Via NHK News :
" The operator of the troubled Fukushima Daiichi nuclear power plant says it will inject nitrogen gas into the containment vessel of one of its reactors as early as Wednesday evening, to prevent a possible hydrogen explosion.
Tokyo Electric Power Company, or TEPCO, said on Wednesday that hydrogen gas appears to be accumulating inside the containment vessel of the Number one reactor.
The utility says damaged fuel rods and water broken down by radiation inside the reactor's containment vessel may be leading to the release of hydrogen gas.
TEPCO added that it is also considering the injection of nitrogen into the Number 2 and 3 reactors.
Nuclear power plants are equipped with a device to inject nitrogen gas into containment vessels, but TEPCO said it plans to use an alternative device this time.
A blast ripped off the roof and walls of the Number One reactor building on March 12th, one day after the massive quake and tsunami hit the plant.
Experts believe that accumulated hydrogen gas was behind the blast."