March 12, 2011 UPDATE 2, 9:30 EST:
The Tokyo Electric Power Company says it has successfully vented the
containment of unit 1 at the Fukushima-Daiichi nuclear power plant in
northern Japan, according to several industry sources.
Japan’s chief cabinet secretary Yukio Edano, told a news conference that
there was an explosion at Fukushima-Daiichi at 15:36 local time, but he
said it has not affected the reactor’s primary system or its containment,
the news service NucNet reported this morning.
Edano said there was hydrogen explosion in the space between the concrete
containment and the reactor’s primary system, but the explosion did not
damage the containment function or the reactor system, the report said. A
portion of the fuel in the reactor was uncovered and TEPCO is using borated
seawater to cover the fuel. Radiation measurements at the site boundary of
Fukushima Daiichi were measured at 11 millrem per hour, but were reduced to
7 millirem per hour a few hours after the explosion.
TEPCO also is preparing to vent the containment structures at Fukushima
Daiichi 2 and 3, as of Saturday morning.
Edano said, "We've confirmed that the reactor container was not damaged.
The explosion didn't occur inside the reactor container. As such there was
no large amount of radiation leakage outside.,"
The Japanese government expanded the evacuation zone around the facility to
20 kilometers, or about 12 miles.
Backup diesel generators and backup batteries have arrived at the Fukushima
U.S. support to Japan for the nuclear plant events and earthquake includes
assistance from the industry and Nuclear Regulatory Commission.
TEPCO also is working to maintain safe condition of Fukushima Daini units
1, 2 and 3, which have lost reactor pressure suppression function.