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INVERTER
FUSE FAILURE
"At 1835 on 5/24/08 CD482 inverter main power fuse failed. This
inverter powers various vital ECCS channel 'C' analog instrumentation
(including 'C' channel EDG start circuitry). The inverter transferred to
the alternate AC power supply as designed with no abnormal plant
response or transient. The main power fuse was replaced and attempts
were made to place the inverter section back in service and return the
inverter to the normal power supply. Logic card checks were performed as
part of the normal restoration process prior to transferring to the
inverter normal output. These checks could not be completed
satisfactorily and indicate that there is an abnormal condition in the
inverter section. The inverter, while on alternate AC, is not operable
per technical specifications [TS] due to the loss of alternate AC on a
LOOP/LOCA, which would prevent the 'C' EDG from starting. Additional
safety related equipment that is unavailable include the 'D' Station
Service Water Pump for a scheduled maintenance window. All other safety
equipment is operable and functioned as required. No personnel were
injured. Unit shutdown commenced at 0930 on 5/25/08 in accordance with
TS 3.8.3.1. The unit is required to be in hot shutdown by 1435. This
four-hour report is bring made in accordance with 10 CFR 50.72(b)(2)(
i)."
The licensee notified the NRC Resident Inspector. The licensee will
notify a local government agency.
* * * UPDATE FROM TOM FOWLER TO JOE O'HARA AT 1415 ON 5/25/08 * * *
The inverter logic power supply has been replaced, and the inverter has
been tested satisfactorily. The inverter has been declared operable, and
the licensee exited the technical specification required shutdown at
1217. Power ascension is in progress.
The licensee informed the NRC Resident Inspector, and the Lower Alloways
Creek Township.
Notified R1DO(Gray)
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