ML19208D426

LER 79-081/01T-0: on 790910,potential Failure Mode for Several Primary Containment Purge & Inserting Valves Discovered.Caused by Design Deficiencies.Design Change Being Investigated

ML19208D426
Person / Time
Site:	Hatch
Issue date:	09/20/1979
From:	Coggin C GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19208D424	List: ML19208D423 ML19208D426
References
LER-79-081-01T, LER-79-81-1T, PM-79-845, TAC-42603, TAC-42604, TAC-51984, TAC-51985, NUDOCS 7909280410
Download: ML19208D426 (2)

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NARRATIVE REPORT o g~}

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LER 1-79-81 w b b- -l With Unit 1 in the run inodo and Unit 2 in the shutdown mode, a jc potential f a ilu r,b mode for several primary c o n t,a i n m e n t purge and inerting valves was discovered by the architect-enginner and valve vendor. These valves are T48-F307, F308, F709, F318, F314, F720, F324, and F326 It was noted that if a LOCA occurred while these valves were open and if they were subjected to peak post-LOCA differential pressures, the LOCA steam pressure could cause these valves to close r a p i. d i v .

This rapid closure could cause the valves to lose thei-seating capability which could result in steam and noncondensible gas leakage to the reactor b u i l. d i n n .

Originally the it was thought that valves T48-F110 and F111, on reactor building to torus vacuum breaker lines, were subject to this failure mode, but it was later decided that they need not be considered since these valves would only he open under a torus vacuum condition to equalize the differential pressure between the r e a'c t o r building and the torus and since the vacuum breakers would act as check valves preventing flow from the torus to the "cactor b u i.1 d i n g . A standing order was issued to keep all ten .of these valves closed. However, the order was rescinded, w'ith MRC aprroval.

This was done because a 1.5 psig drywell to torus differential pressure could not be maintained with valves Th8-F313, F110, F320, and F726 closed. A new standing order was issued which.

required maintained closure of valves T48-F307, F708, F700, F310, F311, F324, F312, and F313 except while p e r f o r m 4. n g drywell vacuum breaker surveillance testing or during drywell inerting or deinerting. Closure of valves T48-F31? and F111 provides isolation which was previous 1v provided by closure of valves T48-F318, F319, F320, and F326. Valves T40-F112 and F313 were tagged closed and may only be opened as deemed necessary by the shift foreman in an emergency condition.

Valves T48-F310 and F311 were incluued in the second standing order because, at the time, they were still considered to be susceptible to this failure mode.

A proposed design change is in progrees which will prevent these valves from opening more than 30 degrees. This will preclude the possibility of valve damage due to rapid closure.

This is a postulat,ed event. Therefore, no danage to equipment or personnel occurred. Nor was there any release of radioactivity. .,

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