ML19270F559

LER 79-013/01T-0 on 790131:scram Received on Intermediate Range Monitor hi-hi Trip.Caused by Favorable Conditions During Startup for High Rod Worth Near Criticality

ML19270F559
Person / Time
Site:	Hatch
Issue date:	02/09/1979
From:	Thomas Greene GEORGIA POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19270F556	List: ML19270F555 ML19270F559
References
LER-79-013-01T, LER-79-13-1T, NUDOCS 7902150440
Download: ML19270F559 (3)

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80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h FoTTll o At 2135 CST, while approaching criticality with a moderator terroerature of 199.50F i o 3 and with effectively zero Xenon inventory, a scram was received on IRM Hi-Hi Trip. I o 4 l This was the result of a criticality with a period of less than five seconds. The l o 5 l scram occurred at notch 26 of rod 42-15 which was the 39th rod to be withdrawn in the]

o e I sequence. This is being reported under Tech Spec Section 6.9.1.2.a.4.c. I O / I , I o a i I 7 8 9 60 SYSTEM CAUSE CAUSE C O*.1 P. VALVE CODE COCE SUSCODE CCvPONENT CODE SUSCODE SUBCODE 7

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CAUSE CESCniPTlCN Afv0 COnaECTIVE ACTIONS h i e 1 Xenon inventory, moderator temnerature and other conditions present durina the start-l L' LiJ l up were favorable for a hich rod worth noar criticality.

__ Reactor conditions wern I i 2 ] altered, i.e. moderator temoerature was increased.and during the subsequent start- l i , l up the control rods near criticality were notched out until the reactor was criti- I i 4 l cal. Analysis on the probable cause is still bein9 conducted and (continued) l 7 8 9 80

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Georgia Power Company Plant E. I. Hatch Baxley, Ga. 31513 Reportable Occurrence Report tio. 50-321/1979-13 Cause Description and Corrective Actions continued:

notch mode will be employed for groups 3 and 4 until the analysis is complete.

An update report will follo'a within 60 days.

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NARRATIVE SUM:tARY At 2135 CST, while approaching criticality with a moderator temperature of 199.50F and with ef fectively zero Xenon ir,ventory, a scram was received on IRM Hi-Hi Trip. This was the result of a criticality with a period of less than five sec-onds. The scram occured at notch 26 of rod 42-15 which was the 39th rod to be withdrawn in the sequence. Xenon inventory, moderator temperature, and other conditions present during the startup were favorable for a high rod worth near cri ticali ty.

Reactor conditions were altered, i.e. moderator temperature was increased, and the control rods near the subsequent criticality were notched out until the reactor was critical. Analysis on the probable cause is still being conduct-ed and notch mode will be employed during startup for groups 3 and 4 until the analysis is completed, at which time a final decision will be made. This is being reported under Tech. Spec. Section 6.9.1.z.a.4.c