05000293/LER-1981-004-01, /01T-0:on 810225,review Indicated That If Backup Scram Solenoids Failed,Actuation of ATWS Sys Would Prevent Closure of Scram Discharge Vol Vent & Drain Valves,Violating Primary Containment.Cause Due to Oversight in Design

/01T-0:on 810225,review Indicated That If Backup Scram Solenoids Failed,Actuation of ATWS Sys Would Prevent Closure of Scram Discharge Vol Vent & Drain Valves,Violating Primary Containment.Cause Due to Oversight in Design

ML19350B514
Person / Time
Site:	Pilgrim
Issue date:	03/10/1981
From:	Mcloughlin M BOSTON EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19350B513	List: 05000293/LER-1981-004, Forwards LER 81-004/01T-0 05000293/LER-1981-004-01, /01T-0:on 810225,review Indicated That If Backup Scram Solenoids Failed,Actuation of ATWS Sys Would Prevent Closure of Scram Discharge Vol Vent & Drain Valves,Violating Primary Containment.Cause Due to Oversight in Design
References
LER-81-004-01T, LER-81-4-1T, NUDOCS 8103200704
Download: ML19350B514 (2)

LER-1981-004, /01T-0:on 810225,review Indicated That If Backup Scram Solenoids Failed,Actuation of ATWS Sys Would Prevent Closure of Scram Discharge Vol Vent & Drain Valves,Violating Primary Containment.Cause Due to Oversight in Design

Event date:
Report date:
2931981004R01 - NRC Website

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BOSTON EDISON CodPANY PILGRIM NUCLEAR POWER STATION DOCKEI NO. 50-293 Attach =ent to Ln 81-004/01T-0_

Descrip tion On February 25, 1981, the ORC reviawed thc operation of the ATWS system i

which was installed on May 12, 1980 during.PNPS Refuel IV Outage. The review indicated that, in the event that the Backup Scram Solenoids failed i

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and the ATWS System initiated to scram the reactor, closure of the Scram Discharge' Volume (SDV) vent and' drain valves would be inhibited because the vent path ~ for their' air solenoids would be blocked. This blockage occurs because actuation of the ATWS/ARE Solenoid Valves isolates the SDV air colenoids air supply header from the vent. Inability of SDV vent and drain valves 'to close' following a scram would result in a breach of primary con-tainment in that a scram discharge water flow path would exist through the SDV Isolation Valves to the reactor building.

f Cause and Corrective Action '

' The root cause of ~ this problem was inappr'opriate review of the design modi-fication.'. On March 3,1981 a SDV. air s apply line design chenge was imple-mented via. Field Revision Notice Number 79-25-44.

TSis -modification revised

,tne original ~ desian to correct its deitaiencies. The modification consisted -

of relocating the half-inch copper air supply line for the SDV Isolation

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Valves. from the upstream to the downstream side of the ATWS/ARI Solenoid JValves so' that isolation of the SDV occurs on actuation of either RP5 or l

ATWS/ARI.

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~PNPS _is 'in the process of revising our methods of reviewing and approving

'modificatio'ns with more emphasis being placed on ' the conceptual phase and l

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increased operational input from the station' which.should minimize the possi-

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- ibility of a recurrence'cf similar' events.

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