ML20082T447
| ML20082T447 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 12/20/1977 |
| From: | GENERAL ATOMICS (FORMERLY GA TECHNOLOGIES, INC./GENER |
| To: | |
| Shared Package | |
| ML20082T428 | List: |
| References | |
| GLP-5588, NUDOCS 8312160021 | |
| Download: ML20082T447 (20) | |
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GLP-5528 5 e.- . u SAFETY ANALYSIS REPORT USE OF H-451 GRAPHITE IN FORT ST. VRAIN FUEL ELEMENTS i 6
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GENERAL ATOMIC COMPANY ; DECEMBER 20,1977 ;. T 0312160021 831202 PDR ADOCK 05000267 PDR P Ii
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! TOPICAL REPORT EVALUATION l
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l Report Nc=ber: GL*-5588 ' !' Report
Title:
Safety Analysis Rep:rt--Use of H-451 Graphite in Fort St. Vrain i l'
. ?-
Fuel Elements Report Data: Dece==er 20, 1977 1; l* il Origina.ing C gant:ation: General At:mic C:cpany 1 i l Reactor Fuels Ser.icn, Core Perf:rmance Branch, Reviewed by: , Division of Systems Safety, March 1379. - [ l . l i Summarv ef Tecical Recer , l 1 This t:pical report was submitted by General At:mic C:mpany (GA) via letter h (G. L. Wessman (GA) to R. P. Denise (NRC), Mar:n 28,1978). In that lettar we
- z. . , . . .
. . . . i were requested to review the report and cencur with GA's opinion that the . !
*substitutien of type'li-45T'gra;htia in the' For. St.' Vrain (FSV) reactah ~cere for t.he.
type (H-327) cu- ently in use,is a::eptacle. T.he reasons for.cesiring . . . ; to su:stitute M-451 for M-327 graphite in FSV were stated to be as f:llows: i
- +
- 1. General Atomic is contractually obligated to supply Public Service :
Ccapany of Colorado (PSC)' with fuel elements. - l: 6
- 2. It appeared to Gd that 11-327 gra:hita, the type currently used, '
e would nct be availahle in the future. f
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- 3. General At:mic believes tnat H-451 gra:htte is superi:r :: H-327, . !
# f both in ter=s Of.di=ensienal s. ability uncer irradia .icn, as well as s rangth. I i I
Thus, NE's approval of H-451 gra;nita for use in the FSV reac :r was soli:itec j i so that the reference core H-307 ;raphite fuel and refle:. r elements c:uld be ' replaced with H-451 ; a;hite elements curing future relcads; the first potential . i substituti:n c:uld begin with relcad " segment 5," currently scheduled f r !
' early 1581. ; .
f The t::ical re; rt was stru::ured int: three :ajor sections: (1) a perf:rmanca , I '
, analysis cf the H-451 elements, enc: passing the nu: lear, ther:al, and structural i ,,
. f:
cesign, (2) a safety analysis of the effect of the H-451 elements en a::idents i l t that had been censidered in the F5V F5AR, and (3) a su= mary cf catarial pre;erty j data for H-451 graphita. In general, the a;proach used was to c:: pare the , g r i analytical results based on H-327 graphita with the results obtained with the jl: l
' assumptions cf H-451 graphite as the core material. The objective was t:
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demonstrat's. that H-451 was'a bettet structural r.aterial thh H-327_ and that , j : the use of H-451 wcul'd (a) result. in negligible. changes in the nuclear and. -
. th.. . .l' behavier c.f the c:re, and (b) net resuTt in aducad safety margins cr erma
. .,. . . . ~ .. . .
reliability ::.sared : the reference H-307 c:re. i . I. j The core nuclear perfor=ance analysis adcressed fuel loading and ex:ess rea:tivity, i I I - power distributien, fuel burnup and ex:esure, shutdown margins and reacter' I- 8
; control, and red withdrawal ac:idents. The -cd withdrawal ac:icent was given
- I, I special attention because it is icentified in tne F5V F5AR as the worst-case ;
reactivity initiated ac:icent; c:nt ci red ejection ac:icents are not censicered
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e- . . :- - ~-
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k 5 . t ' I t . i ! credible f r -he F5V res:.:r and, therefore, the =nsecuen:es =f a r:d eje:tien
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l a::ident are net.analy:ed. i - e i I I The._ccre ther=al analysis addressed the fact that the thermal concuctivity cf l , I , H-451 gra:hite is appr:ximately a fact:r of 1.2 greater than ' hat t cf H-227 ; i graphita. The better ther=al c:nductivity was predicted : result in a smaller ,
' tempera?.ure rise acr:ss tne gra:hite web and in 1cwer feel :entarline tc=e--
atures. The expected reducti:n in fuel te=peratures was ex;ected als: :: rescit in negligible changes in metallic fission pr: duct release and a rece:tien ,
, i in gaseous fission product release. ! ; . i.
I The graphite structural analysis re:crt section addressed'(a) the =echanical I properties of H-327 and H-451 graphites in a c:=parative way, (b) stress I ! . analyses for both types of gra:ihite, and (c) graphite irradiation-induced t i t ;:
. dimensienal changes. The H-451 graphite has higher strength than H-327, but i . .
the H-451 fuel element would have higner stress levels. Design stress margins I, l. 6 6 were, hewever, asserted to be i=preved by the inclusien of H-451 graphite ;
. . . . . . . . . .. 2. .~ .
elements in the F5V c:re because the imprevements in strength were more tnan ;
.. .. . . . . . . . . . s .
required te meet the increase in stress. . i f . . I j The tcpical report's " safety analysis" section was used to examine events and
~ ~
I accidents previously analyzed in Chaptar XIV cf the FSV FSAR te determine .if j. the substitution of M-451 graphite in FSV retcad ::res c:uld altar the con- - sequences of pestulated ac:idents. Events given a re-examinati:n included fuel element "malfunctiens," loss of normal shutd:wn :: cling, ::is ure inleakage, 9
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- 4-I pemanent less of for:ad circulati:n, rapid de:ressuri:a.icn, and the r:d :
withdrawal event mentic.Gd aseve. It was ::n:1uced in :ne report that ; ,
; F existing 75AR results of a::f dent analyses ::nservatively beund any pertur:a- ;
l tions resulting fr m the intr:cu: tion of H-451 gra; nite fuel elements. ; l Summarv of :lecuitterv Evaluatien , l Curing the ::urse cf cur review of GL?-5555, recuests f:r additi:nal I l information were resp:nded to by GA in writing (Refs. 2 :: 5). Our in::uiries i and GA's res;cnses will be ine:rporated into GLS-5555 via amen ment. ! i t Our review fccussed pri=arily on six aspects of H-451 graphite perforcance ' l relative t: H-327 graphite perf rmance in the Fort St. Vrain :cre: :
; i (1) material reproducibtitty; (2) corrosien (exidatien); (3) mechanical and -
lt physical pr:perties; (4) irradiation-induced dimensional changes; (5) 'I i fission product talease and transport; and (6) post-trradiation examination L and surveillance requirements. These subjects will be discussed in crder , j i
- t below.
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Gra:htte Re:recutibili v - This has been a c:ntinuing ::ncern in H7GR fuel g system reviews (Ref. 6) be:ause (a) the properties and performance of graphite t
; materials are strongly dependent upon the nature of the precursor matarials ; . and methods used in manufacture, and (b) the gra:hite used in FSV is not manu-factured by General At:mic. Graphite grades H-227 and H-451 are manufactured '
l by the Great Lakes Carbon Corporation; only the ma:hining and fuel loacing of - 1 i . 1 {) I a ph69m.w we Wb6 6 . 69 W --- i t . l
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. t the as-fa:ricated gra-hite bic:ts are perf: mec :y General At:mic. A:::r:ingly, we asked GA t: indicata h:w acetuate assurance cult be previded that (a) the '
I
; H-451 gra;hite to be used in future F5V reloads is the same as that subjected [ ; . ~
to the qua'lification test pr: gram, and (b) if different precursces or fabrication I l
. para:eters were used fer future relcad =aterial, the same (or predictable l
5 changed in) pr:;erties and thermai/irradiatien :hanges would be cbtained as . with the test qualified material. ! I i The majer thrust of the resp nse to this questien (see resp:nse to C251.la) , L. i was that, for F5V reicad seg=en.s, the H-451 legs will be manufactured fr:m -l i - near-isctropic : ke taken fr:s the same batch as that used fer the manufacture - i 'l l' cf a prepecduction let that is used as a standard fcr production f the F5V reload ele =ents and that is to be used for future H-451 production. This same , ! i
. .I i preproduction lot has also been well characterf ted for pr:pe-ties and irradiation {j behavicr, and the data ettained are used in the design data package for the 1 yc 5
H-451 fuel elements.< ~ The H-451 purchase specification further assures repro . i
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J ducibility of ccke structure by requiring the fabrication and testing of the '
. . . I c efficient of the-cal expansien (CTI) of calculated c:ke sa=:les. . -
The C-~ test =eth:d is specified (Ref. 7). Thus, severai ste:s ara aken to ensure . i that the same c:ke will be used in the future F5V reload H-451 graphite blocks l as was used in the H-451 qualificatien test program. In addition, the H-451 . !I purchase specification iequires that the binder shculd be a c 41 tar. pitch of j I the same type used to manufacture ;r:tstype, propr:ductien or procu tion icgs of . i j H-451 graphite and that the impregnant shall be a type co-tified to the purenaser. I > l
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!i We, therefore, ::nciuca that acequa a assuran:e has been proviced ::n:arning
; the reproducittlity of the H-451 gra::hite fer FSV, so long as the precursor ; i
! . E' materials and ;rocessing remain unchanged. Should the pre:ursor materials j or fabrication process be changed, however (for example, should the current I i'
>t near-iset cpic c ke supply be exhausted, thereby necessitating the pr:ductica 4
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, of a new bat:h with ;ctentially different cualities), we will require GA :: !' '
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' provide evidence te support the perfer=ance predictier.s for the gra: nite ,
; elements produ:ed ft:m the altered materials er pr: cess parameters. l' i .
r A secondary c:ncern regarding the effact =f fabricati:n process en material perfomance invc1ved the method used..to fabricate the fuel r:ds that are c:n- I I t..ined in ver.ical holes drilled int the hexag:nal graphite fuel blocks. Two -
- i . .
processes have been develcped: (1) an out-of-block forming and curing prc:ess; l ; [ and (2) a cure-in place process, sometimes called "in-block carb:nization". ; 1 The cure-in place process can result in a stronger bond between the coated
+
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; fuel particles and the fuel rod matrix; this has been observed't: cause tears j ,i ,-
' I j in the outer pyrocarbon coatings due tu differential irradiatten-induced shrinkage. On tne other ha.nd, the... cure-in-place proces.s i:,.,r',ves, heat transfer . . !.
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,; between the fuel red and graphite bicek because the gap is closed during the j i t curing pr: cess. In response to our q'vestion (Q:31.1b), GA jndicated that the e t.
cure-in place process was not being considered at this time for the fuel rods .. to be used in the H-451 fuel elements, and that if the cure-in place process t' 4 . 1:
; were te be adepted in the future, a se;,arate safety calysis. and re;crt wculd i
- be subsitted., i t
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i . Gra:hite :r esi:n - This subja:t is i=;ertant fr:: the stane:: int f neat l , l generation, ;r:cu:tien ' of fla==able gas mixtures, potential fission product I* I - l release, burnable ;cison oxidation, fuel particle hydrolysis, and effe:ts on , 5-r graphite physical and mechanical pr:perties (and ;ctantial effset, therefore, ' on core integ-ity). Our review fccused, in particular, en ne data base for i H-451 graphite, the effect of c talysts on H-451 graphite exidati n rate, and ! 4 : ' l ' a general c:=; arisen of the effects f H .451 versus H-227 gra:hite oxicatica f i en c:re perf: :anca. One review questien (q131.10), for exa=:le, ac:ressed i the effe:: of gra;hite type en the rir: tion rata as a fun:ti:n cf percent g 3 i* ' l graphite burnoff; this questi n also addressed the Overall effect of H-451 , 1 . . graphite cxidation rate en the predicted ac:ident ::nsecuences discussed in ((g. -
, the report safety anaiyses. Ancther questien (Q221.11a) adcressed the . relationship bet een graphite reaction rata, fuel hydrolysis rate, and ,
(: t .. associated release of ncble gas fission products. ,
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The respenses t: the abeve questicas are contained in reference 2. Experi-i i . mental data on a variety of graphites were cited as evidence that the chemical - l ( l' j ! . reactivities cf H-451 and H-327 graphites are similar. Parametric calcula-j tions were perf:r:ed :: cetermine the sensitivity of tne exicatien effects , e . .
! (hydrolysis rates, for example) ts the coolant canditions (suca r F nure t t-
~
j levels). The results of these calculations are documented in refere. q: 4. . . j~ Results of the parametric calculations showed that a factor of ten increase in 3: l' reaction rata decreased the acble gas release due to hydrelysis by 15::, wnile j - a threefeld ce rease in reaction rate increased the noble gas release by atcut
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, 20%. 7hese are relatively s all effects when c:=;arec : ne assumed Orcar:f- ~
l l magnitude change in reacticn rate. The t:tal a:cun't cf gra: nite exiciced ; t
; throughout a simulatec reacter steem ingress accicent, calculated using the i i ! OXIDE-3 computer code (Ref. 9), varied by atout a fact:r of two for a tenfeld change in reaction rate (:ur CXIDE-3 review conclusions are reperted in , j !.
i reference 10). We c:nclude, therefore, that ce substitution cf H-451 graphite for H-227 grachite in the FSV c:re will not significantly alter the :xidati:n j characteristics and c:nsequences as predieted in ce 75V FSAR. l , L i Mechanical and 5vsical 7-::erties and Stress-St sin Relati:nshi:s - Secti:n a i E t . l of the t:pical report listed un materials pr:perty data for both the H-451 i 1 I and H-327 gra;:hites. Our review c:n'centratad en the H-A51 graphite data tase, l Iti , j + 8 ue c:m; arisen cf H-451 graphite pr:perties with ucse f:r H-327 graphite, and i the en going and planned experimental program. These mechanical pr:perties , : i t; that are identified in G1*-5588 as the ones that deter =ine the element stresses, ' I stress-strength margins, and element deformations are (1) modulus of elasticity,
. l (2) tensile strength, (3) creep properties, (a) irradiation-induced dimensional j.
.E changes, (5) thermal expansion, and (5) t.*iermal c:nductivity. As ; art cf our
, i review, we asked GA (Q231.5) t: illustrate ne relative impertance of these .
; properties to the calculatics of the. abcve parameters. Dimensional changes are discussed separately below, i i
t t i GA's respense was in terms.cf the effect of material pr:perty charges at the ! i
. time of maximum stress, for both cperating and shutdown c:nditions, and at the I time of maximum dimensienal change. This appr:ach was fellowed because ef. the
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( b-- p , l. . ecmplexity cf the effe: cf matarial property variaticns en stress, design 5 margins, etc., i.e. the effect of any specift: variatica is cependent uten the
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i intera: tion with varicus other preperties whi:h vary with time. Thus, the { l -maximum-eperating stress was reported to cc:ur at :ere days and was due *c , startup thermal stresses. At that time there are no creep effects, and any - I
. change.in creep parametars, therefore, has no effect en stress and stress cargins. Although, as indicated in reference 3, at end cf life in the element, a ; ,: a *2C variation in the stancy-state :rees coeffteient :an result in a -23 f, in:rease in%ating s ress, the cperating stress at this time is re:crtec to be sufficiently 1cw that even this 2 5 increasa precu:es a stress of only one quartar the stress during initial startup. We, therefore, conclude, based ,
j cn a calculatten of the maximum str'sses during normal operation and using the ' f , available H-451 prcperty data, that there is reasenable assurance that the
< H-451 graphite element design will ac:c::medate the maximum stress with adequate [
margin. I f
~
As indicated earlier, the off-ncrmal case that produces the maximum graphite i e stress (negie: ting, for the mement, sets:fic censidera .f ens) is the maximum-worth 1. t . red withdrawal event. This event pr: duces the greatest temcera.ure differences ! I across the web between fusi and coolant hcles and, therefore, results in the .l.
. l' greatest thermally induced stress. However, as indicated in the response te -
[ i
. questien Q7.31.8, the H,451 fuel elements retain censiderable margin (* 1550
[i
; psi and
- 1150 psi in the axial and radial directions, respectively) for the
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, wors . case r:d withdrawal. These margins are greatar than'these calculated .,
a for the H-38 graphite elements (* 100 and
- 700 psi, respectively).
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{ The ateve-dis: ssed :alculatiens f =perating and snu-d:wn stress anc strain .
; distributiens were perf:rmed using the ::e; uter pr: grams FESIC anc SAFE /
GRAPHIT, whien were used in the design and analysis cf the F5V Initial ::re. t
'. t 4 As noted in cur evaluation of the FULTON plant (Ref.11), we had not yet [
t . l reviewed FESI: cr SAFI/GRAPHIT, and since these c: des have been suter:eded by '- t core recent 0: des, we still have net reviewed them. FE5I: and~SAFI/GRAPHIT -
- have been cr:ss-:he:ked, however, by hand calculattens and c:m: arisen with
- these newer ::ces. Therefore, we find tnat the use of FE5IC and SAFE /GRAPHIT are a::eptable in this appli:stien. ,
I -
- I j Regarding the acquisition and current availability cf H-451 graphite mechanical i
and physical property data, a censiderable bccy cf such data exists, as shown 4 in section 4 of GLP-558. This information was generated fer the c:ost part
, )
i under CCE-funded programs. The details of the tast procedures and results i are provided in the quarterly progress reports on the "hTGR Fuels and Care i 1 ' Development Pr: gras." These quartarly repcrts are supplemented by extensive ! i - 1 suusary reports. H-451 graphite property measurements are continuing in ce-tain areas (n=tably, c sep), but the data acquisition schedule has been stretched out be:ause of the redirectica of the HTGR ::mmer:iali .ati:n effert I in recent years. The creep tests en H-451 graphite will not be ::::pleted
, until late-1982, whereas H-451 graphite reload segments could be placed in FSV I
by early 1981. The creep tests wfil lead the FSV elements in irradiation 3 _. exposure, however, sc that full-expcsure : es; data will be available ver the range of temperatmres. expected in FSV (see GA response to Q231.21 (Ref. 4)).
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! l . f We will require General At:mic :: provide timely re::r s :n the results and j future test pr:Jec-icns for the H-451 grapnite test ;rogram, which incluces ; i not only creet tests but other mechanical and irradiation tests as well. , j4
, 4 l
2 l With regard to seismic stresses and analysis and their relationship to H-451
- l ! mechanical preperties, GA indicated in res; nse to our review questi:ns that 1 .
H-451 fuel elements weuld be expected to see increased seis=ic leading c:m:ared with H-327 because Of H-451's higher elastic ecdulus in the radial cirection , i (see modulus data in repert tables 4-3 and 4-9). Using simple s: ring / mass j k relations, H-451 fuel element impact forces were expected to be 3C% greater , than that cf H-327 elements. Eecause H-451 fuel slemen.s have mere than !!% *I'
- l. ,
higher radf ai strength, however, the seismic structural damage petantial for , o H-451 elements is less than that fer M-327 elements. The method of analysis .
.l-used to detemine the seismic stresses in the graphite fuel and reflector ' !!i elements was essentially the same as that used for t.'e FSV FSAR. Testing of , !l
. , i full scale. structures under simulated seismic loadings have also been conducted j ,
I to ' substantiate the strength of the fuel elementa. We conclude that adequa.e I
. .
- i assurance has been provided that ne H-451 g. a:hite ele *ments seismic res; case is at leas:' equal to or tetter than that of the referenca M-327 elements. ,
i
- l I
( The fatigue behavior of H-451 graphite is addressed in the topical report in 5 i i, l terms of the homologous st ess, which is defined as maximum applied fatigue , il 4 Il stress diviced by tensile strength. In response ta staff question Q120.1, GA 'l asserted that both primary and sec ndah (tiermal) loadings are below .he i, l i l t . 1 l
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hemoleg:us stress limits, and snat no fatigue anaiysis -as ne: essa y, tnere- ' fore, f:r the H-451 elemer.ts. The resp:nse :: a su':se;uent questien (Q130.2) I cn the relationship of hemolog us ilmits = per:en survival indi:ated that i* 1 j both see:n'dary and primary limits have been calculated to be. well balcw the l stress ilmits for 99% survival. Cycli: fatigue behavier =f near-isctrepic ! graphite is discussed in detail in reference 12. T-radiatien-fnduced Dimensi:nal Chances - Irradiati:n =f gra:hite causes
- l 3
damage en an at:mic scale (lattice defects) nat is manifested in tulk dimensional I changes which vary as a function net only of irradiati:n tamperature and fluence, but which are also sffectad by graphite struct5rai variables. A l facter that usually determines the usefulness f a ;raphite in remeter design 7 is the maximum radial c:ntracti:n, which influences the stability of a gra:hite , ; ;. stack. Another fa:ter that recuired censideraticn in cur review was the f dimensional c:mpatibility of H-451 graphite elements with H-327 elements since .
. only one-sixth of the : re would be replaced at each refueling. In addition, l' t
because cf the current theories relating the power fluctuations in TSV to gap ; f ' si:es between "uel c:1umns and regi ns, we recuired an assessment cf the j potential for c:mponen damage that might se caused by gap ficw-induced mo i:n j and ac::unting for the different dim'ensional change behavior cf H-451 and !. H-327 graphites (see Q231.5). - I: a c . . . !
] In respense to our questions regarding the effe: s of i- adiation-induced ,
l dimensional changes, GA pointed out the following pertinent facts: (1) The g transition t: H-451 graphite fuel elements will take place en a region :- . I i i l 1 .
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1 1 - j regten basis. H-451 and H-327 gra:hite elements will, ineref:re, n ::e mixe-in the same layer within a regi:n during tne transiti:n. (2) The =axi=us l . radial shrinkages =f the H-227 and H-451 fuel elements are calculated :: i differ by abcut 9.1%. Theref:re, the characteristics of the power fluctua-tiens (assuming that they are related te cpening and closing f inte--regional . J gaps, as postulated in referenca.13) should be unaffected. (3) P:tential ; i inpact leads calculated for the H-451 elements were 21% higher than the f1'uctua- !
$ tien 1 ;act 1: ads f r M-?27 elements. Secause H-151 graphite has a 55% greater I
radial strength than H-227, h wever, the likelthece cf damage cue to flu nuati:n- i i induced leadings is decreased with the su:stitutien cf H-451 fer H-227 gra: nite. l We thus c:nclude, based en the above reas:ning, that the su stitutten of H-451 , ss j graphite should net have any =easurable adverse effects due :: irradiation- ; i induced dimensional changes en the charactaristics of care fluctuatiens er [ i
)3 on the overall stability of the cere.
l i . j i Fission P oduct Release and Trans:cet - The improved thermal c:nductivity of Il e j H-451 graphite relative : tha Of H-327 is cited by GA as reasen :: expect a I r slight reducticn in gasecus fissi:n pr:duc releasa. Metallic fission pr cuct *
~! releases are nct se directly assessable, however. In centrast t: lig..: water t'
d reacters, metallic fission products do not proceed directly fr:m failed fuel i . d to the primary c olant, but must migrate thr: ugh the fuel red ntrix material !;' r
, and graphite element web : the graphite-helium inter.f. ace Metallic fission +
e 1 9 - 0
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, ,,r: duct trans::rt fr:m failed fuel particles is tnus a multi-ste; ;r::ess I wht:n is, in part, a functicn cf the scr;tivity and diffusivity of tne fission h
- i. I t product in gra: nite, j
; .. -- I In GLo-5588, GA claimed that the fission pr: duct retentien characteristics of i j ;,
f
- H-451 graphite are similar :: H-327. In general, h: wever, most of the fission -
j
- product trans;:rt data have teen chtained en the current reference H-327 -l graphite, not :n H-451. In s me cases, no data exist fer H-451; f:r exas:le, ;
I there are ne data fer the diffusien cf str:ntium in H-451 gra: nite. We, ! J therefore, asked GA to ;r: vide additicnal support f r their claims regarding I l fission pr: duct transport in H-451 graphita.
- I GA respended wita some previcusly unpublished data (en sceptivity of :esium en
,}
H-327 graphita; ses response to Q231.12). By c:mparing data in ter=s of : I general ft: functions (Fig. 2 of respcase to Q231.12), they showed that there [ i, was no significant difference in sorptivib cf Cs en H-327 and H-451 graphites. I I j . I. j Data on serptivity of strentium en H-327 gra; nite (provided in 7 ables I thr ugh { -III of the GA res ense) were cec:ared wi .h data en H-451 in Fig.1 cf GA's 4 . 4 respense te sn:w that there is reass'na:1e agreement ::etween the serption - 3 8 Ii isotherms for H-327 and H-451 graphites. . Although no data exist en the dif- 1i 1 I j - fusion of Sr on H-451 graphita, data were presented. (Table VII and Figure,3 of { j GA's respense) that indicated that'there is ne dependence on graphite type.
'!I y I.] These and ether results discussed at length in GA's responses t: questions i
3 i Q231.12 and Q23I.22 lead us :: ::ncluda that there is reasenable assurance ; J . I 1 - d 1 7 . 1 g a g j 0 I y _ 7 _ - ===e- - * * = - - - -
e n e - y l (
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. # . ; l I 1 that fissicn pr: duct trans:crt behavier has been ecdeled c:nse-vatively. As ,
t , I indicated in the, resp:nse tc Q221.22 m, for example, even if the Cs-127 l; sour:e tem is increased by about a fact:r of seven, the two-neur exclusion- I* i area-bcundary bene dose fer FSAR " Design Basis Accident No. 2" (Rapid ' Depressurizatien E1:wd:wn) is increased by enly about 0.5 res. This is still .
~ '
- well belcw 10 CFR 100 timits and is the only dese significantly affected by , ,
I i the hypotheticaT ine ease in Cs invent:ry. i : I post-Ir-adiation Examinati:n and surveillance - Although there is a c:nsid- ;. erable bcdy of experimental cata c:ncerning the behavier of H-451 graphite, jiig surveillance, including intaris and ,; cst-irradiation exa'minations, is required , j} te c:nfim the safety analysis of any new fuel design feature. We have in recent months issued several pcsttten statemen.s regarding surveillance and
- 1;E i
PIE cf both test and reference fuel in F5V; e.g., Refs.14 and 15. These j statements ddress, in part, the planned insertion of eight test elements (Ref.16), c:cpesed of.H-451 graphite, in ' reload ." segment 7" (currently being I 8 loaded into the reacter during the spring 1979). Although we had no formal i . I 1 survet11ance requirement for the eight te": elements as a c:ndition of this .
! I j insertien, we have n:ted (Ref.14) that safety analyses su;perted by results !
I ' l l cf such pcst-irradiatien survalilance may be required for future leads of fuel . cf new designs. Thus, befers final approval cf future reloads of H-451 graphite . j
. can be granted, we will require (a) results of surveillance examinations en j the eight H-451 test elements, and (b) a commt ment to perferz ?!E :n future Il t r large-scale H-451 relcad eiements. With regard :: the eight tes elements .
9
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, r. '. j } ? . ' l, i FT5-1 :nr ugn FTI-3, the :urrently planned C05-fun ec post-irradiati:n pr: gras described in Amendment 2-(A;;endix A) of reference 15, shculd pr:vice a ::n- i "i
siderable a unt cf ::nfir:a. ry infer: nation and should pr: vide sufficient , I inf:r:ation for licensing purposes. - *
~
k Reeulat:rv *esition ,
- We have ::cpleted our review cf t pical report GL -5528, which is intended : i i serve as a reference t: ;tevide the basis for allcwing .ne substitution of ,
I i nea--isotrepi: H-451 gra:hite fuel and reflect:r elements f:r the curren-jl needle-::ke H-327 grapnita elements in the Fert St. Vrain rea Or. In cu. . ,I evaluation we f :used pri=arily en six aspects of H-451'gra:hite performance I relative to H-327 graphita perfer:ance in the FSV ::re: (1) graphite repr:du:- ' ibility; (2) corresion (exidation); (3) mechanical and physical properties; j i (4) irradiatien-induced dimensional enanges; (5) fissien produ:: release and' j t b, transport; and (5) ; cst-irradiation examination and surveillance requirements. Based on cur evaluation cf the information provided in the topical report and ' the responses to our requests for additional information, we ::n:1ude that ;
~
k ' reasonable assurance has been provided that tne substitution cf H-451 for t
? H-327 graphite elements in the FSV care will (a) result in negligible cnanges -
in the nuclear and thermal behavice of the care, and (b) will not result in~ i i
! I reduced safety margins or reliability compared to the reference H-327 care.
lj t 6 9 f 1 Because data acquisition en H-451 properties and themal tr adiation perform-
- ance is engoing (via 00E-funded programs involving test-react:r irradiations and test elements to b'e irradiated in FSV), we will require, as part of any 1
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future applicati:n f:r insertion of rel:ad M-451 elements, that General A ::ic ; Cc:pany pr:vice , timely reports en tast results involving H-ail graphita. , Specifically, we will require that reports be previced en the results Of (a) I' i I . the cn going f r adiation reep pr: gram and (b) post-irradiation examinations !I L l e j and surveillanca en the eight H-451 elements that are being insertad as p?rt :
, cf reload Segment 7. In additien, shculd changes be mace in the c:ke er I methods of fabricatien of the H-451 gra hite biccks, we will recuire GA u !
t provideevidencetesupporttheperfermancapredicti:nsf:rtnegra:r.ita l elements pr:duced f-:= the altered =atarials :r pr::ess parameters. i This evaluatien a: plies nly to H-451 graphite :: be used in the port St. Vrain !
- l; reacter, because the analyses were performed in tor =s of 'the transier.t
~
analysis fer F5V and the c:=parative effect of H-451 versus the F5V reference j
,i H-327 graphite. A separate analysis would be required for any application =f :
H-451 graphite in a high temperature gas-c:cled reacter having a design differing fr a Fort St. Vrain's. ! -
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[, i .- .. . q t , I Refarences i f *
- 1. G. L Wessman (GA), letter t: R. P. Denise (NRC), Mar:5 23, 1978
- 2. - G. L Wess=an (GA), letter to William Gammill (NRC), 0:::cer 30,1973.
' 3. G. L Wessman (GA), letter t Villiam Gumill (NRC), Nevuber 17, 1973.
t, i 1. i .
- 4. G. L Wess=an (3A), letter :: William Ga: mill (NRC), February 5,1979.
l . 3 l
- 5. G. L Wess=an (GA), letter t: Villiam Gammill (NRG, Fe:ruary 15, 1979. i j -
- 6. Victor Stells, Jr. (NRC), Memorandum t: Ray G. Smith, " Comments on ERDA l
, Division of Rea:t r Research and Devele;mett Draft Standard RDT-1, f
Near-Isotropic Petroleum-Coke Based Graphites fer High 7emperature
, Gas Cooled React:r Core C:mpenents," June 9, 1975. I
, g i
; i ..
, i:
- 7. RDT Stancard Ei-17, "Near-Isetr:pic Petroleum-C ke Based Gruhite fer '
; . I High-7emperature Cas-C:cled Rea ::r C:re Cem;cnents," 0:tcher 1977. -
J .
- 8. A.' W Barse11 and M. 3. Peroomian, Censequences of Water Ingress 1
into the K7GR Primary C alant," General At:mic Report GA-A12171, : e April 15, 1975. - f . I'. . 1 t l
. . . t a
1 j .
.j l
. r. . _ _ s. . - - _ '
e k + -
r i s s. 1** *
. ;j,
-u-j ,
, . . I*
e t f 9. M. E. Pere mian, A. W. Earsell, and J. C. Saeger, "0XIDE-3: A
~
Computer Cmde f:r Analysis =f H7GR 5 team er Air Ingress Accidents,"
.l'i General At:mic Re; rt GA-A12tS2, January 15, 1974.
1 i e . . . . 10: D. L Ross (NRC), Me:crandum t: R. P. Denise, " Support t: GASSAR !!ER " :
~ . December 15, 1975. -
i
- 11. " Safety Evaluatten =f the Fult:n Generating Station, Units 1 anc 2," '
! NUREG-75/015, March 1575. ., l, i
e g
! 12. R. J. Price, " Cyclic Fatigue c' Near Is:t :pic Graphite: Influence of '
1 3 I i Stress Cycle and Neutren I. radiation," General At:=ic Report GA-A1452E,
! I i
i November 1977. I i : 1 J ! i 1 l! '
- 13. "Cere Fluctuation Investigatten Status and Safety Evaluation Report," ,
, . transmitted via lettar ?-78137 from J. K. Fuller (PSC) to William !
* ) '
Gammill (NRC), August 11, 1978. ' t . I
- 14. R. L Tecese: (N?.0), Me: rancum :: W. J. Gamill, "Fuei Surveillance -
y & Pol. icy--Applicati n t: Fort St.'Vrain," Decem:er 13, 1978.
!I '.
g i i
- 15. R. L. Tedesco (NRO) Memorandum t: W. Gammill, "Fert St. Vrain Fuel -
Surveillance," February 15, 1979. - l i . . . g O 1 * *l I, 1 ,-
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. i ,1 20 - ?
i 98 *.. r* . t
- 15. Saf ety Analysis Ra;;:r: for F:rt St. Vrain Kelca:! Tes- Elements FTE-1 .
i* througn FTE-2, General At:=t: Raccr GL. -5494, Juna 30, :577. j
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