ML20084D027

Discusses Fourth Insp of Bergen-Paterson Shock Suppressors. Twelve of 31 Snubbers in Drywell Found Inoperable Due to Insufficient Fluid Contents.Failed Snubbers Repaired

ML20084D027
Person / Time
Site:	Dresden, 05000000
Issue date:	02/21/1974
From:	Worden W COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084C998	List: ML20084C995 ML20084D010 ML20084D018 ML20084D022 ML20084D027 ML20084D040 ML20084D271 ML20084D275 ML20084D285
References
125-74, 1502, RO-740221, NUDOCS 8304080451
Download: ML20084D027 (2)

Text

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Comm eaMh Edison One First N _ tion-J Pfan, Chicigo, Illinois

• h" f.o . 50-237 I Address Reply to: Post Office Box 767 Chicago. tilinois 60690 -

WPW Ltr.4125-74 Dresden Nuclear Power Station '

R. R. #1 Morris, Illinois 60450 ttIr.- - l February 21, 1974

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Mr. J. F. O' Leary, Director 5 FEB251974> $

p- g.3, m , g n.g y Directorate of Licensing RCwes U. S. Atomic Energy Conunission Washington, D. C. 20545 g NQ y, Al s

SUBJECT:

LICENSE DPR-19. DRESDEN NUCLEAR POWER STATION, UNIT #2, REPORT ON INSPECTION OF BERGEN-PATERSON SHOCK SUPPRESSORS AND RESTRAINTS.

Dear Mr. O' Leary:

This letter is to report the findings of the fourth inspection of Bergen-Paterson shock suppressors on Unit 2. The unit was shutdown on February 11, 1974 because of excessive drywell floor drain leakage.

The inspection of the Bergen-Paterson shock suppressors revealed that twelve (12) of the thirty-one (31) snubbers in the drywell were found to be inoperable. Of the twelve (12) failed snubbers, fiva were found extremely low on fluid, and seven were found without any fluid level indication. Following is a list of the failed snubbers giving the actual and indicated piston extension and the seal material used:

ACTUAL EXTENSION SNUBBER PISTON INDICATED BY SEAL

• I. D. NO. EXTENSION OIL LEVEL MATERIAL 1 3 inches 6 inches Untreated polyurethane 12 3 inches 4% inches Untreated polyurethane 13 3-7/8 inches Not visible Untreated polyurethane 19 2 inches 5 inches Untreated polyurethane 20 2 inches 5 inches Untreated polyurethane 22 3 inches Not visible Untreated polyurethane 23 3 inches Not visible Untreated polyurethane 26 2 inches Not visible Untreated polyurethane 27 6 inches Not visible Untreated polyurethane 28 3h inches Not visible Untreated polyurethane 30 3-7/8 inches 6 inches Ethylene-Propylene 31 3-7/8 inches Not visible Untreated polyurethane y

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~ t O Mr. J. F. O' Leary O F-bruary 21, 1974 As shown by the above list, all but number 30 enubber had untreated polyurethane seals. Number 30 snubber had all ethylene-propylene seals-except for the main piston and accumulator piston seals, which were untreated polyurethane. On examination of all seal material, it was found that the untreated polyurethane seals were deteriorated to the extent that a satis-factory seal was not possible. The ethylene-propylene seals from shock suppressor number 30.were inspected and found to be in satisfactory condition.

It is believed that number 30 anubber failed because of leakage by the win and accumulator piston seals which were untreated polyurethane.

At present, all of the failed snubbers have been repaired with new seals and "O" rings installed. The new seals and "O" rings material was ethylene-propylene, including the main and accumulator piston seals. However, snubber number 13 was of a size which the ethylene-propylene seals were not available. The seals which were installed in this snubber were the untreated polyurethane. It is believed that with the installation of' ethylene-propylene seals, the failures experienced on these snubbers will be substantially minimized.

In addition to the above repairs, the remaining snubbers with untreated polyurethane in Unit 2 will be overhauled with the ethylene-propylene seals as time and seal material are available.

Sincerely,

. bb W. P. Worden Superintendent i

WPW:do

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