Mihama, Japan Plant Operator Delayed Safety Checks 

MARI YAMAGUCHI / AP 10aug04

MIHAMA, Japan - The faulty cooling pipe at the center of Japan's deadliest nuclear power plant accident had not been inspected since 1996, despite a warning last year that it was a safety threat, the plant operator said Tuesday.

The dangerously corroded pipe — which carried boiling water and superheated steam — burst at the Mihama reactor on Monday, burning to death at least four workers and injuring seven others, two of them seriously. No radiation was released, officials said.

The announcement came as dozens of police agents and nuclear energy officials arrived Tuesday at the plant in Mihama, about 200 miles west of Tokyo, to investigate operator Kansai Electric Power on suspicion of negligence resulting in death.

The accident and suspected lapses deepened concerns about the safety of Japan's 52 nuclear plants, which supply about a third of the country's electricity. Two workers died in a radioactive leak at a plant northeast of Tokyo in 1999.

It was unclear how the accident would affect the operation of Japan's other nuclear plants. The country's nuclear agency was considering a call for all plants to inspect their cooling pipes, a spokesman said.

Kansai Electric deputy plant manager Akira Kokado said private contractors conducting inspections for the company notified management in April 2003 that the cooling pipe was overdue for a thorough safety check.

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."

The national government in Tokyo — which plans to build another 11 nuclear power plants by 2010 — called for an open probe of the accident as investigators headed to the site.

"Prime Minister (Junichiro) Koizumi told me it is important that nothing be hidden from the nation," said Economy, Trade and Industry Minister Shoichi Nakagawa.

Officials, however, balanced the call for an aboveboard probe with warnings that the accident should not further dim the reputation of nuclear power in Japan.

"Nuclear power has a significant impact in our lives," Koizumi told reporters Tuesday. "We have to pay close attention so that our lives won't be affected by this accident."

Kyodo News service reported that the country's Nuclear and Industrial Safety Agency had ordered four power companies to check nuclear plant cooling systems for corrosion. The report, citing unidentified officials, said plants failing the tests would be temporarily shut down.

Agency spokesman Sachiko Muranaka, however, denied that such an order had been issued, adding that the agency's actions would depend on the outcome of the Mihama investigation.

Monday's leak was caused by a lack of cooling water in the reactor's turbine. After the accident, Kansai Electric officials found a hole in a condenser pipe. The water flowing through the pipe was about 300 Fahrenheit.

The plant's No. 3 nuclear reactor automatically shut down when steam began spewing from the leak. Its two other reactors were operating normally.

Though the burst pipe had originally been 0.4 inch thick, the pipe had eroded to as thin as .06 inch in the 28 years since the reactor was built in 1976.

An ultrasound test might have detected the thinning, but Kansai never carried out such inspections, Kokado said, adding the company may have to review the way it conducts checkups.

Kansai revamped its safety guidelines after the United States suffered a similar accident at the Surry nuclear power plant in southern Virginia in 1986. Four people died in that accident.

The Mihama accident followed a string of accidents, leaks and other safety lapses at Japanese nuclear power plants, and was clearly troubling to people in the area.

The Mihama deaths also come as Japan is bidding to host the world's first large-scale nuclear fusion plant, the $12 billion International Thermonuclear Experimental Reactor. But the project's sponsors — the European Union (news - web sites), the United States, Russia, Japan, South Korea (news - web sites) and China — remain deadlocked over whether to build the plant in Japan or France.

In Japan's 1999 accident, a radiation leak at a fuel-reprocessing plant in Tokaimura, northeast of Tokyo, killed two workers and caused the evacuation of thousands of residents. That accident was caused by two workers who tried to save time by mixing excessive amounts of uranium in buckets instead of using special mechanized tanks.

Several major power-generation companies have since been hit with alleged safety violations at their reactors, undermining public faith in nuclear energy and leaving Japan's nuclear program in limbo.