ML20084L453

AO 50-237/1974-42:on 740824,during Snubber Insp,Eight Snubbers Found Low on Oil.Two Snubbers Leaked Upon Refilling.Cause Undetermined.Snubbers Will Be Disassembled

ML20084L453
Person / Time
Site:	Dresden
Issue date:	08/30/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084L448	List: ML20084L445 ML20084L453 ML20084L462 ML20084L472
References
626-74, NUDOCS 8305230212
Download: ML20084L453 (5)

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BBS Ltr.#626-74 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 6045,0 g;[ d n,,,

August 30, 1974 .f ,,

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(('(?[$g L h SEP6 1974N Mr. James G. Keppler, Regional Director Directorate of Regulatory Operations-Region III E 2 ln.E[:[

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U.-S. Atomic Energy Commission k ,

799 Roosevelt Road Glen Ellyn, Illinois 60137 50-237 e a-' i gr

SUBJECT:

REPORT OF AENORMAL OCCURRENCE PER SECTION 6.6.B 0F THE TECHNICAL SPECIFICATI0"S.

INSPECTION OF BERGUI PATERSON SHOCK SUPPRESSORS AND RESTRAINTS.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

-2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura, 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br /> on August 26, 1974 Telegram: Mr. J. Keppler, 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on August 26, 1974 Report Number: 50-237/1974-42 Report Date August 30, 1974 Occurrence Date August' 24, 1974 ,

Facility: Dresden Nuclear Power Station, Morris, Illinois IDENTIFICATION OF OCCURRENCE At approximately 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on August 24, 1974, during a routine snubber inspection, it was found that eight snubbers were low on oil. Two of these snubbers were noted to leak subsequent to refilling.

CONDITION PRIOR TO OCCURRBJCE Prior.to the occurre,nce,' Unit 2 was in a scheduled shutdown for the removal'of two control rod drives that were suspected to be uncoupled.

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DESCRIPTION OF OCCURRDiCE On August 24, 1974, an inspection was made of' the thirty-one (31) anubbers contained in the drywell._ The inspection of the Bergen Paterson shock suppressors revealed that eight (8) of the snubbers were low on oil.

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p Mr. James G. Kepp-.c -

August 30, 1974 Following is a list of the findings on the drywell snubbers giving the actual piston extension, fluid level indicated position and seal material contained within:

SNUEEER AS-FOUND CONDITION Snubber Actual Piston Fluid Level Seal I.D. No. Rod Extension Indicated Position Material 1 30 . 2.0 E-P 2 3 75 6.0 (low) PU 3 35 4.0 PU 4 3 75 2.0 PU 5 30 2.0 PU 6 3 25 25 PU 7 30 30 PU 8 3 25 3 25 PU 9 3 75 2.0 E-P 10 3 25 30 E-P 11 3.25 2.0 PU 12 3 75 4.0 FP 13 25 4.0 (low) E-P/PU 14 5 25 30 PU 15 4.25 1.0 PU 16 3 25 3 25 PU 17 4.0 6.0 (low) PU 18 1.5 2.0 E-P 19 1.25 1.0 E-P 20 l'.75 2.0 E-P 21 4.25 50 PU 22 15 2.0 E-P 23 4.25 4.5 E-P 24 35 5 5 (low) PU 25 4.25 6.0 (low) E-P 26 2 75 6.0 (low) E-P 27 30 3 75 E-P 28 1 75 6.0 (low) E-P 29 30 4.0 (low) E-P 30 30 1.0 E-P 31 3.25 25 E-P E-P - Ethylene Propylene Seal Material PU - Polyurethane Seal Material DESIGNATION OF APPARENT CAUSE OF OCCURRENCE (Design Deficiency)

The mode of leakage of oil from five of the snubbers; 2r 13, 17, 24, 29, could not be dotermined at the time of inspection. The mode of suspected failure of the three remaining snubbers, 25, 26 and 28 are as follows:

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o Mr. James G. Kep p r

.n August 30, 1974 Snubber #25 - Subsequent to refilling, the oil was [loted to be leaking out of the shaft end of the snubber. Leak path appears to be through the shaft seal.

Snubber #26 - Subsequent to refilling, the oil was noted to be leaking past the accumulator cylinder indicator. Leak path appears to be

- past the spring loaded accumulator piston.

Snubber #28 - Subsequent to refilling, no leakage path could be noted.

Note: The above snubbers were installed in June, 1974 and contain the ethylene propylene seal material.

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Upon the disassembly of each snubber (3), the probable cause of failure can be determined. The disassembly of these snubbers will be wit-nessed by a representative from Crawford Manufacturing Co., Rex Hanna Co.,

CECO head metallurgist and an assistant,.and a station representative.

1 ANALYSIS OF OCCURRENCE In evaluating the safety implications of the low oil condition of the snubbers, the health and safety of the public were not jeopardized at this time. Even though the snubbers were low on oil, they did pocsess-enough oil to function in an earthquake situation.

• CORRECTIVE ACTION i

The initial corrective action was to refill the eight (8) snubbers that were low on oil. The three snubbers that were questionable were refilled to check for leakage paths due to a history of~ leakage. As a result of observations, the decision was made to replace the leaking snubbers f' with new snubbers.

As a result of the failure of these snubbers containing ethylene propylene seal material to hold oil, they will be disassembled. Subsequent to disassembly, the findings will dictate further steps in the continuing investigation of the cause of failure of the snubbers'containing ethylene '

propylene-seals. ,

I l In addition, the results of the as left condition of the thirty-one

~ (31) drywell snubbers are listed below

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Mr. Ja:nes G. Keph_'c)r

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August 30, 1974 SNUBBER AS-LEFT CONDITION Snubber Actual Piston Fluid Level Seal I.D. No. Rod Extension Indicated Position Material 1 30 2.0 E-P 2 (no indicated leakage) 2.75 1.0 PU 3 35 4.0 PU 4 3.75 2.0 PU 5 30 2.0 PU 6 3.25 25 PU 7 30 30 -FU 8 3 25 3 25 PU 9 3 75 2.0 E-P 10 3 25 30 E-P 11 3 25 2.0 PU 12 3 75 4.0 E-P 13 (no indicated leakage) 25 .75 E-P/PU 14 5 25 30 PU 15 4.25 1.0 PU 16 3 25 3 25 PU 17 (no indicated leakage) 4.25 1.0 PU 18 15 2.0 E-P 19 1.25 1.0 E-P 20 1.75 2.0 E-P 21 4.25 50 PU 22 15 .

2.0 E-P 23 4.25 4.5 E-P 24 (no indicated leakage) 4.5 .5 PU 25 (leakage out of shaft coal) 4.5 50 E-P (new) 26 (leakage out of accum. scal) 2 75 1.25 E-P (new) 27 30 3 75 E-P 28 1-7/8 15 E-P 29 (no indicated leakage) 3 75 .5 E-P 30 30 1.0 E-P 31 3 25 25 E-P E-P - Ethylene Propylene Seal Material PU - Polyurethane Seal Material 9

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Mr. James G. Kepp br August 30, 1974 FAILURE DATA Prior to June, 1974, all snubber failures were related to the usage of the polyurethane seal material. In June, 1974, a snubber inspection was conducted on the drywell snubbers and revealed that eight (8) anubbers were considered inoperable. Six (6) of the eight (8) failed snubbers contained all ethylene propylene seals with the remaining two containing the polyurethane seal material. The mode of failure of the ethylene propylene snubbers could j not be determined at that time. Therefore, an investigation was begun. At the present, the failure mechanism is still undetermined but with the addition of the new failed snubbers, additional information will be obtained.

Sincerely, y  ?

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(A.Af)h.

B. B. Stephenson Superintendent BBS:RLW:do 0

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