TOKYO (Kyodo) -- Cooling functions at the quake-hit Fukushima No. 1 nuclear power plant's No. 2 reactor have failed, the plant operator said Monday, raising fears that the problem could lead to another explosion at the plant following a blast earlier in the day at its No. 3 reactor. Tokyo Electric Power Co. reported the loss of cooling functions as an emergency to the government and began injecting seawater into the No. 2 reactor to cool it down and prevent the melting of its core due to overheating.
Similar measures have been taken at the plant's No. 1 and No. 3 reactors and explosions occurred at both reactors during the process, blowing away the roofs and walls of the buildings that house the reactors.
Chief Cabinet Secretary Yukio Edano said the water level in the No. 2 reactor has fallen sharply, nearly leaving upper sections of fuel rods exposed. He said, however, that radiation levels had not risen sharply at the plant.
TEPCO admitted the fuel rods in the No. 2 reactor were partially exposed and that the injection of seawater into the reactor was not leading to a rise in the water level.
The company has also begun work to depressurize the containment vessel of the No. 2 reactor by releasing radioactive steam, the government's Nuclear and Industrial Safety Agency said. Such a step is necessary to prevent the vessel from sustaining damage and losing its critical containment function.
The utility firm said a hydrogen explosion at the nearby No. 3 reactor that occurred Monday morning may have caused a glitch in the cooling system of the No. 2 reactor.
The nuclear agency said the 11:01 a.m. blast may also have caused damage to four fire pumps that were prepared for seawater injection operations.
At present, only one fire pump is working and TEPCO is placing priority on injecting water into the No. 2 reactor, although both the No. 1 and No. 3 reactors still need coolant water injections, according to the agency.
To prevent a possible hydrogen explosion at the No. 2 reactor, TEPCO said it will study opening a hole in the wall of the building that houses the reactor to release hydrogen.
The blast earlier in the day injured 11 people but the reactor's containment vessel was not damaged, with the government denying the possibility of a large amount of radioactive material being dispersed, as radiation levels did not jump after the explosion.
TEPCO said seven workers at the site and four members of the Self-Defense Forces were injured. The Defense Ministry said one SDF member suffered broken bones.
Since the magnitude 9.0 quake hit northeastern Japan last Friday, some reactors at the Fukushima No. 1 plant have lost their cooling functions, leading to brief rises in radiation levels. As a result, the cores of the No. 1 and No. 3 reactors have partially melted.
The government ordered residents within a 20-kilometer radius of the plant to evacuate Saturday in the wake of the initial blast at the plant's No. 1 reactor. A total of 483 people are still attempting to leave the area, according to the nuclear agency.
The agency ruled out the possibility of broadening the area subject to the evacuation order for now.
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