ML20055J074
| ML20055J074 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 07/24/1990 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Samworth R Office of Nuclear Reactor Regulation |
| References | |
| CON-NRC-90-075, CON-NRC-90-75, REF-PT21-90 VPNPD-90-343, NUDOCS 9008010037 | |
| Download: ML20055J074 (2) | |
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IAttention:
Mr.nRobert B. Samworth, Project Engineer s
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Gentlemen:
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i DOCKETS 50 266 AND 50-301 I
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' ERROR IN ECCS DECAY HEAT MODEL 0-3 P_QINT BEACH NUCLEAR PLANT. UNITS 1 AND 2' o
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c On July 10, 1990, Westinghouse tie'lephoned WisconsinhElectrico to C 5 discuss!an? error;'in the decay heat model"used-to. perform.
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Large-Breaks Lossiof Coolant!' Accident (LBLOCA) analysis'for Point Beach Nuclear, Plant.
Westinghouse also reported the'erior to the "i
U.S.CNRC-in~a2 telephoned 10'CFR Part'21, notification on July.12, 31990,~and in.a' written report dated July'16,11990.
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=The' error results iniaMnon.-conservative,.decaycheatasource. c:Thei decay heat:so'urce in theicurrentHlicensing' calculation *is 10 to-20 percsnt less thanttheidecay heatisource required by' Appendix K 1
3 rto.10tCFR Part.50'for the"LBLOCA' analysis; ; Prelim'inary."
scalculations with the correct decay' heat! source indicated tihat -
e jthe peak claddingctemperature (PCT)'may exceed the licensing 0
' limit >of.2200 F,
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. Westinghouse'informedeus'that_only;the< Appendix K licensing '
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' calculation is affected by the error.
Two1best-estima e
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calculations, submitted:.-with the 1icensing,calculati'cnoa's 1
Lrequired: by 'SECY-83-472, shos-that significant: margin exist's
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- within the 2200 F limit.
An estimate of the; peak claddinge C
temperature which bounds more than 95% oflall'possibleLpeak cladding temp'ratures is 1953 F.' The most grobableipeak cladding.
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. temperature?(50% probability' level) bis 1382 F.,
WeIhave thusJ
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,.3 concluded that'this modeling error does potsco'n'stitute an actual operational, safety concern."
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9008010037 900724 W
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'l O 'qWestingkouse has'pe'rformedla recalculation;of the PCT lfor the
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- LBLoCA analysisi assuming -a maximuin tallowed' height dependent: heat i flux-hot channel f actor,: F (Z), of;L 2.'4'0 ~.
Th'is' calculation g
J< incorporated'a number,of changes relative to the version of
- HCOBRA/ TRAC'used_in theforiginal Appendix 1K' analysis.1 First,3 the-
' decay ~ heat"model'= error was corrected.
Secondly,4 changes were
~ made to'the fuel' rod conduction and'stral*4 model"to improve the!
fuel rodeenergy' balance.>.This reca'lcu'.ation yielded.a PCT-of 0
2099 F; wel1 within 5the. Appendix ~ K at, cept.ance criteria, and,
assumed no changes'in the current,technicel specifications ^for.
the relaxed' axial offs.t. control (RAOC) or rod _ insertion. limits bands.
Wisconsin?ElectrJc has, therefcre,; adopted a reduced'F' of2.40fromethe2.5describedinTechnicalSpecification$15.2!105-mas an* interim administrative ~ limit for' operation of the Point->
Beach Nuclear' Plant,' Units 1E: and'2.
Westinghouse has. completed anLevaluation'which demonstrates'that for the. remainder.of the current < Unit 1.and 2; operating' cycles, assuming existing bands forfRAOC arid rode 11.sertions' limits, F should not. exceed 2.32.
- We have-concluded that7 continued
' g operation'of the Point Beach Nuclear; Plant units 1 and 2.with the existing Technical Specification limits and an Fo 'dministrative.
a limit:of 2,40 is, conservative'and satisfles the 10'CFR'50-Appendix K_ licensing' hsis for the plant.
A meeting has been sch'eduled-with the NRC, Westinghouse and representatives of the affected licensec for. August 7, 1990,to:
(i discuss'this subject in greate'r detail.
Following that meeting L
.and the.results of those discussions, we shall determinefa' plan li
- for ultimate resolution oflthis concern.> We shall then notify you.of our pr'oposed> final-corrective actions..
Very truly yours,
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C '.' gW. Fay x
Vice President Nuclear Power Copi'es to NRC Resident. Inspector-
- 0 NRC Regional-Administrator, i
Office'of Inspection and Enforcement, Region ~III t
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