05000443/LER-1989-001, :on 890121,automatic Isolation of Control Room Ventilation Sys VI Occurred Which Resulted in Transfer of Sys from Normal Mode of Operation to Recirculation Mode. Caused by Failure of Radiation Detector

:on 890121,automatic Isolation of Control Room Ventilation Sys VI Occurred Which Resulted in Transfer of Sys from Normal Mode of Operation to Recirculation Mode. Caused by Failure of Radiation Detector

ML20235M461
Person / Time
Site:	Seabrook
Issue date:	02/21/1989
From:	Pucko T, George Thomas PUBLIC SERVICE CO. OF NEW HAMPSHIRE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-001, LER-89-1, NYN-890017, NUDOCS 8902280264
Download: ML20235M461 (3)

LER-1989-001, on 890121,automatic Isolation of Control Room Ventilation Sys VI Occurred Which Resulted in Transfer of Sys from Normal Mode of Operation to Recirculation Mode. Caused by Failure of Radiation Detector

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
4431989001R00 - NRC Website

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NAME TELEPHONE NVM6ER AREA CODE Timothy G. Pucko, Senior Engineer (extension 4428) 610l3 417l4 l-t 915l714 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRISED IN THf3 REPORT (13)

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,v--., it.,,, o.1 On January 21, 1989 at 3:41pm EST, en automatic isolation of the Control Room Ventilation (CBA) System [VI) occurred which resulted in the transfer of the system from its normal mode of operation to the recirculation mode. The cause of the event was determined to be a failure of the radiation detector, RM-RE-6506B, associated with the east air intake radiation monitor, RM-RM-6506B.

Upon determination that the CBA isolation was a spurious high signal from the east air intake radiatin nonitor, RM-RM-6506B, manual actions were taken to reset the CBA isolation signal.

The emergency cleanup filtration subsystem was left operating in recirculation with CBA-FN-16A running and with makeup air supplied from the west air intake.

At 5:08pm EST, a second automatic isolation signal was received from RM-RM-6506B., Radiation monitor RM-RM-6506B was subsequently removed from service, and the CBA isolation signal war reset.

There were no adverse consequences to safety as a result of this event. When RM-RE-6506B failed, an automatic isolation occurred and all equipment operated as designed.

The root cause of the monitor's failure can be attributed to a failure of the detector.

Bench testing of the' detector is being conducted in an attempt to isolate the exact cause of the failure. The detector assembly was replaced, and RM-RM-65065 vas returned to service the following day.

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ume mu, asso im On January 21, 1989 at 3:41pm EST, an automatic isolation of the Control Room Ventilation (CBA) System [VI) occurred which resulted in the transfer of the system from its normal mode of operation to the recirculation mode. The cause of the event was determined to be a failure of the radiation detector, PM-RE-6506B, associated with the east air intake radiation monitor, RM-RM-6506B. At Seabrook Station, CBA normally takes a suction from one of two widely separated remote air intakes (designated east and west) located on the site property at least 350 feet from the Unit 1 containment structure. The air is then drawn through piping to one of two parallel, 100% capacity, vane axial fans (FAN), FN-27A and B, and associated fan discharge dampers (DMP), DP-53A and B, which supply makeup air to the Control Room and surrounding complex. Exhaust air is removed via an exhaust fan, FN-15, and a modulating exhaust damper, DP-28.

Each remote air intake is i

provided with redundant radiation monitors, either of which is capable of initiating isolation of CBA and placing the system in a recirculation mode. When CBA transfers to the recirculation mode, normal makeup is isolated and control room ventilation air is then recirculated through an emergency cleanup filter enclosure and returned to the Control Room via a 100% redundant, two train system with each train consisting of an emergency cleanup fan, FN-16A and B, and associated damper, DP-27A and B.

Upon determination that the CBA isolation was a spurious high signal from the east air intake radiation monitor, RM-RM-6506B, manual actions were taken to reset the CBA isolation signal. The emergency cleanup filtration subsystem was left operating in recirculation with CBA-FN-16A running and with makeup air supplied from the west air intake.

At 5:08pm EST, a second isolation signal was received from RM-RM-6506B.

Radiation monitor RM-RM-6506B was then removed from service and the CBA isola-ior signal reset.

PLANT CONDITIONS

During this event the Reactor Coolant System (RCS) [AB) was at a temperature of 115 degrees fahrenheit and a pressure of 85 psig.

SAFETY CONSEQUENCES

I There were no adverse consequences to safety as a result of this event. When RM-RE-6506B failed, all equipment operated as designed; i.e., the running supply fan FN-27B tripped and discharge damper DP-53A shut, exhaust fan FN-15 tripped and its exhaust damper DP-23 shut, emergency cleanup fan FN-16A started and its associated discharge danper DP-27A opened.

COPRECTIVE ACTIONS An event evaluation team was appointed to evaluate the inadvertent actuation of the Control Room Ventilation System. The root cause of the monitor's failure can be attributed to a frilure of the detector for RM-RM-6506B.

Bench testing of the detector is being conducted in an attempt to isolate the exact cause of the failure.

The monitor detector assembly was replaced, and RM-RM-65063 was returned to service the following day. The Control Roon Ventilation System was then returned to its normal mode of operation.

I Previous isolations of the CBA system have occurred and are reported in LER 443/B6-003-00 and LER 07-001-00.

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Georg3 S. Thomas j

Vica Pradde..l Nuclear Production j

pm seny;e of New s' ;wpihire NYN-890017 New Hampshire Yankee Division February 21, 1989 i

United States Nuclear Regulatory Commission Washington, DC 20555 Reference Facility Operating License No. NPF-56, Docket No. 50-433 Attention:

Document Control Desk

Subject:

Licensee Event Report (LER) No. 89-001-00:

Control Room Ventilation System Isolation Due to Radiation Monitor Failure Gentlemen:

j Enclosed please find Licensee Event Report (LER) No. 89-001-00 for Seabrook Station.

This submittal documents an event which occurred on 4

January 21, 1989, and is being reported pursuant to 10 CFR 50.73(a)(2)(iv)

'Should you requ'ye further information regarding this matter, please contact Mr. Timothy G. Pucho at (603) 474-9574, extension 4428.

I Very truly yours,

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George S. Thomas

Enclosures:

NRC Forms 366, 366A cc Mr. William T. Russell R?gional Administrator United States Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Mr.' David G. Ruscitto NRC Senior Resident Inspector P.O.. Box 1149 Seabrook, NH 03874 INPO Records Center 1100 circle 75 Parkway

-[/M Atlanta, GA 30339 l

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P.O. Box 300. Seabrook, NH 03874. Telephone (603) 474-9574 l

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