ML20042E174

LER 90-011-00:on 900306,actuation of Control Room Emergency Air Cleanup & Filtration Subsystem Occurred.Caused by Failure of Geiger-Muller Tube.Monitor Removed from Svc & Tube replaced.W/900405 Ltr

ML20042E174
Person / Time
Site:	Seabrook
Issue date:	04/05/1990
From:	Belanger R, Feigenbaum T PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-011, LER-90-11, NYN-90088, NUDOCS 9004200341
Download: ML20042E174 (4)

Text

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pe* Hbmpshire 1ed C. L. ,

Senior % President and Chief Operating Officer NYN- 90088 April 5, 1990 United States Nuclear Regulatory Commission Washington, DC 20555 Attention: Document Control Desk <

Ref ere: ice s (a) Facility Operating License NPF 67. Docket No. 50-443 (b) Facility Operating License NPF-86. Docket No. 50-443

Subject:

Licensee Event Report (LER) No. 90 011-00s- Actuation of

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Control Room Emergency Air Cleanup and Filtration Subsystem-due to Failed Radiation Monitor Gentlemen Enclosed please find Licensee Event Report (LER) No.-90-011-00 for Seabrook Station. This submittal documents an event which occurred on March 6. 1990, and is being reported pursuant to 10CFR.40.73(a)(2)(iv).

Sbould you require further information regarding this matter, please contact Mr. Richard R. Belanger at (603) 474-9521 extension 4048.

f Very truly yours.

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• Ted C. Feigenba

Enclosures:

NRC Forms 366. 366A 90042[ [.[ h,k 43 PDR S

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New Hampshire Yankee Division of Public Service Company of New Hompshire P.0, Box 300

• Seabrook, NH 03874

• Telephone (603) 474 9521 D

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United States Nuclear Regulatory Commission- April 5, 1990

-Attention Document Control Desk Page.two

-cca Mr. Thomas T. Martin Regional Administrator United States Nuclear Regulatory Commission

. Region I 475 Allendale Road King of Prussia, PA 19406 Mr.1 Victor Nerses, Project Manager Project Directorate I-3 United States Nuclear Regulatory Commission Division of Reactor Projects Washington, DC 20555 Mr. Noel Dudley NRC Senior Resident Inspector P.O. Box 1149 Seabrook.-NH 03874 INPO Records. Center 1100 circle 75 Parkway Atlanta, GA 30339 l'

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T} wo i  ; 1 A ni n Act m , ,. e m <., , . . . ,,, ,..i . .y. <. -,n.. o n e, On March 6.1990, at 3:14 p.m. a Control Room Emergency Air Cleanup and Filtration Subsystem (CBA) automatic recirculation signal va9 received after

, an east air intake radiation monitor. RM-6506B spiked into a high alarm condition.

The root cause of this event has been determined to be a is,ilure of the Geiger-Huller (GM) tube. This resulted in a spike which caused the monitor to enter a high alarm condL lon, which in turn caused the transfer of CBA to its recirculation /filtrati mode.

The monitor was removed from service and the GM tube was replaced. The monitor has been operating, without further problems. A long term corrective action which is presently being evaluated is introducing redundant CBA actuation logic. Also being evaluated is moving the east air intake monitors into the Diesel Generator Building where the west air intake monitors, which have a history of more reliable performance, are located.

There were no adverse safety consequences as a result of this event. All equipment other than the monitor functioned as designed, fulfilling the Engineered Safety Features (ESP) function.

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Ol 0 Ol2 0F 012 text n -. nao an.w nn On March 6, 1990, at 3:14 p.m. EST. the train B east air intake radiation monitor, RM-6506B. spiked into a high alarm condition. This condition initiated the Control Room Emergency Air Cleanup and Filtration Subsystem (CBA) [VI) and the subsequent transfer of the system to its recirculation /

filtration mode.

ROOT CAUSE Upon investigation, it was determined that the Geiger-Muller (GM) tube had failed. This caused a spike, which caused the monitor to enter a high alarm condition and subsequent CBA actuation.

CORRECTIVE ACTION RM-6506B was removed from service and the GM tube was replaced. The monitor has been operating without further problems since that time.

Due to the number of events that have occurred involving this system, long term corrective actions are being evaluated. New Hampshire Yankee is evaluating a Design Coordination Report (DCR) to relocate the east air intake monitors to the Diesel Generator Building. This will allow the monitors to experience warmer process air conditions. Presently these monitors are located close to the air inlet while their counterpart west air intake monitors are located in the Diesel Generator Building over 400 feet away from i the inlet. This would place the east intake monitors in approximately the sw.e conditions as the west air intake radiation monitors which have a history of more reliable performance.

Currently, CBA is actuated by any one signal from either the train A or B.  !

east or wast air intake radiation monitor. This is one of one actuation logic. A redundant actuation logic or other appropriate modifications for the air intake radiation monitors are being evaluated. The intent of modifications being considered will be to reduce spurious initiations of CBA vhile assuring continued reliability of the system. (

SAFETY CONSEOUENCES There were no adverse safety consequences as a result of this event. All equipment other than the monitor functioned as designed, fulfilling the Engineered Safety Features (ESP) function. The failure of the monitor in this manner does not impair the ESF function of the Control Room Emergency Air Cleanup and Filtration Subsystem, and automatically places the CBA system in the configuration required by Seabrook Station Technical Specification 3.3.3.1.

PREVIOUS OCCURRENCES Previous occurrences of Engineered Safety Features (ESP) actuatione involving failed radiation monitors were reported via Seabrook Station LERs 90-010-00, 90-007-00, 90-006-01,90-005 00, 89-003-00, 89-001-00 and 87-001 00.

At the time of this event. Seabrook station was in MODE 3. Hot Standby. with a Reactor Coolant System temperature of 557' and pressure of 2,235 psi,

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