ML19210C666

LER 79-032/01T-0:on 791026,piping Restraints 1/2-7504-164 & 165 Had Safety Factor of Less than Two.Standby Gas Treatment Sys a & B Declared Inoperable.Caused by Improper Design of Safety Factors.Restraints Modified

ML19210C666
Person / Time
Site:	Quad Cities
Issue date:	11/06/1979
From:	Swales J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19210C662	List: ML19210C661 ML19210C666
References
LER-79-032-01T, LER-79-32-1T, NUDOCS 7911190409
Download: ML19210C666 (2)

Text

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7 8 60 61 DOCKET NUYSER 63 69 EV ENT DATE 74 75 REPORT DATE 6J EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h a  : I While evaluating piping restraints in accordance with NRC IE Bulletin 79-02, Standby o 3 l Gas Treatment Systems A and B were declared inoperable at 3:00 PM on October 26, 1979.l o , ; Analyses indicated that piping restraints 1/2-7504-164 and 165 had a safety factor Ols f less than 2. The Standby Gas Treatment Systems were at all times functional and l o g  ; the requirements of Technical Specification 3.7.B.I.b were met.

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36 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h ilo l Reevaluation of the design of restraints 1/2-7504-164 and 165 found the desion I i i i safety factors to be less conservative than oriqinally analyzed. TWe restraints were

, 7 l modifled to a safety factor of greater than 4. and at 6:51 AM, October 27. 1979, I y[ the Standby Gas Treatment systems were declared operable. I i 4 l l 7 8 9 80 STA S N POWER OTHER STATUS ISCO RY DISCOVERY DESCRIPTION t s l E l@ l 0 l 9 l 8 l@l NA l lDl@l External Source l ACTivt TV CONTENT RELEASED OFHELEASE AVOUNT OF ACTIVITY LOCAT60N OF OELEASE 1 6 8 9

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1. LER NUMBER: LER/R0 79-32/0lT-0 ll. LICENSEE NAME: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit One IV. DOCKET NUMBER: 050-254 V. EVENT DESCRIPTION:

While inspecting piping restraints in accordance with NRC IE Bulletin 79-02, Standby Gas Treatment Systems (SBGTS) A and B were declared inoperable at 3:00 PM, October 26, 1979 Analyses indicated that piping restraints 1/2-7504-164 and 165 had a safety factor of less than 2. A complete failure of these restraints during a seismic event would have resulted in the stress in pipe 1/2-7504-24" exceeding 1/2 of the ultimate stress. Restraint 1/2-7504-164 had been repaired before the SBGTS were declared inoperable and repairs had also begun on restraint 1/2-7504-165 At the time the SBGTS were declared inoperable, both units were governed by the Technical Specification 3 7.B.I.b. limiting condition for operation.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE:

All piping and equipment on the SBGTS were operable at the time of this occurrence. In addition, primary and secondary containment were in effect. Restraints 1/2-7504-164 and 165 did have a factor of safety greater than 1 and therefore should not have failed in the event of a design basis earthquake.

Therefore safe plant operation was not affected by this occurrence.

Vll. CAUSE:

The cause of this occurrence was a design deficiency. Analyses of restraints 1/2-7504-164 and 165 in accordance with NRC IE Bulletin 70-02, found the design factor of safety to be less conservative than originally analyzed.

Vill. CORRECTIVE ACTION:

Restraints 1/2-7504-164 and 165 were modified such that their factors of safety were greater than 4 by 6:51 AM, October 27, 1979 At this time the SBGTS were declared operable.

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