05000324/LER-1981-017-03, /03L-0:on 810207,operator Noticed That Reactor Level Instrument B21-LIS-N017D Pegged High & on 810212, Noticed N017D Instrument Reading Higher than Other Level Instruments.Caused by Low Level in Instrument Ref Leg

/03L-0:on 810207,operator Noticed That Reactor Level Instrument B21-LIS-N017D Pegged High & on 810212, Noticed N017D Instrument Reading Higher than Other Level Instruments.Caused by Low Level in Instrument Ref Leg

ML19350A763
Person / Time
Site:	Brunswick
Issue date:	03/09/1981
From:	Poulk R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19350A761	List: 05000324/LER-1981-017, Forwards LER 81-017/03L-0 05000324/LER-1981-017-03, /03L-0:on 810207,operator Noticed That Reactor Level Instrument B21-LIS-N017D Pegged High & on 810212, Noticed N017D Instrument Reading Higher than Other Level Instruments.Caused by Low Level in Instrument Ref Leg
References
LER-81-017-03L-01, LER-81-17-3L-1, NUDOCS 8103160774
Download: ML19350A763 (2)

LER-1981-017, /03L-0:on 810207,operator Noticed That Reactor Level Instrument B21-LIS-N017D Pegged High & on 810212, Noticed N017D Instrument Reading Higher than Other Level Instruments.Caused by Low Level in Instrument Ref Leg

Event date:
Report date:
3241981017R03 - NRC Website

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8 80 61 oOCK ET NuM8 E R ed 69 EVENT oATE F4 75 R EPoRi o AT E SQ EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h [TTT1 I While performing normal surveillance of the Reactor Buildine, the Auxiliary Operator l g l noticed that the reactor level instrument B21-LIS-N017D was pegged high.

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[;; 771 l February 12, 1981, it was discovered that the N017D instrument was reading higher thang g ( the other level instruments. The N017D instrument is used to initiate a reactor scram l g l signal and a group 2, 6, 7, and 8 isolation signal at Low Level No. 1.

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JJ J4 JS J6 31 40 el 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h [TTT1 i Both events were caused by a low level in the instrument reference leg.

Af ter the first l ITTTI I event. the instrument was recalibrated, the reference lee filled, and the inserumene i l restored to service. Following the second event. the hizh-low-eeualizine valve block I g I was rep 1' aced. parallel instrument 11nes were isolated. the instrument recalibrated l and returned to service.

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2-7-81 Following the initial event, after a calibration check determined that the instrument was in calibration, further investigation determined that the reference leg was partially drained. The instrument was checked for leakage (none found), the reference leg refilled, and the instrument returned to service. It was felt at this time that the equalizing valve for the N017D had not been properly seated when last operated (debris on the seat or just not fully tightened).

Five days later when the N017D instrument was observed reading higher than normal and a calibratier, check determined that the instrument was good, the three valve block manifold was replaced. The manifold was taken to the shop and pressurr tested to 1000 psid (normal pressure is 77 inches of water dif-farentia;;. Upon completion of this test, a thorough investigation was per-formed to determine any lealrage on the entire system. Liquid penetrant tests were performed on the condensing pot and all welds associated with this reference leg in the drywell with no indications noted. Further investigation outside the drywell revealed three small packing leaks on the parallel level instruments' N017D-1 and N017D-2 isolation and equalizing valves, totaling approximately 20 drops per minute. These instruments are part of the digital to analog conversion scheduled for later this year. The isolation valves to these instruments were shut and placed under clearance to prevent any future reference leg level loss.

An Engineering Work Request has been written requesting that Engineering evaluate the adequacy of the makeup capability of the condensing pots for the reference legs. Since these actions have been taken, the N017D instrument has exhibited normal characteristics and has been operating satisfactorily.

Operation of this instrument is monitored at least once per eight hour shif t by three shifts each day.

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