ML19262A942

LER 79-054/01T-0:on 791119,notified by Westinghouse That Possibility Exists That Current Negative Rate Trip Setpoints May Not Provide Reactor Trip During Single or Multiple Rod Drop Events.Caused by Designer Calculation Errors

ML19262A942
Person / Time
Site:	Farley
Issue date:	12/03/1979
From:	Hairston W ALABAMA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19262A938	List: ML19262A937 ML19262A939 ML19262A940 ML19262A941 ML19262A942
References
LER-79-054-01T, LER-79-54-1T, NUDOCS 7912110339
Download: ML19262A942 (1)

Text

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. LICENSEE EVENT REPORT -

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o 'i l Based on information presented to APCo by Westinehouse on 11/19/79. there exists the I o la l possibility that current necative rate trio setpoints may not orovide a reactor trip I o 14 l during some sinzular or multiple rod drop events. Also, when certain calc _ulations werd n !sl l repeated with conservative assumptions (previously calculated using non-conservative l c 6 l assumptions), results indicated that some drooped rod events without reactor trio could Q QJ [ result in violation of DNBR limits above 90% nower if the rod control system was in I

oinj iAutomatic and had sufficient rod worth available to compensate for the dropped rod (s) . I e s 9 This is a notential item of reportability under Tech. Spec. 6.9.1.8.h. So SNSTEa1 CAUSE CAU. E C O' ' 8 VALVE CODE CCDE SUNOUE COf'PONEN T COD SUSCC M Su r,000

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CAUSt CCCRIPTION AND CO3RECTIVE ACTICNS h o lThe potential events described in item 10 can be attributed to deciener calg.glation _]

lilitierrors which resulted from certain non-conservative assumotions. e.e. me of ncn-  !

i 7 l conservative reactivity insertion rates and profiles. and errors in assumine " worse _ l i , l case" multiple rod dron locations. Plant operating procedures have been revised to I i 4 l require that the rod control system be in Manual when .bove 90% power unless control _ T 7

c Uciti?Y 9 bank D is withdrawn to > 215 ste -

Long term corrective acti'n Uf 13 600 CJ o is being evaluated. a 1,TAitG ".POh'.'C R CISC OVI:R Y DISCOV El1Y DESCWP110,3

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