The blown fuse that caused Davis-Besse's emergency shutdown Wednesday morning apparently is not a symptom of larger equipment problems at the nuclear plant.
Both FirstEnergy Corp. and the Nuclear Regulatory Commission agreed yesterday that the fuse in question blew because it was simply worn out.
The utility is doing additional maintenance over the weekend and gearing up for a Monday restart. It hopes to have the nuclear plant back online Tuesday, a company spokesman said.
FirstEnergy and the federal regulator came to the same conclusion after completing a follow-up analysis of the plant's four reactor trip circuit breakers. The devices are grouped into two parallel sets and are part of a safety system that automatically shuts down the reactor when computers sensed a problem.
Workers weren't aware that one of those two sets was holding a blown fuse when they performed a routine test on breakers Wednesday morning, something that's done once every three weeks. The reactor automati
cally shut down when the only fully operable set of breakers was opened for the test, Jan Strasma, a NRC spokesman, said.
The NRC isn't classifying what happened as a procedural error. But it has told the utility to amend its procedure for future tests by waiting to do tests on either set of breakers until it knows all fuses are operable on the opposite set, he said.
"As a result of this happening, they will improve their procedure," Mr. Strasma said.
The agency has placed "no restraints" on FirstEnergy's restart schedule, he said.
The utility said it also plans to recalibrate or fix a safety valve between the steam generator and turbine before restart. The valve opened early as the reactor was being shut down, but posed no safety threat.
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