05000369/LER-1981-176, Forwards LER 81-176/03L-0.Detailed Event Analysis Encl

Forwards LER 81-176/03L-0.Detailed Event Analysis Encl

ML20062M794
Person / Time
Site:	McGuire
Issue date:	12/04/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20062M797	List: 05000369/LER-1981-176, Forwards LER 81-176/03L-0.Detailed Event Analysis Encl
References
NUDOCS 8112180260
Download: ML20062M794 (3)

LER-2081-176, Forwards LER 81-176/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3692081176R00 - NRC Website

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DUKE Powea CO31PANY

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\ s WILLIAM O. PA R K E R, J R.

v.cr e es.or~v December 4, 1981 m c~o~c: ^a ca 7o*

STEau Pacoucticae 373-4083 Mr. J. P. O'Reilly, Director U. S. Nuclear Regulatory Commission Region II 4 /

101 Marietta Street, Suite 3100 U B Atlanta, Georgia 30303 y H E C !Df M' ' '-

3 DEC171981> T e

Re: McGuire Nuclear Station Unit 1 2 3 " ,g. a ; y ,

Docket No. 50-369 /

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Dear Mr. O'Reilly:

Please find attached Reportaoie Occurrence Report R0-369/81-176. This report concerns T.S.3.6.1.3, "Each containment air lock shall be operable with...". This incident was considered to be of no significance with respect to the health and safety of the public.

Very truly yours,

. C&%- 't.

William O. Parker, Jr.  !

PBN/j fw Attachment ec: Director Records Center Office of Management and Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C. 20555 Atlanta, Georgia 30339 Mr. P. R. Bemis Senior Resident Inspector-NRC McGuire Nuclear Station O

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DUKE POWER COMPANY McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NO.: 81-176 REPORT DATE: December 4, 1981 PACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: Failure of the Upper Personnel Air Lock (PAL) Door Seals on the Auxiliary Building Side of the Air Lock.

INTRODUCTION: On November 6, the door seals on the auxiliary building side of the upper personnel air lock were discovered to have developed air bubbles or blisters on the seals. These blisters were large enough that they began interfering with the opening and closing of the door, and it was determined that the seals should be replaced before they ruptured. The upper PAL auxiliary building door was declared inoperable, and the upper PAL recctor building door was locked closed. Prior to the occurrence, Unit I was in mode 1 power operation at approximately 48% power. This incident is report-able pursuant to Technical Specification 3.6.1.3. The outer and inner seals on the door were replaced, the door was functionally verified, and the airlock successfully passed its leak rate test. The upper PAL was declared operable on November 7, 1981.

EVALUATION: On November 11, 1981, a meeting was held with vendor representa-tives from Woolley and Seal Master to determine why the seals failed. .The seals were supplied by Woolley and were manufactured by Seal Master. These seals were the first of this design to fail under the seal's designed conditions. The Sesl Master representative discovered that the inflation stem had been pulled into the door frame and caused the flat base plate which is bound to the inner tube to be bent and allowed air ta become trapped in a determined area between the inner tube fabric and the carcass of the seal. The hole size for the stem on the Unit 1 door is believed to be greater than the specified "less than 1 3/16" " diameter hole be-cause the Unit 2 door stem hold measured 1 7/16" in diameter. The stem flange shculd contact metal if installed in a properly sized hold. The seal failed due to an oversight of the door's manufacturer, Woolley. _ Seal Master had notified Woolley in a letter dated August 26, 1981 that the seal should provide satisfactory service if the design parameters and installation requirements are met. It is believed that the stem was overtightened due to the type of seal previously u9ed from Pressrey. Other reportable occurrence reports concerning seal failures are 369/81-11 and 81-36.

CORRECTIVE ACTION: The seals which developed blisters were replaced with new seals. After the meeting with representatives from Woolley and Seal Master, it was determined that the seal stem nut should only be hand tightened. The " Personnel.

Airlock Door Seals Corrective Maintenance" procedure was revised to have the seal stem nut hand tightened only, and the nuts on the seal stems which were tightened on November 6 were loosened. Modifications to eliminate the over sized hole will be made at the next outage when work is done to make unrelated improvements to the hinges on the door. The necessary instructions to make these improvements are to be supplied by Woolley. Also, Woolley and Seal M aster are looking at better ways to install the stem in the seal so that over tightening will not allow air to cause a delaminated area between the inner tube fabric and the seal's carcass.

'e Report No.81-176 Page 2 VERIFICATION: After the seals were replaced, the door was functionally verified to be operating correctly, and a leak rate test was performed which showed the seals were operating as required.

SAFETY ANALYSIS: The failure of the seals on the upper PAL auxiliary building door reduced the means of isolating the containment vessel from two doors to one.

Both doors are to be closed except when personnel are entering or exiting the reactor building and then only one door at a time is allowed open. In accord-ance with the action statement of Technical Specification 3.6.1.3, the operable door was locked closed, and the repair of the inoperable door was initiated. The l plant was capable of operating safely under these conditions as long as the inner i I

door was closed. Containment integrity was maintained; therefore the health and safety of the public were unaffected by this incident.

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