ML19319B764

RO NP-33-77-50:on 770804,RCS Watertight Valve Pit Deliberately Opened to Retest Isolation Valves DH11 & DH12. Valve Packing Adjusted,Valve Retested & Valve Pit Leak Tested

ML19319B764
Person / Time
Site:	Davis Besse
Issue date:	08/30/1977
From:	Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19319B659	List: ML19319B658 ML19319B764
References
NUDOCS 8001270228
Download: ML19319B764 (3)

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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-50 DATE OF EVENT: August 4, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: The Reactor Coolant System to Decay Heat Pump Suction Line Isolation Valves DH11 and DH12 were determined to be inoperable.

Conditions Prior to Occurrence: The plant was in Mode 3, with Power (MWT) = 0 and Load (MWE) = 0.

Description of occurrence: On July 29, 1977, the valve pit containing two Decay Heat System Valves, DH11 and DH12, was opened to check the packing on DH11 and DH12. Before the pit was opened, the Technical Specification requirements were considered and determined not to affect the va.'.ve pit.

/'"% DH12 was leaking slightly around the packing so the packing was adjusted to stop

( ) the leak on July 30, 1977. This further affected the operability of DH12 but the

\+ retest requirements on the valve were not recognized at this time.

On August 4,1977, a review of the events revealed that the opening of the valve pit made one of the two flowpaths for post Loss of Coolant Accident (LOCA) boron concentration control inoperable. At the same time, the packing adjustment of DH12 was determined to be maintenance requiring a retest of the valve.

Plans were immediately made to retest DH12 and then seal and vacuum test the valve pit. The valve was successfully tested on August 5 and the valve pit was sealed and tested on August 6, 1977.

Designation of Aoparent Cause of Occurrence: The valve pit was opened deliberately to check the valve packing wnich was adjusted because of a slight leak. The fact that these events placed the unit in the Action Statement of Technical Specification 3.5.2, was not recogni:ed due to a mis-interpretation of the specification.

Technical Specification 4.5.2.f references the testing of the valve pit as a part of verifying the operability of the Emergency " ore Cooling (ECCS) subsystems. The valve pit and the valves DH11 and DH12 cannot L2 associated with a specific sub-system since it is common to both. The first interpretation of the operability requirements for the valves and pit was that they were not part of the Limiting Condition for Operation (LCO) and that the requirement of a retest of the water-7-~ tight pit after opening the enclosure applied with no specific time limit.

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wJ TOLEDO EDISO'N COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-50 PAGE 2

' l When the valve packing was adjusted, no retest was considered nea_essary since the valves are normally closed during operation and repacking would not affect their function as containment isolation valves.

During the August 4 di m. ussion, the post LOCA boron concentration control flow-path function of DHil e.d DH12 and the valve pit was considered. The Technical Specification was re- f

• 4ted to consider the valves and pit as one of the two post-LOCA boron .5 ,  ? tion control flowpaths. Although neither flowpath can be considered a pe ; +

scific ECC subsystem, the interpretation of the specification was that una ? ..bsystem was inoperable and that the Action State-ment allowed continued operation in Mode 2 for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. At the same time, the valve packing adjustment was determined to be maintenance which could affect the post-LOCA boron concentration control flowpath function of the valve.

Analvsis of Occurrence: The post LOCA boron concentration control function of ,

the valves was not required during the period they were considered inoperable, consequently, the health and safety of the public and of station personnel and equipment were not affected.

Corrective Action: The valve pit was closed and tested af ter DH12 was tested and the proper interpretation of the Technical Specification was determined and dis-cussed with station personnel.

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Failure Data: No previous similar events have occurred.

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