upsets.

Of the control projects inprogress, ATLAS has by far themost advanced capabilities.Designed to encompass mostof the unit operations on theNitrate Recovery flow sheet forComplex 21, ATLAS presentscontrol challenges common tolarge, multiple process plants.To meet these challenges, three80386- and 80486-based Compaqcomputers running the 0S/2operating system are networkedtogether to run a commercialcontrol software package.Each computer is located near adifferent unit operation, and anetwork link to other areas ofTA-55 allows system design andsupemision to be performedoutside the laboratory. Eachpiece of input/output hardwareuses a commercially suppliedsoftware driver. A networksecurity system tracks man-power usage and helps ensurethat only qualified personnel areallowed access to the system.

S4 Nuclear Materials Technology Divk[on Annual Rcvlew

“Designed to encompass most of the unit operations onthe Nitrate Recovery flow sheet for Complex 21, ATLASpresents control challenges common to large, multipleprocess plants.”

All ATLAS operators havebeen trained to create their owncustom control screens. Acomplete, automatic data-logging capability allows largequantities of information to becollected for on-line or post-process analysis. ATLAS in-cludes both batch and recipecontrol capabilities, and an on-line statistical quality controlpackage will be incorporated toassist operators in processdiagnostics. A complete super-visory process alarm system isavailable. Development time hasbeen reduced to a minimum bythe use of proven, commerciallyavailable technology.

Nitrate Recovery

NMT-2 has developed a clearmethodology for upgrading LosAlamos’ process capabilities toinclude a process measurementand control system of the typedescribed here. The transitionfrom computerized processcontrol to automation of theprocess itself requires carefuldeliberation based on experiencegleaned from work with simplersystems. Future processingsystems should be designedwith control system constraintsin mind. The challenges pre-sented by Complex 21 demandthat technical developments bebased on sound engineering andscientific experiences. NMT-2has made the required invest-ment in the area of processcontrol and automation as partof our continuing effort to meetthe needs of the nuclear weap-ons complex. +

55

NITRATE

R E C O V ER Y

Process Chemistry

by Gordon D. JarvinenNuclearMaterialsProcessingGroup:NitrateSystems

The innovative separationschemistry needed for the DOEto accomplish its goals ofcleanup of the nuclear weaponscomplex and more efficientoperations in Complex 21 guar-antees that research, develop-ment, and demonstration(RD&D) activities in processchemistry at Los Alamos willremain essential. The nextgeneration of production facili-ties, regardless of type or loca-tion, will integrate advances inseparations technology with on-line sensors and computercontrol systems to increasesafety, reduce personnel radia-tion exposure, minimize waste,and improve product qualityand yieId. Developments at theLos Alamos Plutonium Facilitywill lead to the prototype sys-tems to be integrated into thereconfigured production com-plex. Even now, the cleanup of awide variety of actinide-contami-nated wastes and sites within theDOE complex requires theability to tailor separationschemistry to address widelydifferent conditions.

The ongoing RD&D workin the nitrate systems group(NMT-2) covers a broad range ofactivities, from short-termimprovements in operatingprocesses to Iong-term efforts toobtain fundamental knowledgeof separation processes andmetal coordination chemistry.The improvements in operatingprocesses that can be imple-mented in the near future will beincorporated into the baselineflowsheet for Complex 21. Thelonger range RD&D efforts willprovide alternative processingmethods that enhance the Com-plex 21 baseline. The followingparagraphs summarize recentprogress by tracking the flow ofa plutonium-containing residuethrough the nitrate recoveryoperation, which includes thefollowing steps:

● sorting, decontamination,and dissolution,

● feed pretreatment,Qmetal ion separations,“ product preparation,● recycling of reagents, and● waste treatment.

Many of the accomplishmentsdescribed briefly here are theresult of collaborations with othergroups in the Nuclear MaterialsTechnology Division, groupsfrom other Laboratory divisions,and employees of other DOEfacilities, universities, and indus-trial firms.

Sortiizg,Decotztailziizatiotz,amiDissolution. Several new tech-nologies related to the first stepin the plutonium recove~ pro-cess are in various stages ofdevelopment.

. Magnetic separation ofcertain finely divided pluto-nium-containing solids into asmall fraction that is relativelyrich in plutonium and a largefraction that can be discarded aslow-level waste has been demon-strated on a process scale, usinga commercially available open-

gradient device. After separa-tion, the plutonium-rich fractioncan be dissolved and the pluto-nium recovered by aqueousprocessing methods.

56 Nuclear Materials Tduwlogy Division Annual Review

“Developmentsat theh AlamosPlutoniumFacilitym“llleadto theprototypesystm to be integratedinto thereconfigzwedp~oductioncomplex.”

Results from preliminary testsusing a high-gradient magneticseparation system are veryencouraging. Advantages of thehigh-gradient system relative tothe open-gradient device includethe capability to separate smallerparticles and operate onaqueous suspensions,

. An electrolytic cell con-structed in a plutonium glove-box line now enables researchersin NMT-2 to examine the use ofthe silver(I) /silver(II) couple topromote the dissolution ofplutonium oxide in nitric acidunder relatively mild conditions.

● Collaborators in the Isotopeand Structural Chemistry Group,INC-4, have found thatsiderophores and syntheticanalogues of siderophores showpromise in the removal of ac-tinide contamination from soilsand surfaces. The siderophoreenterobactin was found to bemore effective than 0.1 M nitricacid and a variety of otherchelating agents in dissolvingan aged plutonium hydroxidepolymer.

Nitrate Recovery

Feed Pretreatment. Fluoride isusually present in the nitric acidsolutions from the dissolversbecause hydrogen fluoride isadded to increase the disso-lution rate of plutonium oxide.Presently, aluminum nitrate isadded to complex the fluorideto prevent interference withthe subsequent ion exchangepurification of the plutonium.An octaazacryptand synthesizedby INC-4 appears to bind fluo-ride very selectively andstrongly, even in the presenceof a great excess of nitrate.NMT-2 is testing the use of thismaterial to remove fluoride fromthe processing solutions and toeliminate the need to add alumi-num nitrate, which adds to thevolume and complexity of thewaste solutions.

Metal Ion Separations.A number of investigations arecontributing to efforts to facili-tate the separation of plutoniumand americium ions from aque-ous solutions.

● Reillex HPQ is apolyvinylpyridine-based anionexchange polymer developed atLos Alamos in collaboration withReilley Industries. For severalyears this polymer has beenroutinely used at TA-55 for theion exchange purification ofplutonium in nitric acid solu-tions. Recently, we found thatresin in use for 3 years andbeginning to lose effectivenesscould be largely regenerated bytreatment with 1 M sodiumhydroxide. The regeneratedresin showed improved kineticsof plutonium sorption relativeto new resin, and the improvedkinetics of the regeneratedmaterial is being studied in thehope of improving the kineticsof new resin as well.

57

Process Chemistry (continued)

● Spectroscopic studies ofplutonium nitrate complexes inaqueous and organic solutionssorbed on ion exchange mem-branes are providing moreinformation on the plutoniumcomplexes involved in the ionexchange process. Carefulanalysis of the visible spectra ofplutonium(~) in 1 to 13 M nitricacid indicates that three majorcomplexes or groups of com-plexes are present in variousconcentrations of nitric acid. Thecomplex that exists at intermedi-ate nitric acid concentrations hasnot been previously studied, butthe intensity of its absorptionspectrum correlates with thedistribution coefficient ofplutonium on anion ex-change resin as a function ofnitric acid concentration. Thus,this unstudied species may bethe complex most crucial to theion exchange sorption process.Further studies include measure-ments of ultraviolet, visible, andnuclear magnetic resonancespectra images.

● The use of chelating poly-mers and extractants sorbed onpolymeric supports to removeplutonium and americium fromthe ion exchange effluent and theoxalate filtrate solutions is beinginvestigated. Duolite C467(made by Rohm & Haas) showspromise for reducing the amountof plutonium remaining in theoxalate filtrate to quite lowlevels. We are also studyingseveral novel extractants ofactinides [tetradentatebis(acylpyrazolones), tridentatetriphosphoryl and phosphoryl/N-oxide Iigands, and octadentatetetrahydroxamates] for applica-tion in process operations.

● We tested the liquid-liquidextraction capability of a mem-brane contactor module soldby Hoechst-Celanese usingtributylphosphate in an aromaticsolvent to extract uraniumfrom nitric acid. Under testconditions, the 25-centimetermoduIe performed as theequivalent of one to two-and-a-half theoretical stages.

These promising initial resultsindicate a need for furtherexamination of the use of suchcontractorsto extract plutoniumand americium from waste andprocess streams.

Product Prep-zratiom Our grouphas been responsible for twoimportant contributions in thearea of product preparation.

. A recently completednew-generation metal prepara-tion line is now in operation.It produces plutonium metalfrom plutonium oxide by two-step hydrofluorination to pluto-nium tetrafluoride followed byreduction to metal using cal-cium. The new design incorpo-rates computer-controlledequipment to minimize labor-intensive operations and subse-quent neutron exposure. Weare testing use of a stirred-bedfluorinator to reduce hydrogenfluoride consumption andyield a free-flowing product.

58 Nuclear Materials Teclmdogy Dividon Annual Review

“The ATLAS facility is being used to examine therecycling by evaporation ofa considerable portion of thenitric acid used in nitrate recovery operations.”

We examined a technique thateliminates the corrosion prob-lems caused by iodine by usinga carbon dioxide laser to initiatethe plutonium tetrafluoride/calcium reaction. Helium tubesin the furnace monitor the alpha-neutron reaction in plutoniumtetrafluoride, thus improvingprocess control. Presently, analternative method is underinvestigation for the recyclingof unreacted hydrogen fluoridein which sorption occurs in astirred bed of sodium fluoride.Such a method would eliminatethe need for the large volume ofaqueous potassium hydroxidesolution now used to trap theexcess hydrogen fluoride.

. Downstream waste treat-ment operations will benefitfrom an investigation of thehomogeneous precipitationof plutonium hydroxideas an alternative to precipitationof plutonium(III) oxalate afterelution of plutonium from theion exchange column.

The major advantage of thehydroxide precipitation is themuch lower concentration ofplutonium remaining in thesupematant solution. Thedecomposition of formamideand urea homogeneously gener-ates hydroxide in the nitric acidsolution. Unlike precipitationsusing alkali or alkaline earthhydroxide solutions, formamideand urea decomposition gener-ates a readily filterable solid.Because the bench-scale studieshave been quite promising, thismethod will be compared withoxalate precipitation in thecourse of operations on theAdvanced Testing Line forActinide Separations (ATLAS).

Recycling of Reagents. Therecycling of reagents used inplutonium processing will resultin reduced waste production.

● The ATLAS facility is beingused to examine the recycling byevaporation of a considerableportion of the nitric acid used innitrate recovery operations.

Recycling by evaporation willsignificantly reduce the volumeof nitrate effluents that must betreated by the Waste TreatmentFacility (TA-50). The LosAlamos-developed high-acidsensor will allow rapid monitor-ing of nitric acid concentration inthe distillate.

● The recycling of hydrogenfluoride in metal preparationline operations, described previ-ously under Product Prepanz-tion, is also an important accom-plishment in this area.

Waste Treatment. Althoughwaste treatment activities aredescribed in another chapter,some nitrate recovery operationsare directly applicable to thisincreasingly important concern.

● Some residues generatedduring processing operationsare presently processed withoutbeing considered “waste.”

59Nitrate Recovery

Process Chemistry (continued)

For example, cotton cloths usedto clean glove boxes often be-come partially nitrated and cancontain significant quantities ofplutonium. At present, theregulatory situation prohibitsincineration. With the agree-ment of state regulators, we arenow testing a thermal decompo-sition operation to reduce theinventory of nitrated rags andgenerate a solid residue that canbe leached to recover plutoniumshould the amount warrant theeffort.

● We are collaborating withRockwell International in thepreliminary testing of a moltensalt reactor for destroying rags,paper, plastic, and other com-bustible materials contaminatedwith plutonium. A molten saltsystem based on calcium dichlo-ride/calcium difluoride orsodium chloride/potassiumchloride is being consideredbecause both salt systems arewastes generated from theoxygen sparging ofelectrorefining salts or from themultiple-cycle direct oxidereduction process. Substantialwaste reductions, in addition tothe voIume reductions resuItingfrom the destruction of theorganics, could be achieved bymultiple use of these salts. This“thermal treatment” methodmay prove acceptable whereincineration is prohibited.

The implications of processchemistry studies and technol-ogy innovations are enormousfor the nuclear weapons corn-plex of the next century. Thecontributions of the nitratesystems group at Los Alamoswill continue to play a majorrole in the development ofacceptable plutonium proces-sing capabilities. +

60 Nuclcar Materials Tmkolo~ Division Annual Review

NITRATE

R E C O V ER Y

Systems Integration

by Bill McKerleyNuclearMaterialsProcessingGroup:NitrateSystems

Los Alamos efforts todevelop and demonstrateefficient and effective nuclearmaterials processing andrecovery technologies applica-ble throughout the DOE com-plex have already been provedbeyond the bench, or pilot,scale. Research, development,and demonstration work at theLos Alamos Plutonium Facilityat TA-55 centers around threeprimary activities:

● optimizing existing pro-cesses to minimize waste gen-eration and operator exposure,

● developing additionaltreatment or polishing opera-tions that will convert a largefraction of the total waste vol-ume to benign effluents thatcan be discharged with reducedimpact on the environment, and

● evolving new technologiesthat will result in significantlylower total waste generation andreduce operator exposure.

These activities can beconducted successfully onlyif researchers in several areascombine their efforts to resolvethe complex issues involved inplutonium recovery operations.Therefore, the Nuclear MaterialsProcessing Nitrate SystemsGroup, NMT-2, conducts aninnovative process engineeringprogram that brings togetherspecialists in process chemistry,process analytical chemistry, andprocess control.

The conduct of many opera-tions within DOE’s nuclearweapons and nuclear powerprograms requires many differ-ent processing steps, and processupsets in one operation canadversely affect other operations.

For example, the fluoride addedto facilitate the nitric acid disso-lution of oxide may result inhigher levels of plutonium in theion exchange effluence becausefluoride interferes with pluto-nium. This conflict can beresolved by integrating theprocess elements through appro-priate planning and by develop-ing prototype integrated experi-mental facilities. The conceptintegrating the various processesin plutonium recovery opera-tions is successfully demon-strated in the Advanced TestingLine for Actinide Separations(ATLAS), a testing facility thatcan process and recover a widevariety of actinide-bearing scrap.Such a broad capability is neces-sary because each process in therecovery operation produces itsown unique plutonium-contami-nated residue, such as metalshavings, crucibles, oxides,pyrochemical salts, and ash.

Nitrate Recovery 61

Systems Integration (continued)

ATLAS plays a dominant rolein such DOE programs as com-plex reconfiguration and radio-isotope recycle and recovery. Itincorporates such technologiesas enhanced process control andon-line analytical chemistry tooptimize the plutonium recoveryprocess and to minimize wasteproduced at the source andreduce waste treatment andstorage requirements. Waste isfurther reduced by couplingsuch optimized processing withimproved processing methodsin dissolution, ion exchange,precipitation, waste polishing,and final treatment techniques.Once these technologies havebeen properly demonstrated onATLAS, they can be easilyintegrated into the currentprocessing facilities at LosAlamos, the Rocky Flats Plant,and Westinghouse Hanford.

The solid operating dataprovided by ATLAS experi-ments will accomplish primarygoals in waste minimizationand will support activities inthe reconfiguration of the DOEcomplex. Furthermore, ATLAS,other equipment and instrumen-tation at the Plutonium Facility,and the integrated systemsapproach at Los AIamosensure the smooth transferof information among Labora-tory scientists and personnelat other DOE sites. +

62 Nuclear Materials Technology Division Annual R.xicw

CHLORIDE

RECOVERY

Chloride Recovery Overview

by Joel WilliamsNuclearMaterialsProcessingGroup:ChlorideSystems

Many of thepmcessesplanned for the Complex 21Plutonium Processing Facilityare chloride-based unit opera-tions. These include americiumextraction from the feed metal,electrorefining of the impuremetal, dissolution in HC1media,aqueous chloride purificationusing solvent extraction and ionexchange, precipitation, calcina-tion of the precipitate to oxide,and conversion of the oxide tometal through multiple cycledirect oxide reduction.

These unit operations can begrouped into two major catego-ries: high-temperature, molten-salt, pyrochemical processes andthe more conventional chloride-based aqueous operations. Abrief review of chloride recov-ery operations, as envisionedfor the Complex 21 PlutoniumProcessing Facility, includes allof the aforementioned processesexcept americium extractionand electrorefining. For pur-poses of process grouping,these two unit operations areincluded in the site-returnprocessing discussion.

Current chloride recoveryprojects that support Complex 21cover a broad range of activities.In the area of aqueous chlorideprocessing, the most importantprocess improvement is thealternative diluent work forsolvent extraction. This workhas been ongoing for approxi-mately a year and replacestetrachloroethylene (TCE), anenvironmentally objectionablechemical, with an acceptableorganic diluent for tributylphosphate. This work usesdodecane as the primary diluentwith decanol as a phase modi-fier. The most significant opera-tional effect of this change hasbeen the reversal of the light andheavy phases from the replace-ment of the TCE. As a result,extensive cold testing has beenrequired to confirm the perform-ance of the centrifugal contractorswith the new diluent system.

The use of an alternativediluent has created the need fora more sophisticated techniquefor evaluating the compositionof the organic phase.

A method that shows greatpromise is the use of gas chro-matography to analyze theorganic stream. Private industryhas long used this techniquesafely and reliably for just suchapplications.

Other major projects currentlyunder way that will impact thedesign of any new facility in-clude

1. dissolution studies toquantify process efficien-cies for a variety ofmatrices,

2. additional work on chlo-ride ion exchange, and

3. the application of sensorsfor process monitoring andcontrol.

For some of this work, we arecollaborating with the processdevelopment section of theNuclear Materials Processing—Nitrate Systems Group. Thisapproach has allowed ouraqueous chloride operations touse research being done tosupport ATLAS in the nitratearea.

Chloride Recovesy 63

Chloride Recovery Overview (continued)

Future plans for the aqueouschloride operations include thereplacement of virtually anentire glove box line. The experi-mental chloride extraction line(EXCEL) project calls for theremoval of the existing solventextraction glove boxes and theirreplacement with chloride-compatible, plastic-Iined boxesas the start of this upgrade.

Another part of our long-range plan is to incorporate on-line analytical techniques andspecialized process diagnostics.Because of special materialsrequirements in a chlorideenvironment, the developmentof wet chemistry techniques andother noninvasive methods suchas sensors and spectrophotomet-ric measurements must bemodified and adapted to theglove boxes that will use the newtechnologies. These new diag-nostic and process-monitoringcapabilities will be incorporatedinto unit operations as they aredemonstrated and will become apart of the design of any newComplex 21 facility.

The sole pyrochemicalprocess included in the chlo-ride recovery portion of theComplex 21 flow sheet is themultiple cycle direct oxidereduction (MCDOR) operation.This process for converting oxidefrom aqueous operations tometal has undergone severalsignificant changes during thepast few years. The introductionof chIorine sparging to convertthe reaction by-product, calciumoxide, to the calcium chlorideprocess salt has resulted indramatic reductions in waste.In addition, the use of chlorine inhigh-temperature operations hasopened the door to new tech-nologies such as in situ genera-tion of the plutonium trichloridenecessary in americiumextraction.

This technology improvementhas also required the develop-ment of more sophisticated off-gas monitoring capabilities. Theuse of a newly installed spectro-photometric technique fordetecting chlorine will becomean important tool for optimizingthe regeneration step of theMCDOR process.

Once demonstrated, this samediagnostic technique can beimplemented in any process thatuses chIorine as a reagent or thatmay generate chlorine as a by-product. Because the techniqueis noninvasive, we need only asimple modification of the off-gas piping to implement thetechnology.

Optimization of the MCDORprocess is under way to reduceoverall cycle time, further n~ini-mize waste generation, andimprove the purity of the metalproduct. The off-gas monitoringsystem has already been dis-cussed as one of the optimizationefforts. Automation of feedpreparation, handling, andintroduction into the reactioncell is under current develop-ment. The aim of this effort isto improve MCDOR throughincreased product consistencyand decreased personnel radia-tion exposure. Additionalautomation will configure andoperate cells and remove andproduce the final products.

64 NucIear Materials Tcchnolugy Division Amual Revkw

“The implementation ofa universal salt system for allpyrochemical operations has long been a goal of our processdevelopment.”

After the completion of a setof reductions, the chlorinationof the calcium oxide to calciumchloride results in a salt excess.This salt, however, is free of theimpurities found in commer-cially available calcium chlorideand could be used to produceproduct metal with the samechemical composition as thefeed oxide. An initial set ofexperiments to determineproduct metal purity producedmixed results. Most of the metalshowed no increase in impuritylevels compared with the feedoxide. Some runs, however,showed elevated levels of impu-rities that were not in the feedmaterial. In the future, carefulevaluation of product purityrequirements will be necessaryto produce a product with thesame chemical composition asthe feed oxide.

The implementation of auniversal salt system for allpyrochemical operations haslong been a goal of our processdevelopment. Calcium chloridehas been implemented as thesalt-of-choice in americiumextraction and is currently beingdemonstrated in electrorefining.Potential advantages of a univer-sal salt include consolidation ofsome pyrochemical unit opera-tions, simplification of theaqueous recovery flow sheet,and reduction in the volumeof aqueous solutions processedbecause calcium chloride issignificantly more soluble inHCI media than the sodiumchloride/potassium chloridesalts historically used in ameri-cium extraction andelectrorefining.

A program is being devel-oped to demonstrate an inte-grated chloride processingscheme. However, production-scale aqueous chloride process-ing is relatively new; andchanges in the pyrochemical

operations, such as oxygensparging of electrorefining salts,have also resulted in changes inthe composition of the feed torecovery. Although all of theindividual unit operations havebeen fully demonstrated, noevaluation has been made of theoverall, integrated flow sheetperformance. Not only will sucha demonstration confirm thehigh level of confidence forsuccess, but also the use of theexact feed stream specified forComplex 21 will demonstrate thedirect applicability of the entireflow sheet for the future facility.

The purpose of this programis the demonstration of eachsequential process step:

1. americium extraction of thesite-return feed metal,

2. electrorefining,3. recovering all chloride-

based residues, and4. converting the recovered

product oxide to metal inMCDOR.

Chloride Recovery 65

Chloride Recovery Overview (continued)

The goals of this work includethe evaluation of process effi-ciencies on a known feed, thedemonstration of an integratedflow sheet for residue recovery,and the conversion of oxide tometaI based on the pyrochemicalprocessing of that feed. Thisdemonstration will identifyproblems and provide an oppor-tunity for process improvement.

Overall waste generationrates will be determined from aspecified throughput of typicalsite-return feed. This will givemore accurate information tohelp specify waste stream con-tent and quantities. Such infor-mation will be invaluable insizing waste-handling require-ments and may identify poten-tial problems with specific wasteconstituents. By taking thisapproach, the program wilIexactly duplicate the waste-stream characteristics expectedfrom the Complex 21 flow sheet.

Issues not fully evaluated inthe existing flow sheet includethe requirements for analyticalor nondestructive assay equip-ment, materials surge-capacityrequirements, critical processequipment redundancy require-ments, and the effect of differingreliability, availability, andmaintainability (RAM) character-istics of the specific operations.One of the significant problemswith Building 371 at Rocky Flatswas the incompatibility of someprocess unit operations. Thisbuilding could not perform at itsdesign capacity because unitoperations with different RAMhistories were implemented inlock-step fashion.

In conjunction with processing,I

materials control and accountabil-ity (MC&A) requirements mustbe carefully evaluated beforefinalizing any process flow she&.As part of MC&A requirements,we will need surge capacity andassurance of safeguards for suchexcess material storage.

The integrated demonstrationof the chloride flow sheet willprovide information and insightinto these areas and help identifypotentially significant problems. + I

66 Nuclear Materials Technology Divklon Annu.d Review

c H LO R I D E

RECOVERY

In Situ Chlorination of Plutonium Metal

by Eduardo GarciaNuclearMaterialsProcessingGroup:ChlorideSystems

IntroductionPlutonium trichloride is used

as a reagent in the molten saltextraction (MSE) andelectrorefining (ER) processes.Presently, plutonium trichlorideis made by combining pluto-nium oxide and highly toxicphosgene. Because of thistoxicity, an alternative syntheticroute to plutonium trichloride ishighly desirable. By makingplutonium trichloride during theprocesses in which it is used,with less toxic reagents, we cangain in overall safety, decreasewaste generation, reduce radia-tion exposure, and reduce thenumber of accountability steps.

A simple way to accomplishthis goal is by direct reaction ofelemental plutonium and chlo-rine. Alhough chlorine is a toxicmaterial, it is an order of magni-tude less toxic than phosgene.

Furthermore, the reaction be-tween chlorine and plutoniummetal is expected to be muchmore efficient than the reactionbetween phosgene and pluto-nium dioxide, thus smalleramounts of gas are needed togenerate equivalent amounts ofplutonium trichloride. Prelimi-nary work shows the feasibilityof in situ chlorination for produc-ing the required plutoniumtrichloride.

ApproachIn the conventional MSE

process, quantities of calciumchloride, plutonium trichloride,and plutonium metal are loadedinto a crucible. In situ chlorina-tion generation, however, elimi-nates the need to add plutoniumtrichloride at the beginning of arun and will be accomplished bysparging chlorine gas throughthe molten plutonium. Concep-tually, the chemical reaction isve~ straightforward and simple:

2 Pu + 3 cl —> 2 ruc~.

Chloride Rerovery

Unfortunately, although thechlorination reaction is veryhighly thermodynamicallyfavored, the reaction is so exo-thermic that there must becareful control of chlorine flowrates in order to prevent un-wanted temperature excursions.In the direct chlorination ofplutonium metal for purificationpurposes, the reaction tempera-ture can be maintained at accept-able levels by proper flowcontrol of the chlorine.*

Another concern thatchlorination of plutoniummetal introduces, and a concernof pyrochemistry in general, isthat of materials compatibility.Chlorine gas is a highly corro-sive oxidizing agent, but moltenplutonium metal is a highlycorrosive reducing agent.

*T.R.Jarosch,J. B.Scaade,andS.D.Fink,SavannahRiverLaboratory,unpublishedresearchconductedatLosAlamosNationalLaboratory,1991.

67

In Sitn Chlorination of Plutonium Metal(continued)

This kind of environment pre-sents materials compatibilityproblems because materialsthat can withstand highlyoxidizing conditions are usuallychemically incompatible withhighly reducing conditions andvice-versa.

There are two possiblesolutions to this problem. Thefirst is to use magnesia cruciblesbecause they have demonstratedminimal chemical attack inplutonium pyrochemical pro-cesses and are, of course, inert tochlorination. A magnesia cru-cible has the disadvantage of notbeing reusable because it mustbe broken in order to recover theproduct.

The second solution is to usetantalum crucibles, which arecurrently used in MSE, becausethey are reusable. Tantalum, orany other metal, would seeminappropriate as containermaterial because it is attackedreadily by chlorine at elevatedtemperatures. However, it maybe possible to have a completereaction between the chlorineand plutonium metal so that the

tantalum crucible never comes incontact with chlorine gas.

There are two possible meth-ods by which contact betweenchlorine and plutonium can bemaximized. One of these wouIdinvolve redesign of the crucibleto increase contact time betweenthe two reagents and minimizethe amount of unreacted chlo-rine escaping from the melt. Thesecond method uses stirringwhile sparging, which maintainsintimate contact between the gasand the metal throughout themelt, thus optimizing the reac-tion.

Znsitu production of pluto-nium trichloride for MSE wouldhave several benefits. It wouldreduce accountability stepscurrently required for separateplutonium trichloride produc-tion. Although chlorine is a toxicmaterial, it is much less toxicthan the phosgene currentlyused, and the reaction with themetal is predicted to be muchmore efficient, reducing both thetime required to effect the reac-tion and the amount used.

Another advantage is that noadditional glove boxes and spacefor separate MSE oxidant synthe-sis would be required. Becausevery little, if any, chlorine willescape from the furnace duringin situ generation of plutoniumtrichloride in MSE, gas scrubberwaste that is normally generatedfrom these processes will beminimized to a large extent.This process will not increase thepersonnel radiation exposurenormally received from the MSEprocess but will, of course,eliminate the exposure receivedfrom a separate plutoniumtrichloride synthesis procedure.

MSE is the logical process forinvestigating in situ chlorinationbecause of the simplicity of theprocess. Electrorefining isanother process that wouldbenefit from in situ generation ofplutonium trichloride, but theincreased number and con~plex-ity of the mechanical compo-nents render this process lesssuitable. After in situ generationhas been perfected for MSE, theknowlege and experience gainedwill be applied to ER. +

68 Nuclear Materials Technology Division Annual Ret+?w

CHLORIDE

RECOVERY

Opportunities for Magnetic SeparationApplications in Complex 21

Larry R. Avens, Laura A. Worl, and Karen J. deAgueroNuclearMaterialsProcessingGroup: ChlorideSystemsNuclearMaterialsTechnologyDivisionF. Coyne Prenger, Walter F. Stewart, and Dallas D. HillAdvancedEngineeringTechnologyGroup,MechanicalandElectronicEngineeringDivision

The Magnetic SeparationProcess

Magnetic separation is a physi-cal separation process that segre-gates materials on the basis ofmagnetic susceptibility. Becausethe process relies on physicalproperties, separations can beachieved while producing aminimum of secondary waste.

When a paramagnetic particleencounters a nonuniform magneticfield, the particle is urged in thedirection in which the field gradi-ent increases. Diamagnetic par-ticles react in the opposite sense.When the field gradient is ofsufficiently high intensity, para-magnetic particles can be physi-cally captured and separated fromextraneous material.

Because all actinide compoundsare paramagnetic (Table 1), mag-netic separation of actinide-con-taining mixtures is feasible. Mag-netic separation on recycle pluto-nium chemical process residueshas been demonstrated on anopen-gradient magnetic separator.The advent of reliable supercon-ducting magnets makes magneticseparation of weakly paramagneticspecies attractive.

Chloride Recovery

TabZe1. Magneticsusceptibility ofselected compounds and elements.

Compound/Element Susceptibility,10+I?aramagnetic

FeO ...................................................................+7200FezO~.................................................................+3586CrZOa.................................................................+1960—.

GULL. ......,.,,,.........,=...................... ......................+2370.- .- -“*-P~ .......; .......:.......:.:...:::::..............................+1760- .,..-...t . -

rn.A........p.............:.:.:.......!t.........................,.....+1000GO:.:..;::...-..::.;................,..:...:............................+730IIE+L

.*’.

.-— 1 .. .,.—.— .— — .-

E!.

+“-..

N~::........... ....................... ...............................+66U‘U ....:......:. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +610

“ .-..” ..’” ,- . .. -.

..,.::..Jf f**...-.....,.. . . . . . . ..... ... . . . . . . . . . . . . . . . . . . . . . . . ................ +409——.. ---@~~":::~""".>:"::.:;":"""""""""""""""""::"""""`"".:":.'""’173‘h........................................................................+134

LEO:.::................:.:......:..... .:.:.....................:........+40.-.—

Ca ..........................................................................+40Al ..........................................................................+16

DiamagneticSi ...............................................................................4Graphite .................................................................. -6MgO........................................................................lOCaO.........................................................................l5Th02. ...................................................................... -16MgF2.......................................,..........

CaF2........................................................................-28Si02. .......................................................................-30NaCl .......................................................................3OA1203. .....................................................................-37K Cl ........................................................................-39CaC~......................................................................-54Calz.......................................................................-109

69

Opportunities for Magnetic SeparationApplications in Complex 21 (continued)

Magnetic Separation MethodsAlthough numerous magnetic

separation methods exist, thetwo we have selected for ourwork are the magnetic-roll, ordrum-type separator, and thehigh-gradient magnetic separa-tor (HGMS). The usefulness ofthe open-gradient separator usedin the early work is limited by itslow processing rate.

A diagram of a roll separatoris shown in Fig. 2. In practice, apowder is delivered onto a thinbelt that moves over rollers. Thefront roller is fabricated from apermanent magnet. Ferromag-netic and sufficiently paramag-netic particles are attracted to themagnet and adhere to the belt inthe region of the magnet. As thebelt moves away from themagnet, the ferromagnetic andparamagnetic particIes disen-gage from the belt and arecollected in a catch pan. Diamag-netic and nonmagnetic particlespass over the magnetic rollerrelatively unaffected and arecollected in a different catch pan.The operation results in a sepa-ration.

()FeedFig. 2. Dingrmnojn roll-or drum-type

Hopper )nagrreficseparator.1’,,. ..!.~$.,. .-,. ,...:.: :;,

.,, .-:.,.:/ FeedTray

~;;’1:.

~-~:.:::,:::t

/. .

Thin StainlessSteel Belt ..-. ‘:,““’’’ty+

F,_Ma~,]: Drum

...’+,>-’1,$-- ;_.. ,.-. ,_.-< ,,.. .

.... A ‘;::? Snlitter..........

The roll separator we arecunently using contains thelatest in permanent magnettechnology: a neodymium-iron-boron rare-earth magnet. Theroll is constructed of rare-earthmagnetic disks separated byferromagnetic spacers. Thisgenerates high fieId gradientson the surface of the roll. Theroll separator has been installedin a glove box for a demonstra-tion with actual residues.

The HGMS method is used toseparate magnetic fractions fromgases or liquids. A diagram ofthe method is shown in Fig. 3.Most commonly, the feed isslurried with water and passedthrough a magnetized volume.Field gradients are produced inthe magnetized volume by aferromagnetic matrix material.The matrix can be steel wool,steel balls, nickel foam, etc.

70 Nuclear Matericd.sTethnology Division Annual Review

Feed Fig. 3. Simplified HGMS Diagram.Suspension Water

An

Pv:“a”.~?+i;a<,:N. .,:-..::..-9/”\ >---!<; ,=.,.,:,./.Z., .>.,- .., L-,.*: >--, >..:.:<.:/.%.

FluxReturn

Shell

MatrixCanister

StainlessSteel Wool

Ferromagnetic and paramag-netic particles are extracted fromthe slurry while the diamagneticfraction passes through themagnetized volume unaffected.The magnetic fraction is flushedfrom the matrix later when themagnetic field is reduced to zeroor the matrix is removed fromthe magnetized volume.

Much higher electromagneticfields are routinely availablewith today’s superconductingmagnet technology.

Higher fields offer the possibil-ity of a broader range of HGMSapplications than is afforded byconventional electromagnets,which are limited by the satura-tion of iron.

For our HGMS work at LosAlamos, we have a laboratory-scale l-inch-bore, cross-field,conventional magnet and alarger, warm-bore supercon-ducting magnet.

Magnetic Separation Applica-tions in Complex 21

Several applications ofmagnetic separation will beexamined for Complex 21:

1. concentration of recycled-plutonium, chemicalprocessing residues,

2. extraction of actinidesfrom liquid wastes, and

3. development of reusablemagnetic gas filters.

We have shown that chemicalprocess residues, such as reduc-tion slags, crucibles, graphite,and silica, can be segregated intoa plutonium-rich and a pluto-nium-lean fraction. The pluto-nium content of the lean fractionfrom these demonstrationexperiments is sufficiently lowin plutonium that it isuneconomical to recover theplutonium value. Therefore, theplutonium lean fraction can bediscarded directly in grout.Processing of dry residues isimportant not only for Complex-21 processing but also for vol-ume reduction of the currentDOE backlog.

Chloride Recovery 71

Opportunities for Magnetic SeparationApplications in Complex 21 (continued)

HGMS might also be useful asa selective filter for fluid wastegenerated during actinidechemical processing. Our mag-netic separation model predictsthat HGMS can reduce theactinide concentration in liquidwaste streams by several ordersof magnitude.

An identified need in ura-nium and plutonium operationsis the reusable filter for glovebox and hood exhaust. A reus-able high-efficiency magneticfilter for paramagnetic particu-late appears feasible, but only asmall amount of work has beenconducted in this area.

Benefits of Magnetic Separation Magnetic filtration of fluidin Complex 21 waste may be a method to cut

The benefits of interjecting transuranic (TRU) effluents frommagnetic separation as a head- DOE facilities to near zero. Thisend unit operation include the would greatly reduce wastegeneration of only a very small treatment cost.volume of secondary waste. The Magnetic gas filters on gloveability to concentrate the actin- box process exhaust would alsoides from extraneous materialsbefore processing begins yie~-1

‘-B

more efficient recovery~ ra--’ =G:%;i.hi:ition. This is true be u~e r

?must be chan ed. A r~usable

(acid) use is redu~geeds

isso t“ &w filter based ‘“of more conce~?ate ne appea=e=$~?~-yields more

F

centrated sol - A ,.- --. -.

tions to ion ‘‘- ~ &‘ichan e or solvent ‘.’

%%_extraction nit oper =—- ‘“”#Because 1 s extr P &ous-rnateria –=

is leache an \;::::~c$~::~;!’+ ‘ ‘“

—

I

72 Nuclear Materials Tcchnolwg Division Annual Review

“Acooperativeresearchand developmentagreementwasrecentlysignedwithAWC/Lockheedtoexamineparamagneticseparationfor soildecontamination.”

Project StatusCold testing of the roll separa-

tor has been completed and ithas been installed in a glove box.Soon, process demonstration willbegin. The roll separator repre-sents a pilot-scale demonstrationfor this technology. Data ob-tained from this unit can be used,to design and fabricate a full-scale processing unit with virtu-ally any number of separationstages and processing rates.

The conventional HGMS unitat Los Alamos is currently beingused in cold testing. Throughthe use of

1. various nonradioactivesurrogate materials withdifferent magneticsusceptibilities,

2. different surrogate particlesizes,

3. parameter variation suchas flow rate, solids loadingin the slurry, fluid viscos-ity, etc.

4. magnetic matrix param-eters, and

5. magnetic field strength,a performance-based HGMSmodel is being developed.The hope is that given a separa-tion problem, we will have theability to select the processingcriteria that will achieve anecessary per-formance level.Currently, numerous experi-ments must be conducted todetermine optimumperformance.

The superconducting HGMSis due in Los Alamos very soon.After cold testing and modeldevelopment, one of the HGMSseparators will be relocated forplutonium residue processingtests.

There are other importantaspects of magnetic separationwork at Los Alamos that do notstrictly involve Complex 21.A cooperative research anddevelopment agreement wasrecently signed with AWC/Lockheed to examine paramag-netic separation for soil decon-tamination. In addition, a soildecontamination study withRocky Flats is anticipated.Use of HGMS to segregateunderground storage-tankwaste, a problem at theHanford site, is also beingstudied. +

Chloride Recovery 73

CHLORIDE

RECOVERY

Oxygen Sparging

by Eduardo GarciaNuclearMaterialsProcessingGroup:ChlorideSystems

IntroductionBefore the advent of oxygen

sparge as a recovery process,calcium salt was used to stripplutonium from salt residues.In the resulting sodium chlo-ride/potassium chloride salts,excess calcium produced metal-lic and potentially pyrophoricalkali metals. These waste salts,though below the economicdiscard limit, did not meetWaste Isolation Pilot Plant(WIPP) criteria because of theirpotentially pyrophoric nature.To make these molten wastesalts acceptable to WIPP, workwas started in 1988 on airsparging because with thisprocess any pyrophoric materialwould be converted into a moreinert oxide. In the course ofthese experiments, it was notedthat even further plutonium wasbeing recovered than before.Literature* surveys revealed thatoxygen sparging work had beenconducted as early as the 1960s.

* L.J. MullinsandJ. A. Leary,“MoltenSaltMethodofSeparationof

Although this earlier effort had concentrated on actinide separationand not specifically on plutonium recovery, it was still a goodfoundation on which to build.

Air sparging of salts was replaced by oxygen sparging in whicha controlled mixture of oxygen and argon was used to provideimproved process control. As new information was gained, processparameters were continually changed in order to improve perfor-mance. Oxygen sparging has now almost completely replacedcalcium salt stripping as the method of choice for treatingelectrorefining salt residues.

ApproachOxygen sparging has been used to treat salt residues, mainly

from electrorefining, on the kilogram scale. Sodium chloride/potassium chloride or calcium chloride salts derived from thisprocess contain plutonium in the form of dissolved plutoniumtrichloride as well as some uncoalesced metal. To minimize thequantity of material that must be treated to recover this plutonium,and thereby minimize waste from the recovery process, plutoniumis concentrated into a fraction of the volume of the residue salt byoxygen sparging. The major portion of the salt is thereby madesuitable for discard. Concentration of the plutonium is accom-plished by oxidation of the soluble chloride species into an in-soluble oxide species. Chemical reactions of interest are as follows:

2PUC4 + 202—> 2PU02 + 3C12

2PUC13+ 02 —> 2PUOC1 + 2C;

2PUOCI + 02 —> 2PU02 + C12

AmericiumfromPlutonium,”U.SPatentNo.2,420,639(1967).

74 Nuclear Materials Technology Division Annual Review

“Oxygen sparging has now almost completely replacedcalcium salt stripping as the method ofchoice for treatingelectrorefi”ning salt residues.”

Oxygen sparging has under-gone several modifications andindeed continues to evolve asinformation and experiencegained are applied towardsprocess optimization. However,the basic process has remainedthe same.

This basic procedure typicallyresults in a multilayered prod-uct. At the bottom of the cru-cible can be found metallicplutonium, usually poorlycoalesced. Above the metal is asolidified “black salt” matrixlayer that contains plutoniumdioxide, plutonium oxychlonde,and plutonium metal. Abovethis black layer is usually abrownish layer of plutoniumdioxide that is considered partof the “black salt” layer. Finally,the uppermost layer that makesup 5070to 75’%oof the bulkvolume is the “white salt” thatcontains only very smallamounts of plutonium andis suitable for discard.

Plutonium oxychloride is more easily handled in the aqueoushydrochloric acid recovery process. In 1991, work was started onefforts to maximize plutonium oxychloride production with respectto plutonium dioxide. This effort resulted in a closer look at thechemistry and kinetics of the oxygen sparging process. The firstthing that became clear was that the product is not at chemicalequilibrium because plutonium metal and plutonium dioxide cannotcoexist in chemical equilibrium. Depending on the limiting reagent,the equilibrium products of a mixture of metal and dioxide shouldbe either metal and i3-plutoniumsesquioxide or cx-plutoniumsesquioxide and plutonium dioxide. Another mystery was thelocation of plutonium oxychloride in a layer below plutoniumdioxide. Because plutonium dioxide has a density of 11.5 g/cc,significantly higher than that of plutonium oxychloride at 8.8 g/cc,it should sink to the bottom of the molten salt.

In order to overcome the perceived kinetic barriers to the reactionbetween plutonium and plutonium dioxide, a procedure for stirringwas added to the basic process. The anticipated chemistry was

Pu + 3PU02 —> 2P~03

Pu,O, + CaCl, —> 2PuOCI i- CaO

Pu,O, + 2NaCl —> 2PuOCI + N~O.

Stirring did indeed eliminate plutonium dioxide in cases wherethere was a metal excess. The product typically consisted of a well-coalesced metal button, a “black salt” layer (plutonium oxychloride)that had a pronounced blue-green color, and a “white salt” layer.

Chloride Recovery 75

Oxygen Sparging (continued)

The chemistry occurring during stirring in the case of calciumchloride salts was as expected. However, in the case of sodiumchloride, the actual chemistry is

Pu + PuO, + 2NaCl —> 2Na + 2PuOC1.

After stirring, a second oxygen sparge oxidizes the pyrophoricmetallic sodium that deposits on the furnace head.

Oxygen sparge experiments on clean calcium chloride saltscontaining pure plutonium trichloride revealed that onIy plutoniumdioxide is produced when plutonium trichloride reacts with oxy-gen. The large amounts of plutonium oxychloride in oxygen-sparged electrorefining salts can be attributed only to the presenceof pIutonium metaI in those saIts. A possible reaction scheme thatexplains experimental observations has been theorized below.

When the salts are first melted, some coalescence of metal occurs,but a large fraction of elemental plutonium remains suspended in a%lack salt” layer. After sparging is initiated, plutonium dioxidebegins to precipitate and initially is intimately mixed with pluto-nium metal in the black salt layer. Some of the plutonium dioxidewill be in sufficiently close contact to react and produce plutoniumoxychloride. Although the mixture is probably not adequate tocause a complete reaction between all the precipitated oxide andmetal, some of it will be in sufficiently close contact to produceplutonium oxychloride. As the sparging continues and plutoniumdioxide continues to precipitate, the %lack salt” layer becomes soviscous that plutonium dioxide begins to pileup on top of the“black salt” layer. This is the oxide layer that was usually observedin traditional oxygen sparging. The material in the “black salt”layer is a mixture of plutonium metal, plutonium oxychloride, andplutonium dioxide. These have all been observed by powder x-raydiffraction. This scheme explains why plutonium oxychloride is

found below the oxide layereven though it is much lessdense than plutonium dioxide.Furthermore, the variability ofthe size of the oxide layer can beunderstood because it is a func-tion of the amount ofuncoalesced plutonium metal inthe electrorefining salts thatseems to vary widely.

Future WorkAn improvement to the

process will be made by adapt-ing a chlorine spectrophotomet-ric in-line detector developed formultiple cycle direct-oxidereduction, thereby providingreal-time analytical capabilitiesfor detecting chlorine. A by-product of the oxygen spargeprocess is chlorine, and a dimin-ishing concentration of thischemical substance in the off-gasstream will signal completion ofthe run. Eventually this detectorwill be connected to a computerthat will automatically terminateoxygen flow.

76 Nuclear Materials Technology Divfdon Amud Review

Fig.1. Closed-looprecyclingsystem.

l—@-l

El

MSE

n

Lm;R

Plutonium oxychloride iseasier than plutonium dioxiderecover by aqueous chloridemethods. This was the initialimpetus for optimization of

to

plutonium oxychloride produc-tion. There is now anotherreason for producing a homoge-neous plutonium oxychlorideproduct. If plutonium trichlo-ride can be produced fromplutonium oxychloride, then aclosed-loop recycling system canbe setup as shown in Fig. 1. Ifthe conversion step can beaccomplished with a minimumof waste generation, then thisclosed-loop system will loweroverall waste generation associ-ated with plutonium trichloridesynthesis and recovery. J?relimi-nary experiments using ammo-nium chloride to convert pluto-nium oxychloride to plutoniumtrichloride are very encouraging.

Molten salt extraction is envisioned as a baseline process forComplex 21. Residue salts from this process contain dissolvedplutonium trichloride but very little metal. Because oxygensparging requires plutonium metal as a reagent to produce pluto-nium oxychloride, oxygen sparging would not be a process ofchoice for the closed-loop recycling system described above, but asimilar process could be used. Instead of using elemental oxygen toproduce a plutonium oxide species, calcium oxide can be usedaccording to

PuC~ + CaO —> PuOC1 + CaC12.

There is no oxidation agent in this reaction; therefore, plutoniummust remain in the +3 oxidation state, and no plutonium dioxidewill be produced. With calcium chloride salts, all the compoundsare soluble except plutonium oxychloride, so a clean reaction can beexpected. In several successful experiments that used sodiumchloride/potassium chloride salts, calcium oxide remained in the“black salt” layer. An issue that must still be addressed is ameri-cium separation.

To produce plutonium trichloride from plutonium oxychloride,americium must first be separated. Otherwise, unacceptably highlevels of radiation exposures will be encountered. Separation doesoccur with oxygen sparging where the americium remains in the“white salt.” We have not yet explored americium separation withcalcium oxide. +

Chloride Recovery 77

CHLORIDE

RECOVERY

Materials Development for PyrochemicalApplications in the Weapons ComplexReconfiguration

by Keith M. AxlerNuclearMaterialsProcessingGroup:ChlorideSystems

IntroductionCurrently, a large contribu-

tion to the volume of contami-nated waste is from nonreusablecrucibles and ancillary furnacecomponents that fail in service.The objective of our work is toidentify alternative constructionmaterials that will reduce wasteby providing extended serviceand that will improve processquality by remaining nonreactivein the chemical system.

Compared with analogousindustrial studies, materialsdevelopment for plutoniumapplications presents exceptionalconsiderations because of thereactivity of plutonium and thehydroscopic salts. With anextensive array of capabilities,the Nuclear Materials Technol-ogy (NMT) Division at LosAlamos is uniquely suited toconduct materials developmentresearch in this field.

1. The Los Alamos plutoniumfacility is the only currentlyoperating laboratory equippedfor complete experimentaltesting of materials for pluto-nium pyrochemistry.

Specifically, this testing com-bines the abilities to conductexperimental work both withreactive gases and with salt andalloy systems containing actinideelements.

2. State-of-the-art analyticaland metallographic capabilitiesin support of research on radio-active materials are fully opera-tional at Los Alamos.

3. NMT Division maintainsthe most advanced capabilitiesfor thermodynamic modeling ofcomplex chemical systems.Computer modeling is used toevaluate potential candidatematerials from a standpoint ofchemical thermodynamics.Thermodynamic modeling alsoserves in process optimizationstudies to identify effects causedby variances in process condi-tions.

Candidate Materials Evalua-tion: Methodology

The criteria for alternativematerials are defined by thespecific conditions of the se-lected process application.

Each pyrochemical processperformed in the weaponscomplex presents a differentset of materials requirements.Among other considerations,the criteria for materials selec-tion are based upon the processthermal profile, chemicalcomposition, and the functionsof internal furnace components.Additionally, product purityspecifications are carefullyconsidered in materials selec-tion because of the strictlydefined tolerances for specificelements in our product.

An evaluation process hasbeen designed to use time andresources and to obviate unnec-essary experimental use ofplutonium. This is accom-plished through a demonstratedseries of tests.

1. First, an evaluation ofcurrent materials performanceis conducted. This often re-quires examination of the finalproduct to characterize materi-als interactions.

78 Nuclear Materials Technology Oivlsion Annual Rwicw

“...intlwexaminationof productmetalinplutoniumelectrorefi”ning,electronmicroscopyrevealedan oxychlon”desurfacephaseassoctitedwith theuncoalescedmetal.”

2. Computer modeling isthen conducted to determine theviability of candidate materialsbased on system thermodynam-ics. Computer models areconstructed for each pyro-chemical process and reflect thechemical environments in whichthe candidates must perform.

3. If positive results areobtained in the modeling, “cold”testing is conducted to partiallyconfirm the modeled predictionsby compatibility testing withoutplutonium. This includes high-temperature salt containmentand thermal cycling tests.

4. If promising performancehas been indicated in the initialstages of the evaluation process,work will proceed with “hot”testing of the candidate. At thisstage, small-scale exposure testsare conducted with plutonium inchemical environments simulat-ing actual service conditions.

5. Finally, successful candi-dates are then demonstratedin service application. Thisprovides thoroughly docu-mented performance for finalconsideration.

Evaluation of Current MaterialsPerformance.

Current incompatibilitiesbetween pyrochemical systemsand construction materials areidentified by studying thereaction products of the selectedprocesses. Interactions with thecrucible or furnace hardware areindicated by the appearance ofinterfering species in the prod-ucts. For example, in the exami-nation of product metal inplutonium electrorefining,electron microscopy revealed anoxychloride surface phaseassociated with the uncoalescedmetal. This observation wasconsistent with the partialreduction of magnesium oxidecomponents predicted by com-puter modeling.

In addition, failed compo-nents are examined to identifythe mechanisms of corrosionthat define the microstructuralproperties desired in a viablecandidate. Materials selectionfor the multiple cycle, directoxide reduction of plutoniumdioxide presents one example.Based upon the characteristiccorrosion mechanisms of chlo-rine gas and liquid plutonium,metallographic techniques wereused to interpret their relativecontributions to the corrosion ofinternal furnace hardware.This data narrowed the field ofcandidate materials by establish-ing required microstructuralcharacteristics.

Chloride RJXOvery 79

Materials Development for PyrochemicalApplications in the Weapons ComplexReconfiguration (continued)

Computer modelingSystem thermodynamic

calculations are used to providea cost-effective initial evaluationof candidates. Many proposedcontainment materials have beendisqualified by thermodynamicmodels and dramatic savingsrealized by obviating experimen-tal evaluations. These computermodels utilize rigorous calcula-tions to predict equilibriumcompositions based on free-energy minimization for com-plex, heterogeneous chemicalsystems. The models requireinput in the form of Gibbsenergies for all possible speciesand phases as welI as initialcomposition, temperature, andpressure. Large data banks,]which are updated on a continu-ous basis, provide the requiredthermodynamic data.

Processes are modeled withalternate materials for cruciblesand ancillary furnace compo-nents.2~ The modeIing resultsreveal possible side reactionswith the crucibles or the hard-ware. Verification tests havebeen conducted to establish theviability of the computer modeIs.This involved the experimentalconfirmation of results obtainedin the modeling.4 In addition toutilizing these computer codesto evaluate candidate materials,they are used to model phaseequilibria in higher-order sys-tems to aid in process optimiza-tion.5$

Cold TestingThermal cycling tests are

particularly valuable in theevaluation of coated materials.To date, we have examined anextensive matrix of refractorycoatings, prepared by a varietyof deposition techniques.7

Many candidates that appearpromising because of theirthermodynamic stability havebeen disqualified because oftheir inability to maintain integ-rity through a sufficient numberof thermal cycles. Cold testingalso includes salt release tests inwhich compatibility with moltenpyrochemical salts is examined.

Hot TestingExperimental work with

plutonium is indicated only forcandidates that have performedwell in the previous stages of thecampaign. Small-scale cruciblesof the candidate material arefabricated and tested by their usein the containment of liquidplutonium and molten salt overextended time.

Also at this stage, differentialthermal analysis has been con-ducted to determine the rate andextent of the candidate material’sreactivity with plutonium.8

80 Nuclear Materials Technology Divls!on Annual Revk.w

“ The importance of minimizing radioactive wastevolumes continues to promote interest in alternateconstruction materials”

Demonstration workDemonstration involves using

the candidate material to con-struct components used inactual pyrochemical processing.Currently, several candidates areunder evaluation in this ad-vanced stage of materialsselection:

1. Carbon-saturated tantalumis being tested for use in themultiple cycle direct oxidereduction process. This materialwill also be tested in advanced-concept electrorefining and inthe americium extraction processperformed on aged plutonium.

2. Silicon nitride is beingtested for use in reactive gassparging during the in situregeneration of spent salts.

3. High-density yttria isbeing used in plutoniumelectrorefining.

Other materials are at morepreliminary stages of evaluationfor selected applications. Theseinclude carbon-saturated nio-bium and yttria-stabilizedzirconia.

ChkidelZemv5y

SummaryThe importance of minimiz-

ing radioactive waste volumescontinues to promote interest inalternative construction mater-ials. As work continues in thisarea, we will develop a suite ofmaterials for pyrochemicaloperations that will provideextended service without com-promising product quality.

As part of our investigations,we are collaborating with scien-tists in related fields to remainapprised of current develop-ments in advanced materials.One example is the recent indus-trial collaboration with W.R.Grace & Co. and CERMET on theadvanced processing of thorium-based ceramics.9 Other jointinvestigations have includedstudies of engineered materialsl”and refractory ceramics”involving scientists at Lawrence

Livermore National Laboratory,Westinghouse Savannah RiverLaboratory, and WestinghouseScience and TechnologyCenter. +

References1.T. L Barryetal.,MTDATA Handbook:

Documentation for the NP.LMetallurgical andThermochemical Databank, NationalPhysicalLaboratory,Teddington,UK(1989).

2.L.M.Bagaasenetal.,“InvestigationsofCoatedRefractoryMetalsforPlutoniumContainment,”Trans. Am. Nucl. Soc. 62,240-241 (1990).

3. KM. Axler, “ReportonSpecialMetallurgicalProblems,”LosAlamosNationalLaboratoryinternaldocumentNMT-3:91-164(1991).

4. K.M.AxlerandR.LSheldon,“TheEffectofInitialCompositiononPuOC1FormationintheDirectOxideReductionofPuO,;’JournalofNuclear Materials, ~ 183-185,1992.

5. A.M. Murrayetal.,“ThermodynamicModelingandExperimentalInvestigationsoftheCsC1-Ca~-PuCl,System,”RockyFlatstechnicalreleaseRFP-4480,presentationattheThird Int. Symp. Molten Salt Chem. andTechrol., Paris,France,July1991.

6. K M.Axleretal.,“CalculatedPhaseEquilibriafortheCaC~-KCl-MgC~System,”NPLreportDMM(D) 123, National PhysicalLaboratory, Teddington, UK (1991).

7. K. M. Axler, Los Alamos NationalLaboratory internal document NMT-3:91-144(1991).

8. K. M. Axler and E. M. Foltyn, “High-Temperature Materials Compatibility Testingof Refractory Crucible Materials: TaC, Y20J,YzOj-coated MgO, and BN,” Los AJamosNational Laboratory report LA-11586-MS(September 1989).

9. R Brezny, R. W. Rice, and K. M. Axler,“Thoria: A Candidate Material for Use inPyrochemical Processing,” presentation at the1992 Ann. Meet.Am. Ceram. Soc., April 1992.

10. KM. Axler, G. D. Bird, and P. C.Lopez, “Evaluation of Corrosion ResistantMaterials for Use in PlutoniumPyrochemistry,” Proc. 180th Meet..Hectroclrem.Soc. (1991).

11. P. C. Lopez et al. “Investigation ofSilicon Nitride Performance in PlutoniumSystems for Application in Pyrochemistry;’Los Alamos National Laboratory report LA-12322-MS,1992.

81

CHLORIDE

RECOVERY

Pyrochemical Integrated Actinide Chloride Line(PINACL)

by James A. McNeeseNuclearMaterialsProcessingGroup:ChlorideSystem

NMT-3 has identified a needto develop a glove box processand development facility, thePyrochemical Integrated Actin-ide Chloride Line (PINACL), asa means of totally integratingpyrochemical process technol-ogy. This versatile system willfacilitate process developmentand technology enhancement forprocesses that will be includedor have the potential for inclu-sion in the Complex 21reconfiguration effort. PINACLwill include design featuresminimizing space requirements,personnel exposure, and wastegeneration while maximizingpersonnel efficiency, materialthroughput, process reliability,safeguards and security, andsafety. Process automation willbe used where beneficial. State-of-the-art analytical nondestruc-tive array equipment for moni-toring and controlling the pro-cess will be incorporated into thedesign. This facility will be usedas a test bed for bench-scalethrough production demonstra-tion for pyrochemical processesand processing techniques.

Our current pyrochemicalprocess facility was developedfor production support through-put and not as a development/demonstration facility. Some ofthe glove boxes were transferredfrom TA-21 after several yearsof use and then installed intoTA-55. With the changingmissions and modes of operationat TA-55, the present facility isnot adequate for present priori-ties, which include processdevelopment and demonstrationfor Complex 21, development ofnew methods for pyrochemicalseparations, basic chemistryinvestigations of current pro-cesses, and development ofdiagnostic techniques for moltensalt systems. We are designing aversatile process facility that willadequately test chemistry,equipment, and processingtechniques for pyrochemicalprocesses and that will incorpo-rate automation testing facilitieswithin the facility.

The design and reconfigura-tion will be done by stages. First,we will specify general glove boxconditions for atmosphere, work-station size, material transportsystems, utility needs, and esti-mated floor-space usage. Theresultant design will be a modu-lar glove box system. This modu-lar concept will allow enoughversatility to continually changethe configuration of the layout(removing and replacing gloveboxes) to meet the needs ofprojects and demonstration goals.We are beginning the conceptualdesign of the project. Design,fabrication, and installation willtake several years to complete.

Facility integration is closelytied to process chemistry integra-tion efforts. Pyrochernical pro-cessing has always had the goalof becoming a stand-alone opera-tion that would treat all of itsresidues and recycle its reagentsto reduce dependence on theaqueous recovery processes.

82 Nuclear MatwialsTcchnology DivMon Annual Revkw

“PINACL will include design features minimizingspace requirements, personnel exposure, and wastegeneration while maximizing personnel efficiency, materialthroughput, process reliability, safeguards and security,and safety.”

Historical pyrochemical opera-tions used different salt systemsand process chemistries for eachindividual process. Currently,we are perfecting a common saltsystem that will tie all thepyrocemical operations togetherinto an integrated system.Studies for several years haveshown that calcium chloride canbe used in the molten salt extrac-tion (MSE) process and, in theelectrorefining (ER) process.The major pyrochemical saltuser has been calcium chloridein direct oxide reduction (DOR).This process has been improvedand now is the present multiplecycle direct-oxide reduction(MCDOR) process that is a netcalcium chloride generator.Salt produced in the MCDORprocess can be used in MSE andER because each process hasbeen demonstrated using thecalcium chloride system.

Our approach is to developequipment that is compatiblewith use of the salt product fromMCDOR and to demonstrate thefeasibility and effect of this saltin the other operations. From agross chemistry standpoint,there is no difference in recycledsalt, but small impurities re-moved from the salt during thereduction step in the MCDORprocess may contribute to saltbehavior differences.

The salt from MCDOR isenriched in calcium chloridebecause initial impurities arereduced into the product metalduring the first reduction. Asthe salt is reused, some impuri-ties are introduced from corro-sion of the equipment andoccasionally the salt product iscompletely friable and does nothold a cast shape. These con-cerns must be addressed bydetermining the cause andeffect of the observed behavior.Process and product purity datawill be collected and analyzedwhen the tests are completed onthe MSE and ER processes usingsalt from the MCDOR process.

Success of the concept willdepend on the actual process ‘efficiencies and product puritiesfrom the systems. Finding amethod of shaping the regener-ated salt is also a topic that willbe addressed. The feed salt tothe ER process is presently a castcylinder that is smaller than theMCDOR crucible. Methods forcasting the salt after regenerationor a method for loose-salt-loading into the ER cell will bedeveloped. In the interim, saltwill be loaded as pieces into anER cell and melted. Additionalsalt will then be added to themolten salt.

Chemistry-based concepts arealso being combined with equip-ment-based integration schemes.In addition, process systems canand will be combined in futuredevelopment efforts. A recentexample of this concept has beenthe new initiative to combineseparate Complex 21 processesinto one operation. This opera-tion will combine several differ-ing process chemistries so thatwe can take advantage of theconsecutive processing sequence.

Chloride Recovery 83

Pyrochemical Integrated Actinide chloride Line(PINACL) (continued)

The individual processing stepsare combined into a sequentialsingle-location processing flowarray that will minimize han-dling operations, waste genera-tion, and operator exposure.Automation techniques will be

applied to repetitive operationswhere feasible. The intent of thisproject is to address a pertinentComplex 21 mainline processingsequence and to develop han-dling techniques and operationalflows into a coherent whole.

84

The benefit will be to develop asystem of processes that can bedemonstrated as a module andthat can be inserted into thedesign of the Complex 21 flowsheet while using less floor andglove box space for a separateprocessing flow sequence. +

Nuclear Materials Technology Division Annual Review

w ASTE

MANAGEMENT

Waste Management Overview

by Larry R. AustinNuclearMaterialsProcessingGroup:NitrateSystems

IntroductionAll waste streams generated

in the site return, recovery, andmanufacturing areas are sent tothe waste management area.The waste management part ofthe baseline flow sheet is dividedinto two main areas. The firstwaste management area handlesthe liquid wastes, and the secondarea processes and treats solidwastes.

As a rule, processing opera-tions that would involve therecovery and recycle of usablematerials would not be a partof the waste management area.These operations would beincluded in the appropriate partof the site return, recovery, ormanufacturing areas. Wastemanagement is one of the morecritical areas: All materialsprocessed in this area mustcomply with all DOE, state, andfederal treatment, storage, anddisposal regulations.

In addition, discharges from thisfacility must meet the federalClean Air and Water Act, andsolid waste shipped off site mustmeet transportation and WasteIsolation Pilot Plant Wasteacceptance criteria.Flow sheet Considerations

The waste management partof the flow sheet has been one ofthe more difficult parts todevelop for several reasons.

1. The development of theflow sheet depends, to someextent, on the amount and typeof material that is being sent tothe waste management area.The feed streams to the wastemanagement location are thedischarges from the manufactur-ing, site return, and recoveryareas. Thus, the flow sheet forthese sites must be sufficientlydeveloped to define dischargesso that the technical details of thedevelopment programs in thewaste management flow sheetcan be addr%sed.

2. The waste managementlocation has several steps whereeacceptable technologies, havebeen shown to be “productionready” but do not exist today.

3. The waste managementlocation has numerous operatingsteps as shown by the number ofboxes on the flow sheet.

4. Within the DOE complex,fewer technology developmentprograms are aimed at solvingsome of these difficult problems.

On the positive side, for mostof the waste management flowsheet, the operations are rela-tively straightforward, and thedevelopment programs areunder way.

Waste Management 85

Waste Management Overview (continued)

Critical Flow Sheet ConcernsOn the baseline flow sheet,

the areas of critical technologicalconcern for waste managementare the destruction of wasteorganics and the immobilizationof residues and liquids forshipment to WIPP. The tech-nology of choice for destroyingwaste organics is controlled airincineration (CAI). The majorreason for the technical uncer-tainty is concern over the abilityof sites to obtain licensing andpermits for CAI. Several sitesare planning to obtain licensesand permits to perform CAI, butif these efforts are unsuccessful,the Complex 21 facility wouldnot be able to operate.

There are numerous alterna-tives and backups for CAI, butone of the problems is that noneof the alternatives would replaceCAI dh-ectly. For example,existing methods for destroyinghazardous liquid organics wouldnot perform very well on solidorganic waste. Therefore, tech-nology development for destroy-ing organic waste is made moredifficult.

The second major concern isimmobilization or fixation. Thebaseline technology for fixationis cementation. This process isvery sensitive to the compositionof the material to be immobi-lized. If the cement sets toorapidIy, the cement can easiIydewater after a few months.

Also, radiolysis might generatehydrogen gas that can push freeliquid from the cement matrixand rew.dtin surface water.Of the several alternatives tocementation, none are now“production ready.”

Four technical areas will behighlighted with feature articlesunder the waste managementsection. These are super criticaIwater oxidation, waste streammonitoring, and waste streampolishing (removal of heavymetals). +

86 Nuclear Materials Techn&gy Division Annual Review

WASTE

MANAGEMENT

Destruction of Hazardous Wastes by SupercriticalWater Oxidation

by Steven J. BuelowPhotochemistryandPhotophysicsGroup

IntroductionSupercritical water oxidation

(SCW()) is a relatively 10w-temperature process that de-stroys a wide variety of hazard-ous chemical wastes effectivelyand efficiently. It is applicableto the destruction of most or-ganic compounds and someinorganic and therefore couldbe used to destroy toxic organicwaste and to treat contaminatedwater, soil, and sludges. ASCWO system can treat aqueousstreams containing organics inrelatively low concentrations(dO%) and offers completecontrol over emissions, thusmeeting the EnvironmentalProtection Agency’s conceptof a “totally enclosed treatment”facility.

In SCWO, the waste is mixedwith an oxidant (oxygen, air, orhydrogen peroxide) in water atpressures and temperaturesabove the critical point of water(374°C and 218 atm).

Under these conditions,water is a fluid with densitieshigh enough for reasonableprocess throughput to beachieved, but its transportproperties are like those of agas, allowing rapid chemicalreaction.

Supercritical water is aunique solvent medium inwhich oxidation can take placeat temperatures lower thanthose of incineration, limitingthe production of unspecifiednitrogen oxides and char. Thereaction is carried out entirelyin an enclosed pressure vesselcontaining dilute reactants, sothat the heat of reaction is ab-sorbed by the solvent and thetemperature can be maintainedat any desired level, typically inthe range of 400”C to 650”C.Rapid oxidation occurs withinseconds or minutes and pro-duces simple products (ideally,carbon dioxide, water, andnitrogen).

In principle, any organiccompound—that is, any com-pound composed of carbon andother elements such as hydro-gen, nitrogen, phosphorus,sulfur, and the halogens— canbe completely oxidized to rela-tively innocuous products.Because water is the reactionmedium, the process can be usedfor a variety of organic wastescontaining water or for watercontaminated with organiccompounds. The optimumconcentration of organic com-pound in water depends on theheats of oxidation of the particu-lar organic compounds presentand the engineering design ofthe apparatus. An engineeringtradeoff to be considered in thedesign of a plant is the organicconcentration that generatesenough heat to maintain thereaction but not more heat thancan readily be removed from theprocessing vessel.

Waste Management 87

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

Pure or highly concentratedorganic wastes can be dilutedwith water. Conversely, fuel orother organic wastes can beadded to contaminated water.Other factors that influence theengineering design include theresidence time in the reactor(determined by the chemicalkinetics of oxidation of thewaste), the physicaI state of thewaste and its oxidation products,and the amounts of waste to beprocessed.

Our current research at LosAlamos National Laboratoryaims to determine the advan-tages or problems with usingSCWO to treat high-risk wastes.Such wastes include explosives,propellants, and the complexmixed wastes found in theunderground storage tanks atHanford, Washington.

This work evaluates reactordesign, determines destructionefficiencies and products ofdestruction, and models chemi-cal and physical processes insupercritical water. Some of ourresults concerning reactor opera-tion for several waste streams, inparticular, mixing of organicwastes and oxidizers, destruc-tion of explosives, and treatmentof Hanford waste simulants aresummarized here.

Reactor Design and OperationA general schematic for an

SCWO reactor is shown in Fig. 1.The waste, oxidant, and fuel(if needed) are compressed,preheated, mixed, and injectedinto the reactor, which ideallyconverts the waste to water,carbon dioxide, nitrogen, salts,and insoluble solids. The reactortemperatures and pressures aretypically 400”C to 650”C and 250to 350 atm. The solid, liquid,and gaseous effluents are sepa-rated, depressurized, and ifneeded, post-processed.

AIl effluents can be containedand collected so that they canbe tested before release to theenvironment; unreacted oxygencan be segregated and recycled,and energy can be recovered andused to heat incoming waste.

A number of different reactordesigns have been proposed andput into practice, including bothvessel and tubular reactors.A great range of sizes appearsto be possible for SCWO plants.Standard pressure-vessel tech-nology can be used to provideboth small mobile units andpermanent medium-sizedsurface installations for process-ing of laboratory or manufactur-ing wastes. Plants with verylarge capacities have also beenproposed. These plants consistof a cylindrical heat exchangerand reaction vessel emplaced inthe ground by using oil-fielddrilling technology.

88 Nuclear MateAals Technology Divlslon #mmJa) Review

Fig. 1. SimplijSedschematic of supercritical water oxidation unit.

- Power Water Cooling

supply

Waste/Water Reactor

400-650”C250-350 atm.

Heat Exchanger

Solids

aPreheater Separator I

L

Accumulator

r

H20

Pump

To date, our experimentshave examined tubular reactors.Our largest SCWO unit has acapacity of 50 gal./day, istransportable, and operates byremote control by computer.’All important operating param-eters, such as temperature,pressure, and flow rate, arecontinuously monitored andrecorded. The unit is modularso that reactors of variousdesigns can be easily inter-changed. Fig. 2 shows thetemperature distribution alonga 55-ft-long tubular reactormeasured during a test usingacetone as a surrogate waste.

ERemoteComputer

Control

Temperatures are measuredusing thermocouples attachedto the outside of the reactortubing. For the test shown inFig. 2, the acetone/water andoxygen/water feed streamswere mixed and then heated tothe desired temperature bydirect, electrical-resistanceheating of the first 20 ft of thereactor; heaters on the last 35 ftof the reactor helped to balanceconductive heat losses.

7GasLiquid

Separator

?

The total flow was 1 gaL/h at273 atm. The acetone concentra-tion after mixing was 2 wt’YO,and oxygen was present at twicethe stoichiometric concentrationneeded to convert the acetone tocarbon dioxide and water. At adistance of 10 ft, a temperatureplateau occurred (Fig. 2) becauseof the behavior of water near thecritical temperature. In thistemperature range, the heatcapacity of water is relativelylarge, and the temperature risedecreases with constant heating.

Waste Management 89

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

800i

o 10 20 30 40 50Axial Distance(ft)

At a distance of about 15 to 20 ft(450”C to 700”C) the reaction rateof acetone with oxygen in-creased, and the temperaturerose more rapidly because of theenergy release from the oxida-tion reaction. The lack of furthertemperature increase after 20 ftindicates that most of the oxida-tion reaction was complete andthat the temperature slowlydecreased from the heat lossthrough the reactor insulation.Because the reactor was notcooled, the maximum tempera-ture is determined by the heatcontent of the waste and the heatcapacity of the fluid. A heatexchanger at the end of thereactor rapidly cooled the efflu-ent to ambient temperature.

Analysis of the aqueous effluentyielded a destruction efficiencyfor acetone of 99.99985% underthese conditions.

Mixing the waste and oxygenbefore heating the fluid is conve-nient and allows the oxidationreactions to begin at lowertemperatures (which may dimin-ish pyrolysis reactions). How-ever, it is not safe to do so for allwastes. Similar tests using 2’%0hexane solutions produceddetonations in the first severalfeet of the reactor and in a roomtemperature filter located up-stream of the reactor.

Fig. 2. Renctor-tube te)nperuturcasa function of distance from the reactorinlet under steady-state eonditious.The total flo7uwas1 gaL/h at 273 afn;.The ncefone concentmfion nfter nlixitlgwas 2 zut%,and oxygen wns present atfu)jce the stojchio~jlefricconcentrationneeded to convert the ncetone to carbondioxide wzdwater.

Hexane, oxygen, and water arenot miscible at low temperaturesand in the subcritical portion ofthe reactor, they remain sepa-rated into three phases, produc-ing an explosive mixture. Thisproblem does not occur whenthe waste/water and oxidizer/water streams are heated abovethe critical temperature beforebeing mixed.

Figures 3 and 4 show thetemperature distributions alonga reactor with separate preheatersections for the waste and oxi-dant under steady- state condi-tions. The preheater are 12 and13 ft Iong for the feed streams,and are heated by direct electri-cal resistance. Oxidation occursin a 6-ft insulated tube followingthe mixing region.

90 Nuclear Materials Technology Division Annual Review

700

1

Fig. 3. Reactor-tube temperatures as a

600@CfiOn ofdisfance from the oxygenpreheater tube inlet. The totalfi’owwas

~ 500 Mixed lgal./h at 248 atm. The acetone concen-0-

-Jfration after mixing was 3 wt’%,and

P 4003 ,-S---------------------:-:-.-*. oxygenwas present at twice the@ Hexane - -z--—

,/’ . H %—- - .stoichiometricconcentrationneeded to8 300F .,~’O,xygen convert the acetone to carbon dioxide

~

/’ -s~(jo ;’ ,)t’ /

100 ,’” /’,’ /

7001

~ 5000

_] —. ,-,---<,/g 400 +

--—.Ar-ntnnn ---------

------- ,./

‘i,---.“” .”,,”

$---,8 -------

g 300 ,/’g

Oxy~en,,’ , /

+ 200

1

,,/’,/’ /

100 /“ ,’,,’

o//I I I I I I I I 1 I 10 2 4 6 8 10 12 14 16 18 20

AxialDistance(R)

For tests using acetone (Fig. 3),we heated the acetone andoxygen feed lines above 450”Cbefore mixing in order to initiatea rapid oxidation reaction. Theheat of reaction released aftermixing increased the fluidtemperature from 450”C to650”C within 12 in. of the mixerand produced rapid and com-plete destruction of the acetone.

At mixing temperatures below450”C, a temperature increaseafter mixing did not occur andacetonewas not effectivelydestroyed. The hexane oxidationrate was noticably faster. Forhexane, the temperature reacheda maximum only 4 in. after themixer.

Thus far, we have not testeda wide range of organic wastes

and water.

Fig. 4. Reactor-tube temperaturesas afunction of distance from the oxygenpreheater tube inlet. Thetotalftowwas1.1 gal./h at 253atm. The acetoneconcentration aftermixingwas2,5wt%, and oxygen was present at 1.5times the stoichiometricconcentrationneeded to convert the hexane to carbondioxide and water,

to determine which materialscan be safely mixed in the sub-critical region. However, wesuspect this may be a problemonly for volatile, water-insoluble,flammable organics such ashexane. Furthermore, the prob-lem may not occur when air isused as the oxidant because apure oxygen phase will not bepresent in the subcritical region.

Waste Management 91

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

TabIe I. Results for the SCWO Explosive

PETN RDX TNT NQInitial cone. (ppm) 3.8 2.6 35.2 65.5 1700.Destruction efficiencies >0.9825 >0.99 >0.9992 >0.9998 >0.9999NO~a 0.187 0.124 0.101 0.366 0.0003NO: 0.060 0.053 0.141 0.285 0.0004

aGiven as fraction of initial nitrogen.

Destruction of ExplosivesThe traditional disposal

methods for explosives are open-air burning and open detonation.Regulatory agencies, however,are likely to prohibit thesemethods because of the associ-ated uncontrolled air emissions,in particular the huge quantitiesof unspecified nitrogen oxidesthat are commonly formed. Inaddition to conventional formsof explosives wastes, soils andgroundwater at manufacturingplants and military bases havebeen contaminated with explo-sives from normal operatingprocedures. Incineration withthe associated air pollution maybe used for decontamination ofsuch soils, but few satisfactoryand economic methods exist fordecontamination of groundwater.

92

We have investigated thefeasibility of oxidation insupercritical water as an alterna-tive method for the destructionof explosives and propellants.2In Table I, the destruction effi-ciencies for five explosive com-pounds—pentaerythritoltetranitrate (PETN),cyclotetramethylenetetranitrarnine (HMX),cyclotrimethylene trinitramine(RDX), trinitrotoluene (TNT),and nitroguanidine (NQ) insupercritical water—are givenalong with the fraction of theinitial nitrogen converted tonitrate and nitrite in theaqueous effluent. The initialconcentrations of the explosiveswere kept Iow, less than halftheir room-temperature solubili-ties, to prevent precipitation andaccumulation of explosive mate-

used as the oxidizer and wasmixed with the feedstockcontaining explosive before thefluids were heated, In all cases,the oxidizer was in excess ofthat needed to convert theexplosive to carbon dioxide,water, and nitrogen. Typicalexperimental conditions werepressures near 340 atm, reactortemperatures near 600”C, andresidence times near 7s. For allof the explosives investigated,the aqueous effluents did notcontain detectable amounts ofexplosives. The measureddestruction efficiencies wereIimited by the sensitivity of theanalysis method (50 ppb) andthe low initial concentration ofthe explosives, Carbon dioxideand nitrous oxide were identi-fied in the gaseous effluentsusing Fourier transform infra-

rial in the feed line; leading to the red s-pectroscopywith areactor. Hydrogen peroxide was mult~passwhi~~ceil.

NuclearMatwialsTechnolo~Divis[onAnnualIklcw

Fig. 5. Reacfion of TATB in water. The pressure rise because of the heating of

Carbon monoxide, methane,nitric oxide, and nitrogen diox-ide were not observed. Weestimate detection limits forthese species as a fraction ofstarting weight to be 0.1 forPETN and HMX to 0.005 for NQ.It is interesting to note the widevariation in the fraction of initialnitrogen that is converted tonitrate and nitrite ions. For TNT,the amount of nitrogen con-verted to nitrates and nitrite isover 60’%0,whereasfor NQ it isless than 0.1%. The amount ofnitrate and nitrite produced alsovaries with reactor temperatureand oxidizer concentration. Thischemistry is being investigatedfurther in order to minimizenitrate and nitrite production.

Destroying explosives usingSCWO at concentrations at orbelow the volubility limits is notpractical except for the treatmentof contaminated ground water.In order to increase the through-put of the destruction process forbulk explosives, other methodsfor introducing the explosivesinto the supercritical waterreactor are being developed.We are currently investigatingtwo alternatives.

WasieMamgment

fhj water has been subfracfed.

80

60

40

20

0

260 280 300 320 340

Temperature (oC)

The first approach usesslurries to continuously feedhigh concentrations of explosivesinto a supercritical water reactor.To evaluate the hazards associ-ated with heating slurries abovethe critical temperature, we areexamining the behavior of smallpzuticlesof explosives as theyare heated in water. Theseexperiments are performedusing a small batch reactor(200pi). A small quantity ofexplosive is added to 100 ml ofwater, with the balance of thereactor volume filled by air.The pressure is measured at 1-sintervals as the reactor is heated.

13

To determine the pressure risecaused by the rea;tion of theexplosive, a baseline test using anequal quantity of water in theabsence of the explosive is per-formed. The difference in themeasured pressures at a particu-lar temperature for the two testsis the pressure of the gases pro-duced by the reaction of theexplosive. This pressure differ-ence gives a qualitative measureof both the extent and the rateof the reaction of the explosive.Fig. 5 shows preliminaryresults for the behavior oftriaminotrinitrobenzene(TATB) as it is heated.

93

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

For small quantities (<7 mg) ofTATB, the reaction proceedsslowly as the water is heated,producing a controlled release ofenergy. For quantities greaterthan 13 mg, the reaction starts atslightly higher temperatures butproceeds much more rapidly.In the 8-to-10-mg range, thebehavior is not reproducible andprobably depends on the mor-phology of the particle. Thesepreliminary results indicate thatthe behavior of the slurries mayvary and that the slurry particlescan react rapidly. Such uncer-tainties raise concerns aboutusing slurries to feedsupercritical water reactors.

The second method forintroducing large quantities ofexplosives into a supercriticalwater reactor involves process-ing the explosive by hydrolysisat ambient pressures and lowtemperatures (50°C to 100”C).Thus far, we have demonstratedthat NQ, HMX, and nitrocellu-Iose can be decomposed rapidlyinto water-soluble nonexplosiveproducts through hydrolysisunder basic conditions.

We then processed the productsof the hydrolysis through asupercritical water reactor,producing carbon dioxide,water, nitrous oxide, and nitro-gen. For HMX and NQ solutionswith starting concentrationsbetween 1 and 8 wt%, this two-step treatment produced over99.99970destruction of theexplosive and less than 1 ppmtotal organic carbon (TOC) in theliquid effluent. We are examin-ing the possible problems, suchas self-heating, associated withhydrolyzing large pieces ofexplosives. Thus far, none havebeen encountered.

Treatment of Hanford WasteSimulants

Storage tanks at the Hanfordreservation in Washingtoncontain millions of gallons ofmixed wastes composed ofhighly concentrated solubleinorganic compounds andorganic components.

SCWO has been identified asan attractive method ofnonselectively destroying theorganic components of thecomplexant concentrate wastebefore that waste is fed into theGrout Treatment Facility or theHanford Waste VitrificationPlant Feed.

Although SCWO has beenproved efficient for the removalof organic matter, the ability totreat highly concentrated inor-ganic waste streams has not beenfully demonstrated? In the caseof the Hanford tank wastes,thermodynamic calculationsshow that the nitrate alreadypresent in the wastes can serveas an oxidant for organics andother oxidizable compoundssuch as ferrocyanides. Prelimi-nary experiments indicate thatnitrate may be an acceptableoxidant for other components ofthe waste.

94 Nuclear Materials Technulcgy Division Anntul Revkw

checkFig. 6. Schemafic of SCWO reactor

valvewith salt separator.

relief valveFeed Heated ReactorPump 1/4” OD,

0.083” wall2 ft. long

alloy C276.

Collection

HeatedSalt-Separator filter, 140 p48 CC wire mesh

316L SS 150 cccooling Surge Vessel/water

1

SampleReservoir

. .

Reactor*DumpCollection

To explore the feasibilityof SCWO treatment of theHanford tank wastes, a simu-lant was prepared and treated.The constituents of thesimulant (Table II) are mainlysodium nitrate (5 wt%), withsome organic matter (sodiumacetate and EDTA), othersodium salts (chloride, sulfate,and bicarbonate), heavy metals(chromium and nickel), alumi-num nitrate, and nuclides ofconcern (cesium andstrontium).

A schematic of the apparatusused for this experiment isshown in Fig. 6. The heatedportion of the reactor consistsof a short linear tube that flowsinto a heated salt separator.The reactor is mounted verti-cally so that precipitating solidswill settle into the separator.The mass flow rate was 7 g/rein, producing a 51-s residencetime in the reactor. The forma-tion and breakdown of plugsduring the experiment pro-duced some temperature andpressure fluctuations at about508°C and 286 atm.

During the experiment, theeffluent was collected andmeasured for volume and pH.At the end of the experiment,the reactor tube was drained intothe salt separator. The separatorwas then cooled and the contentscollected. The system waswashed with water, followedby a 1.0 N sulfuric acid solution.Finally, solids were filtered fromthe rinse solutions, dried, andweighed.

Waste Management 95

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

Table II. Results of HanfordWaste Simulant Processing

Experiment/Constituent

Volume (L)pHCsNaSrAlCrFe

N@N’

N:!Acetate

TOCTIC

Feed Effluent Brine Rinse Rinse SolidsWater Acid

mg/1 mg/1 mgll mgll mg/1 l-w---- 0.347 0.023 0.202 0.206 ----7.0 6.3- 6.4 12.4 10.0 ---- ----

5.5 0.2 41.6 0.7 0.3 BDL19100 71-72 254000 2360 473 BDL

6.0 BDL 1.10 1.90 0.60 1240463 0.2 1800 20.8 20.4 2460012.9 0.55-0.64 340 21 5.3 14.5BDL BDL BDL 0.9 12.5 133012.8 BDL BDL 6.20 5.70 193

37420 156-167 491000 3990 806 ----

681 8.5 11300 85.7 ---- ----

BDL 46-59 38600 382 ---- ----

2220 1-3 100 211 ---- ----

4300 1-7 23 157 50 ----

4 75-127 0.1 203 0.1 ----

The results from processingthe Hanford waste simulant aregiven in Table II. The content ofthe sodium, nitrate, and organicmatter in the effluent wasreduced by over 99.5Y0 from thefeed. Strontium concentrationsin the effluent were belowdetection limits whereas thecesium concentration wasreduced by over 96Y0.

The aluminum concentration This result is illustrated in Fig. 7,was reduced by 99.95’ZOand the which shows the constituentchloride concentration was distribution in the variousreduced by 98.7Y0. Most of the streams. The large fraction ofconstituents were recovered in the aluminum and strontium inthe brine. the solid phase suggests that

they formed insoluble aluminumoxide and strontium carbonate.

96 Nuclear Materials TechnologyDivision AnnualReview

Fig. 7. Partitioning of constituents for processed Hanford waste simulant.

-1.Na Cs Sr

Chloride and bicarbonate mostlikely precipitated as sodiumsalts. The majority of the so-dium and cesium likely precipi-tated as nitrates. The pH of thebrine was quite high (12.4),possibly because of the precipita-tion of sodium hydroxide andbicarbonate. The feed pH was7.0 whereas the pH of the efflu-ents varied from 6.3 to 6.4. Afterprocessing for 30 rein, plugsbegan to form in the heatedreactor tube, and the experimentwas halted after 50 min.

■ EFFLUENT❑ BRINE■ RINSE WATERH RINSE ACID❑ SOLIDS

-

Cr Ni Al

Constituent

cl N03.

Aluminum and nickel were The results presented in thisdifficult to remove by rinsing and paper show that explosives suchwere not fully recovered. as HMX, PETN, RDX, TNT, andIt is possible that oxides of these NQ can be rapidly destroyed bymetals caused the plugging. reaction in supercritical water.

The problems associated withSummary introducing large concentrations

The use of SCWO to treat of explosives into a supercriticalhazardous wastes such as organic water reactor have not yet beencompounds, explosives, and fully solved. The use of slurriesmixed wastes has been investi- may be viable, but preliminarygated. This relatively low- experiments indicate unpredict-temperature process has been able behavior.proposed as a means of destroy-ing both fuels and oxidants,with full control of effluents.

Was(e Management 97

Destruction of Hazardous Wastes by SupercriticalWater Oxidation (continued)

Preprocessing the explosivesusing hydrolysis in low-tem-perature basic solutions hasbeen demonstrated for NQ andHMX. A Hanford underground-storage tank waste simulantwas prccessed successfullyusing SCWO. At temperaturesnear 500”C, over 99.5’%oof theorganic matter, sodium, andnitrate are removed from thereactor effluent. The resultingwaste brine (nearly 1.4 kg/literof sodium nitrate) was less than3% (by volume) of the totalvolume processed.

Cesium was also efficientlyremoved (>90Yo),indicating asignificant waste reduction andthe potential of SCWO foractivity reduction of theradiocesium in mixed wastes.Tests of different reactor designsshowed that volatiIe, flammabIeorganics that are immiscible inwater can be safely processedin a supercritical water reactor.Our results for hexane oxidationdemonstrate that separatepreheating of such organicsand of the oxidant beforemixing allows for safe andefficient destruction of theorganic compound. +

References1. R. D. McFarland, G. R.Brewer, andC K. Refer, “Design and OperationalParameters of Transportable SupermiticalWater Oxidation Waste Destruction Unit,”Los Alamos National Laboratory reportLA-12216-MS(December 1991).

2. S.J. Buelow,R. B.Dyer, C. K-Refer,J. Atencio, and J. D. Wander, “Destructionof Propellant Components in SupcrcriticalWater;’ Proceedings of JANNAFSafety andEnvironmental Protection SubcommitteeWorkshop, Tyndall Air Force Base, Florida,March 27-28,1990,CPfA Publication 540,March (1991).

3. T. T. Bramlette, B.E. Mills, K.R. Hencken,M. E. Brynildson,S. C. Johnston, J. M. Hruby,H. C. Feernster, B.C. Odegard, andM. Modell, “Destruction of DOE/DPSurrogate Wastes with SuperCriticalWaterOxidation Technology;’ Sandia NationalLaboratones report SAND90-8229(1990).

98 Nuclear Materl.ds Technology Division Annual Review

WASTE

MANAGEMENT

Waste Stream Monitoring

by Rick DayNuclear Materials Processing Group: Nitrate Systems

In light of the new regula-tions and restrictions imposed onfacilities for discharge or transferof liquid waste, the ability tomonitor, ensure SNM account-ability, and characterize wastestreams is crucial. As a lead DOEfacility for the development ofspecial nuclear materials processtechnology, TA-55 has a respon-sibility to set a standard in theDOE complex for effluent moni-toring and control for environ-mental protection. Waste solu-tions generated from plutoniumprocessing need to be character-ized. Flow rates need to bemonitored to ensure regulatorycomliance and to confirm that aminimum amount of waste isgenerated. We also need to verifythe extent of waste reductionachieved through process opti-mization initiatives.

A Waste Stream MonitoringProgram has been initiatedusing experts from NMT-2,NMT-3, NMT-7, NMT-8, andCLS-1 to address the technicalchallenges. The pro~am’semphasis is on

1. determining the volumesof liquid waste generated atTA-55/PF-4 in a given timeperiod;

2. identifying suitable sam-pling techniques for representa-tive sampling, accurate flowmeasurements, temperatures,and so forth;

3. characterizing the compo-sition of the various liquid wastestreams; and

4. applying the appropriateinstrumentation to allow TA-55to properly respond to wastemonitoring requirements bothnow and in the future.

Characterization of the liquidwaste streams (acid, caustic, andindustrial) that leave TA-55 isbeing performed by CLS-1.

The analyses being per-formed include

1. radiochemistry,2. trace elements using induc-

tively coupled plasma-emissionspectrometer (ICP-ES) andinductively coupled plasma-mass spectrometry (ICP-MS),

3. ion chromatography todetermine anions, and

4. chemical oxygen demand(COD). When instrumentationbecomes available, total organiccarbon will replace COD. All theresults are entered into a spread-sheet for tracking purposes.

Waste Management 99

Waste Stream Monitoring (continued)

Thirteen flow meters are inplace at various locationsthroughout the basement ofPF-4 to monitor the solutionflows generated by the variousprocesses. To track total gammaactivity, sodium iodide gammadetectors have been placed atvarious locations on the processpiping in the PF-4 basement. Tohandle the unscheduled flowinto the industrial waste line thatgoes to the waste-handlingfacility at TA-50, a surge tankwas installed in the basementimmediately preceding thepoint where this line leaves thefacility.

To monitor the variousoutputs of the waste streamsystem, an industrial PC-basedcontrol system has been installedwith access in the operationscenter. Four data concentratorscapable of accepting 32 inputchannels and providing up to8 output channels are routedthrough single communicationcables to the operation center.

TA-55 is implementingappropriate instrumentationand methods to ensure bettermonitoring of waste streams.

An inductively coupled ICP-MSwill be acquired to complementthe ICP-ES currently on site toaid in the monitoring of thewaste streams. The processcontrol is upgraded continuallyto ensure monitoring of newlocations and instrumentation asthey are added. New levelsensors will be installed on thesurge tank to provide moreaccurate measurements. Thisproactive approach to wastemanagement will demonstrateour commitment to minimizingthe environmental impact of ouroperations while optimizingplutonium recovery. +

100 Nuclear Materials Technology Division Annual Redew

WASTE

MANAGEMENT

Waste Treatment: Chelating Polymers forRemoval of Heavy Metals from Aqueous WasteStreams

by Gordon D. JarvinenNuclear Materials Processing Group: Nitrate Systems

A]temativetec~olo~es areurgently needed for the treat-ment of waste waters to reducethe concentration of contaminat-ing metal ions to meet increas-ingly stringent regulatory limitsand to decrease waste disposalcosts. We are developing aseries of polymer-supported,ion-specific extraction systemsfor removing actinides and otherhazardous metal ions from wastewater streams. Our work focusesprimarily on metal contaminants(especially plutonium andamericium) in waste streamsfrom TA-55, at the Waste Treat-ment Facility at TA-50, and at theRocky Flats Plant. We are testingligands to identify the com-pounds having the requiredselectivity and binding constantsto remove the target metal ionsfrom the waste streams. Selectedligands are then incorporatedinto poly-meric structures thatwill allow ready separation ofthe target metal ions from thewaste water stream.

The separation properties of the The exploratory work donepolymer-supported ligands are by our R&D team has demon-being evaluated to allow a strated the effectiveness of thiscomplete engineering assess- approach to cleaning up wastement of these polymer systems waters. Collaborators in thisin combination with complemen- work include the Los Alamostary technologiesand to compare them withcompeting technologies.

These new polymer materi-als can provide a cost-effectivereplacement for sludge-inten-sive precipitation treatmentsand yield effluents that meetmore stringent discharge re-quirements. At Los Alamos, weare striving for a 95’70reductionof low-level sludge volume anda 50?10reduction in transuranic(TRU) sludge volume at TA-50.These systems could also beapplied at Rocky Flats, Hanfordand other DOE facilities.

Laboratory groups INC-1,CLS-1,MST-7, and EM-7; Reilly Indus-tries; the University of NewMexico; Texas Tech University;New Mexico State University;and the University of Tennessee.

Removal of metal ions fromaqueous solution is a majorindustrial activity that includesprocesses such as water soften-ing, hydrometallurgical recoveryfrom ores, and detoxification ofwaste waters and contaminatednatural waters. The concept ofattaching metal-ion-specificligands to polymers is an impor-tant approach to solving suchproblems and has receivedconsiderable attention over thepast 20 years. Separationsinvolving transition metals havedominated the work in this area.

Waste Management 101

Waste Treatment: Chelating Polymers forRemoval of Heavy Metals from Aqueous WasteStreams (continued)

Relatively little work hasbeen done for the actinides andlanthanides, with the exceptionof a rather large body of workdealing with the use of chelatingpolymers to recover uraniumfrom seawater. Chelating poly-mers are the basis of a number ofsuccessful industrial separationsincluding removing calcium topart-per-billion levels from brineand removing radioactive ce-sium from alkaIine waste waters.

Reducing the concentrationof a target metal ion to thedesired level will require thatthe chelating polymer have abinding strength that is highenough to accomplish the de-sired separation. However, inthe presence of other cations, theligand wilI require a largeselectivity if the target metal ionis to overcome the competitionfrom these other cations for theIigand binding sites.

In many of the waste streams tobe addressed, the target metalion is present in very low con-centration compared with metalssuch as sodium, potassium,calcium, magnesium, and iron.

Polyhydroxamate ChelatorsWe have evaluated several

polyhydroxamate chelators fortheir ability to bind thoriumand have obtained preliminaryrewdts with plutonium.Some results for thoriumare shown in Fig. 1.Desferrioxamine-B (DFB)is a naturally occurringchelator that is commerciallyavailable, and OZ-118 is anew synthetic chelator pre-pared by Prof. A. Gopalan,our collaborator at New MexicoState University.

The pM value is defined aslog[Th], where [Th] is theamount of free thorium remain-ing in solution at any given pHstarting with equal quantities ofmetal and chelator (both insolution). In this case we aretreating 1 ppb, a typical pluto-nium concentration in theTA-50 waste-stream influent.The figure ih.strates the poten-tial of these chelators, at near-neutral pH and above, forreducing the amount of pluto-nium in low-level waste streamsto levels well below 2pCi/literfor plutonium 235. The value of2pCi/liter has appeared in atleast one EPA proposal as alimit for aIpha-emitting isotopesin drinking water. Thesecalculations indicate that uponattachment of these chelators tosolid supports, it should bepossible to reduce the amountof plutonium to extremely lowlevels.

102 Nuclear Materials Techndow Division Annual Retlcw

18

16

#4

12

10

OZ-118—

H

30 pCi/L limitfor Pu

2 4 6 8 10 12

pH

Polyhydroxamate chelatorssuch as those illustrated aboveare selective for highly chargedmetal ions such as plutoniumand americium(III). Therefore,they are not likely to bind metalssuch as magnesium, calcium, orsodium even in the presence oflarge excesses of these metals, asis often the case in waste processstreams. However, they wouldnormally be expected to bindiron(III) as well as or better thanplutonium.

Iron is typically found in wastewaters at part-per-million levels,which may be enough to saturatethe polymeric chelating resinwith iron. This behavior mightbe expected for the chelator DFB,which has evolved in microbialsystems to bind iron(III) in theenvironment. However, thetetrahydroxamate chelators havebeen designed to be selective forplutonium over iron(HI).

Fig. 1. Calculafionsfor amount ofuncompleted thorium in the presence ofpolyhydroxamate chelatorsindicatethatthorium and plutonium can be reducedto very low kvels.

Gopalan’s group has also syn-thesized the compound 02-184,which has a rneta-xylenebridgein place of the propylene bridgeof 02-118. The thonum(~)-andiron(III)-binding constants of thiscompound have been measuredand show that this compoundindeed binds thonum(IV) 3.5orders of magnitude morestrongly than iron(III). Weexpect plutonium to bindeven more strongly to 02-184than thorium; therefore,02-184 should have even largerselectivity for plutonium (IV)over iron (III).

Waste Management 103

Waste Treatment: Chelating Polymers forRemoval of Heavy Metals from Aqueous WasteStreams (continued)

Bis(acylpyrazolones) with High The extraction system was also We have attached some of theseSelectivity for Tetravalent highly selective for plutonium compounds to poIymers such asActinides over thorium. The high polybenzimidazole through the

The l,3-diketones have been selectivity for tetravalent R“ group on the methyleneextensively studied as extractants actinides over iron(III) results carbon. The extraction propertiesfor actinide and lanthanide ions. from the very slow kinetics of of these chelating polymers isThe linking of multiple 1,3- iron extraction. The selectivity under investigation.diketone units to give compounds of these compounds has potential. A

with increased bi~ding constantsA

uses in novel sensors and separa- SYnthetic Methods for Prepara-for divalent metal ions, uranium(VI), and some Ianthanide ionshas been reported. However,data on metal complexation forsuch compounds are ratherlimited. In a systematic studyseeking to enhance actinide ionbinding by preorganization, wehave synthesized a series ofacylpyrazolone ligands linkedwith four to eight methyleneunits (see Fig. 2) and haveinvestigated their complexationchemistry.

A large increase in selectivity(>103)for plutonium andthorium over uranium,americium(III), europium(III),iron(III), and aluminum(III) wasfound relative to closely relatedbidentate compounds.

tions, and a patent applicati~n t~onof Chelating Polymershas been filed. The major synthetic methods

Because these systems have used in the preparation of chelat-demonstrated an enhanced ing polymers areselectivity and high binding 1. polymerization ofconstants for tetravalent actinides, functionalized monomers,they will be evaluated for 2. polymerization ofremoving plutonium from nonfunctionalizedthe waste streams. At pH >2, monomers followed by

they will also be evaluated for chemical modification,removing americium(lTI). 3. graft polymerization of a

functionalized monomerMalonamides on a prepared polymer,

A liquid-liquid extraction andprocess proposed by French 4. physical entrapment ofworkers for removing trivalent hydrophobic chelatingactinides from PUREX waste extractants during polystreams based on malonamides, merization orRR’NC(0) CH(R’’)C(O)NRR’, postpolymerization.has potential advantages overthe TRUEX process.

104 NucIcar Materials Technology Division Annual Revkw

Fig.2. Bis(acylpyrazolones) have a highselectivityfortetravalentactinicles.

We have used all of these routesin our exploratory studies. Mostof our polymer extractants willbe prepared by attachment ofligands to a prepared polymer,such as polybenzimidazole.However, we feel the graftpolymerization route will yieldchelating polymers with somegreatly improved properties.These materials will bediscussed in more detail below.

Advanced Chelating PolymersWe have an approach that

will advance chelating polymersbeyond current technology.Chelating polymers are cross-Iinked, insoluble, porouspolymer beads with functionalchelating groups. They havehigh surface areas and exchangecapacities that range from lessthan 0.1 to about 10 meq/g.

‘hw’-w,.Our approach is to improve theperformance of the polymerbeads by designing several newfeatures into the polymer struc-ture. The surface area will beincreased by graft polymeriza-tion of chelating groups onto thesurface. This arrangement differsfrom that of standard chelatingpolymers in that a long chain ofchelating groups will extendaway from the surface ratherthan be fixed into the rigidinterior of the resin.

The flexibility of the longchains will have several benefitsover fixed sites. Frequently twoor more chelating sites arerequired to bind a metal. In rigidpolymers, many sites may beunable to chelate because nearbyIigands are not oriented properlyto allow chelation and manysites are unavailable. Long,flexible chains of Iigands willmake many more sites available.

Copolymerization with othermonomers can incorporate otherfeatures. Hydrophilic groupscan be incorporated into thegrafted chains so they willextend freely into the aqueousmedium. The kinetics of bindingwill be enhanced by these chains,which are essentially watersoluble but bound to a polymerbase. Other factors can bedesigned into the graft polymersuch as spacer groups to opti-mize chelation.

The ultimate in selectivity ofcomplexation can be achieved byuse of a ligand preorganized fora specific metal ion at eachfunctionalized site in the graftedpolymer chain. For example,this ligand could be one of thetetrahydroxamates discussedover or a crown ether with acidicarms developed to encapsulate aparticular ion. In this case,cooperation between bindingsites located at different pointsalong the chain or on differentchains would not be required. +

Waste Management 105

106 Nuclear Materials Technology Divldon Annual Re\lew

NMT-DO

NUCLEAR MATERIALS

TECHNOLOGY DIVISION

ORGANIZATION CHART

FINANCIALMANAGEMENTCheryt~arkham

NMT DIVISIONLEADERD.R. Harbur

DEPUTYDIVISION LEADERD.C. Christensen

J wADMINISTRATIVESUPPORT

SusanWhittington

I1

TTA-55SITE-WIDETRAININGOFFICE

C.E. Blackwell APERSONNELANDES&H

COMPLIANCERitaBieri

NUCLEARFUELSTEC;[FJ;OGY

K. ChidesterGroupLeader nNUCLEARMATERIALS

PROCESSING:CHLORIDESYSTEMS

NMT-3J.D. WilliamsGroupLeader

1

PLUTONIUMMETALLURGY

NMT-5M.F. StevensGroupLeader ENUCLEARMATERIALS

MANAGEMENTNMT-7

C.L.SohnGroupLeader

INUCLEARMATERIALS NUCLEARMATERIALS

PROCE~f~W~M~lTRATE MEASUREMENT&ACCOUNTABILITY

NMT-2 NMT-4L.R.Austin R,P. Wagner

GroupLeader GroupLeader

ACTINIDEMATERIALSCHEMISTRY

NMT-6K.C. Kim

GroupLeader

HEATSOURCETECHNOLOGY

NMT-9R,W. ZocherGroupLeader

TA-55 FACILITIESMANAGEMENT

NMT-8D.J.Post

GroupLeader

1(X3 Nuclear Materials TIAUIOIOWDivision Anmml Review

NMT-DO

NUCLEAR

M ATE R IALS

TECH N O LO GY

DIVISION

Nuclear Materials Technol-ogy Division conducts scientificand technical work within thenine operating groups shown inthe organizational chart. The titleof each group indicates thegroup’s major functions or re-sponsibilities. However, mostof our groups carry out a varietyof efforts to support our nationaldefense and energy programs,and most groups conduct activeresearch programs to supporttheir main technological or pro-grammatic emphasis. Our oper-ating groups range in size fromapproximately 20 to nearly 70employees.

The NMT Division Office,along with group managers,provides technical leadership,managerial guidance, and ad-ministrative support to thedivision’s operating groups.The Division Office is also a focalpoint for nuclear materials issueswithin the Laboratory. Alongwith materials and chemistrystaff elsewhere in the Laboratory,the NMT Division Office pro-vides overall direction and lead-ership to the Laboratory’smaterials and chemistry efforts.

Group Profik

I --== \\

~, , _.,,, .—. L—l . IDivision LeaderDelbert R. Harbur

The Division Office manage-ment team works directly underthe division leader and deputydivision leader to provide pro-grammatic and administrativesupport to the division’s staffand management. One of theteam’s most important tasks is tomaintain effective communicat-ion between NMT Division andother Laboratory divisions,Laboratory program offices, andupper management. The man-agement team also works closelywith funding agencies and otherexternal organizations. The realstrength of NMT Division is ourpeople. At present, NMT Divi-sion employs approximately 500people, including part-time andtemporary employees. Morethan 87 percent of the division’semployees are staff members ortechnicians, the vast majority ofwhom are working on scientificor technical activities.

I IK

Deputy Division LeaderDa~a C. Christensen

Approximately 5 percent of ourpeople are postdoctoral appoin-tees, graduate research assis-tants, or undergraduate summerstudents. The remainder of ouremployees provide very neces-sary administrative and nontech-nical management and supportfunctions for the division.

Materials science has amultidisciplinary focus that re-quires insight and support frommany different professional dis-ciplines. Included among ourstaff are chemists, metallurgists,physicists, mathematicians, ce-rarnists, and engineers withmany specialities. Almost all ofour staff members have scientificor engineering degrees; 72 per-cent have either a Ph.D. or M.S.in their respective specialties.Our technicians also representa wide range of disciplinary in-terests, including mechanical,chemical, and materialstechnology.

109

NMT-1

NUCLEAR FUELS

TECH N O LO GY

Our group has 28 employees: 7 staffmembers, 13 technicians, 1 support per-son, 5 consultants, I graduate researchassistant, and 1 postdoctorateresearcher.

The Nuclear Fuels Technol-ogy Group, NMT-1, specializesin research, development, irra-diation testing, and fabricationof uranium- and plutonium-based ceramic fuels. Our groupbacks up the disciplines ofchemicaI synthesis, ceramicfabrication, and metallurgywith expertise in materials char-acterization, analytical chemis-try, nondestructive examination,and quality assurance. We ini-tiate high-risk/high-payoff re-search and development fornational advanced reactor pro-grams. An example is the devel-opment and fabrication ofhigh-quality pelleted uraniumnitride for the SP-1OOspacepower reactor. We develop ad-vanced fuel and cladding fabri-cation techniques, measurefundamental properties, buildfuel pins for irradiation testing,analyze performance, and dem-onstrate fabrication procedures.Our ultimate goal is to turn overdemonstrated fuel technologiesto private industry for potentialcommercial development.

Group LeaderKenneth Chidester

Our nuclear-fuels-develop-ment laboratories support awide range of R&D activities,including phase transformationsand diagrams, high-temperaturediffusion studies; fueI/liner/cladding/coolant capabilitymeasurements, kinetics of high-temperature interactions, devel-opment of novel synthesis andfabrication methods, refractoryalloy weld development, irradia-tion testing, and postirradiationanalysis of fission productsmigration, fission gas release,swelling, and thermochemicalinteractions.

Our group has four sections:Fuel Research, Fuel Develop-ment, Fuel-Pin Assembly, andMaterials Characterization.

1 Iu

Deputy Group LeaderWalter A. Stark

The Fuel Research Section studieshigh-temperature performance ofvarious fuel/cladding combina-tions. Knowledge of high-tem-perature interactions is essentialto choices of new ceramic-fuel/refractory-alloy combinations foruse at high temperatures and/orhigh burnups. We are currentlydeveloping and characterizinghigh-melting-point carbide com-pounds for nuclear propulsionreactors. Before commitmentscan be made to reactor designsthat call for various fuel types,fuel cladding combinations mustbe tested. We test ex-pile compat-ibility and in-reactor performanceon such combinations as nio-bium, rhenium, and tungstenwith uranium nitride and ura-nium carbide.

110 Nuclear Materials Technology Oivls[on Annual Review

“The Nuclear Fuels Technology Group, NMT-1, specializes inresearch, development, irradiation testing, and fabricatiorzofuranium- and plutonium-based ceramic fuels.”

Fuel-development activitiesinclude researching advancedprocesses and fabricating fuelfor terrestrial- and space-basedreactor concepts. NMT-1 hasdeveloped and supplied pelleteduranium nitride fuel for theSP-1OOspace reactor anduranium carbide for the 1iquid-metal fast breeder reactor. Weare currently developing acryochemical process to fabricatespherical fuels for space propul-sion reactors. We synthesizeoxide feedstocks to carbide ornitride powders by carbothermicreduction at up to 15 kg per week.We can fabricate up to 15 kg perweek of nitride or carbide fuelpellets or 30 kg per week of oxidefuel pellets by conventional coldpressing and sintering.

Thirty-five atmosphere-con-trolled gloveboxes, powder-preparation equipment, fourautomatic pellet presses, threelarge-capacity synthesis fur-naces, and three large-capacitysintering furnaces are availablefor production. A small-scalefabrication line is also availablefor developing novel fabricationtechniques.

Our Fuel-Pin AssemblySection develops and qualifiesrefractory alloy welds, annealscladding components, and fabri-cates fuel pins for irradiationtesting of pin-type reactor con-cepts. Up to 60 full-length fuelpins per week can be loadedwith fuel pellets, welded,cleaned, annealed, wire-wrapped, examined, and pack-aged for shipment. Fabricationtechniques include vacuum-annealing, electron-beam andgas-tungsten arc welding,profilometry, eddy currenttesting, gamma scanning,and x-radiography.

Our Materials Characteriza-tion Section examines fuel andcladding components for ad-vanced fuels and heat-sourceprograms, as well as plutoniummetal and alloy samples forweapons programs. This sectionalso provides general photo-graphic support to other NMTgroups. Capabilities includeceramography, metallography,x-ray diffraction, residual gasanalysis, surface area analysis,and image analysis. +

Group Profiles

—

111

NMT-2

NUCLEAR

MATE R IALS

P R O C E SS IN G:

NITRATE SYSTEMSNMT-2 has 73 empIoyees:22 staffmembers,1 limited-termstaffmember,37 technicians,4 supportpersonnel,1 databasemanager,6 Laboratoryassociates,1 Laboratoryconsultant,and 1postdoctoralresearcher.

The Nuclear MaterialsProcessing Group (NitrateSystems), NMT-2, developsand demonstrates processingtechnology for plutonium andother actinides by primarilyusing aqueous-based operations.Our mission has three majorcomponents; First, we supportthe Department of Energy (DOE)complex by developing new andimproved methods for pluto-nium recovery that are safe, effi-cient, and environmentallysound. Second, we demonstratenew operations on a sufficientlylarge scale to make them attrac-tive to the plutonium facilities ofthe future, thus improving fu-ture overall operational effec-tiveness and efficiency.

GroupLeaderLarryR Austin

Third, we support the LosAlamos Plutonium Facility byrecovering and purifying pluto-nium from scrap residues andproducing a pure metal that canbe used for weapons fabricationdevelopment activities. The ma-jor goals of these efforts are toimprove process safety and effi-ciency, including minimizationof all wastes leaving our facility.

We possess the facilities andexpertise to demonstrate on aproduction scale the recoveryand purification of plutoniumfrom a wide range of contami-nants and scrap matrices. Ourfeed materials also consist ofresidues generated at off-sitefacilities. Frequently, thesefacilities do not have the special-ized capabilities to handle themore exotic contaminants, andconsequently we provide thisservice for the DOE complex.

I

DeputyGroupLeaderBillJ. McKerley

Our primary process flow sheetconsists of nitric acid/hydroflu-oric acid dissolution or leachingfollowed by purification withanion exchange. The plutoniumin the concentrated ion exchangeeluate is precipitated with oxalicacid, then filtered, dried, andthermally decomposed to formplutonium oxide. The plutoniumoxide may then be converted to atetrafluoride by reaction with I-IFand reduced to metal by calciumin a high-temperature reductionfurnace.

Our group’s research, devel-opment, and demonstration ef-forts directly support all majorprocessing operations at TA-55.

112 Nuclear Matt.riak Technology Divis[on Annual Review

“The Nuclear Materials Processing Group (NitrateSystems), NMT-2, develops and demonstrates processingtechnology for plutonium and other actinides by primarilyusing aqueous-based opera tions. ”

We continue to improve ourunderstanding of the underlyingchemistry of all the processes,which enables us to improveoperations. Our process-devel-opment activities are concen-trated in four major areas:

1) process chemistry,2) process analytical chemistry,3) process monitoring and

control, and4) process engineering.

Scientists in these major areasfocus on specific projects. Forexample, a sensor for high-acidconcentrations was developedby our personnel and wasselected as one of the top 100developments of the year,earning an RD1OOaward.

In the area of waste minimi-zation, we are developing selec-tive extraction systems to reduceradionuclides in aqueous wastestreams to very low levels. In ad-dition, we are evaluating oppor-tunities to recycle many of ourreagents, such as nitric acid, toalso reduce the waste streamsleaving TA-55. All of these tech-nologies arebeing developed andtested in the Advanced TestingLine for Actinide Separations(ATLAS). This integrated pilotplant operation, housed in sixinterconnected gloveboxes,encompasses all the major unitoperations currently used forthe nitrate aqueous processingof actinide scrap. These includedissolution, anion exchange,precipitations (oxalate, peroxide,and hydroxide), calcination, andevaporation for waste treatment.

The ATLAS uses a distributedprocess-control scheme based ona PC network running a process-control software package, andanalytical support provides nearreal-time results for both the ac-tinide and impurity content ofthe various streams that are usedto optimize process efficiency.Integrating all of the majoraqueous unit operations, alongwith the process control and theanalytical support, is a first forthe industry. It will be used tooptimize process efficiency forminimizing waste generation.Progress in these areas results inpurer product, decreased wastegeneration, and lower personnelradiation exposure. These activi-ties have far-reaching potentialfor aiding modernization andenvironmental cleanup effortswithin the DOE complex and inindustry. +

Group Profiles 113

NMT-3

N U C L t ~ 1<

MATE R IA LS

P R O C E SS IN G:

CHLORIDE SYSTEMS i&zaIOurstaff

group has 52 employees:17 technical:members,30 technicians,1support

Group Leaderloel D. Williams I

person,2 postdoctoralresearchers~~d,- —.—.

DeputyGroupLeader2 Labassociates. S. MarkDinehart

For the most part, theNucIear Materials ProcessingGroup, NMT-3, (ChlorideSystems), supports the residueelimination program at theRocky Flats plant and processdevelopment and demonstrationfor Complex 21. However, wealso have an important role inthe weapons program at the Lab.

Within the group, we are de-veloping an integrated approachto chloride-based processingtechnologies. This encompassesboth the aqueous systems andthe high-temperature, moltensalt systems. New equipment,new reagents, and advancedprocess diagnostics are all beingincorporated into this integratedapproach. We have also broad-ened the emphasis of our weap-ons program support activitiesto incIude demonstration of newequipment and technologies forremoval of low levels of actin-ides from process streams.

Within the group, the scraprecovery activities center aroundthe use of hydrochloric acidmedia as the basis for processchemistry. Dissolution of scrapmatrices, including actinidemetal, results in a solution thatis processed through eithersolvent extraction or chlorideion exchange. The solution assayis the determining factor; richsoIutions go through solventextraction for purification, andlean solutions go through ionexchange. A new set of corro-sion-resistant, Kynar-linedgloveboxes have been installedto contain the solvent-extractionequipment. Development workof the new dodecane/decanol/tributyphosphate-extraction sys-tem is well underway. These sol-vent extraction glove boxes willbegin processing scrap from theTA-55 vault in late FY92. Furtherupgrades to the aqueous chlo-ride processing line include new,corrosion-resistant boxes tohouse the ion-exchange processand, eventually, a set ofgloveboxes for off-gas scrubbingand other process/facility inter-face support.

Long-range plans in thearea of aqueous recoveryinclude at-line analytical capa-bilities. One such technique,gas chromatography, is alreadybeing evaluated as support forthe solvent-extraction process.Recent changes to this processhave necessitated sampling andanalysis of the organic stream toassure proper composition. Gaschromatography, a techniqueused widely in industry, pro-vides an at-line analysis thatwill help assure optimal processperformance.

Improved diagnostic andmonitoring techniques havealso been incorporated into thepyrochemical operations. Theuse of a spectrophotorneter tomonitor chlorine in the off-gasfrom the multicycle direct-oxidereduction process is an excellentexampIe. Enhanced diagnostictechniques, such as the use of ahigh-temperature referenceelectrode in electrorefining, arealso being explored.

114 Nuclear Matcrids Technology Di\ision Amud Rmicw

“For the most part, the Nuclear Materials Processing Group,NMT-3, (Chloride Systems), supports the residue eliminationprogram at the Rocky Flats plant and process development anddemonstration for Complex 21. However, we also have an im-portant role in the weapons program at the Lab.”

Process optimization, throughimproved monitoring capabili-ties, is one of the benefits we ex-pect this work to facilitate.

Process development in thearea of pyrochemistry includesnot only equipment improve-ments but also the definition ofprocess parameters. One ex-ample is the in situ chlorinationwork in the molten-salt extrac-tion process. This uses pluto-nium trichloride as the oxidantto extract decay-product ameri-cium from plutonium metal.Rather than adding the oxidantas a separate reagent, we areevaluating the use of gaseouschlorine sparged through the

Specific goals of this work in-clude the definition of the rela-tionship between gas flow ratesand the production of the pluto-nium trichloride, and the subse-quent americium extraction.During the past 3 years, Savan-nah River person-nel performedfoundation experiments for thiswork at Los Alamos.

Finally, we are expandingthe emphasis of our direct weap-ons program support to includethe incorporation of the latestrecovery technologies for deal-ing with low levels of actinides.

This change is a natural out-growth of our efforts in theareas of waste minimizationand programmatic support ofthe WRD&T activities withinthe Lab. The recovery capabili-ties required to support theweapons program provide anexcellent test bed for demon-strating new techniques for theremoval of the very low-levelactinides present. Although wehave just implemented thischange in direction, we believethe work in this area will pointthe way to the future forComplex 21. +

molten metal to generate the plu-tonium trichloride.

Group Profiles 115

NMT-4

N U CLEARI t

M ATE R IALS IMEASURE M E NT &

ACCOUNTABILITY ;z~

Ourgrouphas35 employees:12staffmembers,21 technicians,and2 supportpersonnel.

N’uclear Materials Mea-surement and Accountability,NMT-4, is a service group thatuses nondestructive assaymethods to measure nuclearmaterials at the TA-55 Pluto-nium Facility. Our group alsohelps TA-55 comply with LosAlamos and regulatory agencypolicies regarding nuclear mate-rials accountability. Successfulaccountability of nuclear materi-als results in quality processcontrols, increased production,timely availability of nuclearmaterials, and increased safetyand safeguards.

Specifically, we provideservices in nuclear materialscontrol and accountability,nondestructive assay, andmeasurement control.

Group LeaderRaymond P. Wagner

Our nuclear materials controlactivities include coordinatingand acting as the focal point forinternal and DOE audits, origi-nating and maintaining process-accountability flow diagrams,investigating and resolving in-ventory differences, interactingwith the Laboratory’s ProgramDirector for Safeguards Assur-ance, and verifying that TA-55personnel are trained to usematerial surveillance procedures.Our group is responsible for de-termining and investigating anyshipper/receiver differences.

Nondestructive assays are es-sential to any safeguards pro-gram. They confirm and verifythe presence and stated quanti-ties of nuclear materials. We alsouse NDA measurements in isoto-pic blending operations.

DeputyGroupLeaderDennisL. Brandt

We operate two neutroncounters, five gamma-ray assaycounters, five gamma-ray isoto-pic counters, and seven calorim-eters. Our InstrumentationSection maintains and calibratesthese instruments, as well as theaccountability instruments usedin the process lines.

We are installing and operat-ing robotic and automated sys-tems to increase our throughputof assayed materials, as well asto enhance safety and security.A full-scale automated assay sys-tem (robotic calorimeter,RbobCal) is being used to assayprocess materials. An automatedlow-level solid waste handlingand measuring system is beingbuilt. +

116 Nuclear M.mmialsTechnology Civision Annual Review

NMT-5

PLUTONIUM

M ETA LLU RGY

Ourgrouphas54 employees:19staffmembers,31 technicians,2 officesup-port,2 graduateresearchassistants,”and GroupLeader2 Laboratoryassociates. MichaelF. Stevens

The plutonium MetallurgyGroup, NMT-5, is a multi-disciplinary organization en-gaged in prototype weapon pri-mary fabrication, metallurgicaland chemical properties studiesof plutonium and other actin-ides, and surveillance and stock-pile evaluation technologies insupport of Laboratory and theDepartment of Energy (DOE)weapons programs. Our groupis principally supported throughthe Laboratory’s weapons re-search, development, and testingprograms, although significant -technology support and devel-opment efforts are fundedthrough production and surveil-lance and environmental restora-tion sources from within DOE.A major new functional respon-sibility for the Plutonium Metal-lurgy Group will be to performpit evaluation studies on stock-pile return pits.

.,.

. .-

Our Fabrication Section con-structs the prototype pits that areprimarily used in Nevada TestSite research. We use moderncasting, machining, and assem-bly technology to providewar-reserve-type plutoniumcomponents in support of thishighly important Laboratoryactivity. We are constantlyupgrading and expanding ourcapabilities in fabrication, asexemplified by our installationsof advanced vacuum-inductioncasting and Nd:YAG laser-weld-ing (1-kW, pulsed) systems.Our flexibility in metal process-ing and fabrication serve as anexcellent proving ground for de-velopment of modern complex,or Complex-21, methodologies.

1 III

DeputyGroupLeaderRuebenL. Gutierrez

In addition to pit fabricationcapabilities, the fabricationsection maintains a uniquefacility for manufacturingisotope detector packages, usedin postshot diagnostic studies.This facility features a robot-op-erated, isotope-powder fillingstation, unique within the DOEweapons complex. Besides accu-rately manufacturing thesedetectors, our studies of radia-tion-exposure reduction to work-ers resulting from the use of thisrobot wiLlserve as a pilot studyfor the appropriate use of othersuch automated stations in thecomplex of the future.

The Process Research andDevelopment Section continuesto expand its role in weaponssafety, surety, and reliabilityresearch. We are completinginstallation of a comprehensivefurnace system for simulatedaccidental fire testing of nuclearprimaries in vacuum, inert gas,and oxidizing atmospheres.

Group Profiles 117

“The Plutonium Metallurgy Group, NMT-5, is a multi-disci-plinory organization engnged in profofype weapon primary fab-rication, metallurgical and chemical properties studies ofplufoniwn and ofher acfinides, and surveillance and stockpileevaluation technologies in supporf of Laboratory and the De-parfnlenf of Energy (DOE) weapons programs.”

In the meantime, we continue toconduct fire-resistance tests forengineering qualification of notonly Los Alamos system designs,but also designs from the UnitedKingdom, with whom we shareother nuclear safety technology.In a simiIar vein, we will also beconducting safety verificationtests in support of LawrenceLivermore National Laboratorysystems presently in the stock-pile. Our materials scientists arealso conducting various experi-ments in order to elucidate theconsequences of aging on theproperties of pIutonium and toextend these findings to supportweapon-reuse studies.

Our Actinides Chemistryand Physics Section continuesworld-recognized work rangingfrom fundamental surface chem-istry to solid-state physics re-search on the actinides. We haveextended our findings on thenature of radio-frequencyplasmas to develop uniquemethods for removing tracequantities of actinides from thesurface of various substrates,providing a decontaminationmethod that produces little or nowaste stream. The push to elimi-nate chlorofluorocarbons (CFCS)in manufacturing has led us tostudy the use of supercriticalcarbon dioxide as a solvent forresidue surface oils on pluto-nium, as well as preliminarystudies into the use of aqueouscleaning agents, such as deter-gents and other surfactants, toremove residues.

To complement this work, wehave adapted our capabilities inFourier transform infrared spec-troscopy (lTIR) to quantify thepresence of contaminants onplutonium and other metal sur-faces. In addition, we continuefundamental studies into themechanisms of surface chemicalreactions and the electronicstructure of plutonium, theactinides, and their compounds.

We are also responsible forthe successful installation andoperation of the 40-mm gas/powder launcher at the Pluto-nium Facility. The launcher willoffer DOE researchers a uniqueopportunity to investigate ilzsitudynamics mechanical propertiesof plutonium. Data from suchtesting will enable weapondesign codes to more accuratelypredict performance. +

118 Nuclear Materials Technology Division Annual Ret’iew

NMT-6

ACT IN ID E

MATE R IALS

C H E M ISTRY

Our group has 24 employees: 14 techni-cal staff members, 8 technicians, 1 officesupport person, and 1 graduate re-search assistant. In orderto accomplishourgroup’smultidisciplinarymission,ourscientificstaff’sexpertiserangesbroadlyin inorganicandphysicalchem-istry,materialsscience,andchemicalengineering.

I — --—-—

ml

GroupLeaderKyuC. Kim

The Actinide MaterialsChemistry Group, NMT-6, con-ducts fundamental and appliedresearch in actinide chemistry todevelop and maintain diversescientific expertise and capabili-ties and to apply the technologybase in support of nuclear mate-rials proc~s~ingand process de-velopment activities in NuclearMaterials Technology (NMT)Division.

Technical and scientific tasksare distributed between the Pro-cess Chemistry and AdvancedSeparation Concepts sections.Main activities include organo-actinide chemistry, plutoniumchlorination and fluorination,plutonium thermochemical stud-ies, process control and diagnos-tic development, actinidespectroscopy, waste gas treat-ment, and chemical and physicalplutonium separation and purifi-cation technology development.

I la

DeputyGroupLeaderThomasW. Blum

Our group focuses on new andemerging technologies and onimproving existing technologieswith strong emphasis on wastereduction, safety, environmentalimprovement, and efficiency.

Our group has establishedbroad collaborations with othergroups, implemented new andimproved recovery and purific-ationprocess concepts and ad-vanced diagnostic techniques,and applied our research exper-tise, especially in spectroscopyand thermodynamics. In addi-tion, we are active in technologytransfer and consultation withother nuclear materials produc-tion sites and other nationallaboratories. +

Group Profiles 119

NMT-7

N U CLEAR I -- —-——.—M ATE RI ALS

MANAGE M ENT

Ourgrouphas39employees:10staff =~members,28technicians,and1support GroupLeaderperson. CarolL.Sohn

Nuclear Materials Manage-ment, NMT-7, manages themovement of nuclear materialswithin the TA-55 boundaries.Group programs include wastemanagement, nuclear materialsstorage, roasting/blending, ship-ping/receiving of nuclear mate-rials, and coordination of nuclearmaterials.

Waste management is one ofour most important functions atNMT-7. Our handling of liquidwaste ensures that acidic andcaustic waste solutions meet theapplicable discard limits and aresuitable for processing by theLaboratory’s central waste treat-ment plant. Our solid waste ac-tivities involve cement fixationof the treated liquid wastes thatmeet pertinent discard limits. Inaddition, we develop the proce-dures to meet Waste IsoIationPilot Project certificationrequirements for solid waste.

We manage the secured vaultin which nuclear materiaIs not inprocess are stored. This opera-tion includes safely introducingand removing material andmaintaining the required docu-mentation. In addition, weblend, sample, roast, and con-solidate various feed materialsfor metal preparation and aque-ous recovery.

We also coordinate the ship-ping and receiving of nuclearmaterials, including packing andunpacking shipments in compli-ance with the current Depart-ment of Energy regulations. Weroutinely ship and receive prod-uct and process feed materials,scrap, analytical samples, andwaste.

DeputyGroupLeaderCharlesL. Foxx

Our coordination of nuclearmateriaIs includes diverse activi-ties in support of programmaticrequirements. We have devel-oped a site-wide nuclear materi-als model that forecasts futureinventories of scrap and wastegeneration and that examinesthe impacts of new technologieson the TA-55 Plutonium Facility.In support of the model, we havecreated a waste generation database that provides detailed infor-mation about waste origins. Weare initiating electronic transmis-sion and generation of the volu-minous records associated withour operations. +

120 Nuclear Materials Tcclmology Divlslun Amual RLW%?W

NMT-8

TA-55 FACILITIES

MANAGE M E NT

Ourgrouphas51employees:11staffmembers,15technicians,19supportpersonnel,and6 casualemployees.

L, !

/L.

I

DeputyGroupLeader

GroupLeader RichardA. Brie.smeisterDavidJ. Post

The TA-55 Facilities Man-agement Group, NMT-8, over-sees all engineering operationsand maintenance at the TA-55plant and manages the engineer-ing design and construction ofnew facilities and renovations ofexisting facilities.

Our site administration re-sponsibilities include warehouseoperations, safety operations,change rooms, access control,telecommunications, computersystems, equipment inspections,and financial management. Wealso communicate on behalf ofNMT Division with the Opera-tional Security and SafeguardsDivision and the Laboratory’sprotective force. +

Group Profiles 121

NMT-9

HEAT SOURCE

TECH N O LOGY

Ourgrouphas38 employees,9 staffmembers, 22 technicians,4 supportpersonnel,and3 casualemployees.

The Heat Source Technol-ogy Group, NMT-9, has long-term experience withradioisotope heat-source devel-opment for terrestrial and spacee~ectricalgenerators. Heat -sources developed at LosAlamos have been used on ra-dioisotope thermoelectric gen-erators (RTGs) to supplyelectrical power for NASAspacecraft, including the Pioneer10 and 11, Voyager 1 and 2,Galileo, and Ulysses deep-spaceexploration missions. Some ofthe spacecraft also requiredsmall radioisotope heaters, de-veloped and produced at LosAlarnos, for thermal input tocritical components.

l— I

Processing of Plutonium 238,which began at Los Alamos inthe late 1950s, has expanded toinclude

1. design of radioisotopeheat sources,

2. development of fuelfabrication processes,

3. fabrication of a varietyof heat-source fuel forms,

4. safety tests and postmor-tem examinations oftested heat sources,

5. safety assessments ofradioisotope powergenerators, and

6. heat-source materialsresearch, development,and service evaluationfor space and terrestrialapplications.

Our group is supporting theupcoming Cassini mission by

1. requalifying the general-purpose, heat-source(GPHS) fuel-fabricationprocess,

2. performing independentsafety assessments on thecomponents and RTGs tobe used, and

3. fabricating lightweight,radioisotope heater units.

GroupLeaderRoyWayneZocher

These heat sources will ther-mally stabilize scientific equip-ment and critical valves duringthe missions.

Our group evaluates thehigh-temperature and impact re-sponse of candidate heat-sourcematerials, incIuding graphitecomposites, noble metal alloys,fuel simulant, and alternative in-sulating materials. We are alsoinvestigating methods to decon-taminate iridium and return thematerial to the national stock-pile.

Our group recently ceasedfabrication of mW-generator(MWG) heat sources that areused in RTGs for weapon com-ponents, but we will continue toperform stockpiIe surveillanceon these heat sources. We arecurrently transferring the mWstockpile surveillance and stor-age characteristics activities atGeneral Electric Pinellas Plant toLos Alamos, +

122 Nuclear Materials Technology Division Annual Rmicw

A WAR DS

HONORS

PATE NTSi

123

AWARDS

HONORS

P AT E N T S

Duringthe year,NMTDivision’speopleachievedmanynotablescientificand technicalaccomplishmentsandreceivedawardsrecognizingtheirefforts.Someof our employeeswhowererecognizedfordistinguishedcontributionsin scientificor technicalareasarelistedhere.The individualswithinNMTDivisionwhowereawardedpatentsduringthe yearare listedalso.Here,too,we applaudtheseindividualsfor theircontributionsin areasthathavehigh potentialto benefitnotonlythe Laboratorybut ournation.

H. L..Nekimken (NMT-2), FY 1991 R&D 100 Award for development ofthe “Optical High-Acidity Sensor,” (issued September 1991).

H. L. Nekirnken (NMT-2), Federal Laboratory Consortium Award forExcellence in Technology Transfer for 1992 (issued February 1992).

H. L. A?ekimken(NMT-2), “Optical High Acidity Sensor,” S-72,805, S.N.07/770,388 (patent application filed October 3, 1991).

Q. Fernando, N. Yanagihara, J. T. Dyke,K. Vemulapalli, (NMT-2),“Forn~ationof Rare Earth Carbonates Using Supercritical Carbon Diox-ide,” U.S. Patent 5,045,289 (issued September 3, 1991).

S. F. Fredric Marsh (NMT-2), Member of the DOE Red Team (Phenom-enology Subteam) assigned to provide an independent assessment ofWHC plans and strategy for the Hanford Tank Waste Project to Leo Duffy,DOE Headquarters.

S. F. FredricMarsh (NMT-2), Member of DOE delegation sent toFrance, August 26-30, 1991, to evaluate French technology that might beapplicable to the Hanford Site Restoration Project, at the request of JohnTseng, DOE Headquarters.

124 Nuclear MakiakT&mology Divklon Annual Ibxiew

S. F. FredricMarsh (NMT-2), Invited presenter of “The Effects of Exter-nal Gamma Radiation and ZrzSituAlpha Particles on Five Strong-Base An-ion Exchange Resins,” at the 1987 Godon Research Conference on ReactivePolymers, Ion Exchangers, and Adsorbants, Newport, Rhode Island, Au-gust 19-23,1991.

S. F. Fredric A&rsh (NMT-2), One of three invited Los Alamos partici-pants to the Fint Hanford Separations Science Workshop, Richland, Wash-ington, July 23-25, 1991.

S. L..Yarbro (NMT-2) ATW Chemistry Team Leader, Accelerator Trans-mutation of Waste Program.

Heat Source Technology Group (NMT-9), 1991, National Aeronautics andSpace Administration, Group Achievement Award for Galileo Safety forContributions to Design, Analysis, Testing, and Documentation required toensure safe use of radioisotopic thermoelectric generators and radioisotopeheater units for the Galileo Ulysses missions.

R. W.Zocher (NMT-9), Certificate of Recognition for Achievements in“Nuclear Fuel Elements,” US Patent No. 5,002,723 (issued March 26, 1991).

Awards, Honors, Patenb 125

126 Nuclear Materials Technology DivMon Annual Review

P U B LI CAT I O N S

127

P U B LI CAT I O N S

Another important component of our scientific and technicaleffort is the communication of results and conclusions to oursponsors and the scientific community at large. During the pastyear, our staff published many scientific papers and reports(listed on the following pages). Documents of unlimited distri-bution cannot cite classified or limited access publications.For this reason, this is not a complete listing of NMT-Divisionpublications.

Nuclear Fuels Technology (NMT-1)

In the following publications list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Nuclear Fuels Technology Group, MailStop E505, Los Alamos National Laboratory, Los Alamos, New Mexico87545.

1. “Advancing Liquid Metal Reactor Technology with Nitride FueIs:’R. B. Baker, R. D. Legget, W. F. Lyon, R. B. Matthews, InternationalFast Re-nctors and Related Fuel Cycles, Los AIamos National Laboratory documentLA-UR-90-4343 (December 1990).

2. “Reactor Fuel Production in Western Europe;’ R. B. Matthews,H. T. Blair, K. M. Chidester, SAIC Study of Western European Reactor Capa-bilities, Los Alamos National Laboratory document LA-UR-91-0481 (Febru-ary 1991).

3. “Ceramic Fuel Development For Space Reactors,” R. B. Matthews,Cenun.Bull. 71,96 (January 1992).

4. “Experimental Investigation of Uranium Dicarbide Densificationand The Influence of Free Carbon Diffusion,” K. M. Chidester, Thesis,Los AIamos National Laboratory document LA-11954-T (April 1991).

5. “Review of Experimental Observations About the Cold FusionEffect,” E. K. Storma Fusion TechrzoL20,433 (December 1991).

6. “Carbide Fuels For Nuclear Thermal Propulsionl’ R. B. Matthews,H. T. Blair, K. M. Chidester, K. V. Davidson, W. A. Stark Jr., E. K. Storms,Proc. AIAA/NASA/OAl/Advanced SEI Technologies, Los Alamos NationalLaboratory document LA-UR-91-2317 (July 1991).

7. “Effect of Fuel Geometry on the Lifetime-Temperature Perfor-mance of Advanced NucIear Propulsion Reactors,” E. K. Storms,D. L. Hanson, W. L. Kirk, P. Goldman, Proc. AMA/NASA/OAI/AdvmzcedSE] Technologies, Los AIamos National Laboratory document LA-UR-91-2428 @IIY 1991).

128 Nuclear MatwialsTcchnoIogy Oivision Annual Review

8. “SP-1OOSeptember Quarterly Report;’ C. W. Hoth, N. A. Rink, JetPropulsion Laboratory, Los Alamos National Laboratory documentLA-I-JR-91-3199(October 1991).

9. “Behavior of ZRC 1-X and UYZR 1-Y Cl-X in Flowing Hydrogenat Very High Temperatures,” E. K. Storms, Los Alamos National Labora-tory document LA-12043-MS (January 1992).

10. “Relationship Between Surface Curvature and Local Active-To-Passive Transitions During Oxidation,” D. P. Butt, Proc. Am. Cerarn. Soc.,Los Alamos National Laboratory document LA-UR-92-0307 (January1992).

11. “Directional Zone Sintering In UCZCompacts,” K. M. Chidester,Proc. of the Am. Cerarn. Society, Los Alamos National Laboratory documentLA-UR-92-0111 (January 1992).

12. “Diffusion of Carbon Through The Niobium Carbides (NiobiumCarbide and Diniobium Carbide),” R. W. Schmude, T. C. Wallace, NuclearMaterials, pending, Los Alamos National Laboratory document LA-UR-92-0016 (January 1992).

Nuclear Materials Processing: Nitrate Systems (NMT-2)

In the following publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Nuclear Materials Processing: NitrateSystems Group, Mail Stop E501, Los Alamos National Laboratory, LosAlamos, New Mexico 87545.

1. “Evaluation of Different Solvent Extraction Methods for RemovingActinides From High Acid Waste Streams,” S. L. Yarbro, S. B. Schreiber,S. L. Dunn, and J. D. Rogers, Los Alamos National Laboratory documentLA-I-JR-91-3253(1991).

2. “Homogeneous Precipitations for Separations and Waste Treat-ment,” S. L. Yarbro, S. B. Schreiber, and S. L. Dunn, Los Alamos NationalLaboratory document LA-UR-91-2409 (1991).

3. “Los Alamos Technology Office Assessment of the Rocky FlatsPlant Criticality Alarm System,” D. Smith, S. Vessard, R. E. Malenfant,and A. F. Muscatello, Los Alamos National Laboratory document LA-UR-91-1118 (1991).

Publications 129

P U B LI CAT I O N S

4. “Optical High Acidity Sensor,” B. Jorgensen and H. Nekimken,1992 ResearchFIigldighfs (1992).

5. “Report on Indicators for Optical High-Acidity Sensor,”B. Jorgensen, H. Nekimken, and D. Sellon, internal NMT Division report(1991).

6. “Separation Studies of Yttrium(III) and Lanthanide(III) Ions with4-Benzoyl-2,4-dillydro-5-methyl-2-phenyl-3H-ppazol-3-tMon andTrioctylphosphineOxideUsinga RoboticExtractionSystem:’WNekimken, B. F.Smith,G. D. larvinen,C.S.Bartholdi,revisionsubmittedto Solwwf Exfr. Ion Exck,(January1992).

7. “Synthesis of Lanthanide Carbonate Using Supercritical CarbonDioxide,” Q. Fernando, N. Yanagihara, J. T. Dvke. J. Less-CovvnonMet. 167(1991).

8. “Advanced Testing Line for Actinide Separations (ATLAS),”S. L. Yarbro, S. B. Schreiber, N. G. Pope, R. Dav, 1992 Resem’chHighlights(1992).

Nuclear Materials Processing: Chloride Systems (NMT-3)

In the following publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Nuclear Materials Processing: ChlorideSystems Group, Mail Stop E511, Los Alamos National Laboratory, LosAlamos, New Mexico 87545

1. “An Investigation into the Spectroscopic and Intercalative Proper-ties of Hydrogen Neptunyl Phosphate,” P. K. Dorhout, P. G. Eller, A. B.Ellis, K. D. Abney, R. J. Kissane, and L. R. Avens, Inorg.Ckrn. 28,2926(1990).

2. “Magnetic Separation as a Plutonium Residue Enrichment Pro-cess,” L. R. Avens, U. F. Gallegos, and J. T. McFarlan, Sep.Sci. TechnoL 25,1967 (1990).

3. “Synthesis and Characterization of Bis(pentamethyl-cyclopentadienyl) Uranium(IV) and Thorium(IV) Compounds Containingthe Bis(trimethylsilyl)phosphide Ligand,” S. W. Hall, J. C. Huffman,M. M. Miller, L. R. Avens, C. J. Burns, and A. P. Sattelberger, submitted toOrganomet. (January 1992).

130 Nuclear MaterialsTechnology Oivislon Annual Rmlew

4. “The Reaction of Dibenzylmercury with SecondaryF’hosphines:Phosphorus-Phosphorus Bond Formation Versus Benzyl Substi-tution,” J. T. Yeh, L. R. Avens, and J. L. Mills, Phosphorus, Sulfur Silicon Relaf.Elem. 47,319 (1990).

5. “Transuranic Organometallics: The Next Generation;’ L. R. Avens,B. D. Zwick, and A. P. Sattelberger, Submitted to ACS Books (1990).

6. “Calculated Phase Equilibria for the CaC~-KCl-MgC~ System,”K. M. Axler, N. J. Pugh, T. G. Chart, H. Daniels, and G. S. Perry, NationalPhysical Laboratory Report DMM(D) 123 (December 1991), National Physi-cal Laboratory, Teddington, UK.

7. “Evaluation of Corrosion Resistant Materials for Use in PlutoniumPyrochemistry,” K. M. Axler, G. D. Bird, and P. C. Lopez, Proc. 180th Meef-ing Elecfrochern. Soc. (1991).

8. “Investigations of Coated Refractory Metals for Plutonium Process-ing,” L. M. Bagaasen, G. L. DePoorter, and K. M. Axler, Trans.Am. Nuc/. Soc.62,240 (1990).

9. “VolubilityStudies of the Ca-CaO-CaC~ System,” K. M. Axler. LosAlamos National Laboratory report LA-11960-T (July 1991).

10. “VolubilityStudies of the Ca-CaO-CaC~ System,” K. M. Axler andG. L. Del?oorter, Materials Science Forum, Vol. 73-75 (1991), Proc. Third ln-fernafional Symposium on Molten Salt Chemisfy and Technology, Paris, France(June 1991).

11. ‘The Effect of Initial Composition on PuOC1Formation inthe Direct Oxide Reduction of PuOz,”K. M. Axler and R. I. Sheldon, ]. Nucl.Mater. 187,183-185 0992).

12. ‘Thermodynamic Modeling and Experimental Investigations of theCsC1-CaC~-PuC~System,” E. M. Foltyn, R. N. Mulford, K. M. Axler,J. M. Espinoza, and A. M. Murray, J. NUCLMater. 178,93-98 (1991).

13. ‘The Structure of <PuC1,,” K. M. Axler and R. B. Roof, submittedfor publication in the J. Nucl. Mater. (1992).

14. “Kynar PVDF assists Los Alamos Labs with Plutonium RecoveryProcess,” S. M. Dinehart, J. Chem. Process Equip. Des. (1991).

131

15. ‘Preparation and Structural Characterization of the First Bismuth1mide Complex Bi3(OtBu)7(NSiMeq),”N. N. Sauer and E. Garcia, submitted]. Am. Chem. Soc. 0991).

P U B LI C AT I O N S

16. “Shock Initiation of I?entaerythritol Tetranitrate Crystals: StericEffects Due to Plastic Flow,” J. J. Dick, E. Garcia, and D. C. Shaw, Proc. APS1991 Top.Conf. on Shock Compression of Condensed Matter, Williamsburg, Vir-ginia (June 1991).

17. “Structure and Initial Characterization of 4,6-Bis-(5-amino-3-nitro-IH-1,2,4-triazol-l-y) -5-nitropyrimidine,” K.-Y. Lee, E. Garcia, andD. Barnhart, Los Alamos National Laboratory report LA-12248-MS (March1992).

18. “Structure of the Laser Host Material LiYF,,” E. Garcia andR. R. Ryan, submitted Acta Crystogra. Sect. C (1991).

19. “Structure of3-Amino, 5-Nitro-l,2,3-Triazole, ~H,N,02,”E. Garcia and K.-Y. Lee, accepted Acta Crystogra. Sect. C. (1991).

20. “Structure of the Hydrazinium Salt of 3-Amino, 5-Nitro-l,2,4-Triazole, Nz~.C#$N~Oz,” E. Garcia, K.-Y. Lee, and C. Storm acceptedActa Crystogra. Sect. C (1991).

21. “Radiometallating Antibodies and Autogenic Peptides,”J. A. Mercer-Smith, J. C. Roberts, D. Lewis, D. A. Cole, S. L. Newmyer,L. D. Schulte, P. L. Mixon, S. A. Schreyer, S. D. Figard, T. P. Burns,D. J. McCormick, V. A. Lennon, M. Hayashi, and D. K. Lavallee, NezoTrends in Rmfiophmvnaceufical Synthesis, Quality, Assurance, and RegulatoryControl, A.M. Emran, Ed. (Plenum Press, New York, 1991).

22. “Synthesis of 4-Alkyl-4-(4-methoxyphenyl)cyclohex-2-en-l -onesand 5-Alkyl-5-phenyl-1, 3-Cylohexadienes fromBis(tricarbonylchromium)-Coordinated Byphenyls,” L. D. Schulte,R. D. Rieke, B. T. Dawson, and S. S. Yang, J. Am. Chem. Soc. 112,8388-8398 -(1990).

23. “Energy Transfer in the “Inverted Region,” Z. Murtaza, A. P. Zipp,L. A. Worl, D. Graff, and T. J. Meyer, J. Am. Chenz.Soc., 113,5113-13 (1991).

24. “Local States in One-dimensional CDW Materials; Spectral Signa-tures for Polarons and BipoIarons in MX Chains,” B. I. Swanson,R. J. Donohoe, L. A. Worl, A. Bulou, C. A. Arrington, J. T. Gammel, A.Saxena, and A. R. Bishop, Mol. Cryst. .Liq.Cryst. 194,43-53 (1991).

25. “Metal-to-Ligand Charge-Transfer (MLCT) Photochemistry: Ex-perimental Evidence for the Participation of a Higher Lying MLCT State inPolypyridyl Complexes of Ruthenium(II) and Osmium(II):’ R. S. Lumpkin,E. M. Kober, L. A. Worl, Z. Murtaza, and T. J. Meyer, }. Phys. Chem. 94,239-43 (1990).

132 Nuclear Materials Technology Division Annual Revimv

26. “Mixed-halide MX Chain Solids: Effect of Chloride Doping on theCrystal Structure and Resonance Raman Spectra ofIPt(en),Br,llPt(en),l(CIO,),,”S. C. Huckett,R.J. Donohoe,L. A. Worl,A. Bulou,C. J. Burns,J. R. Laia,D.Carroll,andB. I. Swanson,Chem.Mater.3,123-7 (1991).

27. “On the Origin of the Resonance Raman VIDispersion and FineStructure of [Pt(en)2J[Pt(en),Br2](C10,),(PtBr),” S. Huckett,R. J. Donohoe,~A. Worl, A. Bulou,andB. I. Swanson,SyrzthMet. 42,2773-6 (1991).

28. “Photoinduced Electron and Energy Transfer in Soluble Poly-mers,” S. M. Baxter, W. E. Jones, E. Danielson, L. A. Worl, and T. J. Meyer,Coord.Che?n.Rev. 111,47-71 0991).

29. “Photophysical Properties of Polypyridyl Carbonyl Complexes ofRhenium(I)~’ L. A. Worl, R. Duesing, P. Y. Chen, L. Della Ciana, andT. J. Meyer, J. Chem.Soc., Dalton Trans. (150fh Anniu. Celebration Issue) 849-58 (1991).

30. “Polarons and Bipolarons in Weak-lD CDWSolids: Spectral Stud-ies of Local States in [Ptn(en)211Ptw(en)2Br21(C IOA)qand[ptn(en)2][pt~(en)m](C10,),,” R. J. Donohoe, L. A. Worl, B. I. Swanson, andA. Bulou, Synfh. Met. 42,2749-52 (1991)

31. “Production and Storage of Multiple, Photochemical RedoxEquivalents on a Soluble Polymer,” L. A. Worl, G. F. Strouse,J. N. Younathan, S. M. Baxter, and T. J. Meyer, }. Am. Chem. Soc. 112,7571-8(1990).

32. “Spectroscopic Studies of Polaron and Bipolaron Defects in theStrongly Localized CDW Solid [PtU(en)2][PtW(en),C~](C10,),R. J. Donohoe, L. A. Worl. A. Bulou, B. I. Swanson, J. Gammel, andA. R. Bishop, Synth.Met. 42,2745-8 (1991).

33. “Ultragap Edge States in Mixed Halide Chain Solids,”B. I. Swanson, R. J. Donohoe, L. A. Wcn-l,J. T. Gammel, A. Saxena,I. Batistic, and A. R. Bishop, A, Synfh. Met. 42,2733-8 (1991).

Publications 133

—

P U B 11CATION S

Nuclear Materials Measurement and Accountability (NMT-4)

In the following publication list, the single underline identifies the author asa group member. If YOUwould like to contact any of these authors, pIeasewrite to them in care of the Nuclear Materials Measurement and Account-ability Group, Mail Stop E513, Los Alamos National Laboratory, LosAlamos, New Mexico 87545.

1. “A Versatile Passive/Active Neutron Coincidence Counter forIn-Plant Measurements of Plutonium and Uranium:’ J. R. Wachter,J. E. Stewart, R. R. Ferran, H. O. Menlove, E. C. Horley, J. Baca, andS. W. France, European Safeguards Research and Development Corporation,Avignon, France, Los Alamos National Laboratory document LA-UR-91-1566 (1991).

Plutonium Metallurgy (NMT-5)

In the following publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to the Plutonium Metallurgy Group, Mail Stop E506, LosAlamos National Laboratory, Los Alamos, New Mexico 87545.

1. “A Generalized Model of Heat Effects in Surface Reactions, Part 1:Model Development,” J. C. Martz. D. W. Hess, and E. E. Petersen, LosAIamos National Laboratory document LA-UR-92-190, submitted to]. AppL PhyS. (1992).

2. “A Generalized Model of Heat Effects in Surface Reactions, Part 2:Application to Plasma Etching Reactions;’ J.C. Martz, D.W. Hess, andE. E. Petersen, Los Alamos National Laboratory document LA-UR-92-346,submitted to J. Appl. Phys. (1992).

3. “A Mass Spectrometric Analysis of CFi/O, Plasmas: Effect ofOxygen Concentration and Plasma Power,” J. C. Martz, D. W. Hess, andW. E. Anderson, Plnsma Chem. Plasma Process. 10,261 (1990).

4. “A Plasma-Chemistry-Based Plutonium Contamination RemovalProcess~’ J. C. Martz, WeaponsComplex Monitor. 1(26),6 (1990).

5. “Alternative Solvents for Cleaning Plutonium: Thermodynamicand Kinetic Considerations,” J. M. Haschke and S. J. Hale, Los AlamosNational Laboratory report LA-12255-MS (March 1992).

6. “An )(I?SStudy of the Electronic Structure of Am Metal and AmDihydride;’ L. E. Cox, T.W. Ward, and R. G. Haire, Phy. Rev. B: CondensedMatter (accepted).

134 Nuclear Materials Technology Division Annual Re\icw

7. “Characterization of Hypervelocity-Microparticle-Impacts (HMI)Utilizing Scanning Electron Microscopy,” J. I. Archuleta, Los AlamosNational Laboratory report LA-UR 91-2063 (July 1991).

8. “Core-Level and Valence-Band X-ray Photoelectron Diffraction inUO,(1OO),”L. E. Cox and W. P. Ellis, Solid State Commun. 78,1033 (1991).

9. “Debye-Wailer Factors of d-Phase PuO,g~AIO,Kbetween 15 and90 K,” A. C. Lawson, J. Vaninetti, J. A. Goldstone, R. I. Sheldon, and &~ in LANSCE Experiment Reports, Los Alamos National Laboratory re-port LA-12194-PR (October 1991), p. 128.

10. “Demonstration of Plutonium Etching in a CFq/OzRF GlowDischarge,” J. C. Martz. D. W. Hess, J. M. Haschke, J. W. Ward, andB. F. Flamm, J. Nucl. Mater. 182,277(1991).

11. “Elastic Properties of Materials by Pulsed Neutron Diffraction,”A. C. Lawson, A. Williams, J. A. Goldstone, D. T. Eash, R. J. Martinez,J. I. Archuleta, D. J. Martinez, B. Cort, and M F. Stevens, ]. Less-CommonMet. 167,353-363 (1991).

12. “Electronic Structure of Hydrogen and Oxygen Chernisorbed onPlutonium: Theoretical Studies:’ O. Eriksson, Y. G. Hao, B. R. Cooper,G. W. Fernando, L. E. Cox, T.W. Ward. and A. M. Boring, Phys. Rev. B 43,4590 (1991).

13. “Electronic, Structural, and Transport Properties of (Almost)Rare-Earth-LilceActinide Hydrides,” J . W. Ward, B. Cort, J. A. Goldstone,A. C. Lawson, and L. E. Cox, in TrarzsuraniumElements: A FIalj-Centuy,American Chemical Society (May 1992).

14. “Hydrolysis of Plutonium: The Plutonium-Oxygen PhaseDiagram,” J . M. Haschke, in Transuranium Elements: A Half-Centuy,American Chemical Society (May 1992).

15. “IBM-PC Software for Analysis of Internal Friction Peaks toObtain Relaxation Time Spectra,” J. R. Cost, Los Alamos National Labora-tory document LA-UR-91-2430, September 1991.

16. “Kenetics of Helium Outgassing from FCC-Stabilized Plutonium,”J. C. Kammer and J. R. Cost, Los Alamos National Laboratory documentLA-UR-91-1445 (1991).

17. “Magnetic Structures of Actinide Materials by Pulsed NeutronDiffraction,” A. C. Lawson, J. A. Goldstone, J. G. Huber, A. L. Giorgi,J. W. ConanL A. Severing, B. Cort, and R. A. Robinson, J. AppL Phys. 69(8),5112-5116 (1991).

Pubkatiom 135

—

P U B LI CAT I O N S

18. “Mechanical After-Effect Studies of Oxygen Relaxation in YBaz:’J. R. Cost and T. Stanley, Los Alamos National Laboratory document -LA-UR-91-2736 (September 1991).

19. “MechanicalAfter-EffectStudiesof OxygenRelaxationinYBazC~Ozd”R. CostandJ. T. Stanley.LosAlamosNationalLaboratorydocumentLA-UR-911569(1991).

20. “Neutron Diffraction Study of Alpha, Beta, and Gamma Phases ofNeptunium,” J. A. Goldstone, A. C. Lawson, B. Cort, and E. Foltyn, inLANSCE Experiment Reports, Los Alamos National Laboratory report LA-12194-PR (October 1991).

21. “Partial Pressure Analysis of CFqOzPlasmas,” J. C. Martz,D. W. Hess, and W. E. Anderson, in Plasma Surface Interactions and Process-ing of Materials, O. Auciello et al., Eds., (Kluwer Academic Publishers,Netherlands, 1990).

22. “Plutonium Dry Machining,” M. R. Miller, Los Alamos NationalLaboratory document LA-UR-91-2261 0991).

23. “Structures of the Three Phases of PaDP” J. W. Ward, B. Cort,J. M. Haschke, A. C. Lawsoq R. B. Von Dreele, and J. C. Spirlet, in LANSCEExperiment Reports, Los Alamos National Laborato”~report LA-12194-PR(October1991).

24. “Tantalum Etching in Fluorocarbon/Oxygen RF Glow Dis-charges,” J . C. Martz, D. W. Hess, and W. E. Anderson, ]. Appl. Phys. 67,3609 (1990).

25. “Vibrational Properties of PuH<” J. A. Goldstone, A. C. Lawson,J. Eckert, L. Diebolt, B. Cort, l.W. Ward and 1. M. Haschke, in LANSCE Ex-periment Reports, Los Alamos National Laboratory report LA-12194-PR (Oc-tober 1991).

Actinide Materials Chemistry (NMT-6)

In the folIowing publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Actinide Chemistry Group, Mail StopE51O,Los Alamos National Laboratory, Los Alamos New Mexico 87545.

1. “A Small-Scale Study on the Dissolution and Anion-Exchange Re-covery of Plutonium from Rocky Flats Plant Incinerator Ash:’ T. W. Blum,R. G. Behrens, V. J. Salazar, and l?. K. Nystrom, Los Alamos National Labo-ratory report LA-11747-PR (June 1991).

136 Nuclear Malwi.IlsTcchnology Divlslon kmual Rm&v

2. ‘The Irreversible Adsorption of Plutonium Hexafluoride,”G. M. Cam~bel~ Los Alamos National Laboratory document, Chern.Eng.Commun., in press.

3. “A Kinetic Study of the Equilibrium Between DioxygenMonofluoride and Dioxygen Difluoride,” G. M. Campbell, ]. HuorirzeChem,46,357-366 (1990).

4 ‘Trimethylborane,” W. Rees, M. Hampton, S. W. Ha11,and J. Mills,A. P. Ginsberg, editors, Inorg.Synth. 27,339 (TexasTech University, 1990).

5. “vibrational Properties of Actinide (U, Np, Pu, Am) HexafluorideMolecules,” K. C. Kim and R. N. Mulford, J. Mof. Sfruct. 207,293 (1990).

6. “Sublimation Studies of NpO,F,,” P. D. Kleinschmidt, K. H. Lau,and D. L. Hildenbrand, submitted to J. Chern.Phys. (1990).

7. “Free Energy of Formation of CS,PUC1,and CsPu,C~,” M. A.Williamson and P. D. Klein~chmidt, submitted to the}. A?ucl.ivlafer. (1992).

8. “A Chemical Exchange System for Isotopic Feed to a Nitrogen andOxygen Isotope Separation Plant,” T. R. Mills, M. G. Garcia, R. C.Vandervoort, and B. B. McInteer, Sep. Sci. TechnoL 24,415 (1990).

9. “Silicon Isotope Separation by Distillation of Silicon Tetrafluonde,”T. R. Mills, Sep. Sci. Technol. 25 (3), 335 (1990).

10. “PracticalSulfurIsotopeSeparation by Distillation:’ T. R. Mills,Sep.Sci. TechnoL25(13-15), 1919 (1990).

11. “Synthesis of Liquid-phase Dioxygen Difluoride,” T. R. Mills,J. Fluorine Clzem.52(3), 267 (1991).

12. “Superheavy Isotope Enrichment Using a Carbon Isotope Enrich-ment Plant,” B. B. McInteer and T. R. Mills, Sep. Sci. Techrzol., 26(5), 607(1991).

13. ‘Thermodynamics Modelling and Experimental Investigation ofthe CsC1-CaC~-PuC~System,” E. M. Folytn, R. N. R. Mulford, K. M. Axler,J. M. Espinosa, and A. M. Murray, J. NUCLMater. (1990).

14. “Cooperative Two-Photon Induced Chemical Bond Formationduring a KrFzCollision to form KI-F,”T. O. Nelson and D. W. Setser, Chem.Phys. L.eff., 170,430 (1990).

15. “Two-Photon Direct Laser-Assisted Reaction between Xe and ClY:’J. Qin, T. O. Nelson, and D. W. Setser, J. Phys. Chem., 95,5374 (1991).

Publications 137

P U B L! CAT I O N S

16. “QuenchingConstants of KrF(B,C) by Krand Xeand the KrF(B,C)Equilibrium Constant:’ W. Gadomski, J. Xu, D. W. Setser, and ~Nelson, Che~. Phys. Left. 189,153(1992).

17. “interpretations of the Two-Photon Laser-Assisted Reactions of Xewith Cl, Fz,CIF, and Kr with Fz,”T. O. Nelson, D. W. Setser, and J. Qin,j. Phys. Chem. submitted (1992) KSU.

18. “Quenching Rate Constants of the Xe(5ps6p) Excited States and theAssociative Ionization Reaction of the Xe (5p56s[3/2],)Atoms:’T. O. Nelson and D. W. Setser, J. Phys. Chem., submitted (1992).

19. “F-Element Compound Synthesis Employing Powerful Halogenat-ing Agents,” P. G. Eller, S. A. Kinkead, and J. B. Nielsen. 50th Anniversary of

the Discovery of the Transuranium Elements, Nonseries ACS Book, 1991, Ac-cepted. Los Alamos National Laboratory document LA-UR-90-2712 (1990).

20. “A New Synthesis of XeOF4,”J. B. Nielsen, S. A. Kinkead,P. G. Eller, Inorg. Chem. 29,3621 (1990).

21. “Synthesis of New Perfluorotertiary Amines Containing GeminalPentafluorosulfanyl, SF~,Groups:’ J. B. Nielsen,J. S. Thrasher, ). Fh{orine Chem. 48,407 (1990).

22. “New Syntheses of Xenon Hexafluoride, XeFb and Xenon Tet-rafluoride, XeFq,”J. B. Nielsen, S. A. Kinkead, J. D. Pu~son,and P. G. Eller,I~lorg.Chem. 29,1779 (1990).

23. “Studies on Advanced Oxidizer Systems Containing theFluoroperoxide Moiety,” S. A. Kinkead, P. G. Eller, and J. B. Nielsen,Los Alamos National Laboratory document LA-UR-90-651 (1990).

24. “Synthesis and Identification of (NH4)ZPUC1Gand (NH,)zUClbandPreparation of PuC~,” J. Nielsen, S. A. Kinkead, and P. G. Eller, 50fh Anni-versary of the Discovery of the Transuranium Elements, Nonseries ACS Book,1991, Los Alamos National Laboratory document LA-UR-90-2692 (1990).

25. “Direct Comparison of Low Light Level Detectors: The ImagingPMT and CCD,” D. K. Veirs, J. W. Ager III, and G. M. Rosenblatt, to besubmitted (1992).

26. “15NNuclear Magnetic Resonance Spectroscopy Studies of theNitrate Complexes of Thorium;’ S. W. Hal~ L. R. Avens, D. K. Veirs, andB. D. Zwick, to be submitted (1992).

27. “Spatially-Resolved Raman Studies of CVD Diamond Films;’]. W. Ager III, D. K. Veirs, and G. M. Rosenblatt, Phys. Rev. Sect. B 43,6491(1991).

138 Nuclear Materials Technol~ Division Annual Review

28. “Materials Characterization by Imaging Raman Spectroscopy,”D. K. Veirs, J. W. Ager III, and G. M. Rosenblatt, Adv. Compos. Mater. 19,1043 (1991).

29. “Raman and Resistivity Investigations of Carbon Overcoats ofThin Film Media - Correlations with Tribological Properties,” B. Marchon,N. Heiman, M. R. Khan, A. Lautie, J. W. Ager III, and D. K. Veirs, J. Appl.Phys. 69,5748 (1991).

30. “Vibrational Raman Characterization of Hard-Carbon and Dia-mond Films:’ J. W. Ager III, D. K. Veirs, B. Marchon, N.-H. Cho, andG. M. Rosenblatt, Applied Spectroscopy in Maferial Science, D. D. Saperstein,Ed., Proc. SPIE 1437,24 (1991).

31. “Spectrophotometric Investigation of the Pu(IV) Nitrate ComplexSorbed by Ion Exchange Resins,” S. F. Marsh, R. S. Day, and D. K. Veirs,Los Alamos National Laboratory report LA-12070 (June 1991).

32. “Mapping Materials Properties with Raman Spectroscopy Utiliz-ing a Two-Dimensional Detector,” D. K. Veirs, J. W. Ager III, E. T. Loucks,and G. M. Rosenblatt, Appl. Opt. 29,4969 (1990).

33. “Chemical Structure and Physical Properties of Diamond-LikeAmorphous Carbon Films Prepared by Magnetron Sputtering,”N.-H. Cho, K. M. Krishnan, D. K. Veirs, M. D. Rubin, C. B. Hopper,B. Bhushan, and D. B. Bogy, ~.Mater. Res. 5,2543 (1990).

34. “TransientSubcriticalCrack-GrowthBehaviorin Transformation-ToughenedCeramics,”R. H. Dauskardt,D. K. Veirs,W. C. Carter,andR.O.Ritchie,Acta Mefall. Mater. 38,2327 (1990).

35. “Laser Heating Effects in the Characterization of Carbon Fibersby Raman Spectroscopy,” J. W. Ager III, D. K. Veirs, J. Shamir, andG. M. Rosenblatt, ). AppL Phys. 68,3598 (1990).

36. “Raman Characterization of High Temperature Materials using anImaging Detector,” G. M. Rosenblatt and D. K. Veirs, High Temp. Sci. 26,31(1990).

37. “Mapping Chemical and Physical Properties of Advanced Materi-als Using Spatially-Resolved Raman Spectroscopy,” D. K. Veirs, J. W. AgerIII, and G. M. Rosenblatt, Proc. Twelfth International Conference on RamanSpectrosc., J. R. Durig and J. F. Sullivan, Eds. (John Wiley and Sons,Chichester, 1990), p. 898.

38. “Interference Effects in the Raman Spectroscopy of Thin Films,”G. M. Rosenblatt, J. W. Ager III, and D. K. Veirs, Raman Spectrosc.,J. R. Durig and J. F. Sullivan, Eds. (John Wiley and Sons, Chichester,

Publication 139

P U B LI CAT I O N S

Nuclear Materials Management (NMT-7)

In the following publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Nuclear Materials Management Group,Mail Stop E524, Los Alamos National Laboratory, Los Alamos, NewMexico 87545.

1. “Addressing Mixed Waste in Plutonium Processing,”D. C. Christensen and C. L. Sohn, Proc. Spec. Symp. Evzerging Technol. forHazard. WasteManage., Am. Chern. Soc., Atlanta, Georgia, 8-11 (October,1991).

2. “Waste Management: A Integrated Modeling Aproach for Ana-lyzing Change in NWC Production Processes;’ D. C. Christensen,C. L. Sohn, T. M. Helm, and T. J. Fansh, Proc. 7fh Annu. Dep. Energy ModelConf., Oak Ridge, Tennessee, (October 1991).

3. ‘Treatment of Off-Spec Cemented Waste at LANL,” G.W. Veazev,to be published in Proc. Workshop Radioacf. Hazard. and/or Mixed Wasfe Man-age. (ORNL), Knoxville, Tennessee, Los Alamos National Laboratory docu-ment LA-UR-90-4389 (December 1990).

4. ‘The Cement Solidification Systems at LANL,” G.W. Veazev, to bepublished in the Proc. Workshop Radioacf. Hazard. and/or Mixed Waste Man-age. (OR.AUJ,Knoxville, Tennessee, Los Alamos National Laboratory docu-ment LA-UR-90-4161 (December 1990).

5. “Radiolysis Effects in Gypsum Cements Used for Fixation of TRUWastes;’ G.W. Veazev and P.D. Shalek,-to be published in Issue 21 of WasfeMmmgemenf Research Absfracfs, IAEA, (1992).

6. “Modular Plutonium Processing Facility Simulation,”K.M. Gruetzmacher, P.K. Nvstrom, T.F. Yarbro, and C. Alton Coulter,Los AIamos National Laboratory document LA-UR-91-1807 (1991).

140 Nuclear Materials Tcchamlogy Dirlslon Annual Rcvtew

Heat Source Technology (NMT-9)

In the following publication list, the single underline identifies the authoras a group member. If you would like to contact any of these authors,please write to them in care of the Heat Source Technology Group, MailStop E502, Los Alamos National Laboratory, Los Alamos, New Mexico87545.

RefereedPublications

1. ‘Twinnin gin Monoclini Beta Phase Plutonium:’ T. G. Zocco,R. I. Sheldon, and H. F. R.izzo,). Nzfcl.Mater. 183,80-88 (1991).

2. “Correction to the Uranium Equation of State,” R. I. Sheldon andR.N. R. Mulford, ]. Nucl. Mater. 185,297-298 (1991).

3. The Effect of Initial Composition on PuOC1Formation in the Di-rect Oxide Reduction of Pu02,” K. M. Axler and R. L Sheldon, to be pub-lished in]. Nucl. Mater.

OtherPublications

Group Profiles 141

“Milliwatt Generator Project, April 1986- March 1988/’T. W. Latimerand G. H. Rinehart, Los Alamos National Laboratory report LA-12236-PR(in press).

142 Nuclear MaterLdsTcchnology Division Annual Re\lcw

* U.S. GOVERNMENTPRINTINGOFFICE: 1992 -S73.20S+53069

LALP-9241June 1992

c R E D I T s

credits

-

DesignandProduction......................................................... SusanL. CarlsonWnthgmd Mtig........... . . . . . . . . . MableAmadorandMaryMannCoordination.......................................................................SusanWhittingtonPhotography.....................................................JohnFlowerandho J. ReidelPrintingCoordination. . . . . . . . . . . . . . . . . . . . . . . . . ...GuadalupeArchuleta

Contibutors..........ti. .............................RitaA. Bien, SheilaM. Girard,MymaP.Marstellar,ConnieB.Norris,NoraA.Rink,MaryE.Salazar,

M. PatriciaSanchez,BerthaT. Sandova~MicheleA. Gubematis,WihnaI. Stout,andFredMaestas.

Los Alarnos National Laboratoryis operatedby theUniversityof Californiafor theU.S.DepartmentofEnergyundercontractW-7405-ENG-36.

An Affiiative Action/Equat Opportunity Employer

This report was prepared as an account of work sponsored by the United States Government.Neither the Regents of the Universityof California, the United States Governmentnoranyoftheiremployees makes any warranty, expressed or implied, or assumes legal liability or responsibilityfor the accuracy, completeness, orusefutness or any information, apparatus, product, or processdisclosed, or represents that its use would not infringe privately owned rights. Reference hereinto any specific commercial product, process, or service by trade name, mark, manufacturer, orotherwise,does notnecessarily constitute or imply itsendorsement, recommendation, orfavoringby The Regents of the University of California, the United States Government or any agencythereof. The views and opinions expressed herein do not necessarily state or reflect those of TheRegents of the University of California, the United States Government or any agency thereof.

143

June 1992LALP-92-41

\

.

—