ML19337B596

Forwards Updated LER 80-022/03L-1

ML19337B596
Person / Time
Site:	Cooper
Issue date:	09/12/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19337B598	List: ML19337B596 ML19337B604
References
CNSS800555, NUDOCS 8010070480
Download: ML19337B596 (2)

Text

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i" ' COOPER NUCLEAR STATION i

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Nebraska Public Power District " * * "A*e" , *o"!%5; U*".^ii' ' " " ' ' '

CNSS800555 September 12, 1980 Mr. K. V. Seyfrit, Director U.S. Nuclear Regulatory Cammission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Drive.

Suite 1000 Arlington, Texas 76011

Dear Sir:

This amended report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on June 29, 1980. An updated licensee event report form is also enclosed.

Report No.: 50-298-80-22-1 Report Date: September 12, 1980 Occurrence Date: June 29, 1980 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

Conditions leading to operation in a degraded mode permitted by a limiting condition for operation as delineated in Section 3.7.D of the Technical Specifications.

Conditions Prior to Occurrence:

Steady state power operation at approximately 99% reaccor power.

Description of Occurrence:

During routine discharge of water from the Residual Heat Removal System (RHR) to radwaste, the inboard throttle isolation valve (RHR-MO-57) failed to close either remotely or manually.

Designation of Apparent Cause of Occurrence:

The subject 4", 300#, motorized, globe valve was disassembled to determine the cause of the occurrence. Upon disassembly the valve seat, which is screwed into the body of the valve, was found un-threaded from the body and had lodged itself between the disc and body so that the valve disc could not move. This occurrence has been re-evaluated by the valve manufacturer. Their findings were that this valve design was not intended for throttling purposes and they were not aware of this when the valve was supplied. A mod-ified valve dise design is available to prevent chattering of the disc, which caused the failure. This is an isolated occurrence and operating experience indicates there have been no similar problems with other throttle valves.

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Mr. K. V. Seyfrit '

September 12, 1980 Page 2.

Analysis of Occurrence:

As described, RHR-MO-57 is the inboard throttle isolation on the RRR drain to radwaste. Upstream of RHR-MO-57 is RHR-MO-67 which is the outboard isolation valve which was operable. In the event the valves had received an isolation signal, RHR-MO-67 would have closed.

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

Corrective Action:

Immediate action upon identification of occurrence was to tag shut RHR-MO-67 in accordance with the Technical Specifications. The damaged seat was removed and a new seat was installed. To prevent recurrence, the seat was tack welded into place. In addition, a new valve has been ordered that 4.s designed specifically for throt-tling applications. Upon receipt, the new valve will be installed during the next scheduled outage of sufficient duration.

Sincerely, W

~( h L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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