ML20086C113

Interim Deficiency Rept Re Auxiliary Feedpump Bearing 11 & 12 Failures.Initially Reported on 760315.Cause Still Under Investigation.Low Flow Orifice Modified to Allow 200-gpm Flow & New Rings Machined & Installed for Bearing Retainers

ML20086C113
Person / Time
Site:	Salem
Issue date:	04/02/1976
From:	Schwalje E Public Service Enterprise Group
To:	Knuth D Office of Nuclear Reactor Regulation
Shared Package
ML20086C111	List: ML20086C113
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311220573
Download: ML20086C113 (2)

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/ O PSIBG C Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/622-7000 April 2, 1976 l Dr. Donald F. Knuth, Director U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement 7920 Norfolk Avenue Bethesda, Maryland 20014 D. car Dr. Knuth:

NO. 11 AND 12 AUXILIARY FEEDPUMP BEARING FAILURES NO. 1 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-272 On March 15, 1976 a verbal report was made to Region 1, Office of Inspection and Enforcement, advising that the outboard bearing of No. 12 Auxiliary Feedpump failed. This failure was similar to the outboard bearing failure of No. 11 Auxiliary Feedpump. This report was in accordance with provision of 10CFR50.55(e).

The following is a detailed analysis and report on the subject failure:

Description During Hot Functional Testing of the No. 1 Unit, the Auxiliary Feedwater pumps, (9 stage, horizontal split casing type) were being operated for extended periods at minimum flow conditions to supply make-up water to the steam generators. During this testing, both No. 1 Unit Auxiliary Feedwater pumps experienced thrust bearings failures, requiring replacement of their entire rotating elements. Thrust bearings for these pumps are ring lubricated, two row, balitype bearings.

Analysis of Occurrence We .

SNQ om Investigation subsequent to the failures has revealed o$a 40 the following:

Kn o During operation of the pump, at minimum flow, an kg abnormal amount of axial oscillation of the pump shaft

$8 was observed, which could put considerable stress on Wo the thrust bearings. According to the pump manufacturer, this type of movement is common to this model pump but E$ it is greatly aggravated by operating at minimum flow.

etm Under these conditions, damage to the thrust bearings is possible.

The Energy People dd MM' 952001 (400M) 573

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. Dr. D. F. K r-+gh 4/2/76

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, Corrective Acticn .

The manufacturer (Byron-Jackson) is still investigating this problem; however, several actions have been taken to minimize the-forces exerted against the thrust bearings.

1. The low-flow orifice originally designed for 50 gpm flow was modified to allow approximately 200 gpm flow.

2. New rings were machined and installed for the bearing retainers.

3. The two thrust bearing rows were originally installed to take thrust in two directions.

On the manufacturer's recommendation one bearing row was reversed so that both races resist in the direction of greatest thrust.

4. The bearing clearance from the retainer was reduced from .0005/.0007 to .0002.

5. The oil level in the bearing housing was lowered.

Safety Implications There are no safety implications of these failures. Hot Functional Testing is conducted prior to initial core load. As such, the pumps were being operated in a mode different from that which they were designed for. ,

During normal operation of the plant, the-Auxiliary Feedwater pumps will not be required to operate for extended periods on minimum flow and therefore this type of problem would not~ be expected to occur.

If you desire additional information on this s ubj ec t , we will be pleased to discuss it with you.

Very truly yours, *

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E. N. Schwal e Ma ager of uality Assurance Engineering and Construction Department CC Mr.,J. P. O'Reilly-King of Prussia, Pa.

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