ML20086K928

AO 74-6:on 740228,setpoint Shift Found on Switch LIS-2-2-3-101B.Caused by Inability of Switch to Hold Precise Setpoint.Switch Reset & Functionally & Calibr Checked

ML20086K928
Person / Time
Site:	Peach Bottom
Issue date:	03/08/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086K932	List: ML20086K928 ML20086K935
References
AO-74-6, NUDOCS 8402070079
Download: ML20086K928 (2)

Text

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March 8, 1974 Mr. A. Giambusso Deputy Director of Reactor Projects United Statqs Atomic Energy Comission Directorate of Licensing Washington, D.C. 20545

Subject:

Abnormal Occurrence The following occurrence was reported to Mr. R. A. Feil, A.E.C. Region I Regulatory Operations Office on March 1, 1974. Written notification was made to Mr. James P. O'Reilly, A.E.C. Region I Regulatory Operations Of fice on March 1,1974. 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.

Reference:

License Number DPR-44, Amendment Number 1, Technical Specifications Table 3 2.8 Report No.: 50-277-74-6 Report Date: 3/1/74 Occurrence Date: 2/28/74 Facility: Peach Bottom Atomic Power Station - Unit 2 R. D. 1, Delta, Pennsylvania 17314 Identification of Occurrence: .

Setpoint on LIS-2-2-3-1018 which provides a Reactor High Water Level turbine trip input to the HPCI and the Reactor Feed Pump Turbine trip logics shifted.

Conditions Prior to Occurrence:

l Reactor was critical at approximately 34% power and stable.

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Description of Occurrence:

During instrument surveillance testing, LIS-2-2-3-IO18, switch

1. 3 tripped at approximately 46 5" Reactor Level instead of f 45" Reactor Level as specified in the Technical Specifications.

Designation of Apparent Cause of Occurrence:

This type of differential pressure switch has shown a repeated.

inability to hold a precise setpoint within the tolerance as specified by the manufacturer. The operating point of the switch shifts slightly between test intervals.

Analysis of Occurrence:

The setpoint shif ts of the' subject switches would not nave de-feated the logic to produce the required safety actions. The other oper-able switches would have caused trips at the proper setpoints. These setpoint shifts were minor and have no safety implications.

Corrective Action:

LIS-2-2-3-1018, switch #3 was reset to the proper value and functionally and calibration checked per the applicable instrument sur-veillance test. Investigation by the Philadelphia Electric Company Engineering & Research Department is continuing. An accelerated testing frequency'has been established.

Failure Data:

These differential pressure switches have required frequent re-calibrations to correct setpoint shifts. During the past 27 weeks setpoint shif ts have required recalibration on 20 occasions. . Shifts to values in excess of Technical Specification limits occurred five times including this occurrence. Most of these deviations were only slightly above the reouired setpoint and did not constitute a safety hazard.

Very truly yours, -

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Klf M. J. Cooney As's't Gen't Superintendent Generation Division cc: Mr. J. P. O'Reilly Director, Region 1 United States Atomic Energy Conunission 631 Park Avenue King of Prussia, PA 19406

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