ML19260B174

LER 79-039/03L-0:on 791105,while Performing Average Power Range Monitor Surveillance Test & calibr,100% Flow Rod Block Setpoint on Channel 1 Found to Be 107% of Rated Neutron Flux.Caused by Instrument Drift.Channel 1 Readjusted

ML19260B174
Person / Time
Site:	Oyster Creek
Issue date:	12/03/1979
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19260B167	List: ML19260B166 ML19260B174
References
LER-79-039-03L, LER-79-39-3L, NUDOCS 7912070364
Download: ML19260B174 (3)

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h c :, i During normal operation, while performing the APRM Survelliance Test and l Oia l Calibration, the 100%. flow rod Olock setpoint on channel I was found to l O 4 I be 107% of rated neutron flux. The required normal alarm setpoint is to l 0 3  ; be less than 106%. Since the "as found" reading was outside the toler- l C is t i ance, the setpoint was readjusted to 105% and the remainder of the test j

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m ,n,,,,,,,,, Donald A. Ross PHONE: 201-455-8784

Jersey Central Power & Light Compaay Madison Avenue at Punch Bowl Road Mornstown, New Jersey 07960 (201)455-8200 OYSTER CREEK NUCLEAR GENERATING STATION Forked River, New Jersey 08731 l.icensee Event Report Reportable Occurrence No. 50-219/79-39/3L-0 Report Date December 3, 1979 Occurrence Date November 5, 1979 Identification of Occurrence Operation in a degraded mode as permitted by the Technical Specifications, paragraph 2.3. (2)a, when performing APRM Surveillance Test and Calibration, channel I normal rod block setpoint was found less conservative than specified.

This event is considered to be a reportable occurrence as defined in the Technical Specifications, paragraph 6.9.2.(b)1.

Conditions Prior to Occurrence The plant was operating at steady state power. The major plant parameters at the time of the occurrence were:

Power: Reactor, 1852 MWt Generator, 640 MWe Flow: F.ecirculation, 14.8 x 10" gpm Feedwater, 6.91 x 106 lb/hr Stack Gas Flow: 3.19 x 104 pC1/sec Description of Occurrence On Monday, November 5,1979, at approximately 1:15 p.m. , while performing the APRM Surveillance Test and Calibration, the 100% flow rod block setpoint on channel I was found to be 107% of rated neutron flux. The required normal alarm setpoint is <106%. Since the "as found" reading was outside the tolerance, the setpoint was readjusted to 105% and the remainder of the surveillance test was completed.

Apparent Cause of Occurrence The cause of this event is attributed to instrument drift.

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), ). d Jersey Centra! Power & Lrgnt Cornpany is a Memcer of me General Pubhc UtMt.es System

Reportable Occurrence No. 50-219/79-39/3L-0 Page 2 December 3, 1979 Analysts of Occurrence The Average Power Range Monitor (AP8M) system consists of eight channels, four in each Reactor Protection System. Each channel averages the signals from eight Local Power Range Monitors (LPRM's). The reactor is divided into four quadrants and each Reactor Protection System has an APRM in each quadrant.

Any one channel may prevent rod motion to prevent excessive power in a local area.

The APRM system responds to changes in neutron flux. The APRM is checked and calibrated near rated thermal power usi,g a heat balance, so neutron flux is measured as a percent of rated thermal power. The rod block setpoint is not to exceed 106% power at 100% flow. The safety significance is considered minimal because only channel I was affected, and all other APRM channels were functioning properly.

Corrective Action APRM channel I was immediately readjusted by the technician when it was found out of required tolerance.

Failure Data Not applicable.

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