200,000 evacuated as N-crisis escalates

TOKYO — Japanese officials struggled on Sunday to contain a widening nuclear crisis in the aftermath of a devastating earthquake and tsunami, saying they presumed that partial meltdowns had occurred at two crippled reactors and that they were facing serious cooling problems at three more.

The emergency appeared to be the worst involving a nuclear plant since the Chernobyl disaster 25 years ago. The developments at two separate nuclear plants prompted the evacuation of more than 200,000 people.

Japanese officials said they had also ordered up the largest mobilization of their Self-Defense Forces since World War II to assist in the relief effort.

On Saturday, Japanese officials took the extraordinary step of flooding the crippled No. 1 reactor at Fukushima Daiichi Nuclear Power Station, 170 miles north of Tokyo, with seawater in a last-ditch effort to avoid a nuclear meltdown.

Then on Sunday, cooling failed at a second reactor — No. 3 — and core melting was presumed at both, said the top government spokesman, Chief Cabinet Secretary Yukio Edano.

Cooling had failed at three reactors at a nuclear complex nearby, Fukushima Daini, although Edano said conditions there were considered less dire for now.

With high pressure inside the reactors at Daiichi hampering efforts to pump in cooling water, plant operators had to release radioactive vapor into the atmosphere. Radiation levels outside the plant, which had retreated overnight, shot up to over twice Japan's legal limit, Edano said.

NHK, Japan's public broadcaster, flashed instructions to evacuees: close doors and windows; place a wet towel over the nose and mouth; cover up as much as possible. At a news conference, Edano called for calm.

"If measures can be taken, we will be able to ensure the safety of the reactor," he said.

One result of the venting may have been to set off an explosion, caused by either steam or hydrogen, that tore the outer wall and roof off the building housing reactor No. 1, although the steel containment of the reactor remained in place, officials said.

Edano warned Sunday that a hydrogen explosion also could occur at reactor No. 3.

Even before his statements, it was clear from radioactive materials turning up in trace amounts outside the reactors that fuel damage had occurred.

The existence or extent of melting might not be clear until workers can open up the reactors and examine the fuel, which could be months.

A meltdown occurs when there is insufficient cooling of the reactor core, and it is the most dangerous kind of a nuclear-power accident because of the risk of radiation releases.

The radiation levels reported so far by the Japanese authorities are far above normal but still too small to pose a hazard to human health if the exposure continued for a brief period. The fear was that more core damage would bring bigger releases.

The Japanese Nuclear and Industrial Safety Agency said that as many as 160 people may have been exposed to radiation around the plant, and Japanese news media said that three workers at the facility were suffering from full-on radiation sickness.

Even before the explosion on Saturday, officials said they had detected radioactive cesium, which is created when uranium fuel is split, an indication that some of the nuclear fuel in the reactor was already damaged.

Officials told the International Atomic Energy Agency (IAEA) that they were making preparations to distribute iodine, which helps protect the thyroid gland from radiation exposure, to people living near Daiichi and Daini.

Worries about the safety of the two plants worsened on Saturday as executives of the company that runs them, Tokyo Electric Power, and government officials gave confusing accounts of the location and causes of the dramatic midday explosion and the damage it caused.

Late Saturday night, officials said that the explosion at Daiichi occurred in a structure housing turbines near its No. 1 reactor at the plant, rather than inside the reactor itself. But photographs of the damage did not make clear that this was the case.

They said that the blast, which may have been caused by a sharp buildup of hydrogen when the reactor's cooling system failed, destroyed the concrete structure surrounding the reactor but did not collapse the critical steel container inside. This pattern of damage cast doubt on the idea that the explosion was in the turbine building.

After a full day of worries about the radiation leaking at Daiichi, Tokyo Electric Power said an explosion occurred "near" the No. 1 reactor at Daiichi around 3:40 p.m. Japan time on Saturday. It said four of its workers were injured in the blast.

The decision to flood the reactor core with corrosive seawater, experts said, was an indication that Tokyo Electric Power and Japanese authorities had probably decided to scrap the plant.

"This plant is almost 40 years old, and now it's over for that place," said Olli Heinonen, the former chief inspector for the IAEA.

Both Daiichi and Daini were shut down by Friday's earthquake, but the loss of power in the area and damage to the plants' generators from the ensuing tsunami crippled the cooling systems. Those are crucial after a shutdown to cool down the nuclear-fuel rods.

The emergency at Daiichi began shortly after the earthquake Friday afternoon. Emergency diesel generators, which kicked in to run the cooling system after the electrical-power grid failed, shut down about an hour later. There was speculation the tsunami had flooded the generators, knocking them out.

With no substantial coal or oil, Japan relies on nuclear power for just over one-third of its electricity.

Material from The Associated Press is included in this report.