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Docket File (ENVIRON)
AEC PDR Local PDR GErtter(DR62 DR Readig JCook mN L Reading)
.Moroff DEC 10...
Dochet No. 50-219 RP Reading EHughes EP-4 Readin OCR(3)
Chairman (2)
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JF0' Leary AGiambusso Senator Clifford P. Case DMuller OCC United States Senate WRegan RBevan
Dear Senator Case:
SSheppard This is in response to your coccunication of !!ovember 20, 1973, transmitting Mr. l'urt='s letter of Uovember 15, 1973, regarding the operation of the Oyster Creek Nuclear Generating Station.
The inadequacies in the radiological conitoring program mentioned by Mr. Kurtz are well known to the Commission. These have mainly to do with sampling methods and frequency and will be corrected in the forth-coning program of Environmental Technical Specifications for the Oyster Creek Station which will comprise Appendix D of the I'ull Term Operating License.
Vith regard to Mr. Kurtz's questions concerning the effect of dredging
. spoils containing radioactive caterials on the health and safety of residents and raritm wners, the Conmission is currently reviewing the State of Ucv Jersey coc=ents on the Oyster Creek Draf t Environnental Statement cited by Mr. Kurtz, along with other studies pertinent to f
Resolution of this question is expected in the near future, this matter.
and our findings along with a description of any actions which are deemed appropriate will be sent to you at an early date.
Sincerely,
%&tl sired by Ro,:r 3. g y M M.' Giambusso, Deputy Director
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for Reactor Projects Directorate of Licensing 1
Enclosure:
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December 7, 1973
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Mr. A. Giambusso
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Dear Mr. Giambusso:
Subject:
Oyster Creek Station Docket No. 50-219 Main Steam Isolation Valve Inspection and Repair In a Ictter dated September 21, 1073, we reported that main stcam isolation valve NS03B 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 ccurse of action that would be followed to visually and dimensionally check valve NS03B to j
determine the failure mechanism.
The purpose of this letter is to submit a i
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 Elcetric Company, Atwood 6 Morrill Company and MPR Associates met with Jersey Central Power G Light Company personnel to discuss possible failure mechanisms and methods of repair.
Until the latest development, it was believed j
that the lack of straightness of the valvo stem was resrcnsibic 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 leakage prbblem.
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 G Morrill Company.
An Atwood 6 Morrill representative was present for the entire inapection and repair program.
Prior to disassemblinr, the valve, special instruments were installed to indicate'and/or accord ambient temperature, valve body temperature, stem l
- travel, and operator air and oil pressures.
The. valve was opened and closed several times to veri fy the rep. at ability of measurements.
Data was obtained to enable plots of operator air pressure versus open-close stem travel to be j
mado.
During the disassembly of NS03B, dimensional data was obtained on all
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Mr. Giambusso December 7, 1973 4
4 cri ti cal. parts. The data recorded during the inspection along with the procedures followed for the disassembly and reassembly of the valve are on file at the plant.
Copies ofothis information will be made availabic upon request.
An analysis of the inspection data revealed that there was excess t
l clearance between the main poppet guides and the valve body guides.
The 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 4
by the main poppet guide pads was found to.be:23.456 inches.
It is believed
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that the-large clearance between pappet and body guides, as much as.048 inches near the valve seat, permitted excessive misalignment of the poppet on.the valve scat, a condition that.is not favorable for a tight seal.
The desired guide cicarance is.027 to.030 inches on the diameter.
j The repair consisted of building up the main poppet guide pads to gi"e the desired cIcarance.
First, the guide lugs were cleaned by machining and 4
'then built up 1/8" with Stellite 21 overlay.
The guide pads were then renachined and dye checked.
Th.e diLmeter of the circle formed by the remachined guide pads is 23.4815 inches.
The weld overlay was donc in accordance with Atwood G Morrill i
Company Specification No. PTil-3, Revision No. 8, entitled " Procedure Specification i.
for Gas : Tungsten Arc liard Surfacing of Valve Trim".
An Atwood 6 Morrill welder, i
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 near, because there was no~ mechanism availabic for dimensional boring of the body guides.
Additional work performed'on valve NS03B to inprove scaling performance 1
consisted of machi,ning 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
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ca the stem spring plate to reduce the possib'ility of metal-to-metal contact of the spring coils while in compression.
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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 stcan isolation valves.
The two valves, NSf*A and NSO4B, outside the drywell failed to meet acceptabic icakage rate requirements.
(Re-ported to the Directorate of Licensing by letter dated October 12, 1973).
The icakage path in both valves was identified as being the stem packing.
As a i
precautionary measure, all four isolation valves were repacked.
In subsequent tests, the Icakage rate of each of the four valves was found to be nondetectable, i.e., <0.1 SCFil.
i Two najor problems have not been identified and corrected in nain steam isolation valve NS03B.
The fixes consisted of (1) replacing the original i
valve stem with one that' was nanufactured to new specifications and (2) reducing
'the poppet guide to body guide clearance.
We expect that the performance of 4
this valve will be uuch ir. proved in the future.
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' Mr. diambusso, December 7, 1973 i
Enclosed are forty copies'of this report.
. Very truly yours, j
/t/N Donald A.~ Ross Manager, Nucicar Generating Stations es cc:' Mr. J. P. O'Reilly, Director '
1 Directorato-of Regulatory Operations, ' Region I
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