ML20084F469

Ro:On 721031,valves Associated W/Primary Containment Sys Penetration X-126 Leaked at Rate Greater than Specified by Tech Spec for Single Penetration.Caused by Grime Coating on Seat & Disc.Grime Removed

ML20084F469
Person / Time
Site:	Dresden
Issue date:	11/29/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084F472	List: ML20084F469 ML20084F516 ML20084F523
References
6639, NUDOCS 8304210142
Download: ML20084F469 (3)

Text

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D " -

O Commonwealth Edison Company 72 WEST ADAMS STREET

• C H I C A G O. IL LI N OIS 4a . i, e., ,

POST OPPICE SOX 747

• C H I C A G O, IL LIN OIS 40490 50-237 Dresden Nucicar Power Station a

r s Illinois 60450 November 29, 1972 [. . '

ls "L% ; u! d Mr. A. Giambusso In DEC 4197a del

~3 "I 'Nt Deputy Director for Reactor Projects k -

Directorate of Licensing 'X,N

. A['/

U. S. Atomic Energy Commission Washington D.C. 20545 '

M ' g f j' 2.; #

n

Subject:

1,1 cense DPR-19. Dresden Nuclear Power Station, Unit #2 >

_Section 6.6.C.1 of the Technical Specifications

Reference:

(1) P & ID No. M-25 (2) Letter to P. A. Morris from W. P. Worden dated May 18, 1972, regarding local leak rate tests of primary containment penetrations

Dear Mr. Ciambusso:

This is to report a condition relating to the operatien of the station, when, during local leak rate testing, the valves associated with primary containment system penetration X-126, had a leakage rate apparently greater than that specified for a single penetration as required in section 4.7. A.2.g. (2) (b) of the Technical Specification. ,

PROBLEM AND INVESTIGATION '

At 1415 on October 31, 1972, with the reactor shutdown for main steam line flow restrictor replacement, local leak rate tests were being conducted on the primary containment rubber seated ventilation valves.

These tests are required each refueling outage, but presently are conducted on a three month frequency due to previously experienced problems with p/(r with deterioration penetration of X-126, the rubber seats. Onwas the leakage the87.965 first testscfh.

of the valves associated This exceeds the leak rate specified for a single penetration (29.34 scfh). These valves were last d<i tested on July 28, 1972, and had a leakage of 17.44 scfh. Refer to Reference d (1) for piping and valve arrangement..

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8304210142 721129 PDR ADOCK 05000 S

COPY SENT REGION MM

____-______-_______g_ _ - - - _ - - -

O O The internals of valve 2-8502-501 were inspected for a possible leak path. This was done, because, at this time, there was no noticable outside leakage escaping from the pipe volume. Also it was assumed that the rubber seated valves were in good condition because of their recent "rescating". During the 1972 refueling outage, valves A0-2-1601-21, A0-2-1601-22 and A0-2-1601-56 had new EPT type rubber seats installed.

The old seats were made of Buna N type rubber, a material su,sceptible to breaking down under high temperatures. Refer to reference (2) for more detailed information regarding "rescating" of these valves.

Investigation of valve 2-8502-501 internals showed that the seating surfaces of both the seat and disc were coated with grime. The seating surfaces were cleaned and a bluing applied. The results of the blue showed that the disc and seat had no imperfections. The seating surfaces were in good condition. The valve was reassembled and another leak test performed.

The leak test, conducted at 1115 on November 1,1972, showed that the Icakage was reduced to,47.366 scfh. Further investigation showed leakage coming from the Estiom trunion assembly of the packing gland of valve AO-2-1601-21. New packing rings were installed and another leak test was performed. The result of this test was 21.091 l

1 scfh, which is essentially the same as that measured in July.

l l Three other leak tests were performed at this time. These l tests were satisfactory. The results are tabulated below.

I Valvas Leakage (scfh) 1601-20A & 1601-31A 6.276 1601-20B & 1601-31B 2.384 1601-23, 1601-60, 1601-24 &

l 1601-63 3.290 In the integrated leak rate test of the primary containment, conducted during the last refueling outage, the total leakage out of the primary containment was calculated to be 0.302 weight percent of the contained air in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. Using the maximum leak rate of 87.965 scfh, the total leakage from the containment would be 0.451 weight percent.

Using the leak rate of 21.091 scfh, the total leakage from the plant is 0.314 weight percent. As can be seen, the leakages are well within the Technical Specification limit of 1.6 weight percent of the contained air in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. Hence, it is concluded that no safety hazard to the public resulted from this condition.

.. s O O The herein reported leakage conditions are the first, of this nature, experienced, and are at this time considered isolated occurrences.

The three month testing surveillance of the rubber seated ventilation valves will be continued until all similar valves have been " reseated" l and their reliable performance has b'en established.

l Sincerely, M . i . Mt(b W. P. Worden Superintendent WPW:sdb ,

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