Nuclear plant accident kills four

MIHAMA, Japan – Japan suffered its deadliest nuclear power plant accident Monday when a bursting steam pipe killed at least four workers and injured seven in another blow to the industry in an energy-poor country already worried about nuclear plant safety.

No radiation was released when the boiling water and steam exploded from a cooling pipe at the plant in Mihama, a small city about 200 miles west of Tokyo.

But the steam leak followed a string of safety lapses and cover-ups at reactors, and Prime Minister Junichiro Koizumi vowed to launch a thorough investigation into the accident. Fears about the safety of the country’s 52 nuclear power plants soared in 1999, when a radiation leak northeast of Tokyo killed two workers and exposed hundreds to radiation.

Monday’s leak was caused by a lack of cooling water in the reactor’s turbine and perhaps by significant metal erosion in the condenser pipe, said the plant’s operator, Kansai Electric Power. The pipe’s wall, originally 10 mm thick, had become as thin as 1.5 mm in the 28 years since the reactor was constructed.

On Tuesday, Fukui prefectural police spokesman Fuminaga Miyamoto said Japanese police were investigating the operator of the plant on suspicion of negligence.

Deputy plant manager Akira Kokado said private contractors conducting inspections for the company notified management in April 2003 that the cooling pipes were overdue for a safety check, but the pipe was not later examined.

Sections of the pipe were last checked in 1996 and deemed safe at that time, said Koji Ebisuzaki, Kansai Electric’s chief manager for quality control. Last November, the plant scheduled an ultrasound inspection of the pipe for Aug. 14 — next Saturday.

“We thought we could delay the checks until this month,” Kokado told a news conference. “We had never expected such rapid corrosion.”

After the accident, Kansai Electric officials found a hole in the pipe that was believed to be the source of the leak. They did not say how big the hole was.

The water flowing through the pipe at the time of the accident was about 300 degrees Fahrenheit, Kokado said Monday.

Four workers died after suffering severe burns. Of the seven injured workers, two were in critical condition, three were in serious condition and the remaining two suffered minor injuries.

Japanese newspapers reported the government might be forced to shelve plans to build 11 new plants.

All the workers were employees of Kiuchi Keisoku Co., an Osaka-based subcontractor of Kansai Electric. They were all inside the turbine building to prepare for regular inspections of the plant, which began operating in 1976.

Government officials said there was no need to evacuate the area surrounding Mihama, a city of 11,500.