05000285/LER-1979-003-03, /03L-1 on 790127:during Containment Pressure Release,Containment Air Monitor Readings Were Abnormally Low.Caused by Closed Isolation Valves.Containment Ventilation Valves Were Closed & Pressure Valves Opened

/03L-1 on 790127:during Containment Pressure Release,Containment Air Monitor Readings Were Abnormally Low.Caused by Closed Isolation Valves.Containment Ventilation Valves Were Closed & Pressure Valves Opened

ML19263E229
Person / Time
Site:	Fort Calhoun
Issue date:	05/29/1979
From:	Gates G OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19263E227	List: 05000285/LER-1979-003, Forwards LER 79-003/03L-1 05000285/LER-1979-003-03, /03L-1 on 790127:during Containment Pressure Release,Containment Air Monitor Readings Were Abnormally Low.Caused by Closed Isolation Valves.Containment Ventilation Valves Were Closed & Pressure Valves Opened
References
LER-79-003-03L, LER-79-3-3L, NUDOCS 7906050338
Download: ML19263E229 (3)

LER-1979-003, /03L-1 on 790127:during Containment Pressure Release,Containment Air Monitor Readings Were Abnormally Low.Caused by Closed Isolation Valves.Containment Ventilation Valves Were Closed & Pressure Valves Opened

Event date:
Report date:
2851979003R03 - NRC Website

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UPDATE REPORT-P'/EVIOUS REPORT LICENSEE EVENT REPORT 23,1979 l l

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DATE FIEEUARY CONTRO8. SLOCK:

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60 di DOCKET NUMBER od 63 EVENT OATE 74 75 REPORT DATE 33 EVENT DESCRIPTION AND PROB A9LE CONSEQUENCES lWhile taking containment pressure release OP-79005 the night shift supervisor noticed l O

2 0 13 lthat the readings on the containment air monitor R'40-50/51 vere abnormally lov.

I l Investigation revealed that the isolation valves (Tk2 F'4H) vere closed. This renderedl o

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s i Pl40-50/51 ineffective for approximately b hours.

During this time the ventilation l

Ivalves from containment vere closed and the cressure raller valves open.

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40 43 42 43 44 47 CAusE cESCRIPTION AND CORRECTIVE ACTICNS rne valves for P240-50/51 vere not successfully reopened after an autc=atic actuation j

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Icheck performed prior to initia?.ing the containment pressure release CP-79005.

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The operators l involved vere reinstructed en release checks and procedures vill be reviewed for l

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LER 79-003 Revision 1 Ocaha Public Power District Fort Calhoun Station Unit No. 1 Docket No. 05000285 Attachment No. 1

Safety Analysis

During a normal release from contain=ent five radiation monitors are available to monitor gaseous effluents.

RMO-50/51 monitors the containment atmosphere and RMO-60/61/62 monitors the ventilation stack.

All of the above monitors have the capability to automatically ter-minate the release upon receipt of a high radiation signal.

Release CP-79005 utilized the containment pressure relief valves and not the large ventilation valves.

The ventilation valves remained closed throughout the four hour period when RMC-50/51 were out of service.

In addition, RM0-60/61/62 remained in service monitoring the stack effluent and were capable of terminating the release if required.

The monitor readings available during the release indicated that a=ounts of radioactive gaseous effluents were within the limits prescribed in the Technical Specifications.

The monitors RMC-50/51 vere returned to service and the readings returned to normal approximately h hours after the release was initiated.

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LER 79-003 Revision 1 C=aha Public Power District Fort Calhoun Station Unit No.1 Docket No. 05000285 Attachment No. 2

Corrective Action

The event has been reviewed with the operators involved.

No indication of the incorrect valve position was i=nediately available to the control room operators. The flow appeared to be normal with no flow fault indicated on the front panel.

This conditien existed due to the opening of vacuum breakers on the radiation monitor pump and allowing ade-quate flow through the monitor.

Release procedures will be reviewed with attention to additional steps or cautions which could help prevent a reoccurrence of this type.

s A review of indicatien available vill be conducted.

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