ML19305C066

LER 80-004/01T-0:on 800306,during Piping Reanalysis,Errors Were Discovered in Seismic Analysis of Common Decay Heat Suction Piping.Caused by Analysis Error.Affected Piping Seismic Analysis Will Be Corrected & Hardware Changes Made

ML19305C066
Person / Time
Site:	Three Mile Island
Issue date:	03/20/1980
From:	Mcphatter C METROPOLITAN EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19305C063	List: ML19305C062 ML19305C066
References
LER-80-004-01T, LER-80-4-1T, NUDOCS 8003250543
Download: ML19305C066 (2)

Text

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(TTT1 l the common decay heat suction piping associated with valves DH-V1 and DH-V2.

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!oi4) IWhen subjected to OBE loads, the piping associated with these valves may exceed 1ois1 icode .1t11ewable stresses.

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l i 1 o 1 IThe cause of the event is analysis error. The affected pioing seismic analysis I

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. o' Attachment 2 TLL 120 NARRATIVE REPORT LER 80-004/01I-0 I. Explanation of Occurrence While performing piping reanalysis of non-conformance identified by inspections required by NRC IE Bulletin 79-14, errors were discovered by the Architect-Engineer in the seismic analysis of the comnon decay heat auction piping associated with valves DH-V1 and DH-V2. Specifically, an incorrect center of gravity was assumed for valves and their motor operstors.

When subjected to Operating Basis Earthquake loads, the piping associated with valves DH-V1 and DH-V2 may exceed Cod 2 allowable stresses as a result of insufficient restraint provided by the original design. This event is considered reportable per Technical Specification 6.9.2.A (9).

II. . Cause of occurrence The cause of this occurrence is classified as a design / analysis error in that an incorrect valve center of gravity was selected as input data for the piping seismic analysis.

III. Circumstances Surrounding Occurrence This error was discovered by the Architect-Engineer while verifying the conformance of the analysis to the "as-built" piping condition as required by IE Bulletin 79-14.

The plant was in long-term cold shutdown with core cooling being provided by the Decay Heat Removal System taking suction from the Reactor Coolant System through the DH-V1/DH-V2 suction piping. The initial error was discovered during the evaluation of DH-V2 piping on 03/06/80. The follow-up analysis of DH-V1, which is an identical valve to DH-V2, discovered similar reportable conditions on 03/10/80 and, therefore, was not included in the report telecopied on 03/07/80.

IV. Corrective Action To Be Taken To Prevent Recurrence Because the unit is in a cold shutdcun mode, no imnediate corrective action is required. Emergency Procedure 1202-35, Loss of Decay Heat Removal, addresses inoperability of the normal Decay Heat Removal suction piping and provides adequate guidance to the operator for this event. Long-term corrective action will consist of correcting the affected piping seismic analysis. If the corrected analysis shows the affected piping exceeds Code allowable stresses when subjected to OBE loads, then appropriate hardware changes will be provided. Because this piping is in service to remove decay heat, these corrective actions will be taken as soon as-practical before 06/30/80. The IE Bulletin 79-14 reanalysis is continuing and will reveal similar analysis errors if they exist; analysis errors similar to this event will be reported within 30 days of discovery as updates to this Event Report.

V. Cempenent Failure Data L Not applicable, as no compone

0s have failed. This event report considers potential piping failure.

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