Hydrogen blast occurs at Fukushima plant's No. 3 reactor: agency

TOKYO, March 14, Kyodo

A hydrogen explosion occurred Monday morning at the quake-hit Fukushima No. 1 nuclear power plant's troubled No. 3 reactor, the government's nuclear safety agency said, urging about 600 residents in a 20-kilometer radius to stay indoors.

Chief Cabinet Secretary Yukio Edano said the plant operator Tokyo Electric Power Co. confirmed that the 11:01 a.m. blast did not damage the container of the No. 3 reactor, allaying concerns that the explosion may have caused a massive release of radioactive substance.

TEPCO said three workers, including its employees, were injured by the blast. All of them suffered bruises.

''According to the plant chief's assessment, the container's health has been maintained,'' Edano told a press conference. ''The possibility is low that massive radioactive materials have spattered.''

Edano said the blast that blew away the roof and the walls of the building housing the container was similar to an explosion Saturday at the No. 1 reactor of the same plant, following Friday's magnitude 9.0 quake.

It had been widely expected that the No. 3 reactor would follow the same path.

The top government spokesman said operations to pour seawater into the reactor to cool it down were continuing and the level of pressure in the container was stable.

The Nuclear and Industrial Safety Agency said wind was not blowing in the area. The radiation level had not significantly risen, it added.

The Tokyo metropolitan government is also examining radiation levels in the metropolis.

The Fukushima No. 1 nuclear plant has been shut down since the quake and some of its reactors have lost their cooling functions, leading to brief rises in the radiation level over the weekend. As a result, cores at the No. 1 and No. 3 reactors have been partially melting.

Earlier in the day, TEPCO reported to the government that the radiation level at the plant had again exceeded the legal limit and pressure in the container of the No. 3 reactor had briefly increased.

On Monday, radiation at the plant's premises rose over the benchmark limit of 500 micro sievert per hour at two locations, measuring 751 micro sievert at the first location at 2:20 a.m. and 650 at the second at 2:40 a.m., according to the report.

The hourly amounts are more than half the 1,000 micro sievert to which people are usually exposed in one year.

The maximum level detected so far around the plant is 1,557.5 micro sievert logged Sunday.

The utility had been pouring seawater into the plant's No. 1 and No. 3 reactors to help cool their cores, which are believed to have partially melted after part of the fuel rods were no longer covered by coolant water when levels fell following the quake.

The seawater injection stopped around 1 a.m. due to the shortage of water left in tanks, but resumed for No. 3 reactor at 3:20 a.m., according to the nuclear safety agency.

The halt of coolant water injection apparently caused rising pressure in the reactor container and an increase in the radiation level at the plant, the agency said.

TEPCO at one point planned to release radioactive steam from the No. 3 reactor container to depressurize it and ordered workers to vacate the site. But as the pressure later lowered, workers resumed operations at the site, according to the agency.

Edano said pressure in the No. 1 reactor container has been stable and seawater injection for the reactor will resume later.

==Kyodo