05000339/LER-1981-065-03, /03L-0:on 810814,power Range Channel N-41 Bistable Setpoints for Low & High Range Overpower Reactor Trips & for Permissives P-8 & P-10 Overpower Trips Were Found High. Probably Caused by Incorrect Calibr.Channel Recalibr

/03L-0:on 810814,power Range Channel N-41 Bistable Setpoints for Low & High Range Overpower Reactor Trips & for Permissives P-8 & P-10 Overpower Trips Were Found High. Probably Caused by Incorrect Calibr.Channel Recalibr

ML20010G714
Person / Time
Site:	North Anna
Issue date:	09/11/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010G711	List: 05000339/LER-1981-065, Forwards LER 81-065/03L-0 05000339/LER-1981-065-03, /03L-0:on 810814,power Range Channel N-41 Bistable Setpoints for Low & High Range Overpower Reactor Trips & for Permissives P-8 & P-10 Overpower Trips Were Found High. Probably Caused by Incorrect Calibr.Channel Recalibr
References
LER-81-065-03L-01, LER-81-65-3L-1, NUDOCS 8109220444
Download: ML20010G714 (3)

LER-1981-065, /03L-0:on 810814,power Range Channel N-41 Bistable Setpoints for Low & High Range Overpower Reactor Trips & for Permissives P-8 & P-10 Overpower Trips Were Found High. Probably Caused by Incorrect Calibr.Channel Recalibr

Event date:
Report date:
3391981065R03 - NRC Website

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U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT CONTROL BLOCK / / / / / / / (1)

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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DOCKET NUMBER EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES (10)

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/ On August 14, 1981, with the Unit in Mode 1, power range channel N-41 bistable

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/ setpo[nts for low and high range overpower reactor trips were found to be less

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/ conservative than i:he Allowable Values srecified by Table 2.2-1.

Setpoints for /

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/ pet.aissives P-8 and P-10 overpower trips were les.s conservative than the allowa- /

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/ ble values specified by T.S. 3.3.1.1, Table 3.3-1.

Since the affected chancel

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/ was corrected within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 3 redundant channelr remained operable, the

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/ public health and safety were not affected.

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SYSTEM

CAUSE

CAUSE COMP.

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CODE TYPE NO.

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ACTION FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD HOURS SUBMITTED FORM SUIL SUPETIER MANUFACTURER [E/ (18) g/ (19) g/ (20) g/ (21) /0/0/0/0/ (22) /Y/ (23) g/ (24) g/ (25) /W/1/2/0/ (26)

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

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/The cause of the event was a suspected incorrect calibration performed on 6/20/81./

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/While starting up the unit after prolonged outage, power range N41 panel read 6% /

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/ higher than the N41 drawer seter and other channels. The affected channel was re-/

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/ calibrated. When it_ was determined that the trip bistables were out of tolerence /

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/an additional calibration was performed and the trip setpoints were reset.

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FACILITY METHOD OF STATE.',

% POWER OTHER STATUS DISC 0VERY DISCOVERY DESCRIPTION (32)

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Operator Observation

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LOCATION OF RELEASE (36)

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NRC USE ONLY

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9109220444 3109T3=' 0F PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 PDR ADOCK 05000339 S

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Virginia Electric and Power Company North Anna Power Station, Unit #2 Attachment: Page 1 of 2 Docket No. 50-339 Report No. LER 81-065/03L-0

Description of Event

On August 14, 1981, with the Unit in Mode 1, power range channel N-41 bistable setpoints for low and high range overpower reactor trips were found to be less conservative than the allowable values specified by Table 2.2-1.

The low range and high range overpower trip setpoints were found to be 28% and 122%, respectively. The maximum Allowable Values specified by Table 2.2-1 are 26% and 110%.

The overpower trip setpoints for permissives P-8 and P-10 were found to be 33% and 11.2%. The Allowable Values specified by Table 3.3-1 are 31% and 11%. This event is reportable pursuant to T.S.

6.9.1.9.a.

Probable Consequences of Occurrence The three remaining power range nuclear instrumentation channels were available to provide 2 out of 3 channel trip protection. The requirement that a minimum of 3 channels be operable was met. The affected channel trip bistables were reset and the chantes was placed in service within I houc of discovery. Thus, the health and safety of the general public were not affected.

Cause of Event

The cause of the event was suspected incorrect instrument calibration performed earlier. While starting up the unit after a prolonged outage, power range N41 panel meter read 6% higher than the N41 drawer meter on the other channels. The affected channel was recalibrated and returned to secvice. On the same day, it was realized that the reactor trip bistables for the affected channel may have been set using the affected meter which indicated 49% power while all other channels indicated 43% reactor power. The bistable trip setpoints were immedistely checked and verified to be out of calibration. The Shift Supervisor was informed and the bistables were reset and verifiad operable by procedure, and the channel was placed into service.

Imme_ciate Corrective Action When it was realized that the bistables trip setpoints could be affected by an incorrect remcte meter indication, the histables were immediately calibrated and the channel placed into service.

Scheduled Corrective Action There is no scheduled corrective action.

Actioas Taken to itevent Recurrepce No further action is required.

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Generic Implications There are no generic implications associated with this event.

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