ML19270G457

RO on 790518:68 Hydraulic Snubbers Failed 18-month Functional Test Verifying Piston Movement.Analysis Being Conducted

ML19270G457
Person / Time
Site:	Davis Besse
Issue date:	05/18/1979
From:	Murray T TOLEDO EDISON CO.
To:	Tambling T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
RO-790518, NUDOCS 7906080283
Download: ML19270G457 (2)

Text

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I May 18, 1979 TO: U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region III Attention: Tom Tambling

SUBJECT:

Reportable Occurrence per Technical Specification 6.9.1.8.f Davis-Besse Unit 1 - Mode 5 Power (MWT) = 0, Load (Gross MUE) = 0 e

e At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on May 18, 1979, it was determined a reportable event existed in that improper field installation of hydraulic snubbers during plant construction could have prevented the fulfillment of the functional requirements of systems required to cope with accidents analyzed in the Final Saf ety Analysis Report.

The following problems were identified with hydraulic snubbers during the conduct of Surveillance Test ST 5044.01, Inspection of Safety Related Snubbers:

a) Snubbers had wrong cylinder vent and tube fittings installed which may not have allowed a proper seal, and permitted air in-leakage to degrade snubber performance. This was co= mon to snubbers rebuilt in October-December, 1976 to replace non-ethylene-propylene seal materials.

b) Fluid reservoirs were installed on three snubbers with improper orien-tations which may have rendered the reservoir inoperable and/or allowed air in-leakage.

c) Installation of brackets mounting the local reservoirs were not per design and required removal of cap head body bolts which would have allowed air into the hydraulic cylinders and possibly disturbed the o-ring seals. This affected at least four snubbers.

d) Five snubbers had non-ethylene-propylene seals.

1 To date, 68 of 97 hydraulic snubbers tested have failed the 18-month functional surveillance testing which verifies correct piston movement, lockup and bleed.

Sixty-seven snubbers were sent to the vendor for test and repair, from which six were found acceptable. The predominant failure area was in bleed rate, which was attributed to excessive air in the cylinders. The current surveillance test acceptance criteria for bleed rate of 3-3 inches per minute is considered too restrictive by the vendor who reccamends 0.5 - 10 inches per minute. An analysis n'77 1r}

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a TO: U. S. Nuclear Regulatory Ccmmission Page 2 of 2 Office of Inspection and Enforcement Region III Attention: Tom Tambling by the architect / engineer is being conducted to resolve this test deficiency.

Tem Tambling of NRC Region III notified in person at 1030 hcurs on May 18, 1979.

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Terry D. Murray Station Superintendent Davis-Besse Nuclear Power Station Toledo Edison Company TDM/SMQ/ljk o,7

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