ML19270F067

Revised Final Deficiency Rept Re High Pressure Fire Protection Pump Failures.Impellers Separating from Pump Shafts Where Lock Collets Are Used;Reattached by Thrust Ring Const Method

ML19270F067
Person / Time
Site:	Sequoyah
Issue date:	12/28/1978
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19270F064	List: ML19270F063 ML19270F067
References
NUDOCS 7901250115
Download: ML19270F067 (1)

Text

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3 ENCLOSURE SEQUOYAh NUCLEAR PLAhT - UNITS 1 AND 2 lilGli PRESSURE FIRE PROTECTION PUMP FAILURES NCR 962 REVISED FINAL REPORT Descriittion of Deficiency The deficiency is the separation of the impeller from the pump shafts after a period of use. In several instances, the high pressure fire protection (llPFP) pumps and motors have been heavily damaged following separation of the impeller frem the shaft.

Safety Implications If this deficiency had remained uncorrected, the possibility (xists that coincident, multiple llPFP pump failures may have led to the inability of the plant to combat potential fires in safety-related areas. If fires occurred in safety-related areas that could not be controlled, equipuent necessary for safe shutdown of the plant may have been damaged or destroyed.

.Cor,'<ctive Action Upon discovery of the deficiency, pressure signature tests were performed on the pumps to aid in determining the cause of the pump . allures. The tests revealed a slight mornentary pressure

. spike during IIPFP coastdown before the upstream backflow check valve closed. Ilowever, this pressure spike was not significant enough to create a hazard to the equipment. 'the separation of the impeller was apparently due to the rrethod of attaching the impeller to the pump shaft. The irpellers were initially attached by means of a lock collet construction which un mitted them to come loose due to a shock on the impeller. The pumps are being repaired by reattaching the impellers by the thrust ring construction method which will prevent the impeller from becoming loose from the pump shaft in future operation.

'lVA has reviewed all the vertical turbine type pumps in Sequoyah and Watts Bar and has found no other pumps with the lock collet construction at either plant. For plants after Watts Bar, the plant fire protection system (FPS) desty;n criteria will he revised to require testing for water hammer on any fire pump having this lock collet construction. This testing will be done before the FPS hcIng used for construction or preoperational testing.

7901'2 50115

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