05000298/LER-1980-049, Forwards LER 80-049/03L-0

Forwards LER 80-049/03L-0

ML19341A663
Person / Time
Site:	Cooper
Issue date:	12/19/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19341A664	List: 05000298/LER-1980-049, Forwards LER 80-049/03L-0 05000298/LER-1980-049-03, /03L-0:on 801120,MSIV 86A Had Slower Closure Time than Tech Specs Allowed.Cause Unknown.Closing Time Adjusted. Further Evaluations to Be Performed
References
CNSS800734, NUDOCS 8101270641
Download: ML19341A663 (2)

LER-1980-049, Forwards LER 80-049/03L-0

Event date:
Report date:
2981980049R00 - NRC Website

text

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COOPER NUCLEAR STATtoN Nebraska Public Power District

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' December 19, 1980 ev es es 23 Mr. K. V. Seyfrit, Director U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Sir:

This interim 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 Novenber 20, 1980. A 4

licenste event report fonn is also enclosed.

77))3,, -

Report No.:

50-298-80-49

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3, Report Date:

December 19, 1980

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Occurrence Date: November 20, 1980

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- Ci Facility:

Cooper Nuclear Station

- 3 Brownville, Nebraska 68321

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Identification of Occurrence:

A condition leading to operation in a degraded mode permitted by

,y limiting condition for operation as delineated in Section 3.7.D of -

'f the Technical Specification.

' ~~2____

Conditions Prior to Occurrence:

The reactor was in a cold shutdown condition.

Description of Occurrence:

While performing routine Surveillance Test Procedure 6.3.9.1, MSIV-86A was found to have a closing time slower than allowed by Tech-nical Specifications.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence has not been specifically i

identified.

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Mr. K. V. Seyfrit December 19, 1980 Page 2.

Analysis of Occurrence:

At least once per quarter, with reactor thermal power less than 75%, the nain steam isolation valves will be tripped individually and closure time verified. The Technical Specification closure time limit, T, is 3 seconds < T < 5 seconds.

This setting is slow enough to prevent a more severe transient on the nuclear system than closure of the turbine stop valves with failure of the bypass valves.

It is fast enough to prevent fuel barrier damage by limiting the loss of reactor coolant. A hydraulic dashput functions as a hydraulic buf fer and is utilized to control the speed with which the isolation valve is closed by the air actuator.

On July 26, 1980, the closure time of MSIV 86A was adjusted to 4.1 seconds.

The increase to 5.6 seconds cannot be attributable to a specific cause. A review of all data on the MSIV's indicates that MSIV 86A is the only valve with repetitive occurrences.

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

Corective Actio,t:

The hydrau..ic dashpot was immediately adjusted to decrease the closing time.

Surveillance Test Procedure 6.3.9.4 was performed and MSIV 86A was found to have a closure time of 4.2 seconds.

Further evaluation of the hydraulic dashpot and its associated hydraulic system will be performed during the next plant shutdown of sufficient duration.

Sincerely,

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L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg r

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