office of scientific and technical information · list of tables list of illustrations figure 1....

6

1 f

REPOSITORY

WASH No . 1095

RAD IO I SOT0 PES 0

PRODUCTION and DEVELOPMENT of

LARGE-SCALE USES I

MAY 1968

U. S. ATOM IC E N E RGY COMM ISS ION

~ ~ ~ ~ ~ 4 2

WASH No. 1095

RADIOISOTOPES

PRODUCTION and DEVELOPMENT of

LARGE-SCALE USES

0

MAY 1968

UNITED STATES ATOMIC ENERGY COMMISSION

160328tr3

TABLE OF CONTENTS

APPENDICES

Page

1

3 3 4 Si 6 6 7 7 8

9 9

13 13

19 19 21 21

24 24 24 25

26 26 26 26

29 29 30 30

32 32 34 35

39

40

... 111

LIST OF TABLES

LIST OF ILLUSTRATIONS

Figure 1. AEC Developitient of Isotope Sources for National Prograins _-____ 3

Power Systenis ________________________________________- -__ - - -__ 5 Figure 2. Trend of Power IJwels and 0l)er;rting Tei i i l~ra tur rs in Space

Figure 3. Specific Weight of Power Systeiiis as a Function of Lifetime, Showing Overlnl) of Typiral Suc1r:ir nntl S o h r Systems of the 1970's ________________________________________-_--__-_--------- 10

Figure 4. Effect of Hot Junction Teniprmture on Fuel Inventory of Thermo- electric System (Optiuiized for hlinimuni Weight) _ _ _ _ _ _ _ _ _ _ _ _ _ _ - 13

Figure 5. Theoretical Perforiiiance of Propellants of Interest _______--_--_- 20

Figure ti. SI)-237 and Pit-238 Av:iil:ible froin I'ower I h w t o r s _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 37

1

!)

INTRODUCTION

Tlie Atomic Energy Cominissioii supports a 1) ro:iclly - 1):i sed p rogr.:i 111 to tlevelop :I i i :it i oil a1 capability for tlie large-scale protluction aiid use of isotopes ;is sources of lieat aiitl ra(1i:ition. I 11 is propx m i ncl ides 11 u 11 I eroiis a p pl ic at ions for pcwefnl and national defense missions in space; n:it ioiial liealtli programs ; conservation o f iiatiiral resources ; a n d the natioiuil progixm for mariiie sciences niitl technology. This report tlesc*ribes t lie c'i~rreri t st:i t us, object ires : i d program plan for developing tliese uses of isotopes.

The isotopes of main interest in this discussion :ire described briefly in 'ruble 1. More detailed infoniltition on tliese isotopes is presented in Appendis "A".

L:irge-scc;tle employment of isotopes is j i i s t beginning. Tlie :uiticip:ttecl growtli in installecl w p c i t y of civilian power reactors slioiil~l provide significant increases in tlie :~vailal)ility of

r ,

,

several inipoi-t:iiit isotx)pes siicli as Pu-238, ('in-244, ('0-60 atid SI.-!)().

It is the responsibility of the AEC to en- (mirage i1s0 of isotopes as a national resource. \F'itIiin the eflort, research and develop- ineiit reqniretl for various :ipplicut.ions is CO- oivlinatetl within several programs, each containing projects haring Coiiiiiion or similar tec-liiiology reqiiirenients.

The h l y of this report tlescribes tlie pro- granis : i id tlie inter-program relationships. Witliin eac-11 prograin description the report re- views the competitive factors which influence clevelopnient objectives niid other information iiecessnry for tlie reader to understand the backgrouiitl of each progr:~in being described. Isotopic system characteristics are compared to those of non-isotopic alternatives to illustrate the likely areas of attractiveness and to explain

Table 1. Characteristics of Isotopes of Interest Half Principa2 Cost Range Shield- Life Gkenaicul Principal $/tkernial ing

~ Yrs. Form Radiation rcntt' Req'd. Ketnarks

C o h l t GO

Strontiiiin 90

Crsiuiii 137 Ceriuiii 111

Prornethiun: 147

Thiiliiirn 170

Poloniuin 210

Plutoniuni 238

5.3

28

30 0.78

2.6

0.35

0.38

86

Y

P

A Y P. Y

P

P

(1

a

73.5

2 5 3 5

20770 1

2004iOo

1 6 2 5

1625

5 w 7 0 0

Heavy

Heavy

Heavy Heavy

Minor

Moderate

Minor

Minor

Crrrreritly in large-scale use principally as radiation source. Reference terrestrial power fuel. Alternative to Co-60. Being considered for short- lived terrestrial heat sources. Being used in tliernial conditioning applications. Being considered as alternative to Po-210. Reference space short-lived fuel. Reference space long-lived fnel.

Curinin I44 18 CI~IZOS (1, 7 . 1w.500 Moderate Being consider4 to supple- inent PII-338.

~~ ~

*For transfers to other Federn1 agencies only, bnw'd on wtiniated costs in late 1970's.

1

.

Rf P'

I l i

grl

SI

t i t !

SUMMARY

der second)

it of propel.

)n ,ator

Power

ROLE OF ISOTOPES IN NATIONAL PROGRAMS

Systems iisiiig radioactive isotopes iis source6 of heat. or radiation :ire making iticreasiiigly i inportant. contributions to severi~l vital wit ioiial gods. Figure 1 illiistrates the inter-relation- 4iips of A I X isotope de.veloprnent progr:inis and the national benefits to be derived, :is well ;is the types of sources and tlie riietliods of prducticni.

Isotopes are in use as heat sources in space ;uid terrestrial electric po\ver, heat, :ind rudia- tioti systems serving tlie nritional d e f ~ n s e , as

MTHOOS OF m w PRODUCTICN SoClRcE

ALPHA EMITTERS PRO- DUCED BY SERIAL ADDITIW OF NEUTRW AM, REWIRING PROCES SING ,I, IJANU- FACrURE

PU-2 38 -244 -210

well :is in other systems wliic-li contribute to national security.

In the nation:il space progr:im, isotopes will serve as lieat sources for peaceful and military space power systems, propulsioii systems, life support and environmental control systems. Isotope-fueled space power systems are expected to improve the capabilities of satellites for weather prediction and rommuniratione as well as for navigation, earth environment research and s p m ~ exploration.

I n the iiational health program, isotqic, lieat sources may be used in systems to power cir-

AEC OEMLcQUwr PROCRAH

NATIONAL m a w BEWFITED

I \ /,m SPACE I

FISSION PRODUCTS BETA EMITERS PRO- WCED INCIOENTALLY TO OPERATION OF ANT FISSION REACTOR

Sr90 -197 -137 Ce-144

I / - \ 1 r/ /--tZP SEARCH c I Lor TAT I ON

n‘

PROCESS RPDIATIOIJ RADIATIW PRESERVA-

CCNSERVATION, TION OF FOOD

IMPROMD CHEMICAL - - - - - - - * -

PROCESSING

FIGURE 1 . ARC nrvplopuirnt of Isotope Sonrc-rs for Sational Programs.

3

4

I':1(~1<:1ge ( .ir,sr4~). 'l'lie 1)q)iirtiiietit of ne- fetw Iias t.equcxstec1 A!l<(' to develop n new p o ~ e i . r i t i i t f o r tlie Navy 0prr:ition:d Naviga- t i o i i S:itsllitr? (N,\T'S.\T) : i t i t1 has :IIW re- ciiiestetl tlevelopttient of tlie 1'0-2tO fueled, SOO- \r:itt, !)O-(Iay-life SN,!I' 2!) iitiit, tlie latter now i n systrtii tecliiiology developttietit. NASA ]ins iwliiestetl .! I%' to develop a i i t l deliver :I 25- tl~ei~in:il-ltilo~v:itt lieat soiiwe during the 1971 period for iise 11 itli tlie isotol)e-Br:Lyton cycle system to lie ground tested a t SAISll's Lewis Re- search ('enter. Tlie N- lVSAT :und the isotope- nrnytoii system programs :we untler discussion with M ) I ) : i t i t 1 ?S,iSA. 111 the area of advntirecl systeriis tecliiiology, :t multi-Iiulvlred watt RTG is being tIeigiiet1 for. possil)le future missions. 'I'liis tlesipii stiidy affords :L convenient ineatis to i ii vest i gat e t I ie safety :it i( 1 gromit 1 1i:iridl i rig protdeiiis of Si-90 ( ~ v l i i c ~ l i lias potential advnn- tngcls of ecoiiomics aiicl availability) in the con- test, of ;I practical power system deign, in :ii(ldit ioii tc: tlie nsu:il Pii-238 tlesigit provisions. Altlv:i~~c+ed tec.Iitiology projecats i n fuel forms ittid

po\vsr coiivei3ioti systems :ire being curried out in a coordin:Ited sffort wit11 N A S A ancl DOD.

Power systeuns nntler tlevelopnietit may be tlivitletl iiitx, sever-:il mtegories. The first cate- goiy cwtisists of ~wtierntor.s for power levels up to ;ilx)ut. 100 electrical watts, iiicorpoixtiiig in one package fuel, tlierrrioc-ouples, : t i i d integrnlly- nioriiitetl wste lieat radiators. This category iiiclntles the ,SNAP 19 a i i d SNAP 27 flight systems as \vel1 as tlie :%O-\v:itt, bLliglit-weigl~t" tliernitdectric generator. .I seroiid c:itegory consists o f iiiternieclia~-sizetl R'IYi's wi th sep- : i t . i i t~~l~-ti io~~lited radiators c.ooling the tlieiwio- elec*ti-ivs. SNAIP 29 is :in ex:~ttiple of this category. *I tliirtl category consists of power systems in tlie iniilti-kilowatt power range. To conserve isotopes these systmis will use liiglily efficient tlyiiaiiiic. poiver convei.sioii systems. 111 all cate- g o r i q pnver. systems coiiiposed of building l)I(x.k "incxliiles" :ire being developed to i r i e e t tlie I\ itlest possible c~oiiibinntioii of potelitid power reqiiireiiieiits. A t l t l i t ioii;il categories or subcategories of system tii:iy be defined in the fu- tiire, :IS reqiiireiiients for these new systettis m e identified.

Fiitiire use of isotopes iii sp:ice niay be piwed I )y t lie i i ttii i 1 1 tiiet i t of :itlv:i ticwl fuel : i i d systeni tec~litiology, esprci:illy :IS tliese enable design of 1 iigli er- t et i i pr:i t 11 re, more-efic ien t systerris.

adv:incscl \Vi1 t t ET(;

3 missions. r means to

ha I id 1 i I ig ial advnn- n tlie con- clesigi, ill

)revisions. forms and ur ied out DOD.

fitst cate- levels np

)rating in ntept l ly-

c:i t egory 27 fligllt

it- we igI 1 t" cntego1-y

with sep- 3 tlierii to- this cate- ?r systems

conserve y efficient I all cate-

building B meet the i d power

in the fu- stems a1'8

be p:iced 18rl system tlesigri of

may be

01' sub-

1s.

r , llie mo5t pi.oniisiiig : i p p r o : i ( b l i t o in(8reasing the useiulne,.;s of isotope systeiiis is to de\ dol) higher svstem efficiency. 'I'liwo :ire two ni:iin

:Lvt?n1les of :lt>t,:lck : 1. Raising the heat soitre t~iii~)eratiirc'

(xI):il)ility to ixicre:i.;r SJ steiii rfficirr1c.y for :i

giwn Iiwt diq)os:il rntlintor arcri.

2. Developing rxiorc efficsirrrt elwtric.al generator cwnvepts, wc-h a s c.:l.wadt?d therliioelec~trics, dynaiiric mac~liinerp :ind therriiionir gerirmtors. (i\liiny of these advancwi gerlertttors also require higher heat sourcv tex~iper:itrirt?s than are cnrrently available. )

The capability of higher temperatures is one of the most difficult goals of the current isotope fuel form development progrilm. Compared to a current 1400'F fuel surface terripsmture caps- bilit.y, tl10 goals for various propulsion and power conversion concepts are as follows :

Advanced Rnnlrine, Rragton, and Theriiic~lectric Generators, and Auxiliary Thriisters _ _ _ 1800 - 2200°F

Thrusters _ _ _ - _ _ _ _ _ - _ _ _ _ _ _ _ 3250 - 365OoF Therinionir Generators and Primary

Figure 9 illustrates tlie trend of power levels and temperatures i n isotopic sp:~ce power systems.

For repetitive space po\ver applications there is :L strong incentive tu use a. cheaper long-lived fuel. Sr-90 is cheaper than the present, reference space system fuel, Pu-238, b u t its radiation sliielcling and safety problems in space systems :Lre difficult to evaluate. It is not yet clear whether Sr-90 can be mxde safe and convenient enough for spac.e nse; investipitioils are proceeding.

A critical factor in the widespread use of space isotope systems is the resolution of safety assur'ance standards and tlie solution of several vital technicnl problems related to safety, such as metliods of fuel encapsulation to ensure. in- tegrity in all expected operating iintl nc~ident conditions. The criteria in all cases is tliat the isotope devices be operated in such a way that no undue risk to the public, occurs. In almost 1111 cases, higher fuel temperatuix capability could assist in resolving the safety problems.

Because of the substantial financial coInniit - ment and several-year lead times needed tu produce the isotopes of innjor interest for space and certain other. specialized applications, there is an urgent need for better long-range fore-

10,000

1,000 u, I- I-

3

!j 100

2 5 - LL + 5 10 w

I

SNAP 9 A . / 1400°F 95O0F /

' 0 SNAP 3 950°F

-L 61 62 63 64 6 5 66 67 68 69 70 71 72 73 74 75 76

CALENDAR YEAR OPERATICNAL

FIGURE 2. Trend of Power Levels and Operating Teiiipera tures in Space Power Systenis.

casting of needs by users. Genarally, the users, paced by mission funding authorization, fore- cast their firm requirements no more than two or three years in a1dv:mce of required delivery. Development of fuel forms and pow0r conversion systems requires lead tkies generally in excess of this two- or three-year lead in firm requirements information ; and for this reason, ttdvunced teclinology work must be scheduled on the basis of preliminary requirements estimates. The level of actual demand for isotope systems will, in turn, be determind largely by the de- gree of s u c m of development progrzms.

Despite the difficulty of forecasting, SASA has encouraged AEC to produce 500 tliermd kilowatts of Pu-238 by 1980 to meet. the space po~rer needs of the peaceful space program. Jleanwhile, quantities of Pu-238 forecasted for 1101) and NASA and required by current AEC tlevelopnierit programs appear now to h ap- proxinintely q u a l to all that AEC cn11 produce, through about FY 1071.

TERRESTRIAL POWER SYSTEMS As with space power, the B E G approach to

development of terrestrial power systems is to study r l imes of potential :ipplicatioiis : i d tlie f ac tois which nffec t. compet itireness with other

eiierKy SOIII-WS in e:wIl d a s ; tlieri, to develop techrlolory :i11(i p ro to typ systems wliiali satisfy the txmipetit ive cr*iteri:i, :ind to wopemte witli user :igwtic:iw in testing in sirllulatetl :ind :u:tiial eniploytricnt sitiwt ions. 111 this niaiiner, tlie lowest po.ssit)ltz totd nutriber of sepra te (level- opnietit pivjwts is reqiiiretl, :inti tlic (-ti:uiging scliotlultxs o f citiploynient by int1iviitlu:il user systems s l~oul t l I ~ v e the least possihle elt’ect on t l i r over-all tlnvclopment, progrsm.

I n terrcstri:d npplimtions, isotope system weight is less important tliali in sp:ica systems. ~ l ~ ~ ~ ~ f ~ ) ~ ~ , shielding for. tmta :inti g:ininia eniit- teis c:in bu provided, :illowing the use of various fission prwluct fuels wliic.11 in the fut,iir.e will be available in large quantities as by-products of the civilian mitral station tiuc.le:tr. power in-

I n most terrestrial applications, reliabilit,y, economic advantage, safety, and portability must be demonstrated to the satisfaction of potential use~s. Facto~s at1v:mtngeous tr, e m - nomic, competitiveness of isotopic power sources include liigli reliability and reproducibility, low operating cost, arid long unattended life. For certain unattended surface and undersea applications, the long life of isotopic systems offers a unique operational regime; tliere are no competitive power concepts. Long-life reliability is also tlie key to attractiveness in applications such :IS isotopic cardiac p:ic~makers.

Proof-of-principle Sr-90 RTG’s have been developed under tlie SNAP 7 program and have operated with reasonable succws a t several hi-rwtrial sites including remote unattsnded weather stations, a navigation buoy, an und‘er- sea resxircll exper.inient, and an off -shore oil rig. Advanced systems, which will capitalize on this SNAP 7 experience to meet evolving economic =id reliability objectives, are being developed for marine (SNAP 21) and land (SNAP 23) :bpplications in the early to middle 1070’s. Pu-238- fueled microwatt arid milliwatt generatois for cardiac pacemakers and low- power electronics power source6 are also being tleveloped. C-60, (h-144 and Pm-147 are k i n g evaluated as fuels for terrestrial power systems, in addition to Sr-90. AEC hopes in the future to initiate an appIicatioI1s engineering and

6

dustry.

par:inietric design stituly of isotopic heat sources :ind t1yn:imie tmversion equipment in the I--%) electricd kilowatt power range for v:wious terr-estri:iI and iintfersm iieetls.

I n m i 1 juwtion wi th specific system-oriented work, t lie terrestrial power pr0gr:ini also in- c:ludes several projects for improvement of hisic ter:ltriology (~~n in ion to one or more curront and future generator concepts. These include devslopmen t of I:etter thernid insulation, improved components of tliermoelectric and otlier electricd generatois, improved fuel forms, and studies of metlids of safe design and employment of isotopic systerns.

THERMAL APPLICATIONS Thermal conditioning systoms such as space-

waft and swimsuit heaters, which may be lighter arid more reliable than electrically- powered heaters, are being investigTtted. Is01 tope-fueled life support systems appear attrw- tive for long-duration space niis.;iorls when com- p a d with solar energy. In this category, a lieat SOI~ITR for a waste wahr r e p r w i n g cycle l i x been demonstrated for m:inned space applications.

Tliermodynamic systems being considered include an energy s o u m for circulatory support devices. The technical problem is an extremely challenging one; and if successfully d‘eveloped, this application alone could conceivably use all foreseen supplies of Pu-238. Pm-147 is also being mnsidered as a candidate fuel. Design studies to define an isotopic-powered engine concept for a henrt assist or replacement are being performed in cooperation with the National Heart Institute.

PROCESS RADIATION SYSTEMS ISOtQPeS .are in use as ra~ia t ion sources in

severd industrial processes wliere this radiation is more economical tlinn nonnuclear p m - eeses or ~welerntors used as radiation sourcm, or where unique products can be produced.

Economic competitiveness is a key criterion even in situations whe1.e radiation produces a better prodnct., since the margin of improvement is usually amenable to some form of

1 as space- 1 may be !lectrimlly - qzted. Iso- ear attrac- when com- ory, a heat 5 cycle 11%

*e applica-

sidered in- CY SUPPOd extremely

developed, bly use all 47 is also el. Design mgine con- , am b e i i . National

S sources in his radia- :lear p m - m sources, *ed.

criterion reduces a

improve- form of

economic :iIinlysis. 111 S O I I ~ O c*:ises. I i o ~ ~ v e r , S I I C * ~ ~

;LS r:Lcliatioii-Drot.~~l \v(xKt-pl;tsti(*s, :L fin:tl ehnrate of the value of t l i e new prwlac.t must : twi i t. gr.ntlu:i1 ac.cq)t;iiicw ( ) I . no11- :itA'e[)t anco by the c.onimercia1 ~n:trliet,.

New and exp:Lnded u s s for r:idiation proc.- m i n g :ire cmntinunIly being irivestipited Sev- eral r a d i a t i o n - p r l m:Lterinls Imve been devdoperf to the point of x t ive industry investment. I'rweaes for ratli:it,ion p:istwirization of foods are be ing developed for eventual wm- niercial iza tiori by developing the khnolo&ry through semi-clonimereial scnle demonstrations, and obtaining Food & Drug Administration cle:ir:inc.fi on a limited numtrsr of foo t i s for which such processing appears to otfer substantial economic benefit.

SPACE PROPULSION Radioisotope-heated thrusters use the thermal

energy p r o d u d by the decay of :in encapsulated radioisotope to heat a propellant, which is ex- hausted through a rocket nozzle to produce thrust. These thrusters cnzii provide relatively low thrust (10" to IO-' lb) and high specific impulse (200 to 800 seconds, depending on propellant salectsd and capsule temperature capabilities) in a simple, lightweight engine.

Two general classes of radioisotope-heated thrusters Iiiive been under investigation: one is ic high-temperature ( 30C)OoF-350O0F) high- specific impulse (750-800 s ~ ) , 0.85 lb-thrust, high-power (5 thermal Kw) c l w which uses hydrogen propellant for primary propulsion :tpplication. The other is a lou-er-temperature ( 1800°F-22000E'), low-thrust (micropound to millipound) , low-power (100 watts) class which, using ammonia propellant, providks specific impulse in the range of 2OO-450 sec for auxiliary spacecraft propulsion. Work on the high-temperature, primary propulsio11 thruster has been suspended pending developnlerlt of the necessary high-ternperr~ture fuel form :ind capsule technology.

The Air Form and tlie hE(: are currently considering a cooperative flight test program of an auxiliary radioi~~pe-lie:Ltect thruster using ammonia propellant to demonstrats flight 1iardw:ire and' make development leadt,imes compatible with spwecra f t development. sched-

i i l e s ; but, no specific: missiolr requii-emetit 11:s

twrn s t : r t d , and no flight program has besn for~rnnlatrrL

PRODUCTION OF ISOTOPES Important :tspects of the production of iso-

topes include the forwasting of quantities of isotopes required, the comparison of these qu:intities with the capacities of existing or pro- jecbd facilities, and the estimation of p d u c - tion ~-ates :ind mts which might m u l t from fu ture production programs: Consideration of tlie special characteristics of each isotope which affect production are of COUISB v i h l to this planning.

The pmblems of obtaining reliable forecasts of isotope requimments have been mentioned above. Because of the uncertainty to the user about availability and costs o€ isotape and the uncertainty to the producer about requirements, the umr :~nd producer l a v e to collaborate closely for the most effective joint program planning.

The current limiting factor on the quantity of important radioisotopes that can be produced is the lack of facilities necessary to prepare targets for irradiation, to process specific isotopes after irradiation, or to manufacture isotopic sources.

The cost to produce isotopic source materials depends upon several critical factors, among which the most important are the quantity and' quality of the msterial to be produced, the isotope product mix produced, and the relative values of these irmdiated p d u c k . These factors can influence sipifimntly the mode of production reactor operation, and' thus the irradiation and fuel cycle costs of the various products. Accordingly, it is not possible to quote firm costs which can be applied in a general WHY

to specific isotopes in the absence of firm requirements. The probable ranges of Costs to produce in Government facilities large quantities of specific isotopes for transfer to other federal agencies have been estimated, and are indicatd in Table 1.

Potential fission product availability will g o w as the number of commercial power reactors starts increasing in the early 19'70's. Within five yenrs, cnmmercixl €1181 reprocessing plants

7

I'iiless i i low-cost metliwl for producing Er- 170 is d iwverd ' , Tm-171, wliicli lias desirable chnracteristics for low-shielding lieat source applications, cannot be made in existing production facilitieri at, costs less than several thou- sands of dollars per watt.

At present, the only capability to process I?* 210 or manufacture Po-210 lieat sources exists at AEC's Mound L:hratory, and i t s enc:Lpsula- tion capability is currently limited to a few hundred grams of 1'0-210 annually. By 1969, however, Monad slioulcl hnve the capability to supply 60 kwt of Po-210 annually. When requirements for Po310 exceed Mound's capacity, facilities will be requird to process annually several liundred tons of irradiated bismuth, recover the bismuth :is metal target billets for recycle, and recover, purify and encapsulate Po-210 in the anlourits required.

Plutonium-238 is m:ide by the addition of a neutron to Np-237. Campaigns to produce large quantities of PG-238 typically require G S years of leadtime. Starting in tlie late 1070's irradiated power reactor fuels will be the primary source of Np-237 supply. Therefore, recovery and conservation by the nuclear industry would be :L major contribution to the future availability of Pu-238 for isotopic power

Cm-244 requires heavier sliielding than Pu-238. Althougli a. considerable nmount of investigation using gram quantities is underway, charzkr- imtioii of Cm-244 for the required' regimm of temperature and metallurgy will not be completed until 1969-70.

Signifi~~ant amounts of high-exposure plutonium, americium, and curium isotopes will become available from the nuclear power reactors starting in the late 1970's. This could increase the availability and reduce the lead time and ca t . to produce large amounts of Cm-244. The cost range of Table 1 is based upon the recovery of Cm-244 from spent power reactor fuel.

OUTLOOK AEC will continue to be faced with import.ant -

teclinical and administrative problems in en- couraging effective use of fission products and other isotopes, forecasting future production requirements, and ensuring availability of desirable isotopes. Nevertheless, important progress lias been made in the first years of isotope developrnent, and a future of ever-increasing value of isotopes to the national interest is to be expected.

R

Fue

1

111011 * 1

8

lest a d d 4 *ary for ctor fuel jotentiaUy ,essing of

accumu- nment or the total

)y be in- c d as a 1 less 1ctor.s be-

through

~rocessing ad to the hown in

makes it xer using +nt, the however,

fission of

%tigation ,haracter- agimes of be cam-

w e plu- )pes will ver reac- muld in- ead time Cm-244. ipon the ’ reactor

-237 cost,

L Pu-238.

nportant : in en- lets and oduction r of de- 16 prog- -‘ isotope creasing is to be

SPACE POWER SYSTEMS BACKGROUND APPLICATIONS

Isotopic heat sourcw are used to supply tliermal energy to space electric power systems. Four generators (SNAP 3, SNAP Oh) have already been oper:&d in Department of De- fsnse navigation satellites, and units now under development will be delivered in F Y 1968 for use on the Nimbus 73 satsllite (SNAP 19) and the Apollo Lunar Surface Experiments Package (ALSEP, SNAP 27) to be left on the moon by Apollo astronauts who land there. Another generator (SNAP 29) is being developed uritler AEC sponsorship to meet several possible DOD and NASA requirements for systems of 3-5 month lifetimes. Important characteristics of these generators are summarized in Table 2? and these projects plus the technologg invwtigations Iwing conducted in support of these system develop-

ment programs :Ire described i n more det.ai1 in the following sections.

CURRENT STATUS AND PERFORMANCE REQUIRE- MENTS

lifetimes of Interest. For long-life space missions (greater than a few months) the radioisotope-t,hernioelectric p i e r a t o r (RTG) ? fueled with Pu-238, is the current state-of-the-art isotopic power system. Po-210 fuel is also under development for mission life xpproximating the lialflife of Po-210 (136 clays). Pu-238 and PO- 210 are alpha emitters vhicli require little or ILO

shielding in unmanned missions and are relatively simple to liandle on the ground’. Son- nuclear competitors of these RTG systems atre solar cells for long missions, and so1:ir cells, batteries and fuel cells for shorter missions. ,4 nuclear competitor, the reactor power. system, will be wmpetitive for long lifetimes, at power levels above a few kilowatts.

Table 2. Rad ioisoto pe-Ther moelectric Genera tors SNAP 3 SNAP 9A SNAP 11 SKAP 17 SNAP 19 SNAP 27 SNAP 29

Applications : Environment Earth Earth Lunar Earth Earth Lunar Earth

Orbit Orbit Surface Orbit Orbit Surface Orbit Ref. Space Nav. Sat. Nav. Sat. W d a y Small Mil. Nimbus ALSEP Various

“B” Mission Surveyor Comsat ~~

Power Level

Specific Power

Fuel * Pu-Metal Pu-Metal Curium-242 Strontium-90 Pu-Oxide Pu-Oxide

Conversion

(elect watts) 2.7 25 21-25 25 25 50 500

.59 .93 .83 1.0 1.0 1.5 1.0 ( watts/pound)

GdPo

Material PbTe PbTe PbTe PbTe&SiGe PbTe PbTe PbTe

Safety Criteria ** Burn-Up Burn-Cp Intact Burn-Up Intact Intact Intact

Flight Ground Not Early Readiness 1M1 1963 Dernonstra- Being 1967 1968 1970’s

tion 1966 Develop&

*tJ&ul lifetimes for the pu-238 systenls ape from 1 to t i yrars: for the Cn-242 and P+210 systems, about 3-5 months.

**Design cr ikro &&&dirk re-entry af ter orbit d~c.al or h u n c h failure.

9

For slioi-t-1ifetiriir.l rnissioiix, primary batltories or fuel cells Ii:~ve I ) w n iiml :iritl will wntinue to be :ulvnnt,:i~~~,us. I lowever, tlie 1aunc:li weights of htteries and f i le1 cells go up dirwtly with integrated energy output. Tlio fuel consunipt.ion weight of nuc1e:ir sources is negligible and of solar systems is ZPIW. Figure 3 illustrates this effect of lifetime on t,he weight of power sources. It is .seen t h t batteries :~nd fuel (*ells :re quite hesvy as primary power sources for long-life systems. On t,lia otlior liartd, nuclear arid solar systems :we uninteresting for very short lifetimes, but :ire tlie main competitors for lifetimes longer thart a. few weeks. (The reactor system improvement in tlie 1070's comes from ii combination of r e d u d unit weights with higher

power :ind sucli tec*linology improvenlents as liiglier efficiency.)

Selection Criteria. The inost ini1x)rtant criteria, for comp:iring alternative sp:ice power concepts are weight, mt and avnilability, ex- pcml am~, reliability, and applicability to special employmeltt situations. Efficiency of isotopic systems is importmt mzinly because of its effect on other criteria, especially cost and fuel avaihbility. These factors are discussed in the following parapraplls, especially from the p i n t of view of their effect on development objectives for isotope power concepts.

Typical weights of current and projected radioisotope and solar cell systems are shown in Table 3. At the sub-kilowatt power

Weight.

3 -

SYSTEM SPECIFIC MIGHT

POCNK PER WAlT

2 -

1-

1 2 3 4 LIFETIN, HCHMS

level

tl1e b ' ? ; O l

tile sun !

circv

ndec of o1W the ver: the exa it i 3 i peii

:1re

ligl1

(tl1;

coli :I c O f

tl1:1

de\ cy ( ati

I

aP!

- C U

ss H;

K:

3. Spec.ific Weight of Power System as :I Function of Lifetime, Showing Overlap of Typical ?u'uc.lwr :ind So1:ir Systeiiis of 1970's.

10

,,,,.I ~ q u i r e d txday, solar cell systems iisually ,I ,, 1 iglitor t.h:ln isotope systems in cases where

, I , h 5ol:ir cell system weight approaches the .. ~ l ) l , ~ i ~ ~ : i I " panel weight, i.e., :it, :L distance from .,!,. i l l l l of 1 a.u. (tlie dist:Lnce o f eart.li from tli0

:lid with solar cells in full-time, full sun- : , f i l t , : whereas, isotopes may be lighter where i,.i,l[lnst:inces require use of unorientetl systems

, 1,;t t . is, sufficient arm of solar cells to intercept ~ I l c ~ ~ ~ i ~ ; i t o sunlight regardless of the orientation ,,( t110 spacecraft), or where the system must ,,lM81.:1te in t,he shade, or far from tlie sun. Since Ijl,. :\llrount of incident .sol:ir energy varies in- ,, .l-i~ly with the square of distance from tlie sun, I j , , . t ) i i tput of a given solar array will he, for ,l,;i~[lple, roughly half a t the orbit of Mars what ,I is 1ieii.r Earth. AS r egads system cost, Table :: iirditxtes that isotope systems are more ex- Iwiisira than solar cell systems except where ,.lmciit,ions are unfavorable for solar cells or if .I I'I~wper fuel such as Sr-90 can he used instead o f (110 c:urrently-proven Pu-238. It is also seen I t 1 : 1 ( , vxpectd technology advancements, suc11 a s tlvwlopnient of thermionics and the Brayton 1 . ( . ( . 1 0 , will tend to make isotope systems rel- . i t I \.irIy more attractive.

ILtdiabiZity. As regards reliability, there .il)l)o:ir to be no inherent characteristics of

solitr cells or isotopic systerris that give either one :L clear :dv:intnge. Both isotope and solar (*ell systems have cm-tain features that cia11 PO- tentidly caiise trouble, hit these uid the tk6ign ad justnients to avoid trouble are well nnder- stood. In applications such as those in earth orbit where storage of elwtricity in batteries is rqui~wl for p e r i d s when the satellite is hidden from the sun, lifetinie of solar system is currently limited by the lifetinie of the batteries, which is currently less than two yenis. This lim- itation does not exist with isotope systems.

Xufety. A\ single safety criterion can be stated: Tlint no undue hazard to people or prop- erty be caused by any foreseeable results of the launch. Mor0 specific design criteria are evolving. I n many isotope space systems designs, one of the most difficult problems is safe return and ultimate disposal or recovery of the fuel. The fuel must be safely contained or d i s p e d of in the event of a launch pad fire, a return to earth on launch abort, o r a short-lived' orbit; finally, in successful missions, the fuel capsule must be predicbably safe after months or years in high-tsmperature operation. Re-entry heat- ing, possible partial or complete burial after impact, and the impact itself, are difficult to analyze and design for. Because of the long

Table 3. Specific Weight, Cost and Efficiency of Isotope and Solar Cell Systems

Approximate Approx. Specific Approximate Approximate

Weight System Cost Overall S Y ~ $l@/ew Efticiency ( % I

Year Available Ibs/ew

('cirrcwt IlTG (SNAP 9A, 19, '27 with PU- Today 0.7-1.0 13* 5

5 Y .\ I' 2) with Po-210 Early 1970's 1.0 1 5 3 X ; 110 shielding required)

I L l l I i o i w t o p e Thermionic Concept Mid-1970's 0.30 4 15 1 Iirishic*ltlcd Cm-244)

- t % )

1; . I (1 i 1 I isolo pe-nragton ( manned, shielded Pu- Early 1970's 0.5-1.0 3* 20-25 .,.,

Uncertain 0.7-1.0 0.5 5 Today 0.1-1.0 0.5-1.0 7-10

l l 'P(;'s usin): Sr-00 fuel unshielded " l l r r ~ t Solar Cells (oriented) ' . h r (!ells in 1070's (oriented) 1970's 0.025-1.0 0.5 10 ,'aihr Cells (moriented or with batteries Today 0.4-1.5 14 2-3

riir shntlc-time operation)

l : i l i i w ( d ) from sun than orbit of earth. Future 6 a= 7-10 Varies as .'"hr Cells, full sunlight a t greater dis- Today or Varies a8

' . \ t c i r t h , d= i a. u.)

11

h l f - l i f e of t l i ~ n t o b t tle5itxl)le fuels, it is 1111-

likely t1i:it prfot*ni:inw (I:it:L on ni:Iteri:ils or norbirig asseniblies \rill be ol)t:iinetl, prior to o1,er:it ion, for t lw full pn&rin:inc~e p~rio(1 re- qu i I'D( I. ( "o:i wq I IP I i t I y , :I si g i i fiwn t f 1 - a ~ t 1 on of :iII tie\ clopiitrnt f u ~ i t l i i r g n 111 cwrit,itiut t o go into s:ifety testing : i i i ( I :~i i : i lys~\ for d l tic\\ stems tleveloptvl.

X ~ Z P . Tlte size of so1:ir systems is tleterrnineul by tlie ::re:i reqiiiretl to interc.ept so1:ir energy: \vIiere:\s, tlie size of isotopes systems tlep'entls on tlie size o f tlie r:idiator wli ivl i disposes of e x ~ e ~ s cycle Iieiit. Isotope systetns :it, 10:1~t :IS sI1i:ill as so1:ir cell systems :we :iv:iil:ihle trxhy, : ~ i t d

be modified to obtain furtIiw size i-eductioiis by increasing r:iltli:itor teitipr:iture, wit l i small efficiency retluctiotls.

Post c r n d Awiilubility. '!&e cost :ind :iviiil- ability of preferred isotopes are of serious con- cern to planners. This concwn stems from the Iiigli cost of producing and processing tlie isotopes, the long leiid times required for prociuc- tion, and tlie lack of exact information on probable mission specifi(xt ions and sclieitl'ules. Tlte rurrent cost of fabricating :Ln isotope power system, including all pnrts :ind material except the fuel, is $5OO-$2OOO per electrical watt; for a R%-efficient Pu-238 or Cm-244 RTG. tlie fuel cost is about $12,000 per e1ectric:ll watt.

life alplia. fuels. These fuel costs are expected to be signific:intly rednred by i~ictwased efficiency iilid iniproved processing tecliniques and by developing :I cheaper fuel such :LS Sr-90. Cost :Ind nv:iilability of fuels are discussed in more detail in the PR0DT;CTION section.

h'pecinl C c ~ e x . As noted, the solar cell- battery combiti:ition is tlie best poner system for many long-life missions. However, tlie wide variety of potential missions in the national sp:~ce program include special coiitlitions wliicli particularly favor isotopic, sol;^, or reactor systelns. Tlie following is a. brief discussion of son18 of tlie more importali t cases :

Lack of h u n l iglit-Solar systems rnust Ix in direct view of tlie sun, or batteries iiiust 1% proviclad, with :idtlitionnl sol:ir cells to charge them (luring siuiligllt Iioais. Isotope systems are not restricted by lack of sunlight. This limita- tion occurs in tlit-ee categories of misaioiis : In most earth orbits, the satellite is ll#ldeil by tlie

' I h S , the It'L'G costs arc3 nlmtly costs of 1011g-

1 0

cyi1-t Ii for soiiie frxc*tioii of ~ : i ( ' I t orbit. Batteries for lo\v-:tltitiitle ;ipplic:itioiis can account for 11101'e tl1:I l l > o p t o f tile total ititsr-pI:iiiet:try :ind out-of-ec,lilipt.ic probes, solar (bells i l l be iwluretl in et'l'cc*tiveiiess with tlie squ:we of tlie distalice from tlie sun. For BX- :tiitple, tlte aw;i of solar paitels for :I given pome,r level itt the orbit of ,Jupiter will ?x 27 times as Inrqe :is ;it earth. Other applications such as on tlie surface of tlie mom, favor nuclear system for missious requiring opemtion during periocls of darltness (e.g. tlie 350-hour luiinr i i iglit. )

T,ow area requirements-Nuclear systems can be designed to present a lower frontal area thin solar systems. This could be an important adran- tage in rertain clilms of military suweillance system3, where desirable low altitudes lead to high ntr!tosplieric drag penalties, anld in missions in w1iic.h large so1:tr cell areas interfere with iinteiinas niid other equipment., or make packaging within a Inunch vehicle envelope difficult. (Propellant required to overcome drag, or rducecl lifetime without drag compensation, is :I func,tion of frontal area.)

Insensitivity to radiation-hTuclear systems are inherently less vulnerable to the belts of trapped electrons tliat surround the earth. These lwlts could be intensified by future higli- altitude nuclear detonations.

IIigli-temperature~re environment-Isotopic systems arc relatire.ly insensitive to environmental temperatures. For example, close to the s u n or in tlie noon-day heat on the lunar surface, solar cAls \vould operate at reduced efficiency as their t en iper i~ t~re increased ; but isotope systems would suffer much less loss of efficiemy.

High radiation backgroun d-Un less shield - ing is provided, radiation from tlie nuclear source can interfere with some types of radiation-sensitive experimental equipment.

T-Tigli po!rer-Becnuse of the liigli cost of loiig-lived alplia emitters :ind tlie favorable \\-eight of renct01.s a t liigli power levels, it appears that r-cmctoors will be preferred over IJotli isotopes and solar cells for initny of the long-life, tans-of-kilowatts space power requirements of tlie future. For the shorter missions ( about 3 months), Po-210, and possibly Tin-170, \rIiirh offer advantages of low radiation shielding (conipnred to reactors) plus low

L A

n:i ttmies ount for eight. 1 1 ~

~ES, solar with tile For ex-

en powr,r times as SLlCll 3s

Aear sys- i i during u r 1un:~r

Jmns can mea t h u iit advan- r v e i l l a ~ ~ z i lead to

in mis- intsrf ere or make envelope

)me drng, )ensation,

systems belts of

e sartli. we higli-

opic sys- mmeii tal ie s u n or ace, solar : as their

systems

i sliield- nucAear

of rad'ia-

cost of Favorable levels, it red over y of the . require- missions possibly m radia- plus low

wst, m:iy be c w i i i p t s t l t i v c into tlie kilon ;itt range. Inipi-o\ ctl so1:ir c.t.1l.i mny also st ill be :ittr.:ic,tive for ~iris~ioiis at ;I fev tells of kilo- \v :1 t t s.

Importance of Temperature a n d Efficiency. Isotope systems c m l t l lw niat~rially improved 11 itIi IiigIier (*o~ iwi - s i a~ efficiency. Tlie fuel i n ventory, wliidi to :I first approximati011 repre- sents tho (Lost o f tlie system, is i.etluc.rt1 tlirectly in proportion t o :ti1 increase in system eficienc?-. \Vel g11 t :iritl r:icl i n t or :i rea vary :ipproxini:i tel j inversely with sgstern efficiency. Other i n - portant clial;icteristic*s :ire siniil:irly benefited by higher efficiency.

Higher ef ic ierq (' i i i i tm oht:iinetl by increasing the heat source temperature :I itd develop ii ig more-efficient poiver convei-sioli tec.linology. Since till isotopic power systems protlnce power by tlie flow of heat, over:dl efficiency is propor- tional to tlieir Caiiiot efficiancy (E) :

E = T h - T, T h

where T h = mean power conversion inlet absolute temperature, and T, = nienn power conversion outlet absolute temperatiire.

Since T, cannot. be reici'uced indefinitely without causing unacceptable increases in radiator area, tlie only way to improve Canlot efficiency is to increase T,, or in terms of technology, to increase fuel surface tempernturw and power conversion system temperature capability.

Figure 4 illustrates the dependence of ideal tlierrnoelect ric system fuel inventory on mean hot junction temperature. Using %stage (SiGe and PbTe) thermoelectrics, increases from tlie l O O O O F hot junction temperature of SNAP 19 to about 1600'F could roughly Iialve the fuel inveiitory requirement, which \vould almost 11:ilve system cost,.

The second :ippro:tcli to greater efficiency and reduced weight and area is to develop more efficient concepts for converting thermal energy to electricity. Some of these advanced power conversion concepts (e.g., ther~nioiiic*s) require high temperature in o d e r to be attmc- tive at all.

OBJECTIVES The objectives the space isotopic power

c i e c e l 4 & ~ ~aggh may be stated as follows:

N T ELECTRICAL Icu

1

FIGZJRE 4. Effect of Hot Junction Teinper;lRlre on Fuel Inventory of Thermoelectric Systems (Optimized for JIininiuni Weight).

1. To increase fuel capsule operating temperature capability and thus achieve increases in system d c i e n c y and reductions in weight.

2. To develop reliable, moreefficient power conversion concepts.

3. To investigate and develop methods of safe eniployznent and ultimate disposal of space i w tow systems.

4. To reduce isotopic system costs. 5. To develop the power systeins or sub-

systems required by user agencies for specified space missions or classes of missions. Wherever possible these requirements will be fulfilled with combinations of standard modular system and components to be developed.

PROGRAM PLAN The program includes projects for the dsvel-

opinent of several categories of space power systems, and technolohy projects in support of one or more of these categories.

Based on analysis of the above facto13 and wlmt is known about likely missions, three categories of isotope power systems, c,haracterized by power level and specific development prob- leriis may be identified. Briefly these categories include the following :

13

1. I~'I'(:'S whic*h rnil)loy iiitrgr:iIIy-c.ontainctl hwt soiirws. radiat iwly- or contliictivc'ly- c ~ ) l l ~ ) l c . t I to thr~rrcwItu~tric* cwuwrtrrs, in turn c.oolt.tl by hwit cwritlucfion to railialive heat dispos:il surfacw. "his c.:itt.gory inclnde.; :ill the grritwitors Ia~inc~hrtl or sc~lic~lriled to be I:irinc.hwd during the l!)(iO's. Power levels of these cur-

teins :ire iiiitlrr SO watts, but the con- (vpt wenis to he pr;ictic:il up to about 100 watts. Following the S N A P 19 incwliilar approach, new devv1ol)nimt;il concepts, in(-lading the S h V S A T unit, will emphasize Inoilulnr tlesigns to meet thr witlwt 1)cmsil)le range of potential reqiiireiiienLs.

2. Mcrt1iil;lr RTG's for :ipproxiniaWly the 100- 1M)O watt power rangr. This power range is trmsitional betwren the sinall, low-efficiency, self-cont;iinecl. caylintlrital. finned. static (no iiioving iuirts) systems of category 1 :ind the more c*oriiplcx. high-t.fficienc.y tlynainir sysbrns being developed for high power applirations of category 3. The category 2 power systeni being derelopetl today is S N A P 29, which has a con- rwtive heat transfer systeiii that cools the theniicwlwtric cold jimction :ind dispn..s of the heat in a separate ratliatnr Icr+lted in some convenient 1oc;ition on the skin of the sp:icwraft. 3. Systems with .separ:itely-packagM heat

soorces, power conversion iiiac*hinery, and heat disposal sub-systems. applic*iil)le to power levels a1)ove about 1000 rli.c.tric-dl wath . The systeni currently under develcrpiiient in this (.ategory is t h e Isotope-Bragton 5.5-kw unit. At the high power levels of cateKory 3, high-efficienc.v power conversion m:icahinery is neiPssary in order to mlucr tlie total quantities of long-lived fuels reqiii red.

Other categories or subcategories will be in- c.lncled :IS 1)rogr:im ryiiirenients dictate. Power sy st enis and t ecI in ology pro j ects currently 1x4 rig fundetl include the following:

CATEGORY 1 SYSTEMS

SN,2P 19 generators :we tlesigned to supply a minimiirn of 50 net electrical watts to the Nim- bus 13 satellite for a t least one year in orbit.. Tlie design calls for two 25-watt cylindrical modules, mountecl in tnndem on tlie Nimbus sp:icwraft,.

SNAP 27 is a one-module cylindrical RTG to supply ;L rnininirlm of 56 witts for one year to the Apollo Lunnr Surf:m Experinientnl 1':icIi- age (AT,SEP). Deliveries of two fueled systems, two backup units, :\nd :m extra test unit are planned during .19G8. Three additional flight units will be delivered during F Y l!)f,D for follow-on Apollo progcim missions.

CATEGORY 2 SYSTEM

S N I W 29 is being developed for a clm of potential national defense missions. It will be fileled with P t r i l I O , as GtlPo, :ml is designed :IS modular units that mny 1% cwnbinutl to pro- tluce power in multiples of 100 electrical watts.

The S N A P 29 project is in tlie stage of system technology development. Satisf actory test re- s t i l t s tmultl 1e:id to full-scale ground test system development and n possible flight system program.

CATEGORY 3 SYSTEM

The AEC and NASA are cooperating in a joint program to develop and test :I 5.5-electrical-kw isotope-Brayton cycle power system for spilce power applications of the late 1970's. Tlie power conversion system will be of the closed cycle I3r:iyton cmncept which has been under development a t NASA IAwis Research Center for several years ; the heat source development is primarlily :I wponsibility of the hE(1 and is a. part of a continuing high-temperature isotopic heat source program.

Tlie A I W plans to deliver, for 1971 ground test ;it the NASA Plumbrook facility, :I 25-thermal-k i Pu-238 heat source and test pack%@. NASA will integrate this heat source package with its power conversion system, and open- tional tests will be conducted under simulated spm conditions.

One pr01iminar-y design Goncspt being con- s i d e d results from a study Oak Ridge National 1,aboratory performed for NASA. An ,2EC con- tractor lias been selected for a capsule fsbrics- tion developnierlt program, the first step in the heat source development. Additional technoloby development activities will be initiated, and :I lieiit source cwntmctor will be selected in the nenr future to perform an over-all heat sour* design and cwndnct the integrated lieat source tlevelopment program.

being tced De- e, using

class of It will lesijiried to pro-

LI watts.

f system test re- , system 3m pro-

i a joint ricsl- kw Mr space 0 power :d cycle ievehp- * several imarlily trt of a

heat

ground 25- ther- )ackage. package

opera- inulnted

ig con- Tation a1 3: con- fabrica- J in the Iinolog

and a in the sou rea source

SPACE POWER SYSTEMS TECHNOLOGY PROJECTS

Multi-hundred Wart Generator Studies. The receii tl y -cwmpl et er 1 in ul t i -1iun tired watt generator engineering study cmnsiderd the feasibility of c*oristruc.ting :in efficient RTG with the cxpa- bility of re-entering the earth's atmtapliore, im- pacting the earth within a previously-designated safe dispos:il area, and remaining intact after impact. The gener:itor system was sizt'rtf to use either Sr-90 or PI-258. The gene~ i to r itself has a power-to-weight ratio greater than 1 watt/lb, but the controlled intact re-entry requirement adds :idditional weight clue to heat sliielvis and the re-entry control mechanism. Further design and development work is now under consider a t' ion.

Sr-30 is attractive chiefly because of i t s low cost and ready availability. Radiation from the Sr-00 requires heavy shields for use in space, or results in a certain amount of inconvenience in remots handling equipment and procedures a t the launch pad. Development of a launch pad handling concept which is compatible with launch operations, combined with a highly reliable capability for intact re-entry appears to be requirerd if Sr-90 is to be used in space systems.

Space Heat Source Development. In the development of advanced fuel form technology, for all categories of advanced power conversion systems and for propulsion thrusters, the fuel surface temprature goals are as follows:

Thermoelectric ( I'bTeradiatively

Advanced Rankine, Brayton and

Therinoelectric (Si@ & tascaded) 2200°F Therxnionic 32.-w O F Primary Propulsion Thruster 3650°F

Qualitication of a fuel formi for use a t it parti- cular temperature involves chamchx-iz:ition of the fuel form and determination of its compati- bility with its container in the operating environment.

The chemical, nuclear and physical characteristics of l'u-%3X fuel forms are fairly well known. ('ompatibility testing to determine reaction rates between the fuel form ;itid the primary materials of contninment has been underway a t 1 8 0 O O F for some titne and is nearly completed. Testing a t 2780OF began in mid-1067. Tlong-term comp:itibility testing is essential to assure fuel containment during : ~ l after the mission.

COU[)led ) 1800" F

Auxiliary Propulsion Thrusters 2OOO"F

Fuel fornis of polonium 310 are compAtible wit11 s,eIectd cont;iinm&nt ni:iterials for ut least 200 days nt 1800'F. This demonstrates the opr - :ilbility o f Po-dlO for spwe missions of limited duration (100 to 150 days) operating at temperatures lees tliari 1800°F. However, i n v s - tigations of the 1'0-210 fuel form are not yet complete. Gadolinum polonide and the coated particles are still under consideration.

Space Power Conversion Technology. s p m electric p w e r conversion technology is being developed by the ,\E<' in close coordination with several other agencies. Included are improved tliermoelectric generAtms which have the advantage of requiring few or no moving pa'*; dynamic turbom:icliinery, which uses moving parts to obtain increased efficiency; and thermionics, which will r q n i r e high limt source tsm- peratum but should attain moderately high conversion efficiencies without the disadvantage of rotating machinery.

TIiermaelec+&s. All nuclear space power systems launched to date or scheduled for launch employ thermoelectric couples operating at hot junction temperatures below 1100OF. The projects for improving this technology involve opti- mization to provide greater compactness and metallurgical stability, and extending operating temperatures from the present 1100OF into the 1100 O--1800 O F rangg. The main tliertnoelectric technology projects are as follows :

The "Lightweight Gemrator" project is developing a converter technology that should yield very low-weight systems using PhTe couples. b a t is received by radiant transfer from the fuel c.:ipside; it floks through the thermoelectric semiconductor pellets, which are highly optimized in geometry to take best advantage of PbTe low-temperature performance characbr- istics. The Iiatt disposal surface is a thin foil radiator bonded directly tu the thermoelectric cold junction. This technology appears t ~ ? :idaptable also to systems in the hundreds-of- watts range, iising lieat pipes for heat transfer. Two-couple submodules have been operated' for more than 14,000 Iionw with low performance degrada t i on during steady -state opera tion. A life-limiting degratlntion of hot, junction bonds WRS recently tliscoveml to occur at about 14,000 Iiours. Corrwtive me;isures have heen taken :~nd :Ire being verified'. Development of this teclinology is cmitinning, :ind investigations of me,tliocls

15

:itaIi iev:i t )le, o n ~ e t lie tiecess:ir.y 1 1 i gh- tonipera t itre Iie:it w i i t * r e : int l Si& technology is available.

of I%-”) per cent, without tlie tieed for tlytinrnic ni:~cliitiery, providing the reqniretl high oper- atiiig teniperatnres can be achieved. The prelim- it1:it-y design of a Cni-244 fueled thermionic module W:IS completed in F Y 1067. Development \ror.k IMS been deferred because of budget pri- wities. The currelit plan is to prowed with the developnetit cwntr:irt, in micl-CY 1968, lending t o \ v : i ~ d :L fnelal ground test denionstration in the early IEO’s.

h EC lias clone devel op - m el i t work on two f a i rl y low- temperatii re tlyti:miic. conversion devices tlint can yield im- provements in efficiency and specific weight; the mercury vnpor combined rotating unit (CRTJ) of tlie S N , l P 2 cwncept; ant1 the organic Ran- kine cycle.

A 3.5-kwe combined rotating unit (CRIJ) witli the turbine, alternator, :ind mercury pump all on one shaft has been develop& for possible use with large isotope heat sources. This mer- c7iry Runhine cycle power conversion systam would I iaw :in eficiency of 6 1 0 % . It operates on 120O0F superheated mercury vapor. Empha- sis iv:is pl:~ced on clevelopnient of the CRTJ, since otlier components such as boilers and radiators :ire less cvniplex.

Approximately two years of CRIJ test time was :icciiniulated in working out be:iring :ind rotor c1yn:imic problems. A reference design CRV operated for 5000 hours, an adequate lifetime for potential space missions of the early Post-Appollo ern. The testing is being cmmpleted tliiring 1968.

-1 potenti:illy attI.:ict,ive space dynamic system, wliicli would not require tlie liigli tempers- t ii res u s i d 1 y :issoc iated wit 11 space operatior;, is the organic Rniikine cycle. It derives its ti:inie from the use of a n org:inic working fluid inste:itl of liquid metal. Chemical instabilities of the orpinic fluid appear to limit i t s peak temperature to the range of 600°F-7000F, but favorable vapor p i w n r e md polytropic expan- sion t.liar:wter.istics sliould resitlt in attr:ictively I r igli power (-onversion cycle efficiency.

tiwhility of the organic cycle. Various alternative organic working fluids are being evaluated.

~ ’ / / P P / ) ? ;ortic,\. ,. I lie t ~ i i i o t i ics 1) t-otii ises effic-ienc:y

D y I I Iol7 i c Xi ic~h i n Pry.

+ r , 1 lie present. pr-ograni will evaluate the prac-

I f i

n re e. ic. iency ynamic . oper- prelim- nmionic 3pment .et pri- ith t,he leading I in the

eve1 o p - era tu re ?Ed im- lit; the (CRTJ) IC Ran-

(CRTJ) < pump possible is mer- s y s h

)per3 tes Zmplia- T, since tdiators

st time ng ancl design

ite life- e early inpletecl

iic sys- ?mpera- berat ioli,

ives its ig fluid abi1it.ie.s ts peak O F , but expan-

actively

0 prac- altenla- nluat4xl.

1):it:i o i l : i l l o n :il)le n oi+iiig t e t ~ ~ p ~ x t ~ t r ~ ~ :1i1(1

preferred benri ng : ~ n t I p11i:ip ( m i figu r:i t ions slioultl :iIlov pre1)'iixt i o i i o f t.ef'ort~tic*c t les ip i n tlie ];ire l!%O*s : ( t i ( [ initiatioti of :L c-ollipoiietlt tleve1ol)iiiriit procixtii i f t I ir cwiicat.pt \ t i l l l t d s :itt rwt ive.

The Ntnyto7~ cycle uses g:iseous working iiuitls. It is cxpable of ncliieving Iiigli tlieini;11 efficiency, :uid tlie IISC of :L sii igle-~)l~:~w \ v o ~ ~ l < t i i ~

fluid nroids wiiie of the problmis iiilieient i n the two-ph:ise I<:iiikine cycle. of iiiert gisees (or a rnixture thereof) avoids : h o s t :ill corrosion.

The reliability of long-term operation of rota- ti ng innvli ine I .y wit I1 g:is-Iubrica tetl Iwa rings is still not est:tblislied, but the c y l e promises effi- cieiicies in excess of 20741. However, low radiator temperatures :ire required if m:ixirnum efficiency is to be attnined, which meatis high r:tdi:i- tor areas. Turbine irilet temperatures of at least 1600'F are desirable, consider:~bly in excetss of that acliievable with current heat source technology. A 5.5-kwe modular gas bearing loop is being developed' for electrically-lieated test in 1068-89. Tliese components will be incorporated into the NLISA--~EC joint system program discussed earlier.

SPACE NUCLEAR SAFETY

Tlie power system projects are suppoi-ted by a tliorough nuclew safety program. Table 4 describes the statiis of approvals of isotopic systems for use in space. The parametric conditions already approved and the progression

to\\ :ii.tL inore : i t l v : i i i c ~ l systems are evideiit in tliis table. 'Yo provide tliis safety suppolf, :1

i i i i c ~ I ~ : t t ~ s:ifetv progixtn consisting of two types of x-tivit1e.s is heing r:irrietl out: (1) System- () 1. ien to( 1 Woi-k-:ict i v i t ias c+ondi~c*t et1 by t he EC safety orgaiiizntio~~ :ind its prime c.oiitractol*, S:tn(Ii:l ('orporatiou, i i i support of specific. systenis; ( 2 ) Supporting Safety I<ese:irc*ll and ' recli i iolo~y-:~~ti~,i t ies applicable to sever:d systems :inti cwntri biitiiig to a basic teclinology t1i:tt will he nsefnl in fiitiire spare power system tl evelopmen ts.

System-Oriented Space Nuclear Safety. Tlif%e projects inclirde both, space power systems niitl other types of s p x e isotope npplica- tions, siicli :is safety annlysis of isotope sources used in propellant tank gages and trace13 for space experiments. In some csses, safety investigations pace the evolut~ion of over-all system design concepts.

Supporting Safety Research and technology. Safety criteria for specific radioisotopes or for classes of space applications are being fomiu- 1 :I t 4 . Ad va I iced safety t ec. 1 I n ol ogy a rem i n cl 11 de standartiizntioii of metliods of safety ;innlysis: improvement of post-mission disposal tnetliocls; assessment of the capability to track nuclear- powered spacecraft in the event of an abort and to lwate and to recover sources in the event of :in accident; study of methods of diminating or reducing launch safety uncertainty, and methods of designing systems which 1tr-e passively safe under all adverse conditions.

Table 4. Status of Flight Approvals of Isotopic Sources Approx. Capsule

Isotope Activity O I H ~ ~ ~ ~ I I ~ Fuel Thermal Comments Level Sur. Temp. Form Power

Curies “F Kwt

9WF Metal 0.060 2 units launched 1961, long- lived* orbits. Designed for complete burnup on reentrY U short orbit occurred. ISR** approved.

1. SSAI’ 3 A Pll-2:38 1,m

0.5 3 units launched 1903-64. Two achieved long lived orbits, 1 reentered atmosphere on launch trajectory due to guidanm failure, burned up as designed, on re-entry. ISR approved.

2. SNAPDA 1’11-238 15,000 %OF Metal

3. S N A P 19 PU-238 18,000 1400F. P110, 0.6 Scheduled for launch on Nim- (25-watt (micro- bus B satellite early 1968. De- module) spheres) signed for intact reentry in

event of abortive launch or short orbit, ISR approved.

4. SNA4P27 Pu-238 45,000 14OOP PUO, 1.5 Scheduled for launch on first (micro- Apollo lunar landing. Protected

spheres) to ensure capsule remains intact in event of abort re-entry. Interim ISR by 9/1/68.

5. SNAP29 P*210 800,000 1800F GdPo 25 Scheduled for ground test in 1970 with intent to be used in short orbits in space in early 1970’s. Preliminary ISR by 7/1/68. Designed for intact re entry.

25 Scheduled for ground test in Brayton (micro- 1971 with intent to be used in System spheres) space in mid 1970’s. Intact r e

6. Isotope- Pu-238 750,000 2200F no,

entry.

7. Water- Pu-238 8,400 150F & PUO, 0.28 Makeshift encapsulation, safe Recovery l2OOF only for ground test.

8. AMSA Pm-147 200,000 600F PmzO3 0.060 USAF has applied for Licensing Unit under routine isotope licensing

procedures for atmosphere OP eration. A F will perform its own safety analysis for the in- tended mission.

9. Radiation Various Insig- -4pprox. Various Insig- Insignificant safety hazard in- sources of niEcant ambient nificant volved due primarily to the Apollo*** small amount of isotopic fuel Surveyor, in these units. OSO, Bio- satellite

A long-lived orbit is one that will last seversl times the hdf-life of the isotope ** ISR-Intaagency SaSaty Review.

*** See above for SNAP 27 thermal source, aka launched with Apollo mission

: beard la- rily to m .wtoplc fud

TERRESTRIAL POWER SYSTEMS

BACKGROUND APPLICATIONS

13)t ( )1) i ( - , power systenis ( S N A P 711-E) iisiiig ,.(. !)o tIe:bt sources xnd Ieid telluride (PbTe) ~ , , . l . l , l l H l ~ ~ ~ ~ ~ t , ~ i ( : power c*onversion :we in use in

.,.,,.,r:ll 11i;lrine arid remots terrestrial sites such , i 5 l l ~ l v ~ ~ l t . ~ ~ ) ~ i tmacmis, weather buoys, polar l I ,c ; l~ l l ,llI:lt,tc?ndd weather stntimis, and unlcler-

(,(.t.:iliogrnpliic inst,nllations. These first- 4rc~~l,~r.:~t.ion units have demonstrated the feasi- t,ilily of long-tkrm, unattenided operation, and 1 t,c.y point the wty toward development, of truly , ' 0 1 1 1 I w t . i tive devices.

.is :L prerequisite to the initiation of ad'vancd , ~ ~ ~ t ~ l o p ~ i w i t programs, considerable effort is 1 I t ~ v o ( i ? t l t o the evaluation of potential applica- I ioiis Iwoping i n mind :ilternate energy miirces, 4'11 v i rori moirt~:il facton, operating lifetime, a.nd ,*,,( ~ 1 o i i I i c s . From such con ti iiuing evaluations, ~ ~ t ~ i ~ f o ~ m i : ~ r i w specifications are established w I i i t * l i , i f :~tt,iiiiied, could result in the extensive IISO ol' isotopic power SourcRs. The systems being th.vc:Iopcwl' h v e a tremendous potential for appli- ~ . : i ~ i o n . I4.or example, a worldwide weather buoy \\stmi siic.11 :IS that being cunsiderd by the \ \ ' I WI i I hft>,tc?o roIogi ral Orgtniz t i t i on, the Panel

1 1 1 1 (h.n:in Errgineering of the President's Nx- 1 tot i d ( 'ouncil on M:~rine Resources Engineering I )t~vt~~lopnient, i d the Weather Bureau, could involve the deployment of many hundreds of ~iii:tl ,t .c?iidotl buoys throughout the world. Isotopic 1 ) ~ ) ~ : r systems have been identified :1s primary (,:iritlicl:ites for these applications as well as for III:lIiy Iiuntlrds of radio and TV mic.rotwve I'chl)t9:it.er stations. Also, hundreds of offshore oil : l l l ( I gas p1:itfomis over the world could utilize I*)l4)[)t? syst.erns for navigational aids. Even if 1111ly :L sni:iII fraction of this potential is realized, its iiccxki caulti exceeri' t11e cumntIy-fomxsted Sr-!)O :Lv:iila.bility. Similar situations exist in 1 i l t rea. of unid'e~erseas and other unattanded W w r applications, wherein hundreds of units ~.oul(l be required annually for acoustic and

. .

son:w beacons, deep-sea. transponders, seismic stations, tsunami (seismic) gauges, -no- gr:ipliic instrument pil(;kt1Ress, cable boosters and pilssive sonar listening sites.

COMPETITIVE FACTORS

The use of isotope power systems is depend'ent, on their economic competitiveness with con- ventional power sources. Tile relatively high procurement cost of isotopic systems must be balartced against their low operation and m:Lin- tenance costs over R long lifetime.

Competitive fators are somewhat different in the use of isotopic systems in ocean bottom and deep-sea. iipplicntions. I n these instances, isotopic power may be the only practicd means of providing reliable power, particL1lilrIy where long life is required (about 12 months or greater).

The results of some of these analyses are summarized in the following ptwagraphs :

Remote Surface Applications (SNAP 23). The following are representative of remote surface xpplicntions that have been analyzed from an ecoriomic viewpoint :

Offshore Oil. Power is sold to operators of offshore oil and gas platforms in the Gulf of Mex- ico a t an average cost of $10-$12 per kilowatt hour. The cost is signifkintly higher in other areas of the world. The 60-watt SNAP 23 generator has as its objective iLn operating cost of less than $10 per kilowatt-hour exclusive of any fuel buyback consideration. As oil operations extend farther offshore, the avemg0 cost of non- nuclew power will increase sharply due to logis- tics; whereas, the cost of isotopic power should be nearly independent of this factor.

Const Guard Buoy7 {rnd Lighthouses. The Coast Guard has extensively evaluated the use of isotopic power, and has concluded that if the SNAP 23 specifications are met the higher-

19

paver :il)pli(a:itioiis ( >O-IOO n i i t t h ) : i s ~ ~ - i : i t ~ i x i t l i liglitlioiises :ire prinw cxiirlid:itrs for aci- vniicecl isotope pov PI. systciiis. Isotopic. pon er sIioril(l lm rqxcially :ittl.nc.ti\ P e~wi ioni ic : i1~~ for light Iioiisrs lor:itc8-l aloiig t lie Ail: isk:i~i twist 1 i ne, n liere ser~icing is expensive :uid 1i:iz:irclous.

weather boat is the foreruiiner o f :in wiattmcletl iiewtork o f (1:it:i-g:itIieriiig weatlier stations to be nimred on the oceans of the \vorld. Huoys using coiriniercially-:iv:iil:it~l~ tIie.se1 generators and batteries must, now be sell-iced a t least every twelve moiitlis. Ilispiitcliing :i Nary vefisel to recover and service a mid-ocean bnoy has been estimated to cost on tlie order of $50,000. Tlie capital cost objectives for :I 60-watt SNAP 2:3 SI-%) power system (IO-year lifetime) is on the order of ! $ ~ o , O O ~ - l f ; G O , ~ O ~ exclusive of fuel buyb:iclc considerations. The S K A i P %3 perforni- :tiwe and cwst objectives are based on what the Navy and other potentid users have intliwtetl to Le :ittr:ictive for operational use.

Air'cwtft Jf arker Benrons. The Feder.nl Aviation Agency in its development of a small airport instrument lanrl'ing systems (II,S), has difficulties in providing reliable power for aircraft t)e:icons, some of wliicli are 1w:itetl 4-10 miles from aircraft touclidown. Batteries, die- sels :ind other portable power systenis are pro- hibitively expensive to use due to servicing requirements. The c.urrently-acceptable solution to the problem is to construct a11 electrical substation at :L ctrst (including ro::ds) of :ilmit $5,000 for each mile from tlie primary power line. Based on projected power supply procurement costs, a 5-10 watt isotopic, power system would be competitive in those instances where [lie substation is more than two miles from tlie primary line. The FAIAI estimates oti :in wo- nomic basis that 25-5096 of tlte sinall :tirpoi-ts could effectively utilize isotopic power soiirres. Airports located outside the IJnitetl States offer even greater promise of use.

Studies of these four potenti:il I applications and others siicli as oceanographic buoys, rnicro\vave repeater stations, iiiinttentlrtl sis- mologiral stations, :inti military comniunic.:itions systems, lixve led to the following critrrin :

Il'etrthrr' IZU0y.L The I-. s. Savy S O J L i I ) Furl 1Inintrnance Po\\-w cwt (excluding

transvortntion, installa- tion. and fuel 1)uybnc.k)

Weight (fiO-watt unit)

IIigh probxbility of 10 yrs.

9.5-100 watts

1 10 ritrerri/hr Free circulxting air, 75"F,

one ;itiiiosl)here, 50-100Y' rela tire humidity

1 Sr-90 Field niaintenance required I

$10 per km-hr Less than 1,ouO lbs.

Altliough these cliaractsristics appear to be nttainable, they are significantly hyond current technology and will require an extensive R&D effort.

Undersea Applications (SNAP 21). In an unattended underseas application, isotope power ofleers :i unique advantape-competitor power concepts will do the job for only up to n few niontlis, and then only at great expense. Analyses of tliese applications led to the following development criteria :

Electrical Power 10-20 \vLI tts Weight (10-watt unit) 600 pounds Sea water 1)rwsnw

Moisture

Life ( miniinim) Fuel Sr-90

0 to 10,OOO psi

100% relative humidity

High probability of 5 years

Watrr teinperatnre 28-41°F

in seawiitw

A premium is being placed in this program on tlie use of rigid quality assiirnnce and reliability techniques coupled with rigorous ant1 long-term testing of :ill rnateri;ds and c.oniponents under laboratory and simulated enviroiinientd conditions. Upon completion of the development activities, cooperative testing programs will be arranged with interested user organizations to provide long-term test data in various environ- men t s.

Milliwatt Generator Applications (SNAP 15).

linl7ttpndsd Znsfrunzcnt Power. For underseas elert ronic tlevicfiy sucli :is cable t m t e r s , soiiic pingers, ant1 other iiiitlersen instruments, it :ippe:irs tha t :in isotopic power sjstem cxp-

tg of 5 gvIIn

Kilowatt System (1-20 KW). A large number of ~)otwiti:il requirements, particularly undersea pro- ~ lx i t i s :iiitl remote arctic activities, (.:in us2 iso- l(q)ic eiiergy in the low kilo\vatt power range. A~ltlioiigh detailed studies have yet to I>e corn- l)lt.te<l, the possible nIteriiative power sources for ' ( p p i i w t ions sucll as tliese appear quite limited. ( 'ollipetitors are diesel generators which require ' ~)l~~i{lei*:il)Ie logistical support, short-livecl battery

systems. fuel (.ells. : ~ n d possibly nuclear reactors. The fiist plinse of :L propirn, initiated in F Y 1968, roiisists of extensive :ippIication engineering :ind p:L":iiiietric design studies. It will identify spetific types of :tpplicnt ions, alternntive power sources, performance object ires a ~ i d criteria, : l i d ecoiioniics, including requirernellts for electrical :uid iriecliariical power and for heat. Fuels iinrler co1isirler:itioii are Sr-90, Co-6O and Ce- 144. T)yn:miic, as well :is static power conversion systenis will be considered.

OBJECTIVES Isotopic Power Program objectives for ter-

1. To tlrrelop. test and deiiionstrate radioisotope power sgstenis for general-purpose oceanographic. and terrestrial applications, specialized military and coiiiniercial applications, and specia lized nieditnl appli ca tions.

2. To c-ontiniie bro:idly-bas& technology prograins applicable to various power systems necessary to bring about iniprovernents in cost effectiveness, power conversion efficiency, reliability and Iifetiine.

restrial applications are as follows :

PROGRAM PLAN POWER SYSTEM PROJECTS

10-200 Watt Isotopic Power Systems. For this power range the AEC program consists of two projects, SNAP 21 :md SNAP 23. SNAP 21 is a 2-pliase program for the development of isotopic power systems (10-60 watts) for deep- sea arid ocean-bottom application. The design and component development effort on tlie basic lo-m-ntt system has been successfully corrrpleted. I n tlie currently-:ipproved phase of development, a series of fueled prototype Sr-90 power systems will be fabricated; assembled and extensively tested. If the concxq't proves to be satis- factory, the 10-watt design concept can be extended to higher-power versions. Arrange- ments are l>eing made with tlie Navy for testing m e or more prototype gener.at013 in both sinin- lated nnd actual environments.

The S N A P 23 pr-ogr:im is directed townrd development of terrestrial (surf ace) systems. W o r k iduring 1967 included tlie developirierit of Iiigl~ly-efficient segmented tliermoelectrics and re:udily - f:i bricnble, reproducible system compo-

91

nents, :in(l the ~ t : i i i ( l : i i . ( ~ i ~ : i t i ( ~ t i of in:iior conipo- nents :itl:il)t:il)Icl t o v:iryiiig po\wr Irvrbls from 35 to 100 \v:itts. ?‘lie p i ’ o p ~ : i n i wi l l eii(*oinp:iss the itppli(h:iti(m of ~ J ‘ O V P I I tmlinology a n t 1 cwniponrnts to systrnrs of bot11 liigllci- anti lo\\er poner a i i d

will incliitle :L fiil)ri(xtioii :iii~(! test effort. Test arr:inpnieiits with iiseiy siiiiilar to SN,iI’ 21 :m-:ingenients, :ire p1:innrtl. The reft.rrric.e tlr- sign will provitle :I 6O-wutt po\\ er source for various ten-estrin1 en\ i 1-onnients.

Milliwatt Isotopic Power Systems. extkn- sive iipp1 ic:itio~is enginwring :ind pnfiinietric design stntly w:is c-onipleted in F Y 1!)68. From the tl;itn obt:iinetl in this study, rl‘eevelopment progixrns :ire sclietluletl to be initirted in FY 1970. Tliey will culminate in the fabricntion, testing and denionstrntion of proven prototype systems in areas where they are expectrd to find greatest use.

S N A P 15L\ is a small milliwatt device beiiig developed for us0 in \veilpons. Ap- proximately :3 gr:ims of 1’11-238 :ire used to provide :i 400°F hot junction temper:Lt,ure to 1300 nietallic tlirt.nicH.oril)l~is. No shielding is required. The 5-year-life iinit, is clesipied to provitle 1.55 elec-tric-:iI niilliwatts :it :i voltage of over 4.5 volts. To (late, 31 fueled prototypes liave been extensively tested to validate tlie extremely Iiigli reliability nsswiatetl with the classified refer~iic*c :ippIicxtion. These systems :ire also :I t t ixr t ive for (no niniun ica t ion :in tl m i c roe1 ec- tronic c-ontiwl :ipplic.:Lt ions. Inipmved uiiits :ire wrrently being f:ibric:ited for fur-tlier testing.

Also in tlie milliwatt range, SNL\P 15C was developed to provide power for use in :I clasified iipplic :i t‘ ion.

Microwatt Isotopic Power Systems (Pace- maker.) In F Y l96fi the ,\E(: initiated :L pro- grmn to develop a plutonium-fueled cardiac, p:tceni:iker. ‘I’lie first pliiise of this 2-pli:ise prograin w i 11 (:oi went rate on ({eta il ed en gi neeri ng tlesign :in({ cwnipoiwit vli*relol)nieitt :ind n-ill c * r i l -

ininate in the asseni1)ly ant1 short-term 1)erfoi.m- mce testing of expei*inient:il models. T l ~ e o1)jec- tive of this plinse is to develop working prototypes w11 i c d t c-onfoi.rii to tlie perfoi.ni:incw and rned icnl conipti t ibil ity speci fic*nt,ions and which C i i I l be :id:ipted easily to tire sevthi-iil e h - tronic pacemaker designs t h t , :ire now corn- I 1 ie IT i it 1 1 y :i v:i i l:ib€e. .is prrssciitly t-onwieved, tlie eiltir-e p:ic*rin:ikei.

system will weigh sM.5 grams : i n d 1~ 6 em. x

4.87 m i . x 2.8 (:In in size. Approxiniately 0.30 griinis o f Pu-M metal will be risd :is fuel. The grneixtor is t o provide :I I (id-microw:it.t oatput over :L 10-ye:ii- lifetime. Tlia second phase (to start in FY 196!1 :issuming :L succ-fiqsful Phaw r ) wi l l include :in extensive fabric:Ltion and test efforts (incliiding :inimwl in uiw tests) to demonstrate tlie reliability and lifetime requirements :LWM i i i t d \v it 11 :I su rgiwll y - i mp1:in tstl nucle:i r- power c:iid‘iac pacem:iker.

TECHNOLOGY PROGRAM

I n addition to progywns to develop systems technology, :L supporting materials and component technology program is being tmnducteti. Tliis technology development program currently includes ivorlc on insillation, thernioe1ect.ric modules and miiteri:tls, fuels development and safety.

Vacuum and Fibrous Thermal Insulation. Tlie vacuum insulakion systsin cmsisting of tIierm:il reflective foils inteIspnced with insulation materiiils 1i;is been developed c~oniniercially for oryogenic applications. It is being improved for use :it liigli temperatures. A V:LCULIIII insii1:i- tion system is being used in the S N A P 21 program, :ind the research effort is also iipplicnble to tllilt program.

Min-K fibrous insulation h:is been used for SNAP :tpplications because of its relatively low tlierm:il c.ondnctivity, good macliinnbility, low cost, and structural stmngth. However, the inaterial liiis degr:ided in air and Iins preseiited diffusion problems with surrounding materials. I eclinology work currently iinder\v:iy includes the analysis of nunierous insulation materials and the clevelopment of protlnction processes to provide :in improved insu1:itor. Min-K insulation rn:iy be used in powler form :ironnd the legs in the tliennoelectric converter in both SNAP 21 iind S N A P 3:3. Rese:irc+ ;ind 1)evelopnient in thermal insulation Ii:is dirwt application to t l i c x e pi-ogr:ims.

Pressure-bonded Segmented PbTe-Bile Ther- moelectric Modules. Segmented PbTe-BiTe thermoelectric! :we capable of high efficiency iilitl :ire being used in the SNAP 21 and SNriI’ 23 genera tor progtxms. h t,liermoelwtric technology pi~ogi~:iin is iinderwiy to produce high- perform:inco segmented tellurides by liot iso- static) 1)wsiiig techniques. Tliis effort i s oriented

r ,

tlie profirmi :ire t o iniprovo generator efficiency, reduce weiglit and roluaio, ; ~ n t l uxtsiitl the teni- pel.:lturr, range.

Sr-90 Safety. To provide full reliability and cmiplete t.onfitlencB in t lie tri’cep-ovs:~~~ ap1)lir:i- tion of S N A P devic~s, :i&lition:il information is iieede~t i.efi:miing tlie etfec-ts of the weill1

environment on fuel and fuel rapsiiles. D a h to he obtained include rates i m l means of disperse- merit of fuel into t h oce;in should a fuel capsule be ruptured, and the effects of corrosion, ero- sion, currents and depth on the capsule and surrounding components. Tests will be performed in the laborxtory and in the m a n using 11;ird- ware from the SNAP 21 deep ocean tliernioelw- tric generator.

23

THERMAL APPLICATIONS

BACKGROUND APPLICATIONS

CURRENT STATUS AND PERFORMANCE REQUIRE- MENTS

lxotopic heat sources can offer :L sipificnnt : \ t i \ :uitage over :tlternntives sucli :is electric Iiwters, since isotopic radioactive decay pro- ~ i ~ i t w 1ie;it directly-no enerky conversion witli i t t t cndant loss of efficiency is involved. Isotope +stems tmt serve applications in Iiostile or i~i:wcessible environments, such as in spac0, in (hkx:inographic, systems, in isolated terrestrinl IIWS. nnd for hly- implant , where non-isotopic :\lttwiativeS wonld impose reliability 01- logistic. l*'straints.

Thermal Conditioning. Radioisotope hent soiirvw for thermal conditioning should be inlier- twr lp more reliable than electrical I.esist,ive h t e r s , since electrical lends and connect.ions, c*~~*~trols, a n d power conditioning equipnient are I \<Y needed. Disadv:int:tges of isotope units in- c.:-:tIe the design inconvenience of being nn:ible r t ' r i i n i off the hext when it is not needed.

4 0 0 0 8 b 9

I3lectric battery power packs for diver wetsnit Iienter :ipplicntions weigli :ibout, X--10 pou11(1s, Iiave :I t1isch:irge period of about tliree I i o ~ i t ~ ,

:ind tlien require :in 18-liour rwliarge. 1sotoI)ic thermal wetsuit conditioners weigli ihout IT, pounds ;inti 1-equire refueliiig only :ifter : ihut one Iielf-life of the isotope selected. Thus, for peiiotls longer than about tliree 1iou15, isotopes offer unique advantages iii tliis :ipplictit,ion.

Process Heat. Solar and isotope energy are efficient tlierrnal energy sources for spacwmft life supl)ort systems on long-duration fl iglits. Altliougli solar energy is :ibuncinnt :ind reliable, its use requims large :ireas for solar concentm- tms, close-tolerance solar attitude controls, and high-temperature energy storage systems for operation in the earth's sbadow. Isotopic systems appear to offer the same :idv:intages and dis- advantages in these areas as in the category of thermal conditioning.

Mechanical Energy Systems. Several energy sources :ire under consideration to power nil engine for circulatory support systems designed to replace or supplement daniaged human hearts. Swnd:Lry batteries are well developed, but require an external energy source for cdaily ra- charging. Biological fuel cells, altliongh ea- tremely attractive, liave not been developed to practical usef uliiess. For these reasons, isotopes appear to be a promising energy source candi- dah for this application.

OBJECTIVES Program objectives are derived in most part.

from the role of the AEC in developing the peaceful uses of nuclear energy. The general program objective is to develop radioisotope heat sources and system modules in which the thermal energy is iitilized directly or is con- wi-teci into mwlianical energy i n n heat engine.

P C:

I ' 1'

I , ('I

11

> t 1' 1

c '

1

t i

1

1

PROGRAM PLAN c I RC U LATORY SUPPORT SYSTEM

INTEGRATED LIFE SUPPORT UNIT FOR MANNED SPACECRAFT

A successful :io-dny test wis i n d e of :I ratiio- isotol)e-powerecl (280 tliermal watts Pu-2X8) pr(x)f -of-princ.iple ,unit for recovery of mater from urine, wasliwater, and condensnte. The unit is cap:ible of yielding about two gallons of water per t h y , which is sufficient for two iiie~i.

Early progress with this unit iwsulted in an investigation of the integmtion of the various 1 ife support cwmponerits, including carbon di- oxide removal, temperature :ind humidity control, \vast0 disposal, arid respirabry support. Con- ceptual designs of integrated life support units for manned spacwrafts have heen evaluated ; and the detailed design, fabrication, and test of a prototype model are sclieduled for completioli by F Y 1971. The applicability of the life support system technology to manned undersea operations \~ouId nlso be investigated.

HEAT SOURCE DEVELOPMENT

Small thermal SOUIT~S are under developmelit for component heator applicat.ions. a 65-themral watt Pm-147 hent source has been delivered to the Air Force to lieat an aircraft instiiiment package.

A Mdioisotope-po\\rered swimsuit heater for divers is being developed by the BEC for the S:tvy. Tlie best method of maintaining the body temperature of divers exposed to the cold of deep O~A:W condit,ions seems to be by means of a circulating water heater system. The diver would wear a suit embedded with vein-like tubes which would circulate warm water. The principle is the same as used in suits for astronauts and aviatois. The lieat to be supplied to the transfer fluid would come from a radioisotope backpack heater. The heater supplies approximately 400 tliermnl watts, which is the amount needed to maintain body temperature a t ambient termperaturw of 45OF. The isotope-heated swimsuit is to be tested by the Navy in the Sea- lab I1 I experiment.

PROCESS RADIATION

BACKGROUND OBJECTIVES

Il l pro- ll assist, pr<lc.ess

'unction b f radi-

'am sup- 11 infor-

and to if n m - m n o m - mnsisk

lopmen t, is appli- m.

ward the nd reac- ,n1ent of

es :iirnecl of inter- I specific ?nteci, in ctvnl u:itect per unit ie purity tdons are potential

IB impor-

Ii:ise free emphasis rew ti on s sul>st:l tes, ,(:tioils a t i t i o i i pro- .-nnt,ion of

RADIATION ENGINEERING

.I sii t)st it ti t i:i 1 po t.t io t i of t lie I'i~uc~~ss 1Ziitli:it ion I )ovelopnient 1'rogr:Lm is tlevotecl to tlie devrl- opnient of engineering tliit:i &sseiiti:il to tlie orderly :~doption of riiI(1i:ition :is an industrid ]""x*ess tool.

Source Development. &\t the preserit time, whit is the nitwt iniportant isotopic ~idi:ition source. Several cobalt r:-ndiation soiirces liave been developetl. ('s-137 and Sr-!)O are currently r ider active tlevelopnient :is p i w m rndi- ntion sources.

Engineering Process Data. Tlieor-et ical and experinieiit:il data are being obtiiietl which c1iar:icterize radiation fluxes for 1)ilSic source configiirations. Tllis inform;ition is :I prerequisite for facility :ind equipment design.

SPECIFIC PROCESS APPLICATONS

Prc~esses wliicli emerge from the l~nsic teclinology developnient effort sliowing definite promise :ind wononiic betiefit are inl-estipatetl further. In itdv:iiicirig spwific process applica- t ions AI:(' strongly eiicouixges inc1ustri:il teclinical arid finnncid paiticip:it,ion to keep research tl i I-ectad towi rd ob j w t i ves \VI i ic 1 i :I re of Ken 11 i ne commerical interest. Several specific. process applic:it ions are currently underway.

Food Irradiation. A4 primary goal of the prograin is to develop to tlie point of com-

nierc.ializat ion the tec-linology for tlie low-dose r:id iation p r c ~ e s ~ of preserving foods. Work is directed tmwivl (leveloping :L liniited niiniber of products with good commercial poi~iitial tlirougli serni-c~oniniei.c.ia1 scale deriioristr:~tion ;tiid approval for consumption by tlie Fo(H~ and Ik~ig ,2driiitiistt.:itioii. A\ neressaiy part of tlie prograni is t,lm development of prototype win- nieir.i:iI fotxl irriil(l'i:itioii facilities. Riitlintioii facilities for footl procwsing either in operation or i111tIe1. cy)nsti.iic't ion include four reseiircbli irr-n-

i n o i 1 n t et1 i ri-:i<I i ;I t o r, a 1 n nd -I):isetl tis1 i piwessi 11g pilot plniit, A I I ~ t n o ~aiid-l~asetl fruit irradi:ltal.s.

At t i intern:itioii:iI go:iI of the program is to pirticipate with other nations iii rtmperative ra- tliiition Ixisteurizntion projects to r~onibnt world- \vitIe sliot.ages of food. Food irradiators liavs bee11

or :ire planned to be installed in Israel, Argen- t ina , India, Pakistan, Iceland, iind Chile.

Radiation-Processed Wood-Plastic Materials. Ra- diation-processed wood-plastic mnterials liave lwei~ iintler deve1oprrient by the SEC since 1961. These mnterinls offer potential :i(lviitit:ige over natural wood for sonic uses. The prodnct is pro- tliwed by irnpregi1:iting wooti with :L liquid ~ ~ O I I O -

inaric m:iteri:il (such :is methyl metliactylate) iind tlien ii-ratliatiiig i t with g:iinmn rays to convert the monomer to a hard plastic material. ('onventioi,nI heat processing tecliniqnes are a campet i tive nl t ema t ive, 1x1 t it a p pea IS that the r:idi:ition twlinique offers a nunihei. of adv:intages.

Two private firms :ire now produciitg specialized radi:itioti-processeci wood-pl:istic materials in tlevelopiriental cwmmercial quantities, and :I

third lias iinriouriced plans to do so.

Radiation Synthesis of Polyethylene and Re- lated Copolymers. A process lins t ~ e n developed in which radiations can produce acceptable polyet.liylene under conditions which will reduce sipni ficantl y the operating pressti res ruri*ent Ig i i s d in the chemic:il peroxide-initiated high- pressure process ant1 the qu:intit,y of highly- specialized organic metallic salts used in the :iltet-ri:itive commercial process. The r:idi:tt i 0 1 i

p r w s offeis sufficient promise from a cost and product-quality viewpoint to hive :ittract& several industrial companies to undeitake constrw- tion of pilot plants employing Cobalt-60.

Com~nission-supportec( work on polyetliylerie lins been discontinued, and attention is currently focused on txdiatioii synthesis of etliyleiie c*opolyniers of potenti:iI interest :tiit1 utility.

Radiation-Induced Emulsion Polymerization. Studies in this :\rea are primarily ainied at (leveloping :i process to produce latex materials nsed in water-base paint for-rnul:~tions. The radiation process c:iti opernte effickntly a t low tem- pera t 11 re ( Oo ( 'I ) , yielding a 11 i gl ier- niolerul:i r weight prodiwt, wIiicIi i n ip r t s giwiter wear I)i.operties to the paint film. Resitlns of the

27

SPACE PROPULSION

900

700

400 v1

100

1000 2000 5000 4000

m E R TEMPERATWE - OR

FIOITXE 5. Theoretical Performance of I’ropellents of Interest.

10,000 scc. o r more, but require large electric power supplies to achieve useful tlinist.

c3tlier important colnp:trisori factors are eqiiipirient weight, reli:Lbility, safety, develop ment ease arid cost :md availability.

Primary Propulsion Applications. Radioisotope- heated tliruste~s for primary propulsion must :whieve a specific impulse on the order of 800 sec. to compete favorably witli high-energy chemical bipropellant competitors. This restricts propellant choice to liydrogeii and requires thmster temperatures in excess of 41OO’F. Typically, sucli tliriisteis would be built in lb tliiiist units; ivould require 5 thermal K w of Po-21O--chosen for i t s high power density and suitable half-life; ~voulcl tlirust conthuously for periods of about tliirty days; and would be c-lustered to provide t l i ~ ~ i s t levels up to a fa\\ pounds. The veliicle typically would weigh less

tli:iii 10,000 l h . , i r i o \ t o f \I I i i c* l i I\ o i i l t l I)e t lie licliiitl Iiy(1rogtw l) imI) t* l l : i i i t a i i t l t l i r p:iyloa(l, : r ~ i t l

\ V O l l l t l be llseflll :I\ t l r c 1:i\t stag” o f :I tlrep 5p:i(X’

pt-ol)e, or to r:iise 5iii : iI l p:iylo:icls froiii a low e;irtli orhit to l i i g i i c n i t l i orhit, or 5iiiiil:ii- O ~ I * : L

tioiis. N, \SAi i s e~;iiiriiiing tile rapn1)ilities o f tliis type of st:igo For l)o”51Me ; i ~ ) p I i c : i t i o i i to its future spice missions.

Auxiliary Propulsion Applications. Once Inunc~lird into spice, iiioht ip:wec.r:\ft still reqiiire stnnll :iusil i :\ ry p i-op ulsioii sys tcnis to cw rrect injection errors, to assist i i i twntr-ol of the ;itti- tude of tlie sp:itwr:ift, to cwicel tlrnp, :iiicI to maneuver.

Cold gas systems--ant1 to a limited extent subliming solitls--\vitIi spet.ific in~l~iilse i n the range of 70-100 sec. liave been used for sen- ice in low-tlirust, low-total impulse missions. Rioiio-propellant :ind bipi*opellaiit liqaitl-fueled chemical rockets (EzOO-:3T,O sec) :inti solitl-fueled chemical rockets (200-:100 sec) Iiave been used for :ipplic~tions requiring higher thrust : t i id

liiglier total impulse. EIib’Iier-perfortrlallca low- thrust propulsion systems at micro-poiinds to a. fe\~-teIitlis-of-:i-poiin~l tlinist levels are under tle\doprrielit and Ii:ire in a few cases berii imd in flight. These are prininrily e1ectric:iI propnl- sion systems of the ion, cdloidnl, or resistojet type. All these 1ioii-tiucle:ir systems reqiiire an externd soiirce of electrical energy.

Rndioisotope-1ie:ite.d tlirnstets would cmnbine tlie simplicity, flexibility :iritl perforniniice of the resistojet with the ndvantage of requiring no external electrical p i ~ e r (except for certnin control functions like valve operxtion). Tlie selection of propellant for it p:irticnl:it* npp1ir:L- t ion depends on niany spacecraft and integra- tion v:triables. The specific impulse data of Figure 5 is of course one primary factor to be consirlerd. Nitrogen, argon, mast0 carbon di- oxide :ind water, liydr:uine, and Iiydrogen all offer certain ar1v:int:~ges; hiit front the stnnd- point of storage volume, storability and performance, ammonia is perhaps the best choice for modest total-impulse missions.

A combination of the nmmonia feet1 system technology which is under development for the resistojet program and tlie near-:tt-li;uitl 2OOO”F radioisotope-heated capsule temperature capabilities will provide a simple, miiltinozzle auxiliary propulsion sjstem with specific impulse in the range of 200-2.50 sei-., tliriiqt in tlie 1-to-

30

4 0 0 0 8 1 5

OBJECTIVES 0l)jecstives in tlie isotope tliruster. progrnni

for prininry and niix i1i:ii-y sp:ic*e propiilsion art’

:is follows : 1. To provide a souiid tecliiio1ogic:il base for

tleveloprnen t :i 11 (1 for c*orrip:irison wit Ii nl terna- tive cmicspts.

2. To develop radioisotope tlii.iistetr; :is requiivtl for 11% hy N h S h id DOD.

PROGRAM PLAN PRIMARY PROPULSION SYSTEMS

The priniary propiilsion thnister requires the use of Iiydrogen as :t propellant, capsule tern- peraturw gmiter tlian R B S O O F , radioisotope therm:il power in the range of 5 kwt., and n thriist level of about lb. Following the cooperative Air Force-AT%’ limited ground test of this rlnss of thruster in February 1965, tlie LIE(” c:ont,iiuietl programs aimed primwily at est&- lisliing the radioisotope fue,l form anti cnpsiile teclinology necessaiy for service ;it this tenipe!.- atnre. TII tlie current progr:mi, work on :3B50°T! capsule technology is being empliasized. A large part of the technology required for this lieat source is being developed under tlie fuels (level- opment program described under ST3AI(:TI: POWER SYSTEMS.

AUXILIARY PROPULSION SYSTEMS

Tlie Commission lias condncted two programs (with NASA and the ,2ir Force) over tlie past two years which include ground tests of mdioisotope- f ueled thrusters.

Tlie unit developed with NASA’s Goddad center is n single-nozzle tlmister, built of super- alloys, fueled with 6O watts of Pm203 mid

designed to produce ”,-niillipound pulses of :I

few seconds’ duration, at a duty cycle of :tbont 5 % . In a. serk of thruster performance tests at Mound Laboratory in 1966, a t 1600 to 175OoIi7 no-flow temperature, tliruster performance \vas good (239 W. peak specific impulse measured). The thruster ground tecitiiig is completed. C:lP- sule post-test, examination is sclieduld for FI‘ 1969.

--

'l'lie .lir Force lias i i i i t i n t d a follow-on prograin to r.eciesigi, reasserrible, :uid retest tliis tlirnstar in 1968.

As with all radioisotope systems, a key prob- le111 is to :issiire safe operation and fuel disposal. 'rowa1icT tliis end, AIX; safety stiiclies of tliese tliriisters :~r0 supported by tho work in isotope safet.y ckscribed iinder SPACE I'OWEX YYS- I 1531 s. I , 7

PRODUCTION

BACKGROUND The p1:uiiiing for isotopes prodnctioii involves

several consitle~~itions. (’ontinuetl long-term planning and analysis :ire required to select those products which will riiake best use of available government facilities, as well :is those which will provide t.ec*linology needed to take best advantage of private procliirtioii capability :is it becomes avai1:tble.

One vital nren for corisideration is the utiliza- tion of the fission products Hr-90, Cs-137, C e 144 and Pm-147. ,4t present these fission products represent a s ip i f iwnt liability to the operators of comrriercial power reactois. One of tlie objectives of tlie AEC isotopm programs is to develop the teclinology to use fission products economicdly, t:ikiiig advantage of their value as lieat aiid radiation sources so that they will be an asset rather than :I liability to tlie n:ition:il economy.

This clinpter discusses the known :iiitl projected isotope requirements, costing factors, arid the production methods wliic.li :ire in use or under investig. t‘ ion.

REQUIREMENTS

long-lived Isotopes (Pu-238, Cm-244, 5-90). The systems described earlier which are under rwearcli and developnient or wlieduled for ;delivery to users will require about 10 kilograms of Pu-238 per year in F Y 1!)68-1!1)70; tliese types of systems :we estimated to require about 60 kilograms per year in F Y 1971-71.:iiitl 120 kilograms per yew in FY 1975-77.

Comp:i risons of reqii i rements \vi tli p rtnl uc-t,ion capability intlicxte tlixt i t is possible to meet c>urrent firm requirements for 1’11-288 but t1i:it potential levels of tlemancl through 1980 may exceed tlie total of A \ 1 4 X ” and private power reactor production capacity. No excess is foreseen tliru 1971, a t least. Tlirougliout the second half of the 1070’s, there cwiild be :I net cumulu-

tive deficiency of pr*ocliic-tiou cwnip:iretl to re- cjui remeiits.

Many requirement forwists for long-lived isotopes assume the use of 1’11-238 because of its current state of tleve1ol)nieiit atid its desirable radiation c1i:ir:ictsristics. Some n1teni:ttive isotope sliould be made :ivail:ible to supplement tlw production and to permit PII-238 to be used in applications ~ I i e r e no other isotope will serve as well. The characteristics of Cm-244 are superior in some respects to Pu-238; but Cm- 244 lias not been available, and the teclinology n d e d for its use has not been developed. The use of Cm-244 probably will be limited in some applications by the need for sliielding from the radiations emitted due to spont:ineuus fission. Similar shielding problems exist for Sr-90, ancl these problems are further compounded by the potential biological hazard of available Sr-90 fuel forms.

(’m-241 may be preferable to Pu-238 in tliermionic power conversion d‘evices because of its liiglier specific power itrid indicated capability to maintnin a liiglier temperature a t the emitter of a tliermionic conveIsioii device.

The requirements for Sr-90 have been asso- ciated mostly with terrestrial applications. The cumulative demand for Sr-90 for terrwtrial power uses is estimated to be approximately 76 thermal kw with a range of 35 to 90 thermal kw by 1975, and 125 tliermal k w with :I rnnge of 60 to 150 thermal kw by 1080. Additional quantities for thermal : t i id radiation applic:tt,ions coultl be as high as 300 tliermal kw by 1975. Supplies of Sr-90 seem to be adeqn:ite to meet current tle- m:rnds, but a processing plant will be required for separation and enwpsulntion when miore tlian about 10 thermal kw per year are required.

Short-lived Isotopes (Po-210, Prn-147, Tm- 170, C040). The only firm requiremeilt for PO-210 is 0.25 kilograms for tlie developrrir>llt, of :L prototype SNAP-^^ geljerator of nro~~ll(l 28 thermal kilowatts. ,klditionnl rewirc.11 : l l ~ l

32

4000811

'.et1 t o 1p-

r-lived iso- 1 1 ~ 0 of its , desir:tl)](1 iative iso- lemeiit. t lie he m e t 1 in will serve

but cni- oped. Tlio b d in soiiio . from tlie LIS fission.

ed by the ble Sr-00

8 in tlier- use of its (.a pnbi 1 i t.y ie emitter

a n asso- ions. The terrestrial

iermal kw nge of 60 quantities

> coultl be ipplies of Irrent de-

required mi more . are re-

147, Tm- ineiit far elopment f around :ircli and

1-944 al.8

kxchnology

4r-90, :inti

rnatdy 75

tlt'vrlopiiieiit iii:iyv iw1iiii.e a l m i t 0.5 kilograms l)er Fear. lTse of T'tr.210 by X,iS.\ and 1)OI) in v x r i o i i s po\\ cis t1rvic.r.s cwnltl reslilt in :L totill iwliiireiueiit of :tiwilt f i kiIogi.:llns 1 ~ - yeiir in 14.y 1!)72-1977.

Film rwluireiiicwts for T'iii-I-k7 in FI' I N 7 - 68 :ire 1-elntively sm:il1-65 tlierriial w t t s for : t u

A\ir Forve Inertial Guidance Ilenter, 50 tliermnl watts for. i t niic.i.otlii.iist~r and 500 t1ieim;iI watts For research :ind development. In subsequent fisv:il ye:irs tlirongli 1!)7() one tlieixi:tl ki1ow:itt per year will be requiretl for HRI). T11e potenti:il -1ir 1470iw lieat er requi renient is 1 :% t lielniiil l<wt per year, beginning in 1969.

Only tleve1ol)nient:il quantities of Tin-170 are currently projectad :is a requirerneiit. For pcfi- sible tleniaiitl levels. Tni-17O may be iissumed to be :LI~ alternative to Po-210.

Co-BO is nsetl ~iiaiiily for radiation processes xnd is scliecluletl for ev:ilu:it~ioii in lieat i ~ n d power sources. ('o-(iO is supplied in a. wide range of specific :ict,ivity, from a few curies per gr:ini to Iiuimtlreds of curies per grani, (iepeiiding on tlie application. Requireinents :ire currently seveixl kilogrmis (several nieg:icuries) per year, itlid may average about 10 kilograms per year in F Y 1969-1972 and about 30 kilograms per year in FP 1973-1077.

COST AND AVAILABILITY PROJECTIONS

Tlie basic rewtor, process, and source eiic.:ip- sulntion taclinology for protlucing radioisotope soiirces exists, :ind it is being iniproved. The program also included plans to demonstrate tlie tei,linology reqiiired for product ion of large quaiit ities of special isotopes a t reasonable costs.

,issuming that requirements for defeiise products woulct permit space in AEC reactors to be used f o r radioisotope p rocluc t i 01 1, tl ie :LIT a i I a - 1)ility in large quantities of important radioisotopes is cwrrently limited by the lack of facilities necessary to prepare targets for irradiation, to clieniically prw~ws sp~rif ic isotopes, or t) manufacture isotopic sources. Tliese facilities woulcl be, specific to tlie pi*oiluc.t or p id iwt s to be inan- ufactured. (locision t,o build these facilities depends on the just ificntion (tlemarid, :uid h ie f i t or value) to support tlie capital investment re- (pired.

Factors Influencing the Major Cost Com- ponents. Tlie irradiation vust to produce

isotopic sourre ni:iterinIs depencls upon several (brit i c d fnctnrs, among wIiicIi the most irnpor- t:int i m the :miouiit and specification of the innteri;il to be prtxlucetl. Other important, f a r - tois are the total isotope product mix produced and tlie relative v:ilueAs of these irradiation pot lwts . 'rllese factors ciin infuelice signifi- (xiitly the mode of production reactor operation, :inicT the irradiation :ind fuel cycle costs of the various products. .\c~cordingly, it is not possible to quote firm costs which can be applied in a general way to specific isotopes; tlierefore, :L cost god range within which the costs for specific isotopes may fxll lias been chosen for general

Tlie influence of several other factors can be seen from ii brief discussion of the W L ~ S they affect the cost of an important neutron produc,t, Pu-238. The cost of an encapsulated Pu-238 lieat source includes tlie following components :

IISB.

a. Cost of Ny-237 and target fabrication b. Irradintion Costs e. Separntion of Pu from Np d. Rwovwv and Preparation of Np-237 targets e. Unrevovemlble Waste (Losses) and Np-237

Inventory Cost f . Conversion to 1'110, fuel form and Waste

Rem very g. Enrapsulation

TIiere will be significant quantities of Np-237 praduced as a by-product. in riuclaar power reactor fuels; and it is expected that Np-237 recovered during irradiated fuel processing will be prociirable a t :i negotiated price more favorable than the cost of Np-237 produced in hE(' production reactors.

Because of the inlierently slow rate of cow version of Xp-237 to Pu-238, the Np-237 inventory may tie up :L substantial amount of money ; arid managenieiit of this inventory may hive :L substantial effect on Pu-238 costs. The cost of conve~sian of the Pu-238, once separated from tlie Np-237 target, into a usable PnO, fuel form, including recovery of tlie wastes which result from tlie process, accounts for almost 30 per cent, of the cost of tlie final Pu-2.38 lieat source. Tlie high current, costs result largely from the early developmental status of the process for manufacture of PuO, microsplieres, which is being done 011 a Iab0,ratory scale. A new process now under development promises to reduce this cost of making microspheres to about one-fiftli of its present value. Finally, the unit

4000818

cost of PuO2 fiiol form eiic~:ip~iil:itioii is expwtel to IF 1.etIlicwl by :it least Ii:ilf t l i i e to m a s pro- durtioii woiiornies 11 l i e n outpiit incL1r:i.w tx) tlir pi*o(\ii(btioii r:itc% rxpwt.c~l by t l i t mid 1!j7Oqs. It is this type of (sost v:iri:ition wliicli lends to tlio witle ixnge of I'ii-%38 cw,t goal5 qiiotml in this report.

-Is regards fission p'.(HlllCtS, .4 E(' cost g u i l r:iii.ges :ire I x i s ~ I on I !)W-M design studies of fission prtdiict prtxessiiig pl;ints, iiorni:11ized to tlie statal :issurnptions. Fission prcduct twsts are very sensitive to tlis tot:il rn:irket for all fission protlucts. For ex:iniple, Si-!)O, Cs-137, :ind ( 'e144 must lw sep:iratPrl' from e:icli otlier and from the rare e:irttis. The I'XIB eai-tlis must be processed :ilong w i t h h i - 1 57, :ind the cask of operation of common fwilities must be chnrged otf against the total market, even if only one of the isotnpes is nertled. The unit cost is therefore also lieavily dependent on production quantities, varying almost inversely with output.

Basis for Preliminary Manufacturing Cost Projections.* It is difficult to project mnnufiw- tiiring c.osts for siipplying i~adioisotopes witliout considering the :tnioiints and spexific:ttions of the material required and other relevant considerations which relate time, money and Iium:in resource requirements. Ilowever, cost information can be a starting point to permit :I potential user to deter-mine wliether the use of a radioisotope may be of potential value, or which radioisotope niiglit have greater value. .lc.rortl- ingly, m:tiiiifacturiiig mst goals for the major radioisotopes Iixve heen icI'eveIol)ed which reflect whit niiglit be :icliir~vable for large quantity isotope productioii in government fncbilities. .Iltliougli tliese cost goals 1.eflec.t primarily the relative rosts of altenintive isotopic energy sources, they niay also be iimi to estimate what the potential costs to federal itge1i('ies rniglit be if large amounts of tliese specific isotopes were supplied from facilities operated by the A i 1 4 x ' .

Operations heyond primary capsule containment require cert;iiii li:indli.ng, weldiiig, nieas- urenieiits and quality :wiir:ince testing tlint wiry with the appliratioii. Since the final encnp- sulation cost could vary from sourre to source clepeiidiiig upon size, coniplexity of design, ninte-

Unless specifically noted, manufactunng mts a s used herein are for the entire p m e 4 s sequence from target. procurement and preparation for irradiation through delivery of the radioisotope In a pnmary containment capsule.

[.ids o f cmistruction, :ind fnbric:ition or quality : I S S U I Y L I I V ~ spwificxtions, t,Iiis cost his not been inc*luded in the nianuf:wturing cost go:tls.

Fission Product Prices. -It preqnt fissioii protlucts I I I :innun1 qii:mtit,ies iip to the :mounts sIiowii :ire :iv:iiI:iMe from tIie :it the follon - ing pricecj:

Sr-!W 510 20 30 CS-137 2 12-1/2 26 1'111-147 6 20 560

'If rgacuri cs /ycur +/ci $/thcrnial tot.

Tlleze prices are for bulk, urianc:ipsul:itet1 prdiic*ts in large quantities and were e t a b - lishel to stimu1:ite use. They :ire based on :L stiidy m:itle to determine tlie prob:tble costs for these isotopes if pr0duc.d in large qumtities in a liypotlietical commerri:il facility i L t Ilanford.

Manufacturing Cost Goal Ranges. Tlie fol- Iowing cast goal ranges have be011 estimated for large quantities for use by federal agencies. Tliese intra-goveniment chirges do not include several factois such as depreciation and profit, wliicli must be included in commercial prices.

Jf anufact wing Cost Goul 12unqe -$/tker?!iul wt. Isotopr Source

sr-90 25-35 CS-137 20-30 I'm-147 200-600 co-ti0 7-25 TIll-170 10-25 Po-210 10-26 1'11-238 rm-700 Clll-2-14 100-500

Tliese estimates assiinie tliat tlie isotopes are produced, processed, convei.tscl to a fuel fo1711,

:ind se:iled in :L primary containment capsule in government-operated facilities. Tlie cost to clieniicnlly process target materials and to convert a. product to a fuel form in l u g e quailtities is small in comparison to the costs for cert:iin target mw tcr i als and target i rrad ia t i on. I Iow - ever, the hulk of the capital and fixed operating c*osts of a new large procasiiig :ind m:iiiufnctur- ing fwility are requirecl even for small quantities; thus, tlie unit cmst of processing niid source iir:iiiufncatur.e for sm:ill quantities may be the m:i jor cwst, element in tlie production of a specific isotope soiirce, espwially i f irr:itli:ition costs :ire sliared by other products.

OBJECTIVES

. quality tot heell

PROGRAM PLAN PRODUCTION TECHNIQUES AND CAPABILITIES*

'rile following are primary considerations \I I i i c s l i il~flueiice the :ivailability of the major rxlioisotopes.

Fission Products. Fission products are formed in reactor fuel elements when IT-‘235, I J-233, and Pu-239 fission. These byproducts (‘:in be recovered from the waste streams which r w i i I t from the chemical reprocessing of reactor f i t r l . ‘I’lieir av:iilnbility is :G function of the fuel (ispowre :ind tlie quantities of nuclear fuel re- pi’(n.csswl. Processes for the recovery, separa- t ion :inti purification of fission prtducts have t)cvaii developed, and they are being improved. .\t present, a few megxcuries annually of Sr-90, (’s-137, and Pm-147 can be processed :It Iran- ford, :ind converted to fuel forms and enciipsu- 1:iktl at the Oak Ridge National Ldmratory.

1 rider the AEC’s Waste Manakgmient Pro- gr:ini :it Hanford, an appreciable quantity of t l i e long-life, heat-producing fission products Sr-!)O and Cs137 will be renioved from current :uid stored chemical reprocessing plant wastes so that the residual waste may be solidified for long-term storage. The Sr-90 and <h-137 crude fractions which will be removed from the wastes :it Ilanford will be temporarily sto~wl as a t i i t r:ite solution.

Ijeginning in 1968, tens of mepcuries un- nudly of Sr-90 and Cs-137 cuuld be made

Papers on “Large Scale Production and Applications on Radio- isotopfa” were p-ted at the American Nuclear Society's National T o p i d Meeting held on blarch 21-23, 1966 in Augusta. Gensia The proaeeditlgs of this meeting wem published in DP-1066. Vol. I and 11. available from the Clearinghouse for Federal Scientific and Technical Information. National Bureau of Standards. U. S. Dept. of Commerce. Springfield. V a

:iv:1il:\Me from the Ihnford crude frnc*tioiis. hltliough I’m-147 is not removed for waste nl:in:igement, a crude Pm-147 fraction also could be mads avni1:ible during w:tste p r ~ ~ s - i n g operations. A facility cap:ibIe of prifyi1lg such large quantities of Sr-90, CS-137 :iml 1’111-157 :d manufxcturing encnpsul:itPtl sotirccs from the fission products a t T I a n f d as estimated to cost about $It~-$15 million i f built :It Hanford :ind operated in conjnrlctioll with the waste m: lna~~ment program. Ho\\-ever, it may be possible to recover large quantities of specific fission products with a lower c:ipital investment, and still meet projected manufacturing cost go:tls.

Small conimerc*ial fuel reprocessing plarlts, capable of annually processing 300 toris of nuclear fuel e x p d to about 25,000 megawatt days per metric ton, c ~ u l d supply Sr-90 and Ps-137 in amounts up to tlie equivalent of 100 kwt of each per year and aged Pm-147 up to tlie equivalent of 5 k w t per year. However, additional facilities would be required to mover these products from the chemical reprocessing w,?stes and to manufacture isotopic sources. Several fission product processing facilities a t different processing sites \vould‘ be required to handle the substantial amounts of the fission products that will be contained in irradiated fuel from the growing nuclear power industty.

Reactor-Produced, Non-Processed Isotopes. 6‘obnJt ti0. This isotope is made by :ddition of x

neutron to readily-av:tilable monoisotopic cobalt, Co-59. Production and distribution of kilocurie quantities of Co-60 began in 1951 and has grown to megacurie quantities. The REV has a. capability for producing hundreds of mega- curies of (IC-60. This is far more than the foreseeable requirements. In May 1061, the AEC withdrew from the production and‘ distribution of CO-60 of greater than 30 curies-per-gram specific activity (modified in 1965 to greater than 45 curies per gram) in view of industry capability to serve routine commercial applications such as teletherapy arid radiography. This has led to the developmerit of :in industry which encompasses C+60 producers and‘ source encsp- sulators. The industry is viable; and as new markets for Co-80 develop additional private participation can be expected. For example, Co- 60 is now being produced in one private nuclear power reactor. The Commission is currently con-

sideriirp \\ t t I i ( l r : t \ \ tiip f i w i r i tlie pro(1uctioii :[tit1

tlist.rihtiori of ( ’ t r ( i O ~ O I I I W ~ of 45 curies per gr*nirr yecifir :icktivity : i i i d Iew, in liplit of pr- iute c:ip:tbility to i)i~otliic.e si~cli rn:itr.rinl. I t is also re:isoi):it)le to espwt t h a t intlustry ni:iy pi-ovii[le (’tv(iO s o u r c ~ r i ic~; i~~si i l :~t io~~ services for. isotopic- lieat. WIIIYT iil)pli(xtions as JWII :is for rat1i:itioii :tpplil*:itians.

I lie user desiring large quantities of Iiigli- specific activity Ctr8O niust :illow :L lead time of ;ibout 12 to 18 nioiitlis or niore for irr:idi:itioti :ilicl enc.npsul:it ion of ( ‘ t r A O , depending upon tlie reactor flus :ivnilxBle and the specific activity of the mnterinl to be produced.

This isotope is n i d e by :ildcli- tion of :i neutron to Tm-169, it rare earth. Be- caus0 of its short half-life (127 days) tlie user must allow for decay of the Tm-170, e.g., : h u t 10% between reactor discharge nnd delivery of the target assembly, ant1 an additional 4% per week during maiiufacturing of the encap- sulnted sources a n d assembly of the power unit for delivery. Thulium-170 could be supplied from hE(’ production reactots in up to megawatt quantities per year. Tlre nv:iilability oi Tm-170 tlspends upon the :ivxilability of Tm- 169 target material, high flux levels to produce a high specific activity fuel form, and facilities to convert tlie irr:idi:ited targets into ii asahle isotopic soiirce.

Tliuliiini-170 was tlie first isotope pracl’uced in kilocurie :imounts in a private re:~ctor. In IOX), Generxl Electric produced approximately 150,000 curies of Tm-1’70, which was used to power :in experinieiital thermionic genei-iitor. Multi-ltilo\v:itt quantities of Tm-170 could be produced in existiiig commercial facilities on relatively sliort notice.

Thulium-l?’l. This isotope has frequently been considered as :i desirable isotopic source because of its 1.9-ye:ir 1i:ilf-life :ind minimal sliielding i’e-

quirement. There are several ways to produce TM-171, but all are proliibititively expensive. Tliere is no knowi economic methtd for isotopic enrichment to produce tlie multiton qii::iitities of enriched 131-170 needed to make Tm-171 in large :unounts. tinless n low-cost metIioc1 for producing Er-170 becomes available, Tm-171 cannot be mntle in AI4W production facilities a t costs less tlinn several tliousands of dollars per watt.

,.

TJi?iZi?o/L-l?‘O.

Reactor-Produced, Processed Isotopes.

P o / ~ ) r ~ ~ / / / / ~ - ~ ~ ~ ( ~ . This isotope is made by atldi- tion of :L neutron to readily-:iv:iilnble monoisotopic. bismutli, 13;-209. Because of the very low cross-section for tlie rwction (O.Ol9 b:iiii), many tons of bismutli must be irradiated i~nt l processed to produce Pe-21O in large qumtities. 1k:inse of the short half-life (138 days), tlie user must nllow for decay of the Po-210 after i t s discliarge from the re:ictor. Furthermore, since its recovery cost is relatad to the amount of bismuth which must be processed, it is preferable to irradiate tlie bismuth at liigli flus levels to obtain as high as possible a concentra- tion of 1’0-210 in the bismuth target tlisclinrgetl from the reactor.

At present, there is no conimercial capability to process Po-210 or mxnufacture Po-210 heat sources. Such capability exists only a t Mound Laboratory, and its encapsulation c,apability is currently limited to a few hundred grams of P-210 :innually. By 1969, Iioivsver, the process facilities a t Mound TJaboratory will liave been improved, and a. new facility for encapsulating Po-210 will have been completed. Mound Lab- oratory will then liave tlie capability to supply 1.0 to 2.0 kg of Po-210 annually.

Ylutonizcrn-%j8. Plutonium-238 is made by the addition of a neutron to Np-237. Nep- tunium-3:37 is a byproduct formed in it reactor fuel element by a) addition of a neutron to IT-236 wliich may be formed in about 20% of the neutron captures by ‘IT-235, niilrl’ b) an (n, 2n) reaction with IJ-238.

Since Np-237 is a, byproduct of nuclear power generation, any increase in planlied nuclear power generating facilities would increase t lie amount potentially available from that source. If the Np-237 expected to be available from the commercial reprocessing of power reactor fuels is recovered and accumulated, a i d then irradiated in Government or private reactors to p r d u c e Pu-238, the total annual supply of Pu-238 in the late 1970’s coubcl more than double that produced from AEC Np-237. At these higher production rates, modest AEC equipment modifications would be required for Np-237 target fabrication, for processing irradiated Np-237 targets, arid for convcmion of tlie Pu-238 to an oxide. Recovery from ir- racliated power reactor fuel, with only modest

3 6

0

1

FISCAL YEAR FIGURE 6. Np237 and Pu-238 Potentially Available froin Power Reactors.

3 T

The General Electric Company, l i n s :innouncsd that N p 2 3 7 will 1~ twwveretl in i t s fuel processing plant :~ncl offered for sale. The New York Statk -itornic :tiid Space Developinelit .!utlloTitw lias revenled plans for rwovering Kp iii the Nuclear Fuels Sewice fuel proce.s4ng plant. The IJnitecl I<ingdoni :ind Eurocheniic have also offered Np-%37 for sale or barter to tlie IJnitecl States.

The .iM’ 11as nintle k i i o \ t n i t s plans tliat, to the extent procwrenient. of some Np will be required, *\I%: ivoultl annually negot iate terms for delivery of Np to AiIW as soon :is R commercial N p recovery capability is avai1:il~Ie. The pur- clinses \voald be (*ontingent upon the successful negotiation of rea.so11 :I ble pn rcliase prices. At the present time, no industry capability exists for producing large qrrantities of PII-”38 from tlie Np-237; this operation could be carried out in facilities.

An important coiisitleration is that the Np- 237, wliicli is part of the “\vast.e prodncts“ of the power reactor fuel processing cycle, sliould be recovered during fuel proccessiiig and stored. Tlie cost of recovery at this stag0 is much lower than it ~ v o u l d he after the n-:istcx is put into long-tsrm storage.

C‘um’urn-ZG. I n 1969, AEC will liave produced’ and piirifietl about 5.5 k g s of Cm-244 for development of :I fuel form and for eraluatioii of this isotope for. potential isotopic power applications.

Tliis isotope is made by addition of :I iieutron to hn-243, which, in turn, is inade by addition of n neutron to Pu-242. Plutoniiw-242 is rn:tde by sequential adtl’ition of a neutron to the isotopes of plutonium. I f high-exposure plutonium is av:1ililble :IS starting m:iterinl, tlie production of Cm-244 is facilitatstl.

Signi ficaiit arnoiiii ts of higli-exposii re p111-

tonium, americium, and curium isotopes will become av:iil:ihle from the nucle;ir power

reactors. This could increase the availability of t:~rget material :ind reduce the lead time ancl cost to produce large amounts of Cm-94.

‘rile cwrrent protluc*tion of Crn-244 requires :I substantial initial iiivestriient for the plu- toiiiiini target matmial and i t s initial irradi:\tion ( 1 year) to produce :L s u l ~ q u e ~ . n t target mater- i d containing the Pu-242 isotope. It in turn must be irradiated (1.5 years) and then chemic:dly processed to purify and recover Pn-242 itnd ,\m-243 for recycle through the reactor, and to recover the Cm-244 product. The pro- diiction facilitiss required to clieniically process large quantities of the irradiated target for recovery of the 1-esidnal Pu-24.2, Am-243, and Cm-244 ; to manufacture target sources from tlie recovered Pu-242 arid Am-243; and to iminufwture Cm-244 encapsulated sources, will hare to he constructed if large requirements clerelop. The manuf:icturinp cost anid goal range of this report is based upon recovery of Cm-244 from spent power reactor fuels.

ISOTOPES OFFERED FOR SALE

A\ catalog of isotopes offered for sale by ARC is :~v:1ilable from the Isotope Sales Department, Isotope Development Center, Oak Ridge Nation- al TJaboratoiy, E’. 0. Box X, Oak Ridge, Ten- nessee 37831.

ENCOURAGEMENT OF PRIVATE PRODUCTION

*is a mattemf policy, the AEC has withdraw1 from supplying approximately 40 radioactive materials and services, a n a the AEC will wii- tinue to review those services which sliould be :~vailable from commercial soiirce6.

In keeping wit11 this policy, AEC has encouraged private industry to consider a) making avi\ilaMe isotopic materials such as Np-237, h) providing irradiation services to produce isotopic materials such as Co-60, and c) tlie recovery and manufacture of fission product sources .

38

ilability ime aiitl

requires he plu- :idintion

mater- in turn 1 chem- Pu-242 reactor,

'110 pro- Dr-

get for '43, and 's from and tr, sources, remerit s 11 range Cm-244

)y AEC &men t,, Natian- ;e., Ten-

ION

hclrawri ioac,t ive ill wn- ,uld be.

ias en- making

n-oduce c) the

poduct

p-237,

39

APPENDIX "B"

BUDGET

FY 1966-FY 1969

nology, anti the Division of Space Nuclenr Systems. Prodiictioii budgets are not included. F Y 1969 figures are tliose Iwomniended to

INTEGRATED AEC RADIOISOTOPE PROGRAM BUDGET

(Excluding Production)

(Millions of $)

Total Oikerating Costs

* See detail following.

1%" (Actual)

$47.3 3.9 0.3 0.4 2.9

$54.8

1968 (Est.)

$37.0 5.9

0.7 2.8

-___

$46.4

$37.5 6.8

0.9 2.6

$47.8

0.2 4.4

Total Program Q1.A $59.6 $49.0

'Total SEPO equipment less Reactor Power and Reactor Safety.

40

$58.0

DETAIL-SPACE ELECTRIC POWER

Nuclear ncliitled. ded to Y 1969,

fOllO\V-

i i i this

$37.5 6.8

0.9 2.6

$47.8

F Y 1966 1967 (Actual) (Actual )

Operating Costs:

Radioisotope Power: $11.7 $28.1 - Pu-238 Space Generators _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9.6 18.5

S N A P 1SB-NIMBIJS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2.0 4.0 SNAP 27/ANSEP . . . . . . . . . . . . . . . . . . . . 7.5 13.6

-

2 X Watt Voyager _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .1 .7 S A N S (NAVSAT) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ .2

P+210 Space Generators (SSAI’ 39) --- .7 7.1

Large Heat Source ( k w ) __________---- 0.3 _ _ _ -

Theriiiionic Generator _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __-- 0.2

Silpporting Technology _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 0.5 2.1

Cm-242 Space Generators (SNAPS 13, 11) 0.6 0.2

Power Cohversion 9.6 6.4

Thernioelectric Power _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4.2 3.8 Dynamic Power (Excl. Potassium

Rankine) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5.4 2.6

-

Space Nuclear Safety

(Excl. Reactor Safety) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5.3 4.3

Isotopic Fuels (Space) 4.1

Plutoniuni-238 Fuels _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1.0 Poloniuni-210 PUPIS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2.0 Curium Fuels (R&D) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1.1 Fission Prod. Fuel Dev. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Materials Development _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

- 8.5

4.5 2 7 1.0 0.2 0.1

Total Space Electric Power $30.7 - - $47.3 - 5.0 0.3

0.1 0.4

-___

$ 5.8

1968 (Est.)

$19.9

10.0

2.7 6.6

0.7

6.7

0.9

0

2.3

_ - _ _

3.7

3.1

0.6

3.7

9.7

5.5 2.7 1.3 0.1 0.1

$37.0

$18.8

6.5

0 1.5 2.0 3.0

6.0

3.0

0.8

2.5

-

4.9

4.3

0.6

3.7

10.1

5.0 3.7 1.1 0.1 0.2

$37.5

$58.0

41 QU. S. GOVERNMENT PRINTING OFFICE : 1968 0 - 299-515

office of scientific and technical information · list of tables list of illustrations figure 1....

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