Japanese officials defend delay in revealing severity of radiation

TOKYO — Japanese officials have been forced to explain why it took them a month to disclose large-scale releases of radioactive material in mid-March at a crippled nuclear-power plant, as the government and an electric utility disagreed on the extent of continuing problems there.

The government announced Tuesday morning that it had raised its rating of the severity of the accident at the Fukushima Daiichi nuclear complex to 7, the worst on an international scale, from 5.

Officials said the reactor had released one-tenth as much radioactive material as the Chernobyl accident in 1986, but still qualified as a 7 according to a complex formula devised by the International Atomic Energy Agency (IAAE).

Japan's new assessment was based largely on computer models showing heavy emissions of radioactive iodine and cesium March 14-16, soon after a magnitude-9.0 earthquake and tsunami rendered the plant's emergency cooling system inoperative.

The nearly monthlong delay in acknowledging the extent of these emissions is a fresh example of confused data and analysis from the Japanese and put authorities on the defensive about whether they have delayed or blocked the release of information to avoid alarming the public.

Seiji Shiroya, a commissioner of Japan's Nuclear Safety Commission, an independent panel that oversees the country's nuclear industry, said the government had delayed issuing data on the extent of radiation releases because of concern that the margins of error had been large in initial computer models. But he also suggested a public-policy reason for having kept quiet.

"Some foreigners fled the country even when there appeared to be little risk," he said. "If we immediately decided to label the situation as Level 7, we could have triggered a panicked reaction."

The Japanese media, which have a reputation for passivity but have become more aggressive in response to public unhappiness about the nuclear accident, questioned government leaders through the day about what government officials knew about the accident and when they knew it.

Prime Minister Naoto Kan gave a nationally televised speech and news conference in the early evening to call for national rebuilding, but ended up defending his government's handling of information about the accident.

"What I can say for the information I obtained — of course the government is very large, so I don't have all the information — is that no information was ever suppressed or hidden after the accident," he said. "There are various ways of looking at this, and I know there are opinions saying that information could have been disclosed faster. However, as the head of the government, I never hid any information because it was inconvenient for us."

Junichi Matsumoto, a senior nuclear-power executive from the plant's operator, Tokyo Electric Power, fanned public fears about radiation when he said at a separate news conference Tuesday morning that the radiation release from Daiichi, in time, could surpass levels seen in 1986.

But Hidehiko Nishiyama, deputy director general of Japan's nuclear regulator, the Nuclear and Industrial Safety Agency, said Tuesday night that he did not know how the company had come up with its estimate. "I cannot understand their position," he said.

He speculated that Tokyo Electric was being "prudent and thinking about the worst-case scenario."

Nishiyama said his agency did not expect another big escape of radiation from Daiichi, saying "almost all" the material that is going to escape has come out. He said the rate of radiation release had peaked in the early days after the March 11 earthquake and had dropped by 90 percent since then.

The peak release in emissions of radioactive particles took place after hydrogen explosions at three Fukujima reactors, as technicians desperately tried to pump in seawater to keep the uranium fuel rods cool, and bled radioactive gas from the reactors in order to make room for the seawater.

Nishiyama took pains to say — and other nuclear experts agreed — that the Japanese accident posed fewer health risks than Chernobyl.

Meanwhile, the chairman of the U.S. Nuclear Regulatory Commission told a Senate committee Tuesday that the condition of the damaged reactors at the Fukushima plant is "static," but with improvised cooling efforts they are "not stable,"

"We don't see significant changes from day to day," said Gregory Jaczko, adding that the risk of big additional releases is smaller as each day passes.

Long-term regular cooling of the reactors has not been re-established, nor has a regular way of delivering water to the spent-fuel pools, he told the Senate Environment and Public Works Committee.

And when an aftershock cut some offshore-power supplies, he said, some pumps failed and cooling stopped for 50 minutes.

New York Times reporter Matthew L. Wald contributed to this report.