ML20086L104

AO 74-2:on 740108,switch LIS-2-3-231D Failed.Cause Unknown Pivots on Mercury Switch Mechanism Loosened & Adjusted, Mechanism Positioned for Optimum Operability & Min Level Setpoint & Mercury Bulb Portion of Switch Leveled

ML20086L104
Person / Time
Site:	Peach Bottom
Issue date:	01/17/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086L107	List: ML20086L104 ML20086L108
References
AO-74-2, NUDOCS 8402070395
Download: ML20086L104 (3)

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PHILADELPHIA ELECTRIC COMPANY s a.R 2301 MARKET STREET

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January 17, 1974 Mr. A. Giambusso 50-277 Deputy Director of Reactor Projects United States Atomic Energy Commission Directorate of Licensing Washington, D. C. 20545

SUBJECT:

Abnormal Occurrence The following occurrence was reported to Mr. Tom Shedlowsky, A.E.C.

Region I Regulatory Operations Office on January 9,1974. In accordance with Section 6.7 2.A of the Technical Specifications, Appendix A of DPR-44 for Unit 2 Peach Bottom Atomic Power Station the following report is being submitted to the Directorate _of Licensing as an Abnormal Occurrence.

Re ference: License Number DPR-44, Amendment Number 1 Technical Specifications Table 3 1.1 Report No.: 50-277-74-2 .

Report Date: 1-18-74 Occurrenca Date: 1-8-74 Facility: Peach Bottom Atomic Power Station - Unit 2 RD 1, Delta, Pennsylvania 17314 Identification of Occurrence:

Failure of the LIS-2-3-231D' switch which provides a Scram Discharge Volume High Level trip input to the RPS logic.

d Conditions Prior to Occurrence:

Reactor critical and vented at 1600F reactor coolant temperature.

Description of Occurrence:

LIS-2-3-2310 failed to trip d'uring an instrument surveillance test.

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2 Designation of Apparent Cause of Occurrence:

The exact cause of the failure of LIS-2-3-231D to actuate during the instrunent surveillance test has not been identified. It appears that this failure was the result of the compounding of a number of minor adjustment deficiencies. Possibic contributing deficiencies noted are as follows:

1. Electrical mercoid switch pivots were adjusted slightly

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too tight.

2. Switch magnetic pick-up was not adjusted at the optimum posi ti on.

3. The mercury bulb physical position adjustment was not optimum.

Additionally, the possibility exists that an interference between the electrical wires and the switch cover could have caused the malfunctioning.

Analysis of Occurrence:

Failure of a single switch to function in a one of two twice logic does not render the logic system inoperable. Scram on high scram discharge volume level would still have occurred with this switch inoperable if excessive 4

control rod drive valve leakage occurred. Valve leakage at this time is negli-gible. No safety implications are associated with this occurrence.

Corrective Action:

Manufacturer's representatives, both from the design department and service engineering were brought to the site to aid in the investigation. F ri c-tion tests on the switch in question and other similar switches were performed, but no deficiencies were identified. The internal mechanism of the switch in-side the pressure housing was x-rayed to ensure no foreign material was present.

The switch designer made a detailed inspection of the switch and completed the following minor adjustments: -

1. The pivots on the mercury switch mechanism were loosened and adjusted. .

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2. The switch mechanism was positioned for optimum operability and minimum level setpoint. .

3. The mercury bulb portion of the switch was 1eveled with the switch in the mid-travel position.

In addition to the above adjustments, larger covers for these switches wa r.e fabricated and installed. The installation of these covers was approved by the switch designer, Philadelphia Electric -Company Engineering & Research Depart-ment representative, and the Plant Operations Review Committee. Addi ti onal ly, the moveable portion of the switch to the terminal block was removed. This wire e

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is not utilized in this application and its removal eliminates the possibility of interference with the switch cover.

Failure Data:

The "D" scram discharge volume high level trip switch has failed to operate on three other occasions. These malfunctions have been reported to the A.E.C.

Very truly yours, f},9 f,,c4pc c <

H.,J. Cooney. f Ass't Gen't Supt.

Generation Division cc: Mr. J. P. O'Reilly Director, Region i United States Atomic Energy Cannission 631 Park Avenue King of Prussia, PA. 19406 O

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