ML20086J510

AO 74-3:on 740820,setpoint of APRM Inoperable Trip Circuit Found Less Conservative than Allowed by Tech Specs.Caused by Slight Setpoint Drift.Bistable Trip Device Recalibr

ML20086J510
Person / Time
Site:	Peach Bottom
Issue date:	08/30/1974
From:	Meyer R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086J513	List: ML20086J510 ML20086J516
References
AO-74-3, NUDOCS 8401240044
Download: ML20086J510 (2)

Text

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o PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET PHILADELPHIA. PA.19101 1215) 841-4ooo August 30, 197 g47-+

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Mr. A. Giambusso ff Deputy Director of Reactor Projects k gh4 hll-i

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United States Atomic Energy Commission Directorate of Licensing [ #3. (l l 78g"

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Dear Mr. Giambusso:

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Subject:

Abnormal Occurrence ~

The following occurrence was reported to Mr. R. A. Feil, A.E.C.

Region 1 Regulatory Operations Office on August 21, 1974. Written noti-fication was made to Mr. James P. O'Reilly, Region 1 Regulatory Opera-tions Of fice on August 21, 1974. In accordance with Section 4.7.2.A of the Technical Specifications, Appendix A of OPR-56 for Unit 3 Peach Bottom Atomic Power Station, the following report is being submitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR 56 Technical Specification Table 3 1.1 Note 11 Report e .: 50-278-74-3 Report Date: August 30, 1974 Occurrence Date: August 20, 1974 Facility: Peach Bottom Atomic Power Station R.D. 1, Delta, Pennsylvania 17314 Identification of Occurrence:

Setpoint of APRM inop trip circuit less conservative than

_ allowed by the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was shutdown in a cold condition.

• Description d Occurrence:

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.I During a surveillance test of the APRM system the inoperative trip signal from the LPRM count circuit was found tc have its setpoint 9401240044 740830 PDR ADOCK 05000278 S PDR COPY SENT REGION, j 910'3'

L u Mr . A. Gi ambusso August 30, 1974 Paga 2 l

l out of the allowable tolerance on one~ APRM channel. The Technical Speci-fication requires that each APRM produce an inop trip when less than 14 operable LPRM inputs exist for that channel. The as found setpoint would have allowed operation of APRM Channe1 B with 12 operable LPRM inputs.

Designation of Apparent Cause of Occurrence:

Slight setpoint drift of bistable trip device.

Analysis of Occurrence:

, The APRM inop signal satisf actorily produced a scram and a rod withdrawal block. The setpoint shift was slight and of minimal safety significance because no LPRMs in the APRM system were bypassed i' or otherwise inoperable. This trip is an electronic enforcement of an administrative lirrtt that was being complied with.

_ Corrective Action

The bistable trip device was immediately recalibrated to pro-

duce an inep trip with less than 14 operable inputs. The surveillance test is being revised to change the LPRM dropout trip setpoint in the conservative direction.

Failure Data:

No previous failures of this type since initial calibration.

Very truly yours,

'M h ih t bL R. D. Meyer General Superintendent Generation Division cc: Mr. J. P. O'Reilly i

Director, Region I United States Atomic Energy Conmission 631 Park Avenue King of Prussia, PA 19406 ,

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