Power went out for one minute Wednesday at reactor 3 of Kansai Electric Power Co.'s Oi nuclear plant in Fukui Prefecture but the outage did not affect the unit's operation or cause a negative impact outside the facility, Kepco said.
The utility said it believes part of the internal power supply at the reactor building was cut off at around 2:30 p.m. as a trainee mistakenly tripped the circuit breaker. The Oi plant's reactors 3 and 4 are the only ones currently in operation amid the nationwide shutdown stemming from the triple-meltdown crisis at Tokyo Electric Power Co.'s Fukushima No. 1 plant that started in 2011.
Kansai Electric reported the power failure to the central government and local municipalities. The Nuclear Regulation Authority later conducted an on-site inspection and confirmed that the power cut had no adverse effects outside the plant.
The NRA said the electricity supply for measuring gauges was disrupted and the water level in reactor 3 rose as valves in some pipes were automatically closed.
Oi Mayor Shinobu Tokioka urged Kepco in a statement to take the incident seriously and ensure the safety of local residents.
The two reactors at the four-reactor Oi plant were restarted last July after all of the country's reactors went offline amid strong public concerns over the safety of nuclear power due to the Fukushima catastrophe.