ML20084J071

Discusses Rev of 730921 AO Re MSIV NS03B Failing to Meet Acceptable Leakage Rate Criterion.Results of Extensive Insp Conducted on Repairs to Renovate Valve Submitted

ML20084J071
Person / Time
Site:	Oyster Creek
Issue date:	12/07/1973
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J070	List: ML20084J068 ML20084J071
References
NUDOCS 8305100020
Download: ML20084J071 (3)

Text

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- o v Gn Jersey Central Power & Light Company g/j h

MADISON AVENUE AT PUNCH BOVA. ROAD

• MORRISTOWN, N.J. 07960

• 201-539-6111 nuun or rue General e [ Public Utihties corporation ersra m December 7, 1973 (Revised)

<t \ 1 8 ' i,9 Mr. A. Giambusso N i.

Deputy Director for Reactor Projects D ECI[ViO f, Directorate of Licensing DEc g - f United States Atomic Energy Commission t$ C Washington, D. C. 20545 e

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Dear Mr. Giambusso:

eA N ha Q*

Subject:

Oyster Creek Station TI Docket No. 50-219 Main Steam Isolation Valve Inspection and Repair In a letter dated September 21, 1973, we reported that main steam isolation valve NS038 failed to meet the acceptable leakage rate criterion specified in Technical Specifications 4.5.F.1.D, in a test conducted during the September 1973 plant outage. The letter also outlined a course of action that would be followed to visually and dimensionally check valve NS03B to de-termine the failure mechanism. The purpose of this letter is to submit a summary report on the results of the extensive inspection conducted and on the-repairs that were made to renovate the valve. '

Before proceeding with the inspection of the valve, representatives of General Electric Company, Atwood 6 Morrill Company and MPR Associates met with Jersey Central Power 4 Light Company personnel to discuss possible failure mechanisms and methods of repair. Until the latest development, it was believed that the lack of straightness of the valve stem was responsible for the failure of NS03B to pass the air tests subsequent to power operation. However, the installation of a specially manufactured stem in the valve during the June 1973 plant outage diminished the probability that a bowed stem was the cause of the recurring Icakage problem. Procedures and tests for the disassembly and re-assembly of the valve and for obtaining the desired measurements and dimensional '

data were developed in a joint effort with the vendor, Atwood 6 Morrill Company.

An Atwood 6 Morrill representative was present for the entire inspection and repair program. '

Prior to disassembling the valvo, special instruments were installed ,

to indicate and/or record ambient temperature, valve body temperature, stem '

travel, and operator air and oil pressures. The valve was opened and closed several times to verify the repeatability of measurements. Data was obtained

. to enable plots.of operator air pressure versus open-close stem travel to be made. During the disassembly of NS03B, dimensional ' data was obtained on all G305100020 731207 n U!,) q n PDR ADOCK 05000219 . vi-g PDR

Mr. Giambusso December 7, 1973 (Revised) critical parts. The data recorded during the inspection, along with the pro-cedures followed for the disassembly and reassembly of the valve, are on file at the plant. Copies of this information will be made available upon request.

An analysis of the inspection data revealed that there was excess cicarance between the main poppet guides and the valve body guides. 1he diameter of the circle formed by the body guides was measured at three elevations in the casing. The dimensions recorded were as follows: Top, 23.515 inches; Middle, .

23.510 inches; and Bottom, 23.504 inches. The diameter of the circle formed by the main poppet guide pads was found to be 23.456 inches. It is believed that the large clearance between poppet and body guides, as much as .048 inches near the valve seat, pennitted excessive misalignment of the poppet on the valve seat, a condition that is not favorabic for a tight seal. The desired guide clearance is .027 to .030 inches on the diameter.

The repair consisted of building up the main poppet guide pads to give the desired cicarance. First, the guide lugs were cleaned by machining and then built up 1/8" with Stellite 21 overlay. The guide pads were then remachined and dye checked. The diameter of the circle formed by the remachined guide pads is 23.4815 inches. The weld overlay was done in accordance with Atwood 6 Morrill Company Specification No. PTil-3, Revision No. 8, entitled " Procedure Specification for Gas Tungsten Arc liard Surfacing of Valve Trim". An Atwood 6 Morrill welder, certified to the procedure, performed the overlay work. The fix was made to the poppet guide pads rather than to the body guides, which indicated wear, because there was no mechanism availabic for dimensional boring of the body guides.

Additional work performed on valve NS03B to improve sealing performance consisted of machining and lapping the pilot poppet and the main poppet seats to 46 for line contact, and machining 1/4" off of the spring seating surface on the stem spring plate to reduce the possibility of metal-to-metal contact of the spring coils while in compression.

Following the completion of the maintenance and repair work on main steam isolation valve NS03B, tests were initiated to determine the leakage rate of each of the four main steam isolation valves. The two valves, NS04A and NS04B, outside the drywc!1 failed to meet acceptable Icakage rate requirements. (Re-ported to the Directorate of Licensing by letter dated October 12,1973). The Icakage path in both valses was identified as being the stem packing. As a precautionary measure, all four is,clation valves were repacked. In subsequent tests, the leakage rate of each of the four valves was found to be nondetectabic, i .e. , <0.1 SCFil.

Two major problems have now been identified and corrected in main steam isolation valve NS03B. The fixes consisted of (1) replacing the original valve stem with one that was mahufactured to new specificatior.s and (2) reducing the poppet guide to body guide clearance. We expect that the performance of this valve will be much improved in the future.

U b/

Mr. Giambusso December 7, 1973 (Revised)

Enclosed are forty copics of this report.

Very truly yours, ,

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je]))LpA... .J. . t}fY i%':1 ~

t Donald A. Ross Manager, Nuclear Generating Stations es cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region I l

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, o, 9 n n, w o Jersey Central Power & Light Company

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~mf' M ADisoN AVENUE AT PUNCH DoWL Ro AD e McHRISToWN. N.J. 079f,C e 539 6111 September 21, 1973 N

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Mr. A. Giambusso s Q Deputy Director for Reactor Projects O-s4 -

Directorate of Licensing & -

United States Atomic Energy Commission i a Q -\:/ -3 Washington, D. C. 20545 h p /') '

Dear Mr. Civ usso:

a fr NY.?

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Subject:

Oyster Creek Station y &

Docket No. 50-219 O F ,i p m. nr unty % .m Ten!,H nn Unive The purpose of this 1ctter 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 Techni cal Specifications, paragraph 1.15.H.

This event is also considered to be an abnormal occurrence as defined '

in the Technical Specifications, parcgraph 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 slmt down on September 8,1973 for the purpose of re-inspecting the licrgen-Paterson shock absorbers at the Oyster Creek station.

'A Icakage 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 Icakage rato for NS03B was found to be approximately 200 bCHI based on tue rate or pressure butlaup octween vanes NS031; and NSO413 the allowable Icakage rate limit, as detailed in the Technical Specificat' ions, is 9.95 SCFil (5". of Lto [20]). The other inside valve NS03A leakage rate was determined to be nondetectable, <0.1 SCFil. The leakage measure-ments for the outside isolation valves will be determined once we have completed the current in;pectica and repair of MSC33.

This failure is similar to one reported to your office by my letter dated June 5,1973. _ As a result of the failure to achieve an acceptable 1cakage rate measurement at that tire, we disassemb]cd NS03B, the pilot stem was removed, and_ rcplaced i;1L. a ne.e c..c ;c.anuiactuad to nc;. cpecificaticas and cicsc qu.uity con trols . . In addition, both the main seat and pilot seat surfaces were relapped.

Following reansembly of the valve, the 20 psi air test inilicated no decta'olo

-Icakage through tho valve (i .e. , <0.1 SCFli) . It was believed at that time that t

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o O O Mr. Ciambusso September 21, 1973 the failure of NS03B to pass the air test was due to the lack of straightness in 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. Ilowever, based on our investigation into the recurring Icakage problems with this particular valve, it was judged that .the stem was re-laxing after operating for a period of time at c1cvated temperatures, resulting in excessive stem bowing and improper pilot valve seating. Therefore, two re-placement stens were m:mufactured by Atwood 6 Morrill Company to special specifi-cations provided by Jersey Central Power 6 Light Company.

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

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

The following course of action was agreed upon by Jersey Central Pcwor G Lir,ht Company, Atwood 6 Morrill Company and two other companics consulting with Jersey Central Power 6 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.

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

, design. Also check packing frictica by loosening and checking sten motion and repeatability.

4. l>ctermine whether stem is installed such that it is not

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

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

NOTE: If neasure ents indicate significant changes during the stroke tests, conduct leakage tests to determine effect on valve Icakage.

G. Al te r l' a w c. b iy O. .3053

1. Perforn complete dimensional inspection' of critical valve parts.

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

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Mr, Giambusso September 21, 1973

3. Refurbish, as required, (Atwood G Morrill indicated they can provide qualified welders and procedures, if required, for re-stc111 ting guide surfaces.)

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

C. Long Term Action It was agreed that a better lapping tool with bearings and in-ternal support s is needed. Atunod G Morrill indicated that such a tool is being developed by them and is expected to be availabic in October 1973. Atwood 6 Morri11 will advise Jersey Central Power G Light Company of the schedule for delivery of a lapping t i .d . . e .m i.a v;a.- t. % . ,.isca.

D. Procedures The in.,p m iuna omi uo.alualvua v tlim,J obuce .111 be pcifai. l under Atwood G Morri11's and Jersey Central Power G Light Company's supervicion in ncenrdance with wri tten procedures. These procedures are the responsibility of Jersey Central Power G Light Company and will be reviewed by General Electric and Atwood G Morrill.

In addition, Atwood G 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 buildup where at least one valve in each steam line was leak tight. These plots compared favorably. This ireplies that. one valve in the "B" main steaa line (i.e., NSO4D) is leak tight. This was confirmed when pressure buildup between the valves was observed to be approxi-nately the same as the reactor pressure. The redundancy feature will be confirmed upon successful completion of the NSO4B leak test.

It i s not nonsible , at this tine, to sneci fy exactiv 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 01 our inspection and tue corrective action 3 dictated by this inapMica.

t.'e are enclosing forty copics of this report.

Very truly yours, l

J j l < l AL l G('s l'i WM!- -

/

Donald A. Ross k Manager, Nuclear Generating Stations es linclosures cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations, Region 1