05000298/LER-1981-008, Forwards LER 81-008/03L-0.Detailed Event Analysis Encl

Forwards LER 81-008/03L-0.Detailed Event Analysis Encl

ML20004D673
Person / Time
Site:	Cooper
Issue date:	05/26/1981
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20004D674	List: 05000298/LER-1981-008, Forwards LER 81-008/03L-0.Detailed Event Analysis Encl 05000298/LER-1981-008-03, /03L-0:on 810426,reactor Vessel Level Switch LIS-72C,Switch-4,caused Continuous Annunciator 9-3-1/8-2 Alarm.Caused by Failure of Yarway Model 4418C Level Indicating Switch,Due to Film Buildup Between Contacts
References
CNSS810276, NUDOCS 8106090638
Download: ML20004D673 (3)

LER-1981-008, Forwards LER 81-008/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2981981008R00 - NRC Website

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COOPER NUCLEAR STATION Mjj Q] Nebraska Public Power District

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CNSS810276 May 26, 1981 Q1 I CJ

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N Mr. K. V. Seyfrit, Director g

g U.S. Nuclear Regulatory Commission g.7 Office of Inspection and Enforcement O IS8[h,

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Suite 1000 Arlington, Texas 76011

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Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cocper Nuclear Station and discusses a reportable occurrence that was d19 covered on April 25, 1981. A licensee event report form is also enc Lsed.

Report No.:

50-296-81-08 Report Date:

May 26, 1981 Occurrence Date: April 26, 1981 Facility:

Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition which could have resulted in operation in a degraded mode permitted by the limiting condition for operation established in Table 3.2.B of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was in the cold shutdown condition for refueling.

Reactor vessel level was approximately 140-150 inches.

Description of Occurrence:

Reactor vessel low level (-37") annunciator 9-3-1/8-2 at control room canel 9-3 alarmed and would not clear with the actual reactor vessel indicated level at control room panel 9-4 approximately 140-150 inches.

Designation of Apparent Cause of Occurrence:

Contacts on auxiliary switch #4 of NBI-LIS-72C were arcing causing alarm on control room panel 9-3 annuncia*.or 9-3-1/8-2.

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Mr. K. V. Seyfrit May 26, 1981 Page 2.

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i Analysis of Occurrence:

NBI-LIS-72C is a Yarway Model 4418C level indicator. There are four Yarway level indicators installsd designated 72A, B, C, & D, respectively. Each Yarway indicator has four sets of magnetically operated contacts designated as switch 1, 2, 3, & 4.

Switch #1 on each of the four Yarway's is a part of the logic sequence for starting CS, DG, and RHR components. Switch #2 on each Yarway is associated with ADS initiation logic. Switch #3 is a part of HPCI initiation logic at -37" reactor vessel level. Switch #4 is a part of RCIC initiation logic and also actuates an annunciator in con-trol room panel 9-3 at -37" reactor vessel level.

t Examination of the #4 switch on Yarway 72C indicated what appeared to be an oily film between the contacts. The switch contacts had l

previously been cleaned with LPS-1, a common contact cleaner. A review of this occurrence with the personnel involved indicates that the use of LPS-1 as a Yarway contact cleaner is not standard practice.

The subject Yarway level indicator was indicating properly and switches 1, 2, & 3 would have actuated correctly to a low reactor vessel water level.

The remaining #4 switches on Yarway 72A, B, & D were operable.

Subsequent to this occurrence, a calibration and functional test L

was performed on the subject Yarway level indicators 72A, B, C, &

D.

During this test, switch #2 on Yarway 72C did not function correctly. Visual inspection of switch #2 indicated a similar oily film on the contacts. These contacts had been previously cleaned with a freon solvent after the #4 switch failure. However, due to

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the physical location of these switches on the Yarway, thorough k

cleaning of the switch contacts is not achievable.

l This occurrence presented no adverse consequences from the stand-point of public health and safety.

Corrective Action

I Switch #4 on Yarway 72C was replaced. The remaining switches on L

Yarway 72 A, B, & D were cleaned with MS-180, a freon TF solvent.

As a result of the calibration and functional test, switch #2 on Yarway 72C was replaced and all the switches on Yarway 72 A, B, C,

& D will be re-cleaned using a freon TF solvent and a close visual inspection of the switches will be performed.

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Instrument and Control personnel have been advised to use only MS-180 freon solvent, vice LPS-1, for contact cleaning. This cor-rective action will be completed prior to reactor startup.

Sincerely, n,

t L. C. Lessor Station Superintendent i

I Cooper Nuclear Station l

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