The operator of the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture, central Japan, has resumed loading nuclear fuel into one of its reactors for tests to put it back online.
Tokyo Electric Power Company began putting fuel into the No.7 reactor on Monday, but work was suspended Wednesday morning when a circuit breaker tripped in a device to operate the reactor's control rods.
Workers detected no trace of a current surge, and could not pinpoint the cause of the breaker trip. They found no abnormalities with the device itself.
They resumed loading fuel before midnight after replacing the breaker as a precaution.
TEPCO says there were no safety problems and no impact on the environment outside the plant.
The company also says that it expects no major delay in its plan to put 872 fuel rod assemblies into the No.7 reactor over a period of about two weeks.
The utility says it will stop and respond to any irregularity if necessary.