ML20086K901

AO 74-29:on 740528,recirculation Pump Switch DPIS-2-2-137A Failed.Caused by Failure of Differential Pressure Cell Bellows Mechanism.Device Replaced

ML20086K901
Person / Time
Site:	Peach Bottom
Issue date:	06/07/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086K904	List: ML20086K901 ML20086K905
References
AO-74-29, NUDOCS 8402070065
Download: ML20086K901 (2)

Text

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(21si s414ooo g *dg, -{ s ige'#, , June 7, 1974 Mr. A. Giambusso Daputy Director of Reactor Projects United States Atomic Energy Conmission Directorate of Licensing Washington, DC 20545

Subject:

Abnormal Occurrence The following occurrence was reported to Mr. Donald Cathton, A.E.C. Region I Regulatory Operations Office on May 29, 1974. Written notification was made to Mr. James P. O'Peilly, Region I Regulatory Operations Office on May 29, 1974. In accordance with Section 6.7 2.A oi' the Technical Specifications, Appendix A of OPR-44 for Unit 2 Peach Bottcm Atmic Power Station. the following report is beino submitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR-44, Amendment Number i Technical Specification Table 3 2.8 Report No.: 50-277-74-29 Report Date: June 7,1974 Occurrence Date: May 28,1974 Facility: Peach Bottom Atomic Power Station R. D. 1, Delta, Pennsylvania 17314 Identification of Occurrence: Failure of the recirculation pump oP switch dPIS-2-2-137A. Conditions Prior to Occurrence:

• The reactor was critical at 65% power, %0 psig.

Description of Occurrence: During a routine functional surveillance test the subject . differential pressure switch failed to operate. This switch provides , an input into the LPCI break detection logic circuit and has a Technical g/l Specification setpoint of 2 + 1 psid. When the device was valved out f of service and the r.1P reduced to zero psid, the indicator and trip L mechanism remained at about 7 psid. g 7 '4t 8402070065 740607 # PDR ADDCK 05000277 S PDR 5186, C@Y SWf REGION ~ _

F. r Mr. A. Giambusso k_s) June 7, 1974 . Page 2 . . _ . Designation of Apparent Cause of Occurrence: The differential pressure cell bellows mechanism had failed, i This failure prevented the trip and indicator from following a change in pressure. Analysis of Occurrence: This failure has minimal safety implications since the logic circuit in which this switch is connected is of the one-out-of-two-twice

type and is also redundant in the other LPCI system.

Corrective Action: For other reasons the plant was shutdown on May 29, 1974. The device was replaced with a spare while the plant was shutdown. A calibration surveillance test performed on the newly installed device indicated satisfactory operation. The f aulty device was disassembled in an attempt to determine the cause of the failure. An inspection of the device internals and a discussion with the instrument technicans who performed the surveillance test revealed: that the bellows mechan-isn had apparently developed a ' pin-hole' si zed leak. Also the "0" ring seal on the torque tube housing had failed allowing the internal seal fluid of the bellows assembly to be forced out by system pressure. When the irestrument was valved out of service for the surveillance test, the !::h:ge p::t the f: ult-/ "0" ring':::! ::ue d the d. cining of the bellows assembly. Thus when the instrument was pressurized, the bellows, now filled with air, collapsed and prevented the operation of the trip and indic'ator mechanism. Failure Data: This is the first failure of this type on switches in this service. Very truly yours, WL" . M: I As/'J. s't Cooney Gen't Superintendent ' Generation Division cc: Mr. J. P. O'Reilly Director, Region i United States Atomic Energy Commission 631 Park Avenue King of Prussia, PA 19406 L}}