uf6 cylinder homogenization study - experimental result with a 10-ton cylinder

8/11/2019 Uf6 Cylinder Homogenization Study - Experimental Result With a 10-Ton Cylinder

1/25

3/4 K/PS449

DE84 011589

Date of I s su e : May 1983

UFg CY LIN DER HOMOGENIZATION STUDY - EXPERIMENTA L RESUL T

WITH A 10-TON CYLINDER

S. H. ParkSyst ems and Equi pment Technol ogy

Process Suppor t Di vi si on

Uni on Carbi de Corporat i on, Nucl ear Di vi si on

Oak Ri dge Gaseous Di f f usi on Pl ant1Oak Ri , dge, Tennessee

DI SCLAI MER

This report was prepared as an account of work sponsored by an agency of the United States

Government. Neither the United States Government nor any agency thereof, nor any of their

employees, makes any warranty, express or implied, or assumes any legal liability or responsi- '

bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or

process disclosed, or represents that its use would not infringe privately owned rights. Refer

ence herein to any specific commercial product, process, or service by trade name, trademark,'

manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom

mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of the

United States Government or any agency thereof. />

BSTOBOTOf Of TWS DflCWiWT IS WllWT!0


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TABLEOFCONTENTS

ABSTRACT - 7

I NTRODUCTI ON 9

I NSTRUMENTATI ON AND PROCEDURE .' 10

General .'" ... .1 10

Q

E x p e r i m e n t a l . D e s i g n 12

T e s t . 16

RESULTS 1 6

o

it ,

CONCLUSION.. 27

ACKNOWLEDGEMENT ' 29

DI STRI BUTI ON 31


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7/8

ABSTRACT

The UFg cyl i nder homogeni zati on process has been i nvest i gatedexper i mental l y wi th a 10- ton cyl i nder . A speci al l y modi f i ed cyl i nderequi pped wi th sampl i ng probes and t emperature sensors was f i l l ed wi thessent i al l y equal amounts of three di f f erent assay mat er i al s. Thecyl i nder was then heated i n an autocl ave wi th saturated steam f or13 hour s. Sampl es were drawn from each of f our sampl i ng port s for11 hours. Temperature measurements i ndi cated that sol i d UFg exi st ed i nthe cyl i nder f or 5 hours, and the assay mi xi ng pat t ern dur i ng thi speri od was fai r l y l ocal i zed. Large scal e mi xi ng of the di f f erent assaymater i al s f ol l owed af ter the compl ete mel t down of the sol i d UFg due coa l arge t emperature gradi ent i n the l i qui d. The t emperature gradi entdecreased t o l ess t han 1F/ f t af ter 11 hours of heat i ng; hencef or th, themi xi ng mot i on by l i qui d convecti on pract i cal l y ceased. The test resul tsi ndi cated t hat the var i ance of assay sampl es, at any gi ven t i me, werenever smal l er t han the var i ance of t he spectrometer measurements dur i ngthe ent i re t est per i od and, hence, i t can be concl uded t hat the cyl i nder

never achi eved absol ute homogenei t y. The def i ni t i on or requi rements f orhomogenei ty of a UFg i s beyond t he scope of thi s report ; however, si ncethe anal ysi s f or assay of a cyl i nder i s consi dered to be accurate to0. 1%, thi s woul d seem to be a mi ni mum requi rement . The assays at t hef our por t s were wi thi n 0. 1%of . each other af ter 8. 5 hours of heat i ng andwi t hi n 0. 05% af ter 11 hours of heati ng. Two l i qui d sampl es were takenat the end of the test through the val ve. The average assay val ue ofthese was 2. 1743%2 3 U whi ch was 0. 02%of f f romthe theoret i cal l y cal cul ated val ue. * @>

o


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I NTRODUCTI ON

I n t he dai l y oper at i on of t ne ur ani um t ol l enr i chment pr ocess,sampl i ng of a cyl i nder t o det er mi ne i t s assay i s an i mpor t ant t ask.

Thi s pr ocess i s al so t i me consumi ng si nce i t i nvol ves heat i ng t he

cyl i nder f or a suf f i ci ent amount of t i me t o ensur e that t he cont ent s ar ei n a homogeneous st ate i n t erms of assay. I n t he U. S. enr i chment process, t he heat i ng of t he cyl i nder i s conduct ed i n an aut ocl ave wi t hsat urated st eam. The procedure adopt ed at t he Oak' Ri dge GaseousDi f f usi on Pl ant ( ORGDP) i s t o pl ace a cyl i nder i n an aut ocl ave i n t heaf t er noon and heat i t overni ght , f ol l owed by sampl i ng t he next ' morni ng.The assay val ue determi ned by t he sampl e t hen, r epresent s t he assay oft he cyl i nder . Thi s heat i ng1 t i me, 18 hours or l onger , may or may notbe suf f i ci ent t o ensur e assay homogenei t y i n t he cyl i nder . Al l i ndi cat i ons woul d evi dence that i t i s a suf f i ci ent amount of t i me f or acyl i nder t o r each assay homogenei t y; however , t her e exi st ed st r ong needsf or i nf or mat i on on t he mi ni mum t i me r equi r ement s f or a gi ven si ze ofcyl i nder t o r each assay homogenei t y under aut ocl ave operat i ng condi t i ons

and how t he var i at i on of oper at i ng condi t i ons mi ght af f ect t he t i me ofheat i ng. Thi s i nf or mat i on i s needed t o det er mi ne t he f easi bi l i t y ofpr epar i ng a cyl i nder f or sampl i ng wi t hi n an 8 hour shi f t and al so i nhel pi ng t o est abl i sh an i nt er nat i onal st andar d f or t he cyl i nder sampl i ngprocedur e. There have been several at t empts i n t he past t o answer t hesequest i ons. One r ecent st udy conducted by R. F. Smi t h* at t he PaducahGaseous Di f f usi on Pl ant ( PGDP) showed t hat a 14- t on cyl i nder r eachedassay homogenei t y i n 12 hours. The st udy was conducted wi t h ni ne cyl i nder s whi ch were spi ked wi t h di f f erent assay mater i al of known amounts.

The cyl i nder s wer e t hen heated and sampl ed at var i ous t i me i nt er val s.One maj or drawback of t hi s met hod was t he sampl i ng t echni que whi chi nvol ved st oppi ng t he heat i ng pr ocess and r ot at i ng t he cyl i nder . Thi si nt er r upt ed t he mel t i ng and convect i ve, mi xi ng mot i on of UFg i nsi de t hecyl i nder and cr eat ed addi t i onal l ar ge scal e mi xi ng by t ur ni ng t he

cyl i nder . The present st udy was desi gned t o i nvest i gate t he assay homogenei t y process wi t h mi ni mum di st urbances of1t he mi xi ng pr ocess- i n or dert o obt ai n unbi ased data. The t wo obj ect i ves of t he st udy are:

1. Determi ne t he mi ni mum t i me f or a 10- t on cyl i nder t o r eachassay homogenei t y.

!: 2. Determi ne a cor r el at i on bet ween t emper ature and assayi, var i at i ons i n t he l i qui d UF6 dur i ng t he heati ng per i od.i, ' -

f.The f i r st obj ect i ve coul d be readi l y achi eved by assay sampl i ng oft he cyl i nder . Thi s , however , woul d not provi de i nf ormat i on on t heef f ect of changes i n cyl i nder si ze and aut ocl ave oper at i ng condi t i ons on

t he mi ni mum t i me r equi r ement t o obt ai n homogenei t y. I t was deci ded t hatt hi s i nf ormat i on coul d best be obt ai ned by devel opi ng a numer i cal moci el

Smi t h, R. F. , St eam Bath Cycl e Requi r ed f or I sot opi c Homogenei t y of14- Ton UF6 Cyl i nder ( U) , KY- 556, Uni on Car bi de Cor p. , Nucl ear Di v. ,Paducah Gaseous Di f f usi on Pl ant , J une 17, 1968. UNCLASSI FI ED. ' j

,"' :

' " \ o - ' " - . . ' ' ' 'K


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of thermal convect i on currents i n t he cyl i nder . The model woul d beconst ructed t o match known temperature gradi ents i n the cyl i nder whi chcoul d be correl ated to assay gradi ent s. I n order t o meet t hi s obj ect i ve, i t was essent i al t o obtai n the var i at i on wi th space and t i me oft he temperature and assay of t he UFg i n the cyl i nder .

I t was paramount t hat t hese parameters be obtai ned wi t h mi ni mumi nter f erence of the heat i ng and mi xi ng moti ons whi ch requi red subst ant i al changes to the sampl i ng t echni ques t hat had been empl oyed i n thepast . , Thi s was accompl i shed by provi di ng f our sampl i ng l i nes whi chpenetrated the autocl ave and t he cyl i nder so that -Sampl es coul d be takenat any t i me wi thout openi ng t he autocl ave or rotat i ng the cyl i nder . Thespace var i at i on of temperature/ assay was obtai ned f rom the posi t i oni ngof t he probes i n the cyl i nder / and the ti me var i at i on was acqui red bysampl i ng at var i ous t i mes dur i ng the heat i ng per i od.

< I NSTRUMENTATI ON AND PROCEDURE ' '

GENERALAs st ated above, one of the requi rements t o accompl i sh t he obj ec

t i ves of the exper i ment was t o obtai n data wi th mi ni mum di sturbance t ot he UF6 content s. Thi s requi red two basi c changes i n t he method of "autocl ave operat i on:

1. The test' cyl i nder , once pl aced i n the aut ocl ave, woul d notbe rotated or t i l t ed. V,, Theheat i ng process woul d not bestopped dur i ng the t est .

n2. The temperature and assay woul d be moni tored cont i nuousl y

,Jthroughout t he heat i ng (peri od. .

u

The exper i ment was conducted, wi t h a 10- ton cyl i nder. The cyl i nderwas modi f i ed t o accept three t emperature/assay probes and one pressuret ap. The probes, descr i bed i n detai l i n repor t K/ PS- 452*, consi st hof1- i nch di ameter steel pi pes, 4 f eet i n l ength, whi ch contai n f i ve t emperature sensors and one assay sampl e por t ; one probe contai ns twosampl i ng port s. The posi t i on of these probes, shown i n Fi gure 1, i ndi cates t he rel at i ve posi t i on of t he \sampl e por t s. The cyl i nder contai ned15 temperature sensors, f our sampl i ng port s, and one (pressure t ransducer . Wi th this' -i i nst rumentat i on, i t was possi bl e to moni tortemperature/pressure cont i nuousl y and draw sampl es wi t hout i nter f er i ngwi t h t he heat i ng process- ; The overal l scheme of the test was t o heatt he cyl i nder wi th t hree di f f erent assay mater i al s of known amounts andsampl e unt i l t he assay of the sampl es reached the cal cul ated val ue of t hemi xture. Unf ortunatel y, the assay of t he sampl es coul d not be deter -

; mi ned i nst antaneousl y, so i t was necessary t o take sampl es over a suf -

- - i l;_, '2

'- *Branam, D. A. , UFg Homogeni zat i on Study Sampl e Probes, ( U) ,K/ PS- 452, Uni on Carbi de Corp. , Nuci ear;i ui v. , TO be i ssued at oak Ri dgeGaseous Di f f usi on Pl ant . UNCLASSI FI ED. tt
http://sample/http://sample/


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S1 S2P1

S3

w

T2()

)> T3( )AB

AD T4()

D W C . N O . K/G-S3

|U)

LAA

L/2.

T 5 Q ^ C

L/6 S1,S2,S3 -TEMPERATURE/ASSAY

O - TEMPERATURE SENSORS

A - ASSAY SAMPLE PORT

PI,P2 - PRESSURE TAP

Figure 1

SCHEMATIC DIAGRAM OF THE TEST CYLINDER


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f i ci ent t i me span to ensure t hat t he cyl i nder reached the homogenousstat e.

EXPERI MENTAL DESI GN

The cyl i nder was l oaded wi th t hree di f f erent assay mater i al s ofal most equal amounts, as shown i n Tabl e 1.

Tabl e 1. Summary of the Feed Materi al s

J>

MaterialNo . ip

Assaywt % 2 3 5 o

2.6098

Amountlbs

1

Assaywt % 2 3 5 o

2.6098 6,752

2 2.1759 6,750

3 1.7394 6,767

Each assay mater i al ' was f ed i nto t he cyl i nder f ol l owed by a mi ni mumof 3 days of cool i ng to sol i di f y the mater i al . Thi s was t o mi ni mi zemi xi ng dur i ng the f eedi ng process and to create the desi red st rat i f i cat i on of assays. The choi ce of three assay mater i al s was made t o reducet he t i me of each f i l l andi mi ni mi ze t he amount of mel t i ng and mi xi ng wi tht he previ ous f i l l . The 2. 6098 wt percent 235a mat er i al was f ed f i rst ,f ol l owed "by 2.1759 and 1. 7394 wt percent Sy mater i al , respecti vel y.Wi th t hi s f eedi ng, the, . theoret i cal assay of the mi xture was 2. 17471 wtpercent 235u% O

!| '>

The i deal si tuat i on woul d be to moni t or the temperatures and sampl ef or assay cont i nuousl y, but i t was physi cal l y i mpossi bl e t o manage atthi s t i me. ._J The t emperatures were moni tored every 10 mi nutes whi l esampl es were drawn every hour. The l onger sampl i ng t i me span was di ct ated by the sampl i ng sequence adopted f or thi s experi ment . Thesampl i ng system, shown i n Fi gure 2, consi st ed of a probe wi t h a sampl epor t , copper t ubi ng, and val ves to t ransf er t he"sampl e to the sampl et ube, and auxi l i ary systems f or dumpi ng UFg and cl eani ng the l i nes.

There were f our i dent i cal systems i n t he exper i ment . Al l t he l i nes wereheated wi th- , heat utape t o prevent sol i di f i cat i on of UFg. The maj orsampl i ng operat i ons i ncl uded f l ushi ng l i nes wi t h l i qui d UFg t o t he dumptank bef ore t rappi ng sampl es. The' ,trapped materi al was t hen t ransf er redi nto the sampl e tube. The amount of UFg t aken i n each tube was approxi =matel y 10 grams , / )

Fi gure 3 and Fi gure 4 pi cture the test cyl i nder wi t h i t s i nst rument at i ons and sampl i ng panel .


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PHOTO NO. K/PH-BZ-41Z2

Figure 3

TESTCYUNDER IN AUTOCLAVE NUMBER 1 WITH INSTRUMENTATIONS


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PHOTO NO. K/PHt2-442f(u) Overal l , i t mi ght be concl uded that t he t hr ee-di mensi on ef f act on t he temperature prof i l e dur i ng the heat i ng per i odwas mi ni mi zed.

^

The rel ati ve shape and posi t i on of sol i d at the pl anes S1 and S3 i sshown i n Fi gure 8 as n f unct i on of t i me. The one-di . Ti ensi onal represent at i on can be pi ctured i n t wo di mensi ons as di sks wi t h no thi ckness atpl anes S1 and S3. The di sks mai nt ai n a const ant di ameter f or 1 hour and20 mi nut es unt i l t he sol i d start s to mel t and the di ameter begi ns t odi mi ni sh at pl ane S3. The mel t i ng at pl ane S1 begi ns 10 mi nutes l at er ,

but occurs at a sl ower rate as i ndi cated by t he l arger di ameter di sk S1compared t o S3. The sl ower mel t i ng rate at S1 i s caused by the l owertemperature and heat i nput at t he end of the cyl i nder whi ch i s asampl i ng at 2 1/2 hours af t er t he st eam was appl i ed, eventhough sol i d UFg st i l l exi sted i nthe system. Because of the exi st i ngsol i d phase, onl y t wo sampl es coul d be obtai ned f rom t he four sampl epor t s i n t he f i r st sampl i ng per i od. The next sampl e per i od yi el ded f oursampl es, as di d t he fol l owi ng ni ne sampl e per i ods. I n al l , 42 sampl eswere anal yzed by mass spect rometry accordi ng to an experi mental desi gnwhi ch assured a f ai r compar i son of t he f our por t s wi t hi n each t i meperi od. There were 3 t o 6 determi nati ons per each sampl e whi ch resul t edi n an average of 4. 57 determi nat i ons per sampl e. The st at i st i calresul t s of t he sampl e, as anal yzed by K. L. McCormi ck*, are l i sted i n

*K. L. McCormi ck, Uni on Carbi de Corp. , Nucl ear Di v. , Oak Ri dgeGaseous Di f f usi on Pl ant , l et ter to S. H. Par k, March 7, 1983.UNCLASSI FI ED. *" ' " ' - c""~" "*"" '


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OWG. NO.K/G-83-1506(U)

2 3 4 5TIME OF HEATING, hr

Figure 7

TEMPERATURE PROFILES OF PROBESS1AND S3


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DWG. NO.K/G-83-2010

(U)

2 3TIME OF HEATING, hr

Figure 8

SOLID UF6SIZE AND POSITION DURING THE HEATING PERIOD


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Tabl e 2. The resul t s are al so pl otted i n Fi gure 9, and can be categor i zed i nto three di f f erent regi mes of mi xi ng. The f i rst regi mecovered t he f i r st 5 hours of heat i ng when the cyl i nder contai ned bothsol i d and l i qui d UFg. I n thi s regi me, t he assays of each sampl e por t swere di ct ated by t he movement of sol i d UF6, and l i qui d mi xi ng. The

second regi me of mi xi ng occur red f rom 5 to 9 hours af ter heat wasappl i ed when l arge scal e mi xi ng mot i ons exi sted i n the l i qui d UFg. Thel ast' ' -regi meprevai l ed after 9 hours and was character i zed by very l i t t l emi xi ng moti on. Thi s l ast regi me coi nci ded wi th the peri od when the temperature gradi ent t hroughout the cyl i nder was smal l .

//The mi xi ng process of the sol i d/ l i qui d regi me, whi ch l asted for

5, hours, was t he most di f f i cul t process t o understand. The assayresul t s f rom the i ni t i al sampl es i ndi cated that mi xi ng had al readyoccur red because t hey di f f ered f rom the assays of any of the f eedmat er i al s. However , the assay at C was st i l l the hi ghest , whi ch i ndi cated that most of each mater i al f ed i nto t he cyl i nder remai ned i n i tsrel at i ve posi t i on. The decreasi ng assays of A, B, and C i n the next 3to 4 hours coul d be expl ai ned by a chunk of sol i d UFg, whi ch consi st edof l ow and medi um assay mater i al , sl owl y si nki ng t o the bot tom of thecyl i nder , and mi xi ng wi th t he hi gher assay mater i al s that exi sted i nthat l ocat i on. The l ower assay exi st i ng at A compared to C dur i ng thi speri od, coul d have resul ted f romexcessi ve mi xi ng when the mater i al s weref ed i nto the cyl i nders and more mel t i ng and mi xi ng occurred at the endthan the mi ddl e of the cyl i nder because of the cl ose proxi mi t y t o thef eed val ve. The mi xi ng i n the 4 hours f ol l owi ng compl et i on of sol i dmel t down was produced sol ey by t he convect i ve moti on of the ' l i qui d UFgwhi ch devel oped f rom the temperature gradi ent . Thi s l arge scal e orrapi d mi xi ng was enhanced by comparat i vel y l arge densi ty di f f erences i nthe l i qui d. As t he temperature gradi ent decreased wi th t i me, the degreeof mi xi ng mot i on subsi ded i n di rect propor t i on. The three di f f erent

mi xi ng regi mes are depi cted agai n i n Fi gure 10 by t he maxi mumdi f f erencei n assay between sampl es at each sampl e t i me whi ch i s normal i zed to themean val ue and pl otted as a funct i on of t i me. The pl ot shows t hree di f f erent pat t erns; i ncreasi ng di f f erences f ol l owed by f ast decreasi ngval ues bef ore r eachi ng an al most f l at pat t ern of smal l di f f erences i nsampl e assays. The i ncreasi ng port i on of regi me coi nci ded wi th thesol i d/ l i qui d r egi me where l ocal i zed mel t i ng and mi xi ng of UFg createdl arge assay di f f erences between port s. The peak of thi s regi me coi nci ded wi th the compl ete mel t down ti me of the sol i d UFg. The f astdecreasi ng regi me i n the next 4 hours cor responds t o the l i qui d mi xi ngregi me whi ch was f ol l owed by a regi me of great l y reduced mi xi ng. Theexternal var i ance of assays between port s was never smal l er, t han thei nternal var i ance dur i ng the test and absol ute homogenei t y of the con-

. tent s was never achi eved. Obtai ni ng compl ete homogenei t y i n a cyl i nderwoul d r equi re an i nf i ni te t i me and i s not f easi bl e, but a degree ofhomdgeni zat i on i s needed. The current methods' f or determi ni ng t he assayof cyl i nders i s not consi dered t o be more accurate t han 0. 1%. I f thi samount of var i at i on i n cyl i nder assay i s consi dered t o be adequate f orhomogeni zati on, then i t was achi eved i n t he t est af ter 8.5 hours and avar i at i on of l ess t han 0. 05%was achi eved af t er 11 hours of heati ng.


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Tabl e2. Summary Stat i st i cs of t he Exper i mental Data

Hours

2. 5

3.5

4.5

5. 5

6.5

7. 5

8. 5

9,5

St andardPort Average Devi at i on

B 2. 2063 0. 000075C 2. 2612 0. 000072

A 2. 1735 0. 000111B -, 2. 1918 v 0. 000132

C 2. 2706 0. 000284D 2. 1831 0. 000164

A 2. 19880

0. 000161B 2. 1374 0. 000080

C 2. 2246 0. 000017D 2. 1829 0. 000167

A 2. 0871 0. 000079B 2. 0936 0. 000043c ' 2. 1999 0. 000081D 2. 2121 rj 0. 000176

A 2. 1784 0. 000106B 2. 1776 0. 000104C 2. 1717 0. 000075D" 2. 1817 0. 000076

A 2. 1799 , 0.000039"

B 2. 1757 0. 000076C 2. 1698 0. 000102D 2. 1766 0. 000147

A 2. 1765 0. 000055B 2. 1754 0. 000102C 2. 1749 0. 0 00025D 2. 1744

rfV> , ,

0. 0 00063

A 2. 1758 *0. 000077B 't 2. 1755 0. 000121

C 2. 1748 0. 0 00022D.m' :

v. 2. 1754 ' 0. 000173


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Tabl e 2. Summary Stati st i cs of t he Experi mental Data ( cont i nued)

Hour s

10. 5

11. 5

12. 5

Por t

ABCD

ABCD

A 'BCD

Average

2. 17592. 17572. 17462. 1758

2. 17562. 17542. 17482. 1750

2. 17562. 17552. 17492. 1757 1

Standar d

Devi at i on

0., 0001770., 0001560. 0001670. 000104

0., 0001190., 0000900., 0001620., 000094

0., 0000830., 0001050., 0001330., 000089


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3inCOCM

7 8 9TIMEOF HEATING, hr

-~ DWG.

(U)

^\ D

2.30

C .

c \

\ B \

S^^T a =jp

2.20A. B

Dvv \ * -JJK""^

A. B

Dvv

A. B

vv

- -- v

A

NJC

/ -

2.10 r

*

z >*

2,00 I ' I I I 1 i " i i 1 1

NO. K/G-83-1509

10 11

Figure9

VARIATION OF ASSAYS DURING THE HEATING PROCESS

- 2.182

2.180

A 2.178

2.176

2.174 $

- 2.172

- 2.170

- 2.168

12 13


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DWG. NO. K/G-83-1368

("1

2.5

\-

*.10-2

uf6 cylinder homogenization study - experimental result with a 10-ton cylinder

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