Radiation Falls At Japan Nuke Plant, Officials Say

Nonetheless, 140,000 people near the plant have been ordered to seal themselves indoors

SOMA, Japan — Japanese data indicate that radioactivity levels fell during a six-hour period on Tuesday at a nuclear power plant damaged by last week's earthquake and tsunami, the U.N. nuclear watchdog said.

"These observations indicate that the level of radioactivity has been decreasing at the site," the International Atomic Energy Agency (IAEA) said in a statement.

The Vienna-based U.N. agency said a radiation dose level of 11.9 millisieverts (mSv) per hour was observed at the main gate of the Fukushima nuclear power plant at midnight GMT on Tuesday (8 p.m. ET Monday).

Six hours later, the rate had declined to 0.6 millisieverts, the agency said in a statement. The IAEA uses the unit to measure doses of radiation received by people. It quantifies the amount of radiation absorbed by human tissue.

Exposure to more than 100 millisieverts (mSv) a year is a level that can lead to cancer, the World Nuclear Association says. People are exposed to natural radiation of 2-3 mSv a year.

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