ML19209D080

LER 79-019/03L-0:on 790910,reactor Bldg Vent Monitor Failed Downscale.Caused by Two Blown Fuses in Monitor Circuitry & Two Failed Capacitors in Monitor Power Supply.New Capacitors Installed & Fuses Replaced

ML19209D080
Person / Time
Site:	Quad Cities
Issue date:	10/09/1979
From:	Hannum D COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19209D077	List: ML19209D076 ML19209D080
References
LER-79-019-03L-03, LER-79-19-3L-3, NUDOCS 7910190371
Download: ML19209D080 (2)

Text

NRC F ORM 366 U. S. NUCL E AR REC.UL ATORY COMMISSION (7-77) '

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7 60 61 DOCKET NUMBER 69 EVENT DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l While the Unit operator was routinely checking the Unit 2 Control Room panels, the 2A l o 3 l Reactor Building vent monitor was found to be failed downscale. The 2B mon tor was l o 4 l operating properly and was functionally checked. The 2A monitor failed in the safe l p , 7 icondition, since either an upscale or downscale trip of the 2B monitor would have l

o e initiated SBGTS and isolated the Reactor Building vent system.

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42 lN 43 l@ 44 Gl0l8lOl@ 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h li l O l lTwo blown fuses were found in the 2A monitor ci rcuitry, and the power supply for the l 3 , monitor had two failed capacitor.;. New capacitors were installed in the power supply, I g yand the fuses were replaced. The monitor was functionally tested within the Tech SOcc l

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1. LER NUMBER: LER/R0 79-19/03L

11. LICENSEE NAME: Commonwealth Edison Company, quad-Cities Nuclear Power Station Ill. FACILITY NAME: Unit Two IV. DOCKET NUMBER: 050-265 V. EVENT DESCRIPTION: On September 10, 1979 at 12: 30 a.m., while the Unit operator was routinely checking the Unit Two Control Room panel boards, the 2A Reactor Building ventilation monitor was found to be failed downscale. The 2B monitor was functionally tested to be operating properly. Unit Two was in the RUN mode, operating at a core thermal power of 1650 MWt and an electrical load of 485 MWe.

VI. PROBABLE CONSEQUENCES OF THE OCCURRENCE: Even though the Channel A Reactor Building ventilation monitor had failed, the 2B Reactor Building ventilation monitor located in the exhaust duct remained operable. The control logic of these units is such that one upscale trip or two down-scale trips will initiate the Standby Gas Treatment System and isolate the Reactor Building ventilation system. Since the 2A Reactor Building ventilation monitor failed in the downscale position, it failed in a safe direction; thus, either an upscale or downscale trip of the 2B monitor would have initiated the required protective function.

Vll. CAUSE: Two blown fuses were found in the 2A monitor circuitry. Also, two capaci tors in the 2A moni tor power supply had f ailed. The power supply is manufactured by General Electric Company, model number Gl.

Vill. CORRECTIVE ACTION: Work request Q00895 was written to repair the power supply. Two new capacitors were installed in the 2A monitor power s pply, the blown fuses were replaced, and the monitor was then found to operate satisfactorily. The 2A monitor was returned to service and functionally tested within the 24-hour limitation specified in Technical Specification 3.2.E.2.

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