In the wake of problems with restarted reactors, concerns have grown that nuclear authorities and power suppliers have been too hasty in putting the idled units back into operation.
On Tuesday, Kansai Electric Power Co. said the emergency shutdown of its reactor in Fukui Prefecture the previous day — three days after it went back online — may have been triggered by an abnormally strong electrical current.
The utility said a monitoring device at the Takahama facility had detected an abnormality, and workers were checking its settings as other monitoring devices were not triggered.
The trouble followed a leak of some 34 liters of radioactive water from a cooling system for the reactor on Feb. 20. The operator found that a valve bolt had come loose.
“It’s very regrettable,” industry minister Motoo Hayashi told a news conference Tuesday. “I hope Kansai Electric will do its best to find out what caused the problems and proceed carefully without rushing the (restart) schedule.”
The reactor is the third brought back online under the new safety standards adopted after the crisis at the Fukushima No. 1 plant.
Reactors 1 and 2 at the Sendai plant operated by Kyushu Electric Power Co. in Kagoshima Prefecture were reactivated last year.
The Sendai reactor 1 had a problem with equipment that caused a seawater leak from a cooling system before shifting to commercial operation mode.
Experts say reactors are prone to problems after being idled for years.
The Takahama unit had been left offline for four years and seven months and the Sendai reactor four years and three months.
“Kansai Electric was so hasty in resuming nuclear power generation that it skipped thorough inspections of the reactor before its restart,” Hideyuki Ban, co-head of the Citizens’ Nuclear Information Center, said of the problems at the Takahama reactor.
He also blamed the Nuclear Regulation Authority, which assesses applications to restart idled reactors based on the new safety standards, for failing to look closely at facilities and equipment in the screening process.
Ban alleged that the NRA has put a priority on examining the safety of reactors 6 and 7 at Tokyo Electric Power Co.’s Kashiwazaki-Kariwa plant in Niigata Prefecture toward their restart even though electric cables for safety-related equipment were installed in a substandard fasion.
“Overhauling all facilities at nuclear power plants is absolutely necessary,” he stressed.