05000338/LER-1979-097-03, /03L-0 on 790803:greater than 12 Step Disagreement Was Noted Between Individual & Group Indication for Rod D-10.Caused by Instrument Drift.Immediate Calibr & Functional Checks Were Performed

/03L-0 on 790803:greater than 12 Step Disagreement Was Noted Between Individual & Group Indication for Rod D-10.Caused by Instrument Drift.Immediate Calibr & Functional Checks Were Performed

ML19261E543
Person / Time
Site:	North Anna
Issue date:	08/21/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19261E541	List: 05000338/LER-1979-097, Forwards LER 79-097/03L-0 05000338/LER-1979-097-03, /03L-0 on 790803:greater than 12 Step Disagreement Was Noted Between Individual & Group Indication for Rod D-10.Caused by Instrument Drift.Immediate Calibr & Functional Checks Were Performed
References
LER-79-097-03L, LER-79-97-3L, NUDOCS 7908280653
Download: ML19261E543 (1)

LER-1979-097, /03L-0 on 790803:greater than 12 Step Disagreement Was Noted Between Individual & Group Indication for Rod D-10.Caused by Instrument Drift.Immediate Calibr & Functional Checks Were Performed

Event date:
Report date:
3381979097R03 - NRC Website

text

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'75 HF PORT D AT E 80 EVEN T DESCHIPTION AND PROH ABLE CONSEQUENCES 10 [o,2 l During normal Mode I operations, a > 2 step disagreement was noted between I

individual and group indication for rod D-10. This is contrary to the limit l

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specified in T.S. 3.1.3.2.

Rod position indication was returned to service within I

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8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, thus the health and safety of the general public was not affected.

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33 24 32 36 31 40 41 42 43 44 di CAUSE DESCRIPTION AND CCRRECTIVE ACTIONS j The cause for this indicator disagreement was due to instrument drift.

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study was performed, possible causes of drift identified, and corrective actions have i been proposed.

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Attachment:

Page.1 of 1 Docket No. 50-338 Report No. LER 79-097/03L-0

Description of Event

During normal mode 1 operations, it was noted that there was a greater than 12 step disagreement between the rod position indications for rod D-10.

This is contrary to T.S. 3.1.3.2.

Probable Consequences of Event Operability of the control rod position indication is required to determine control rod position and thereby ensure compliance with the control rod align-ment and insertion limits.

Since control rod position was verified within the 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period required by the technical specification, there was no effect on the safe operation of the plant and the health and safety of the general public was not affected.

Cause of Occurrence The cause of the indicator disagreement was instrument drift.

Immediate Corrective Action _

Channel calibration and functional checks were performed and the indicator restored to full operability within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

Scheduled Corrective Action Future calibrations of the IRPI's should be performed only when the rod drive line is in temperature equilibrium with the surroundings or after _a suffi-cient stabilization period following rod movement.

Also if a new hardware design, currently being developed by Westinghouse proves to be effective, implementation shall be considered as a corrective action.

Actions Taken To Prevent Recurrences Further corrective actions will depend-on the results of the Scheduled

Corrective Actions

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