Second Hydrogen Explosion Rocks Japan Nuke Plant

TOKYO (The Blaze/AP) -- Japan's chief cabinet secretary says a hydrogen explosion has occurred at Unit 3 of Japan's stricken Fukushima Dai-ichi nuclear plant. The blast was similar to an earlier one at a different unit of the facility.

Yukio Edano says people within a 12-mile (20-kilometer) radius were ordered inside following Monday's. AP journalists felt the explosion 30 miles (50 kilometers) away.

Edano says the reactor's inner containment vessel holding nuclear rods is intact, allaying some fears of the risk to the environment and public.

The No. 3 Unit reactor had been under emergency watch for a possible explosion as pressure built up there following a hydrogen blast Saturday in the facility's Unit 1.

More than 180,000 people have evacuated the area.

TOKYO (AP) — The operator of a Japanese nuclear power plant where a reactor's containment building exploded says radiation levels at the unit are within legal limits.

Tokyo Electric Power Co. says radiation levels at Unit 3 of the stricken Fukushima Dai-Ichi plant were 10.65 microsieverts Monday, significantly under the 500 microsieverts at which a nuclear operator is legally bound to file a report to the government.

There was a hydrogen explosion at the unit earlier in the day.

Officials have been racing to stave off multiple reactor meltdowns after a devastating quake and tsunami incapacitated the Fukushima plant.

More than 180,000 people have evacuated the area, and up to 160 may have been exposed to radiation.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

SOMA, Japan (AP) — The second hydrogen explosion in three days rocked Japan's stricken Fukushima Dai-ichi nuclear plant Monday, sending a massive column of smoke into the air and wounding six workers. It was not immediately clear how much — if any — radiation had been released.

The explosion at the plant's Unit 3, which authorities have been frantically trying to cool following a system failure in the wake of a massive earthquake and tsunami, triggered an order for hundreds of people to stay indoors, said Chief Cabinet Secretary Yukio Edano.

The blast follows a similar explosion Saturday that took place at the plant's Unit 1, which injured four workers and caused mass-evacuations.

Japan's nuclear safety agency said six workers were injured in Monday's explosion but it was not immediately clear how, or whether they were exposed to radiation. They were all conscious, said the agency's Ryohei Shomi.

Earlier, Tokyo Electric Power Co., which operates the reactor, said three workers were injured and seven missing.

The reactor's inner containment vessel holding nuclear rods was intact, Edano said, allaying some fears of the risk to the environment and public. TV footage of the building housing the reactor appeared to show similar damage to Monday's blast, with outer walls shorn off, leaving only a skeletal frame.

More than 180,000 people have evacuated the area in recent days, and up to 160 may have been exposed to radiation.

Earlier Monday, pressure had jumped inside Unit 3, forcing the evacuation of 21 workers. But they returned to work after levels appeared to ease.

Associated Press journalists felt the explosion in the tsunami-devastated port town of Soma, some 25 miles (40 kilometers) north of the reactor. They reported feeling the faint rumble a blast and the ground shaking.

At the time, sirens were wailing as rescue workers were in the midst of evacuating all those in the city to high ground due to a tsunami warning. That turned out to be a false alarm.

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Associated Press writers Shino Yuasa, Tomoko Hosaka, Elaine Kurtenbach and Joji Sakurai in Tokyo contributed to this report.