ML20086J325

AO 74-17:on 741021,HPSW Valve MO-3-10-89B Found Inoperable. Caused by Mechanical Failure of valve-open Limit Switch. Motor Removed & Rewound.Switch Assembly Reinstalled Using Loctite Coated Bolts to Prevent Recurrence

ML20086J325
Person / Time
Site:	Peach Bottom
Issue date:	10/31/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086J326	List: ML20086J325 ML20086J342 ML20086J354
References
AO-74-17, NUDOCS 8401230574
Download: ML20086J325 (2)

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October 31, 1974 -

Mr. A. Giambusso Deputy Director of Reactor Projects United States Atomic Energy Cocmission Directorate of Licensing Washington, DC 20545

Subject:

Abnormal Occurrence The following occurrence was reported to Mr. Walt Baunack, A.E.C. Region 1 Regulatory Opu 2tions Office on October 22, 1974.

Written notification was made to Mr. James P. O'Reilly, Region 1 e Regulatory Operations Of fice on October 22, 1974. In accordance with Section 6.7 2.A of the Technical Specifications, Appendix A of DPR-56 for Unit 3 Peach Bottom Atomic Power Station, the'following report is being submitted to the Directorate of Licer. sing as an Abnormal Occurrence.

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Reference:

License Number DPR-56 Technical Specification Reference 3 5.B Report No.: 50-278-74-17 Report Date: October 31, 1974 Occurrence Date: October 21, 1974 Facility: Peach Bottom Atomic Power Station R. D. 1, Delta, Pennsylvania 17314 Identification of Occurrence:

Inoperable HPSW valve M0-3-10-898.

Conditions Prior to Occurrence:

Reactor pressurized to 900 psig, turbine off.

Description of Occurrence:

While attempting to open the valve to perform routine stem i repacking, the motor operator circuit breaker tripped on instantaneous overcurrent.

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0ctober 31, 1974 Page 2 Designation of Apoarent Cause of Occurrence:

Investigation indicated a mechanical failure of the valve-open limit switch, which permitted the motor to remain energized af ter the valve had reached a full open, back seated condition. After a short period of time in a stalled condition, the motor failed electrically and tripped the circuit breaker. -

The limit switch malfunction was caused by the loosening of the bolts that attach the switch stationary contact block to the opera-tor housing. The loosening was probably caused by valve vibration, and resulted in dis-engagement of the limit switches stationary and movable contacts.

Analysis of Occurrence:

With one HPSW valve out of service; both LPCI loops, four HPSW pumps, and three RHR heat exchangers are operable. Therefore, the safety significance is minimal.

Corrective Action: t C The motor has been removed and is being rewound according to an approved procedure. The switch assembly was re-installed using Loctite coated bolts to prevent a recurrence of the malfunction. The other seven HPSW control valves were inspected and upgraded by the application of Loctite to their switch mounting bolts.

O Failure Data:

There is no record of a similar HPSW valve motor operator failure.

Very truly yours, WY '

. Jr Cooney Ass Gen' t Superintendent Generation Division

-cc: Mr. J. P. O'Reilly .

Director, Region i

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United States Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406-e S

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