ML19347C819

Ao:On 730928,MSIV,NS04A & NS04B Failed to Meet Allowable Leakage Requirement.Caused by Failure of Valve Stem Packing. MSIV Repacked & Tested Satisfactorily

ML19347C819
Person / Time
Site:	Oyster Creek
Issue date:	10/12/1973
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8103040883
Download: ML19347C819 (2)

Text

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S M AolSoN AVENUE AT PUNCH BOWL ROAD 9 MOR RIS T oW N, N. J. 07960 e 5 39 - 6111 Octbpt))g9 000KntD d V

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Mr. A. Giambusso p.

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Dear Mr. Giambusso:

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Subj ect: Oyster Creek Station g., Qf Docket No. S0-219

. Main Steam Isolation Valve Failure The purpose of this letter is to report a violation of Technical Specifications, paragraph 4.S.F.1.D., failure of sain steam isolation valves NSO4A and NSO4e to meet acceptable leakage rate requirements. This event is also considered to be an abnormal occurrence as defined in the Technical Speci-fications, paragraph 1.IS.E. Notification of thi:: f.,ilure, as required by the Technical Specifications, was made to AEC Region I, Directorate of Regulatory Operations, on Friday, September 28, 1973 and by telecopier on that same day.

Following completion of extensive maintenance and repair work on main steam isolation valve NS03B, it was possible to conduct a leakage test on the two main steam isolation valves (NS04A and NS04B) outside the drywell. As a result of the ensueing test, main steam isolation valve NS04B leakage rate was determined to be IS.2 SCFil and isolation valve NSO4A leakage rate measured 96 SCFil.

It was necessary to operate both valves in order to provide adequate ventilation of the reactor vessel while performing maintenance work on NS03B.

Thus, the outside isolation valves were operated after the plant was shut down and were not tested in the "as found" condition, as is normally the case. The air flow path established by utilizing the main steam lines was successful in minimizing the radiogas concentrations in the drywell; thereby, providing maximum radiological protection for maintenance people while repairing NS03B.

Investigation into the cause of leakag'e through the two outside isolation valves resulted in identifying the valve stem packing as the leakage path. Re-placement of the packing and subsequent retesting of the valves indicated essentially all the leakage associated with NS04A and NSO4B was through the stem packing region.

As an additional precautionary measure, the two inside main steam isola-tion valves were also repacked.

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Mr. Giambusso October 12, 1973 In our letter dated September 21, 1973, we indicated that the safety significance of the failure of NS03B depended on the condition of the outside valve in the "B" steam line, i.e., NSO4B. With the failure of NS04B to pass a leak rate test, neither valve in the "B" steam line was capabla of satisfying the Technical Specifications leakage rate limit of 9.9S SCFH.

It should be recognized the leakage through the packing of NSO4B was .

equal to S.7% of the total allowable primary containment leakage; whereas, the allowable Technical Specifications leakage from any one penetration or isolation valve is 5% of this total allowable leakage from the primary containment. There-fore, in the event of a LocA, release of fission products from the primary contain-ment would not be greater tnan the release discussed in Table I.S-2 of Amendment 6S and Section 3.3 of Amendemnt 68 in the FDSAR.

It should be noted that the leakage through the packing of NSO4B would, for the most part, be drawn into the reactor building ventilation system and re-leased through the plant stack. The failure of NSO4A represents a failure of one of' two redundant valves in the main steam line "A". Leakage through the packing of NS04B would also be into the reactor building ventilation system and would still be a controlled release under hypothetical accident conditions.

It should be noted that this is the first time significant stem packing leakage existed in the outer main steam isolation valves.

Based on past experience 5:ith the main steam isolation valves, a failure of this nature has not been previously experienced. Considering this, we intend to investigate a preventative maintenance program whereby a schedule of complete main steam isolation valve inspection can be accomplished. A set frequency will '

be determined for this inspection in order that all four (4) main steam isolation valves be checked within a reasonable time period. This program should preclude future failures of this kind by identifying problems prior to their reaching a point where degradation of valve integrity occurs.

Enclosed are forty (40) copies of this report, ,

Very truly you:.s,

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Donald A. Ross  !

Manager, Nuclear Generating Stations <

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Enclosures cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region I s

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