ML19318A148

LER 80-030/03L-0:on 800517,containment Gaseous & Particulate Monitors Failed Due to Ground in Instrument Control Power. Caused by Water in Plant Page Unit.Monitor Pumps Bridged to Keep Pumps Running While Trouble Shooting Continued

ML19318A148
Person / Time
Site:	Calvert Cliffs
Issue date:	06/13/1980
From:	Bauer E, Davis S BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19318A147	List: ML19318A146 ML19318A148
References
LER-80-030-03L, LER-80-30-3L, NUDOCS 8006180518
Download: ML19318A148 (1)

Text

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EVENT DESCRIPTION AND pro 8ABLE CONSEcuENCES h I

IOl2l lAt 1700 the containment caseous and carticulate monitors failed due to a amund i

10131 lin the instrument control oower (T.S. 3.4.6.1) . The containment caseous and 10 l A l lparticulate monitors were deenercized and returned to service at 2145. The i I O I s I lcontainment sumo level alam system remained operable durino the event. LER 1 I O is l 179-29 (U-2) describes a similar event.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS @

li lO l l Investigation revealed a cround on C0 of instrument bus 2Y10 due to water j_n a I

l i li i l niant oace unit. This around was instrumental in causino a ralfunctinn of the Due to the above i, 121Icontainment caseous monitor and was it:Tnediately isolated.

l i ; 3 l l i.ialfunction the starter contacts of the monitor oumos where bridaed in order to

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iiiAi i keeo the pumps running while trouble shootino continued.

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! LER 740. 80-30/3L DOCKET NO. 50-318 EVENT DATE 05/17/80 L.

REPORT DATE 06/13/80 ATTACHt'ENT CAUSE DESCRIPTION AND CORRECTIVE ACTIONS: (Continued)

Further investigation also indicated a ground at the U-2 radiation monitor system iC22F. This ground has been isolated but the 'F' pnl. internal wiring is still under investigation. It is surmised that when the page unit caused

! C phase of 2Y10 to go to ground and coupled with an existing neutral ground at ,

IC22F, the 10A neutral fuse at IC22F had blown, 208 volts was impressed across various components of the monitor system. Upon replacing various damaged components and isolation of the grounds, the system was returned to operation.

- Investigation is being conducted into replacing the neutral and hot phase

' fuses with switches that would interrupt the hot chases and the neutral in case of i neutral ground fault. There is no readily available system for detecting a neutral to ground c'onottion on the instrument AC busses.

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