Dozens of police officers on today raided the offices of Kansai Electric at the site of Japan’s worst nuclear plant accident as part of a criminal investigation into the tragedy that killed five people last month, an official said.
The electric utility and Nihon Arm Co., an affiliated company, are under investigation on suspicion of professional negligence resulting in death and injury following the August 9 accident at the Mihama nuclear power plant, said Shuichi Nosaka, deputy head of Tsuruga city police.
No charges have yet been brought against the company.
Five people died – four almost instantly – when a corroded cooling pipe ruptured, spewing boiling water and superheated steam on workers at the plant. Six others were injured, including three seriously. No radiation leaked from the reactor.
The water flowing through the pipe was about 150 degrees Celsius (300 Fahrenheit) at the time of the accident.
About 150 police officers searched the companies’ offices, Nosaka said.
Television footage showed busloads of investigators riding into the grounds of the Mihama plant, about 200 miles west of Tokyo, in the early morning raid.
The incident has deepened concerns about the safety of Japan’s 52 nuclear reactors, which supply about a third of the country’s electricity, and about plans to build 11 more by 2010.
Two workers died in a radiation leak at a fuel reprocessing plant in north-east Tokyo in 1999.
Kansai Electric said in a statement that it was “fully co-operating” with the investigation.
“We are taking this accident very seriously,” the company said. “We will do our utmost to carry out an earnest investigation as soon as possible so an accident like this does not happen again.”
Kansai Electric, Japan’s second largest electric utility, admitted after the accident that the ruptured cooling pipe had not been inspected since 1996, despite a warning last year that it was a safety threat.
An internal probe revealed that the wall of the burst pipe had eroded to about one-tenth of its original thickness, since the reactor was built in 1976.
The utility later said an ultrasound test might have detected the thinning, but acknowledged it never carried out such inspections.