ML19325D464

LER 89-021-00:on 890920,control Room Emergency Ventilation Actuation Occurred Due to False High Radiation Signal.Cause Unknown.Wire Connections to Terminal Strip Verified to Be tight.W/891019 Ltr

ML19325D464
Person / Time
Site:	Peach Bottom
Issue date:	10/19/1989
From:	Cribbe T, Danni Smith PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CCN-89-14168, LER-89-021-01, LER-89-21-1, NUDOCS 8910240195
Download: ML19325D464 (4)

Text

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Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555

SUBJECT:

Licensee Event Report Peach Bottom Atomic Power Station - Unit 2 This LER concerns actuation of the Control Room Emergency Ventilation System.

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Reference:

Docket No. 50-277 Report Number: 2-89-021 Revision Number: 00 Event Date: 09/20/89 Report Date: 10/19/89 "

Facility: Peach Bottom Atomic Power Station RD 1. Box 208A, Delta, PA 17314 This LER is being submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(iv).

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l On September 20, 1989 at 1730, a Control Room Emergency Ventilation actuation occurred. The actuation occurred due to a momentary false high radiation signal from the Control Room Ventilation "A" radiation monitor. The actuation occurred while a technician was performing troubleshooting on the radiation monitor sample pump flow switch. A jumper was placed across the flow switch contacts. The flow switch terminal points are on the same terminal strip as terminal points for the radiation monitor check source. Although the cause is unknown, the troubleshooting activity is believed to have created an electrical disturbance resulting in the false high l radiation signal on the "A" monitor. The "B" monitor indicated only background radiation levels. No actual safety consequences occurred as a result of this event.

Attempts to recreate the disturbance did not reproduce the actuation. Wire connections to the terminal strip were verified to be tight. There were no previous similar LERs.

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Olo 012 oF gl3 nxw wa.w a. .ae nmc r -anw.mn Requirements for the Report This report is required per 10CFR50.73(a)(2)(iv) because of the actuation of the Emergency Control Room Ventilation which is an Engineered Safety Feature (ESF) system.

Unit Status at Time of Event Unit 2 was in the Run Mode at 90% power. Unit 3 was in the Refuel Mode, l 1

Description of Event j On September 20, 1989, at 1720 a technician was dispatched to the Control Room j Ventilation "A" radiation monitor (EIIS: MON) sample pump (EIIS:P) to verify I operability of the pump. Earlier that day a low flow alarm had been received in the Control Room which took several attempts to clear. Proper sample pump flow was verified and at 1730, in an attempt to simulate the low flow alarm (EIIS:FA) the technician placed a jumper across the flow switch (EIIS:FS) contacts. The normal l Control Room Ventilation isolated and the Control Rcom Emergency Ventilation System actuated due to a momentary false high radiation signal from the "A" radiation >

monitor. The low flow alarm did not actuate because the one minute time delay built i into the circuit had not elapsed. The isolation was immediately reset and normal l Control Room Ventilation restored.

l Cause of the Event The cause of the high radiation Control Room Emergency Ventilation actuation is .

unknown. The terminal points for the "A" sample pump flow switch are on the same 1 terminal strip as the "A" radiation monitor check source. Electrical leads connected )

to this terminal strip had to be moved aside to access the flow switch terminal  ;

points for jumpering. It is speculated that this activity could have created an l

electrical disturbance resulting in the false high radiation signal on the "A" l radiation monitor. I I

Analysis of the Event l l

No actual safety consequences occurred as a result of this event.

Two radiation monitors continuously sample air from the normal Control Room Ventilation supply duct. If either monitor senses a high radiation condition (>/=

400 counts per minute) the normal fresh air supply fans (EIIS: FAN) will trip and isolate and the emergency fans will start supplying fresh air to the control room l

through the emergency cleanup filters. j 1

In this event only the "A" radiation monitor indicated a high radiation condition and it was only a momentary spike above background. The "B" monitor indicated only normal background radiation levels. Therefore it is concluded that an actual high radiation condition did not exist.

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Corrective Actions The' technician returned to the electrical panel (EIIS:PL) and attempted'to recreate the event in order to determine the exact cause, however the event could not be I reproduced. Wire connections to the terminal strips were verified to be tight. l l

Previous Similar Events l No previous LERs involving inadvertent actuation of the Control Room Emergency Ventilation System during troubleshooting activities were identified.

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i NR PORM Se6A 09.3. GPCs 1908-520 S89,00010

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