ML19263C337

LER 79-001/01X-1 on 790103: Potential Nonconservatism Noted in Calculations Performed in Monitoring Axial Power Distribution FJ(2).Caused by Omission of Sys & Procedures Used to Monitor FJ(2)

ML19263C337
Person / Time
Site:	North Anna
Issue date:	02/14/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19263C332	List: ML19263C331 ML19263C334 ML19263C335 ML19263C337
References
LER-79-001-01X, LER-79-1-1X, NUDOCS 7902220009
Download: ML19263C337 (2)

Text

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[-Qf] [ A potential non-conservatism has been identified in the calculations perf armed in J

monitoring the axial power distribution Fj(z) as per T.S. 4.2.6.1 and 4.2.6.2. The l

[o 3 n 4 [ impact of this situation has been evaluated with the determination that this event I o s  ; did not result in conditions in which the health and safety of the general oublic l gjprj lwere endangered. This is reportable as per T.S. 6.9.1.8.i. l I

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Update Report - Previous Report Date 01-15-79 Virginia Electric and Power Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 1 Docket No. 50-338 Report flo. LER 79-001/OlX-1 Description of Event:

A potential non-conservatism has been identified in the calculations performed in monitoring the axial power distribution, Fj(z), as per T.S. 4.2.6.1 and 4.2.6.2. Based on recent operating data, the amount of this non-conservatism has been estimated to be no larger than 0.4%.

This event is reportable under Technical Specification 6.9.1.8.i since this represents the discovery of a condition not specifically considered in the safety analysis report or technical specifications that requires remedial action or corrective measures to prevent the existence or development of an unsafe condition.

Probable Consequences of Occurrence:

There are no adverse consequences associated with this occurrence. A review of the records has shown that throughout the period of its use, the APDMS has indicated that more than enough margin has existed to accomodate this non-conservatism. In view of these circumstances, it is considered that the health and safety of the general public were not endangered.

Cause of Occurrence:

This event results from the omission of the systems and procedures used to monitor Fj(z) to account for the effects of detector background (when present) on the process signal produced by the moveable incore detector system.

Immediate Corrective Action:

Inmiediate corrective actions were to adjust the input values used by the surveillance systems and to monitor the power shape and background values to insure that the effects of this event are accounted for in a conservative manner.

Scheduled Corrective Action:

The system and procedure used as per T.S. 4.2.6.2 were modified to account for detector background. We are discussing with Westing'.ause suitable corrective measures with respect to the axial power distribution monitorirg system (APDMS). The Fg surveillance program utilized in the P250 computer has been revised to include detector background levels.

Actions _Taken to Prevent Recurrence:

flo actions to prevent recurrence are planned since this event is non-recurring in nature.