ML19296B398

LER 80-001/03L-0:on 800118,during Routine Insurance Insp Testing W/Plant at 100% Power,Turbine Driven Auxiliary Feedwater Pump Became Inoperable Due to Failure of Turbine Inboard,Outboard & Thrust Bearings.Caused by Excessive Wear

ML19296B398
Person / Time
Site:	Millstone
Issue date:	02/11/1980
From:	Criscione J NORTHEAST UTILITIES
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19296B390	List: ML19296B389 ML19296B398
References
LER-80-001-03L-01, LER-80-1-3L-1, NUDOCS 8002200503
Download: ML19296B398 (2)

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o a 1 auxiliar~y feedwater puma became inonerable due to failures of the turbinn inboard, o 4 l outboard, and thrust bearinas. The "A" and "B" motor driven anviliwy food intnr i e s l pumps were verified operable, and the plant was operated in accordance with the I ge ts l l action statement of Section 3.7.12 of technical specifications. Tha bearings were I le l2l l replaced and the auxiliary feedwater pump returned to service within 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br />. I I

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33 34 31 43 41 42 CAUSE DESCRIPTION AND CORRECTIVE ACT!oNS h n o 1 The cause of the failure was excessive bearing wear. This may have been accelerated I i, ii i by previous overspeed testing when the turbine was run uncounled from the pumo. The f

., , i pump normally supplies cooling water to the bearings. The turbine bearings were f i,i3; l replaced, and to prevent recurrence, a source of cooling. water to the bearings will I

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LE180-01/3L-0 Page 1 of 1 ATTACHMEllT EVEtlT DESCRIPTI0il During routine ISI Testing, with the plant at 100% power level, the turbine-driven auxiliary feedwater pump became inoperative due to failures of the turbine inboard, outboard, and thrust bearings. The "A" and "B" electrical auxiliary feedwater pumps were verified to be operable and the plant was operated in accordance with the action statement of Section 3.7.12 of the technical specifications. The bearings were replaced and the auxiliary feedwater pump returned to service within 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br />.

CAUSE DESCRIPTI0tl The cause of failure of.the inboard, outboard, and thrust bearings on the turbine-driven auxiliary feedwater " pump turbine was excessive bearing wear. The turbine vendor indicated that lack of cooling water most likely accelerated bedring wear during previous turbine overspeed testing in which the turbine was run uncoupled from the pump. The cumulative effect of t;.is wear over time ultimately resulted in bearing failures.

During normal operations, the pump ar;d turbine are run coupled and the

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turbine bearings are supplied cooling water from the first stage pump discharge.

The inboard, outboard, and thrust bearings were replaced, Terry Turbine Parts flumbers: 19(47551-52), 33(71225C-C01), and 34(BRG030208 DFL#3666),

respectively.

To prevent future bearing failures when running the turbine uncoupled from the pump, a design change will be implemented prior to the next uncoupled run to provide temporary cooling water for the turbine bearings.