ML20028C354

LER 82-163/03L-0:on 821129,temp Switches 1E31/N612A & B & Temp Differential Switches 1E31/N613A & B Found Out of Allowable Tolerance.Caused by Inconsistency in Procedure for Calibr Temp Switches.Procedure Revised & Switches Recalibr

ML20028C354
Person / Time
Site:	LaSalle
Issue date:	12/27/1982
From:	Masterson V COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20028C344	List: ML20028C343 ML20028C354
References
LER-82-163-03L, LER-82-163-3L, NUDOCS 8301070378
Download: ML20028C354 (3)

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4 6o 61 DOCKET NWM8ER EVENT DESCRIPTION AND PROBA8LE CONSECUENCES h i: l l On November 29. 1982 during the performance of LIS-RI-03, temperature switches l

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I. LER NUMBER: 82-163/03L-0 II. LASALLE COUNTY STATION: Unit One III. DOCKET NUMBER: 050-173 IV. EVENT DESCRIPTION:

Od November 29, 1982 during the performance of LIS-RI-03, "RCIC Pipe routing area high temperature and high vent differential temperature isolation calibration and functional test," temperature switches 1E31-N612A and lE31-N612B and temperature differential switches 1E31-N613A and 1E31-N613B were found out of tolerance in the non-conservative direction.

Technical Specification L.C.O. 3.3.2 isolation actuation instrumentation allowable valve setpoint for the above temperature switches and differ-ential temperature switches was exceeded. ,

V. PROBABLE CONSEQUENCES:

At the time of discovering the out of allowable tolerance temperature switches the reactor was at 48% power with the mode switch in run.

There are 2 ambient temperature switches and 2 temperature differential switches located in the RCIC pipe routing area. One temperature switch and one temperature differential switch comprise one channel. Technical Specificiation 3.3.7 requires one channel to be operating in conditions 1, 2, and 3. With less than one channel operable, a channel must be placed in the tripped condition within one hour. Tripping a channel would have closed the steam line isolation valve to the RCIC turbine rendering RCIC inoperable.

With the RCIC system inoperable plant operation can still continue with the HPCS system operable as adequate core cooling is still assured as defined in the Technical Specifications limiting condition for operation j 3.7.3 and the bases 7.3. At the time of the occurrence the HPCS system was operable.

I After discovery of the affected temperature switches reading approximately l 7 F above allowable tolerance, both channels were immediately calibrated back into allowable tolerance within one hour. This satisfied Technical Specification 3.3.2 and subsequently the channels were not tripped.

As an added precaution all LIS procedures for calibrating temperature and differential temperature switches for leak detection are being per-formed.

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l Plant operation continued without interruption and the health and safety of the public was not affected.

VI. CAUSE:

l A possible cause of instruments 1E31-N612A, lE31-N612B, lE31-N613A, and lE31-N613B being out of tolerance might be due in part to minor incon-

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• J pistencies by maintenance personnel in calibrating the instruments. The procedure used originally appears to be a possible cause as it was not clearly defined as to whether the instrument was to be calibrated to the i temperature indication for the instrument which has its own calibrated I frequency or whether a DC Millivolt was to be used.

Ambient Temperature compensation of the DC Millivolt source if required and if not taken into consideration would also cause the instruments to read high when adjusted to the Millivolt source.

The surveillance for these instruments (LIS-RI-03) is a quarterly surveillance. The procedure has been revised as of October 15,1982 correcting any ambiguity that existed Previously.

Since the instruments where calibrated per the procedure prior to the Revision of October (Rev. 2), this would appear to explain the cause of the instruments being out of allowable tolerance. Once again, this appears to be a problem with the previous surveillance procedure.

VI. CORRECTIVE ACTION:

Upon discovery of the temperature switches being out of tolerance, the affected instruments were immediately readjusted and returned within allowable tolerance within one hour. As an additional corrective measure all LIS procedures for calibrating temperature switches were repeated to confirm setpoints within limits.

The procedure for the surveillance has been revised and does not exhibit the problems with vagueness that the procedure prior to the revision had. Trip setpoints have also been lowered in the conserva-tive direction to minimize the likelihood of a similar occurrence from happening. Trending is being performed AIR (1-82-589) on the instru-ments to determine whether there is an actual instrument drift occurring i or whether it was just a problem with the surveillance procedure.

Prepared by: Vincent Masterson

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