ML19344E078

Forwards LER 80-021/03L-0

ML19344E078
Person / Time
Site:	Cooper
Issue date:	07/22/1980
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19344E079	List: ML19344E078 ML19344E086
References
CNSS800454, NUDOCS 8008260595
Download: ML19344E078 (2)

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CNSS800454 July 22, 1980-Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inapection and Enforcement 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.2 of the

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Technical Specifications for' Cooper Nuclear Station and discusses a reportable occurrence that was discovered on June 22, 1980. A licensee event report form is also enclosed.

Report No.: 50-298-80-21 Report Date: July ??. 1980 Occurrence Date: June 2', . 1980 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

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

Conditions Prior to Occurrence:

The reactor was operating at a steady state ,'eser level of approx-imately 48% of rated thermal power.

Description of Occurrence:

While performing routine Surveillance rest .vtedure 6.3.9.4, MSIV-86A was found to have a closing time daater than allowed by Tech-nical Specifications.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence has been attributed to setting the MSIV closing rate too close to the Technical Spec; ification limit when the reactor was in a cold shutdown conditioa.

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Mr. K. V. Seyfrit July 22, 1980 Page 2.

Analysis of Occurrence:

At least once per quarter, with reactor thermal power less than 75%, the main 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 cicsure of the turbine stop valves with failure of the bypass valves. It is fast enough to prevent fuel barrier damage by limit-ing the loss of reactor coolant. A hydraulic dashpot functions as a hydraulic buffer and is utilized to control the speed with which the isolation valve is closed by the air actuator.

On May 19, 1980, during the scheduled refueling outage, the closing time for MSIV-86A was set at 3.5 seconds. All other MSIV's closing times were acceptable. On June 22, 1980, while performing routine Surveillance Test Procedure 6.3.9.4, MSIV-86A was found to have a closing time of 2.5 seconds. Duringthetest,theuteamfgow through the "A" main steam line was approximately 1.3 X 10 lb/hr.

The steam flow assists the MSIV's closure due to the valve design and position in the steam line and this caused the actual hot closure time to be less than the cold closure time.

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

Corrective Action:

The hydraulic dashpot was immediately adjusted to increase the closing time. Surveillance Test Procedure 6.3.9.4 was performed and MSIV-86A was fo'end to have a closing time of 3.2 seconds.

Surveillance Test krocedure 6.3.9.4 has been changed to provide a closing time limit of 4 to 4.5 seconds when performed with the reactor in a cold shutdown condition.

Sincerely, f Y*

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

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