ML20085K145

Ro:On 731120,during Local Leak Rate Testing,Excessive Leakage Discovered from Valves 3-1601-23,24,60,61,62 & 63. Caused by Worn Rubber Seats on Vent Valves.Seat Matl Changed

ML20085K145
Person / Time
Site:	Dresden
Issue date:	12/19/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085K144	List: ML20085K141 ML20085K145
References
918-73, NUDOCS 8310200210
Download: ML20085K145 (2)

Text

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- @gm, Comhrith One Firs: ..ationalEdison Plam Chicago, libnois (N/ ') d '"

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- 7g Address Resy to: Post Off ce Box 767

- V Chicago, Ilhnois 60690 WPd Ltr 8918-73 Dresden Nuclear Power Station R. R. #1 Morrisg Illinois 60h50 December 19, 19731

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Qpet r J Mr. J . F. O' Leary, Director V

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Directorate of Licensing ,

'I. S. Atonic Energy Connission k ,.']

Washington, D. C. 205h5 A 1 VA /7.,)9

SUBJECT:

LICH:SE DFR-24. DRESDEI NUCLEAR PCfdER STATIQi, INI? '#3mREPORT'0?

U;iU6UAL di._.T Pat Ss0r10:. o.o.b.2 0/ Th TECEilCaL SP.-LilldATIC;S.

PR1"ARY CC.TA1:R.diT ISOIATIGi VALVd LEAKAG6.

References:

1) Letter frca Mr. W. P. Worden to Dr. P. A. Morris dated May 18, 1972.

2) Dwg. P & ID M-356

Dear Mr. O' Leary:

This letter is to report a condition relating to the operation of the unit at about 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on Novenber 20, 1973 At this tine, while conducting local leak rate testing of primary containment isolation vent valves on the drywell and torus, the test of the volume bounded by valves 3-1601-23, 3-1601-2h, 3-1601-60, 3-1601-61, 3-1601-62, and 3-1601-63 revealed excessive leakage. This malfunction is contrary to section h.7.A.2.f.

which specified that the total leakage rate through any one isolation valve will not exceed 5% Lto(h8).

PRO 3LE4 I'!7ESTIGATICU, & CORRECTIVE ACTIGI During local leak rate testing of the Unit 3 drywell and torus vent valves on Novenber 20, 1973, excessive leakage was discovered from the volune bounded by valves 3-1601-23, 3-1601-2h, 3-1601-60, 3-1601-61, 3-1601-62, and 3-1601-63. The leakage discovered was h35.29 scfh which is above the 5% Lt o(h8) (29.381 scfh) naxinun leakage allowed through any one isolation valve, but below Lp(783.h93 sofh) the maxinun total allowable leakage.

Daring subsequent investigation to detemine the leakage flow path, a blind flange was installed in front of the 3-1601-2h valve. This reduced the leckage to 25h.12 sofh on November 21, 1973. Another blind flange was installed in front of the 3-1601-23 valve,which is in series with the 3-1601-2h valve, on November 27, 1973. This reduced the total leakage to h.69 sefh, which is within the linit specified above. Using this infomation, the leakage paths and rates are as follo 3-1601-23 176.h8 scf/hr. i

/ Wr 8310200210 740117 PDR ADOCK 05000249 S PDR 2h 25h.12 scr/hr.

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9-g yy t . byf1 bhNf REGION (\\,

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Mr. J. F. O' Leary O O D cembsr 19, 1973 Since the Technical Specifications do not require shutdown for

, leakage of this nagnitude, Unit 3 has continued operation at power. These i valves will be inspected during the next extended outage to detemine the mode of failure. The blind flanges will renain in place until primary containment integrity is no longer required.

EVAIUATIONS Combining the data from the above described tests and the local leak rate tests conducted during the Spring 1973 outage yisids a total leakage of 272.h3 sefh which compares favorably with the maxinum total allowable leakage (Lp = 783.h93 scfh). (The leakage through two valves in series is not the sum of the individual leaky;es, but the smaller of the two leakages).

Although there nay have been some leakage from the drywell through the reactor building vent stack, the stack was continuously nonitored and the leakage in no way represented an uncontrolled release.

The leakage therefore represented no safety hazard to the plant or the public .

Leakage through the rubber seated butterfly vent valves has been a recurring problem on both Units 2 and 3. The problens have been d related to the rubber seats. The reconnended fix was to change the seat naterial fras Buna-i; rubber to "EPT", a rubber compound. See Reference (1).

The new rubber seats were installed in the two above mentioned valves during the Spring 1973 outage. It is not known whether the leakage is associated with the rubber seats or another unrelated problem. The valves will be inspected and repaired during the Spring 197h outage. A followup 4

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letter will be submitted at that tine.

Sincerely,

- [ E. 5 $ h N Y -

W. P. Worden Superintendent s

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