Nuclear Radiation is being release "directly" into the atmosphere in Japan

By Fredrik Dahl

VIENNA | Tue Mar 15, 2011 2:43pm EDT

(Reuters) - Japan has told the U.N. nuclear watchdog radioactivity was being released "directly" into the atmosphere from the site of an earthquake-stricken reactor and that it had put out a fire at a spent fuel storage pond there.

The International Atomic Energy Agency (IAEA), citing information it had received from Japanese authorities at 0350 GMT, said on Tuesday dose rates of up to 400 millisievert per hour have been reported at the Fukushima power plant site.

It did not give details or comparisons on the radiation level but exposure to over 100 millisieverts a year is a level which can lead to cancer, according to the World Nuclear Association. The Vienna-based IAEA uses the unit to measure doses of radiation received by people.

"The Japanese authorities are saying that there is a possibility that the fire was caused by a hydrogen explosion," the IAEA said in a statement. It later said that the fire had been extinguished at Unit 4 of the plant.

In Japan, authorities warned radiation levels had become "significantly" higher around the nuclear power plant on Tuesday after explosions at two reactors, and the French embassy said a low-level radioactive wind could reach Tokyo within hours.

The IAEA said it had been informed "that the spent fuel storage pond at the Unit 4 reactor of the Fukushima Daiichi nuclear power plant is on fire and radioactivity is being released directly into the atmosphere."

Researchers say people get about 12 millisieverts from a standard CT (computed tomography) heart scan.

The IAEA said Japanese authorities had also informed it that there had been an explosion at the Unit 2 reactor at the Fukushima Daiichi plant, saying it occurred at around 0620 local time in Japan.