05000254/LER-1979-032-01, /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

/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: 05000254/LER-1979-032, Forwards LER 79-032/01T-0 05000254/LER-1979-032-01, /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
References
LER-79-032-01T, LER-79-32-1T, NUDOCS 7911190409
Download: ML19210C666 (2)

LER-1979-032, /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

Event date:
Report date:
2541979032R01 - NRC Website

text

NACTORM L6 U. S. NUCLE AR REGUL ATORY Cc.'? E5!G*4 (7 77)

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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 f less than 2.

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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.

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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.

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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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