Japan's quake-prone atomic plant prompts wider worry

by Martin Fackler

TOKYO, July 24 - After a deadly earthquake struck northwestern Japan last week, the nation was stunned by widespread damage to a nuclear power plant near the quake's center, including minor radiation leaks, ruptured pipes, flooding and a fire that belched black smoke for more than an hour on live television.

But perhaps the most startling discovery occurred in the days that followed, when scientists used data from the magnitude 6.8 earthquake on July 16 to conclude that the Kashiwazaki-Kariwa plant, the world's largest by electrical output, may have unknowingly been built directly on top of an active seismic fault.

That could account for the force of the tremors, which Tokyo Electric Power, the operator of the plant, said were more than twice as strong as the plant's design limits.

The earthquake, which killed 11 people and destroyed hundreds of homes in Kashiwazaki, a city nearby, has raised discomforting questions about the safety of nuclear plants in Japan.

The plants in this earthquake-prone nation are supposed to be nearly earthquake-proof, built to withstand the most powerful punch. The Kashiwazaki plant's surprising vulnerability to damage, however, has distressed many Japanese.

The damage at the plant appeared to offer a vivid reminder of the risks of nuclear power, as the United States, Europe and countries elsewhere are giving atomic energy a second look as a clean, plentiful alternative to oil and other fossil fuels. Resource-poor Japan kept building nuclear plants even after accidents like Three Mile Island in 1979 in the United States and Chernobyl in 1986 in Ukraine froze construction in the United States and parts of Europe for decades.

Nuclear experts applaud the fact that all four of the Kashiwazaki plant's seven reactors that were operating when the earthquake struck were safely shut down, despite the unexpected strength of the tremors.

But Tokyo Electric's failure to predict the size of the tremors that could strike the area, and to detect the fault line beneath the plant, left many here wondering whether regulators and plant operators could also have underestimated the potential for devastating earthquakes at Japan's 48 other nuclear reactors.

"The plant did an excellent job of ensuring the safety of the reactors themselves," said Michio Ishikawa, president of the Japan Nuclear Technology Institute, a research group sponsored by the industry. "But how could they have not known about the active fault line?"

On Tuesday, the Ministry of Economy, Trade and Industry, which oversees energy policy, said it would create an independent panel of academic experts to investigate the damage at the Kashiwazaki plant in Niigata Prefecture. The panel's findings will be presented to the International Atomic Energy Agency, a United Nations group that will send its own inspectors to the plant, the ministry said.

The discovery of the fault line has attracted intense news media attention in Japan, partly because it echoes problems at nuclear plants elsewhere in Japan. Lawsuits have sought the closure of at least four other plants because of nearby fault lines. The plants include one in Shika, a town in western Japan, where a large fault was discovered in 2005, just before the plant was completed.

The earthquake last week also defied expectations by moving differently from previous quakes in the region, Tokyo Electric said. The Kashiwazaki plant was designed to withstand shorter, more intense tremors. But the recent quake struck with a broad, wrenching horizontal swaying that caused water to slosh out of storage pools.

About 317 gallons of this spilled water, contaminated by tiny amounts of radioactive material, reached the nearby Sea of Japan. Tokyo Electric said the levels of radioactivity in that spill and a separate leak of contaminated exhaust were far too low to harm the environment.

It also said damage at the plant had only occurred in less critical areas, which had been built to less stringent standards than the reactors, which were housed in bunkerlike concrete buildings.

Tokyo Electric admitted that it had failed to find the fault where the earthquake occurred. The company said the fault line did not show up in surveys of the area made in the late 1970s, when it started building the plant.

But the company says the plant is still safe because the fault line appears to lie more than 12 miles beneath the plant, too deep to cause the sorts of big cracks and other surface movement that could damage the reactors' thick concrete buildings.

"Not finding the fault was a miss on our part," said Toshiaki Sakai, who leads the engineering group in charge of Tokyo Electric nuclear plants. "But it was not a fatal miss by any means."

Still, critics say the fact that the miss could happen at all points to a bigger problem: the broad discretion that the government gives power companies in deciding whether a site is safe.

Katsuhiko Ishibashi, a professor at Kobe University specializing in earthquakes and urban safety, was a member of a committee that set new earthquake safety guidelines for Japan's nuclear reactors last year. He said some of the committee's 20 members were scholars and engineers with close ties to power companies, including one who advised those companies.

The New York Times