05000298/LER-1982-021, Forwards LER 82-021/03L-0.Detailed Event Analysis Submitted

Forwards LER 82-021/03L-0.Detailed Event Analysis Submitted

ML20028B459
Person / Time
Site:	Cooper
Issue date:	11/19/1982
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20028B460	List: 05000298/LER-1982-021, Forwards LER 82-021/03L-0.Detailed Event Analysis Submitted 05000298/LER-1982-021-03, /03L-0:on 821023,relay 917-16A-K44B Failed to Open Contacts When de-energized.Cause Not Determined.Relay Replaced & Correct Operation Verified.Monitoring Program Implemented to Determine Need for Generic Replacement
References
CNSS820663, NUDOCS 8211300401
Download: ML20028B459 (2)

LER-1982-021, Forwards LER 82-021/03L-0.Detailed Event Analysis Submitted

Event date:
Report date:
2981982021R00 - NRC Website

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Nebraska Public Power District CNSS820663 November 19, 1982 Mr. John T. Collins, Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.1 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occur-rence that was discovered on October 23, 1982. A licensee event report form is also enclosed.

Report No.:

50-298-82-21 Report Date:

November 19, 1982 Occurrence Date:

October 23, 1982 Facility:

Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition occurred which resulted in operation in a degraded mode as permitted by Section 3.7.D.2 of the Technical Specifications.

Conditions Prior to Occurrence:

Reactor was at a steady state power level of 100% of rated thermal power.

Description of Occurrence:

During routine testing of the Main Steam 1.ine Process Radiation Monitor-ing instrumentation, a relay designated 917-16A-K44B failed to open its contacts when deenergized.

Designation of Apparent Cause of Occurrence:

The cause of the relay coil failure could not be determined.

Analysis of Occurrence:

Relay 16A-K44B is associated with the Primary Containment Isolation System.

It is one of four relays connected to the Main Steam Line Process Radiation Monitors. The relay is normally energized and is deenergized when high radiation is detected in the steam lines.

h This relay provides closing interlocks for the Main Steam Isolation f,

Valves (MSIV's), main steam line drain valves, and one of the reactor

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water sample isolation valves. The failure of the relay to open its

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contacts would not have prevented the MSIV's from closing because three relays in the other channels remained operable. The automatic closing of MSIV's on high radiation remained operable.

Failure of this relay would have prevented the auto closing of reactor water sample isolation valve 2-39 on high radiation. However, since there are two valves in series (2-39 and 2-40), the second valve would have closed if high radiation had been detected in the steam lines. Both valves would also have closed on low water level in the reactor vessel.

The relay failure is the second failure of this type at Cooper Nuclear Station. The failures are described in General Electric's Service Information Letter No. 44.

Since cracked bobbins seem to precede fail-ures, HFA re3nys in essential systems were inspected for cracked bobbin material in September 1981. At that time, the relay was not identified as one needing replacement.

If a significant number of relays fail, the bobbins, or the relays will be replaced with qualified replacements.

This occurrence presented no adverse potential consequences from the standpoint of public health and safety.

Corrective Action

The "B" Group 1 isolation system was immediately placed in the tripped condition as required by Technical Specifications. The relay was re-placed and operation verified within eight hours. The failure rate of these relays will be monitored.

If the rate becomes excessive, a long tern replacement plan will be implemented. In the interim, replacement relay coils are being procured for preventive maintenance replacement during subsequent refueling outages.

Sincerely, L. C. Lessor Station Superintendent i

Cooper Nuclear Station LCL:cg Attach.

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