ML19263C908

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Forwards LER 79-040/03L-0
ML19263C908
Person / Time
Site: Cooper Entergy icon.png
Issue date: 01/19/1979
From: Lessor L
NEBRASKA PUBLIC POWER DISTRICT
To: Seyfrit K
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19263C909 List:
References
CNSS790043, NUDOCS 7903120328
Download: ML19263C908 (2)


Text

COOPER NUCLEAR STATION

~

. . P.o. Box 98, DROWNVILJ_E, NEBRASKA 68321 Nebraska Public Power District memo ~E noa 82s-38n CNSS790043 January 19, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Re ion IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This 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 December 27, 1978. A licensee event report form is also enclosed.

Report No.: 50-298-78-40 Report Date: January 19, 1979 Occurrence Date: December 27, 1978 Facility: Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A condition which allowed operation in a degraded mode permitted by a limiting condition for operation established in Section 3.7.D.2 of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was at steady state power level of approximately 97% of rated thermal power.

Description of Occurrence:

While performing a special test of the drywell ventilation system for alternate drywell purging techniques, PC-246AV was found leaking. When the drywell inboard ventilation valve (PC-23DIV) was opened, the drywell outboard vent isolation valve (PC-246AV) was observed leaking 1800 scfh to the Standby Gas Treatment System.

The local limit for leakage through the valve is 3 scfh.

Designation of Apparent Cause of Occurrence:

Examination of PC-246AV revealed it was not fully closed.

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4 Mr. K. V. Seyfrit January 19, 1979 Page 2.

Analysis of Occurrence:

PC-246AV is the drywell outboard vent isolation valve. It is one of two valves in the ventilation line which are shut by a Group 2 isolation signal. PC-246AV is normally shut during operation. The other valve in the line (PC-231MV) was operating satisfactorily and would have provided the isolation had one been required. PC-246AV is a 24 inch Allis-Chalmers butterfly valve with a Bettis Model T444-lSR-41 Robotarm actuator. Investigation of the valve when removed showed it was not fully shut. The seating surfaces were satisfactory with no deterioration or hardening of the rubber in the seal ring. It is believed that the actuator is not powerful enough to fully shut the valve after periods of inactivity. There are four of these valves in the primary containment ventilation system. PC-237AV and PC-245AV are the torus supply and vent out-board isolation valves. We have experienced minimal trouble with these valves. PC-238AV and PC-246AV are the drywell supply and vent outboard isolation valves. Problems have been experienced with both valves not shutting properly and both valve operators have been changed to a stronger type. This occurrence presented no adverse consequences from the standpolut of public health and safety.

Corrective Action:

PC-231MV was immediately shut and tagged. After verification that PC-231MV was not leaking, PC-246AV was removed for repair. The valve was completely overhauled and the operator was replaced with a Bettis Model T 4208-SR1 Robotarm actuator. After repair, local leak rate testing was performed satisfactorily and the valve was returned to service. 10CFR50, Appendix J, Type C (local leak rate) testing is ccheduled to be performed April 1979. The four subject valves will be tested and the results or these tests will be evaluated with respect to future installation of larger valve operators on PC-237AV and PC-245AV.

Sincerely, v wm L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach.