ML20058F598
| ML20058F598 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/31/1990 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Samworth R NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| CON-NRC-90-108 VPNPD-90-451, NUDOCS 9011090018 | |
| Download: ML20058F598 (3) | |
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[3 M TOctober 31, 1990l
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'/ Attention: :Mr. Robert B..Samworth,~ Project Manager
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- ADDITIONALiINFORMATION'ECCS LARGE' BREAK LOCAL MODEL.
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' POINT" BEACH-NUCLEAR PLANT, UNITS 1 AND-2 i
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t Infa91ette'[ dated: July 24,'1990,fwe*notifie'd youlofJan error in the
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! decay heat.model:use.d to perform lthe Large Break Loss lof Coolant; j
AccidentV (LOCA)/ analysis for; the' Point Beach Nuclear: Plant, - Units 1 i
$s iandj.2'. 8Thisperror'and.our proposed; corrective actions.were also W
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W ' ic discussed;in'our Licensee EventtReport!.90-007-00Lwhichtw'as3
%y:Ae ysubmitted-onfAugusti 1 3,.' 1 9 9 0..In the. July 12_4Lletternand the?LER we t
W tstated that Westinghouse, tour:NSSSLvendor, had performed'a 0
]#FM trecalculation for the-large break: LOCA analysis ' assuming La ~ maximumn
' F (Z)Lof'2'.'40.LLThisfrecalculationJincorporated annumber,'of. changes;
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[rel'tive'tolthe versioniof HCOBRA/ TRAC usedyin the;origihall..
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M f N fAppendixiKiECCS' analysis;;includingLcorrectioniofTtheidecay heat-
'M G41 W modellerrorrand changesitofthe fuelErodiconductioniand*,straintmodel l j M " @.1 ~ ! t o t i m p r o v e t h e f u e l r o d ' e n e r g y b a l a n c e.:claddin' g - tempe 1
This recalculation ~ yielded 3
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im g acceptanceicriteriafofD10 CFRU50 46 cWe; adopted Xatlthat. time,ya:
i)ym f reduced:F (Z)?li_mit'of:2.40sas,anvinterimundministrative3 limit =for,
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M Q The; purpose [6f;this(letter!iisvtoJupdatetyoulon;eventsithat have:
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' ;ta meeting lwas: held withfrepresentatives ofttheiNRC(staff')
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/-E'%m* Q' Westinghouse)and[theulicenseesloniAugustL7,31990' to:discussithisi q
subject land;our corrective actions in' greater 3 detail.- On-M LSeptember 6,;1990kiwe received from Westinghouse the?resultslof a; 3
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Lverified recalculation oflthe/large break LOCA transienty,Asinoted:
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'above,:the; version:of HCOBRA/ TRAC lused!in'.this analysisa
- p incorporated La number. of. changes. : LFirst, ! theidecay heat; model..
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? error wasicorrected.
Secondly,. changes were made to the fuel rod conduction and' strain model'to improve the fuel rod energy balance-y?J W
, Land tolmore' accurately calculate cladding. oxidation by employing
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itheistrained fuel: rod area in the Zr-H O reaction' calculation.
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?F, Lastly, the_new gamma: redistribution factorswere employed which b
'bettersaccount for the' redistribution of the decay energy due to
- gammaitransport'.
Together.these changes compensate in part for the' p,,,
increasedLdecay; heat by removing unnecessary conservatism and simplificatio'ns'-in the=model as originally. coded.
This calculation v
.employedLaicore" power.. distribution corresponding:to'a F (Z) of g
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% 2.43: X k(Z), an F.-delta-HLof 1.70,-and a' low power channel radial Hg powerifactor:ofjo.6.E This calculation'also incorporated revised l
+ safety! injection ~' flows,-: injecting into the accumulator line, based?
'oJ l.onLloss. coefficients supplied by, Wisconsin Electric,.as well as the-MCOBRA/TRACL1990: error. corrections.
This. verified recalculation-n..
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.resulted^in a PCT of'1961 F.
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lon Octiober[8 j.s1990, ' wen were advised. by Westinghouse _ in the Reload -
- Safetyf Evaluation-for1 oint? Beach Unit 2 CycleL
- 17 that. a.s1 a result l
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w fganferrorcforithe' core-wide average powerlinput) the values of; o
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T gw totalMpeaking? factor --(Fo ), hot channel enthalpy, rise factor j
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p (F-delta-H);,L hotlassembly averageLpower and ' low power channel i
p" m Sradia11 factors weretunderestimated in the? analysis by approximately J
? JO'5% M To reconcile-this discrepancyfanl evaluation'has assessed a
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y%WE O PCT fincrease s off 20 F to the :large' breaklLOCA[ analysis. supporting n
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fthePF (Z)? peaking? factor ofJ2.43. ; Withcthe Laddition Lof f this.
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@* v"%)penaltyj thelPCTEfors the,large ' break LOCA ;is11981 F.'
.We have
'l subsequently 7 adopted;the12.43fF (Z)'as'theladministrative> limit!for g
sboth;PointhBeachaUnit 1fandi2.operationL
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w 1'(0 n S e p t e m b' e r, 5,g 1990,1 Westinghouse) submit'tedrto th'eiNRCLon-behalf-d j[
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offitsilicensees,"-includi'g WisconsiniElectric, an, Addendum,4,-
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, stitled t " Mode 17 Revisions"j f to : its. WCAP -10924-P-A, - Volume 11/
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fs J w ;"WestinghousejLarge!Brea'kNLOCA?BestsEstimate' Methodology: Modell i
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tDe'scription:and.jValidation."'1Thissreport describes theLmode1" 7
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l revision's1to theLapproved MCOBRA/ TRAC codebtoinddress;theyerrorf_
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~ tasjtho'seidiscussediaboveh specifically, revisions'for gamma energy
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foundiinttheldecay; heats model.1,otherJmodelCrevisions are the same' f%
$ y,,? redistribution and fuel rod conductionDmode10for; swelling,iburst, Jk
%. i,gandEblockageh i nioctober:' licensees,mthQ NRC; staff,Jand; Westinghouse aetiaga O
18,i 1990). representatives'of:'the'4 L
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qWCAPfAddendumland to respondLto the questions ofLthe'NRC staff' 1
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.regarding4the model revisions.
It'istourl understanding;that the-H 1
& i WNRC 'staffinowlhas: a good Lunderstanding of, these imodel. revisions and.
b Q "hasynoisignificant'technica1{ problems'or concerns with these y-4 l
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- M Mr. Robert B. Samworth October 31, 1990 Page 3 issues.
We further understand that a Safety Evaluation Report formally approving these model revisions will be issued by the NRC by February 1991.
As you know, Point Beach Unit 2 is presently undergoing its Cycle 17 refueling.
We have determined that the peak measured F (Z) expected for this cycle is 2.38.
As noted above, we have 9
established an administrative peaking factor limit of 2.43 based on the most recent large break LOCA analysis.
Accordingly, we concluded that there is no safety concern with operation of Unit 2 during this operating cycle.
This conclusion is baset on the extreme conservatism built into the Appendix K calculation, the established margin between our current analysis and the 10 CFR 50.46 acceptance cfiteria for PCT, and the more realistic yet still appropriately c)nservative, superbounded calculation with its calculated PCT of 19f 3 F.
It is our intention to fully recover the peaking factor value of 2.50 which is curteatly defined in our Technical Specifications.
We are proceeding with new calculations and analyses, which will utilize only the model changes and revisions as submitted in Addendum 4, to establish and verify the acceptability of the F (Z) o limit of 2.50.
Until these calculations are complete and until the NRC has formally approved the model revisions in WCAP-10924-P-A Volume 1, Addendum 4; we shall maintain the administrative limit of 2.43.
We shall also notify you of the results of these latest analyses as soon as they have been completed and reviewed.
Please contact us if you have any additional concerns in this matter.
Very truly yours, 3
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C.
t. Fay a
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Vicd. President Nuclear Power Copies to NRC Regional Administrator, Region III NRC Resident Inspector I
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