ML19347C821

Ao:On 730908,during Leakage Rate Test MSIV NS03B Failed to Meet Acceptable Leakage Rate Criterion Per Tech Specs.Cause Unknown.New Procedures Established Before & After Disassembly of NS03B.Analysis Continuing

ML19347C821
Person / Time
Site:	Oyster Creek
Issue date:	09/21/1973
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8103040948
Download: ML19347C821 (3)

Text

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3 0 0700d0i b Jersey Central FoME & Light Company W'\

M ADISoN AVENUE AT PUNCH BOWL Ro AD e MoRRISToWN, N.J. 07960 e 539 611 f September b

1973

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Mr. A. Giambusso Deputy Director for Reactor Projects , d~ SEP271973 %S *W . j.is;f 3 Directorate of Licensing prcmpany 7y - - f ' '.gf United States Atomic Energy Commission m L sEcucN , ,. .

Washington, D. C. 20545 0

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Dear Mr. Giambusso:

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Subject:

Oyster Creek Station Docket No. 50-219 Failure of Main Steam Isolation Valve The purpose of this letter is to report a failure of the main steam isolation valve NS03B to meet the acceptable leakage rate criterion as specified in Technical Specifications 4.5.F.1.D. This event is considered a violation of the Technical Specifications, paragraph 1.15.E.

This event is also considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15.E. Notification of this event as required by the Technical Specifications, paragraph 6.6.2.a., was made to AEC Region I, Directorate of Regulatory Operations, by telephone on September 10, 1973 and personally to Mr. E. Greenman on September 10, 1973.

The reactor was shut down on September 8,1973 for the purpose of re-inspecting the Bergen-Paterson shock absorbers at the Oyster Creek station.

A leakage rate test was conducted on the main steam isolation valves in accordance with previous commitments to the Atomic Energy Commission. As a result of this testing, which is partially completed, the leakage rate for NS03B was found to be approximately 200 SCFil based on the rate of pressure buildup between valves NS03B and NS04B. The allowable leakage rate limit, as detailed in the Technical Specifications, is 9.95 SCFil (5% of Lto [20j). The other inside valve NS03A Icakage rate was determined to be nondetectable, <0.1 SCFli. The leakage measure-i ments for the outside isolation valves will be determined once we have completed the current inspection and repair of NS03B.

This failure is similar to one r'eported to your office by my letter dated June 5,1973. As a result of the failure to achieve an acceptable leakage rate measurement at that time, we disassembled NS03B, the pilot stem was removed, and replaced with a new one manufactured to new specifications and close quality l controls. In addition, both the main seat and pilot seat surfaces were relapped.

Following reassembly of the valve, the 20 psi air test indicated no dectable leakage through the valve (i.e. , <0.1 SCFil) . It was believed at that time that hfh 0

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Mr. Giani. September 21, 1973 the failure of NS03B to pass the air test was due to the lack of straightness in l the original pilot stem. The original stem, on several previous occasions, was straightened and reinstalled in the valve and acceptable leakage test subsequently performed on the valve. However, based on our investigation into the recurring leakage probleus with this particular valve, it was judged that the stem was re-laxing after operating for a period of time at elevated temperatures, resulting in excessive stem bowing and improper pilot valve seating. Therefore, two re-placement stems were manufactured by Atwood G Morrill Company to special specifi-cations provided by Jersey Central Power G Light Company.

The failure which is being reported by this letter reflects the results of the first test subsequent to some operating history on NS03B with the specially manufactured pilot stem.

The cause of the current valve leakage is unknown at this time.

A special meeting was held at the Oyster Creek station on September 13, 1973 to review the most recent developments with this particular valve.

The following course of action was agreed upon by Jersey Central Power G Light Company, Atwood 6 Morrill Company and two other companies consulting with Jersey Central Power G Light Company on this problem:

A. Prior to Disassembling of NS03B

1. Instrument with dial gauge and potentiometer to measure stem stroke at valve closure. Obtain baseline marks before oper-ating valve.

2. Instrument cylinder to measure Ap across cylinder.

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3. Perform stroke tests, measure cylinder Ap and valve stroke repeatability. As a part of this, also measure stem movement at a junction of cylinder Ap for increments from Ap = 0 to Ap =

design. Also check packing friction by loosening and checking stem motion and repeatability.

4. Determine whether stem is installed such that it is not

" bottoming-out" on top or bottom of operator cylinder.

S. Check runout of coupling between valve and operator stem.

NOTE: If measurements indicate significant changes during the stroke tests, conduct' leakage tests to determine effect on valve leakage.

B. After Disassembly of NS03B

1. Perform complete dimensional inspection of critical valve parts.

2. Cylinder examination for obstructions, rust, etc. , and con-dition of seals.

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Mr. Giambusso September 21, 1973

3. Refuroish, as required, (Atwood 6 Morrill indicated they can provide qualified welders and procedures, if required, for re-stelliting guide surfaces.)

4. Repeat stem stroke repeatability and op measurements, note above, after refurbishment.

C. Long Term Action It was agreed tnat a better lapping tool with bearings and in-ternal supports is needed. Atwood 6 Morrill indicated that such a tool is being developed by them and is expected to be available in October 1973. Atwood 6 Morrill will advisc Jersey Central Power 6 Light Company of the schedule for delivery of a lapping fixture for the Oyster Creek valves.

D. Procedures The inspections and examinations outlined above will be performed under Atwood 6 Morrill's and Jersey Central Power 6 Light Company's supervision in accordance with written procedures. These procedures are the responsibility of Jersey Central Power 6 Light Company and will be reviewed by General Electric and Atwood 6 Morrill.

In addition, Atwood 6 Morrill will also furnish a representative to follow this work.

In determining the significants of this valve leakage, the rate of pressure buildup in the reactor was compared to a graph of pressure buildtp where at least one valve in each steam line was leak tight. These plots compard favorably. This implies that one valve in the "B" main steam line (i.e., NSO4B) is Icak tight. This was confirmed when pressure buildup between the valves was observed to be approxi-mately the same as the reactor pressure. The redundancy feature will be confirmed upon successful completion of the NS04B leak test.

It is not possible, at this time, to specify exactly what corrective actions are to be taken to prevent the reoccurrence of this situation. The course of action will be dictated upon completion of the analysis of the extensive dimen-sional inspection described above. It is our intention to keep your office in-formed informally through our Region I compliance inspector; and, following the completion of the program described herein, to forward to your office the written results of our inspection and the corrective actions dictated by this inspection.

We are enclosing forty copies of'this report.

Very truly yours,  !

&Q N Donald A. Ross (

Manager, Nuclear Generating Stations es Enclosures l cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region I