Japan raises threat level to maximum at nuke plant

Japan today raised the severity level of crisis at the crippled Fukushima nuclear plant to a maximum seven, bringing it on par with the 1986 Chernobyl disaster but Premier Naoto Kan tried to reassure the people, saying the facility was stabilising "step by step".

As the nuclear crisis appeared deepening, central and easter Japan was jolted by a series of strong aftershocks, that also prompted a temporary evacuation of workers at the Fukushima plant.

The decision to raise the threat level was made after radiation of 10,000 terabequerels per hour was estimated at the stricken plant for several hours, Kyodo News Agency said.

Japan's Nuclear and Industry Safety Agency (NISA) used the International Nuclear and Radiological Event Scale, or INES, to gauge the level. The scale was designed by an international group of experts to indicate the significance of nuclear events with ratings of 0 to 7.

Japanese authorities notified the IAEA in advance of the public announcement and the formal submission of the new provisional rating.

On March 18, a week after the massive quake, the agency declared Fukushima as a level 5 incident, the same as the accident at Three Mile Island in the United States in 1979.

Until now, Level 7 has only been applied to the Chernobyl accident in the former Soviet Union in 1986 when hundreds of thousands of terabecquerels of radioactive iodine-131 were released into the air.

However, Hidehiko Nishiyama, spokesman for Japan's NISA said: "This doesn't mean people's safety is in danger."

In fact, radiation emissions from the plant, whose cooling system was hit by a massive quake and tsunami on March 11, were only a tenth of the Chernobyl accident, NISA said.

The Chernobyl accident was caused by rupture of a reactor vessel followed by a series of explosions leading to a radioactive fallout that claimed over 4,000 lives.

Prime Minister Naoto Kan too tried to reassure the people, telling them that the stricken nuclear plant is on its way to stabilisation and that the level of radioactive materials released is declining.

"Step by step, the reactors in the Fukushima Daiichi power plant are moving toward stability," Kan said in a televised press conference, asking people to get back to a normal life.

"We have caused a great deal of trouble for the world. We must thoroughly explain our experience. We must make efforts to increase the safety of nuclear reactors," Kan said.

He said if trouble is found, there might be cases where reactors may be stopped. However, he added immediately that "at this point, we have no plan to stop operating reactors".

Parts of Japan were again rattled by strong aftershocks today with three powerful earthquakes of magnitude of 6.3, 6.4 and 5.6 shaking central and northeastern parts of the country.

No tsunami warning was issued following the quakes and there were no immediate reports of any damage or injuries.