Fukushima No. 2 reactor's fuel rods fully exposed; melting feared

Fuel rods at the quake-hit Fukushima No. 1 nuclear power plant’s No. 2 reactor were fully exposed at one point after its cooling functions failed, the plant operator said Monday, indicating the critical situation of the reactor’s core beginning to melt due to overheating.

The rods were exposed as a fire pump to pour seawater into the reactor to cool it down ran out of fuel, Tokyo Electric Power Co said. The firm had reported the loss of cooling functions as an emergency to the government.

TEPCO said water levels later recovered to cover 30 centimeters in the lower parts of the fuel rods.

The seawater injection operation started at 4:34 p.m., but water levels in the No. 2 reactor have since fallen sharply with only one out of five fire pumps working. The other four were feared to have been damaged by a blast that occurred in the morning at the nearby No. 3 reactor.

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.

Similar cooling down efforts have been taken at the plant’s No. 1 and No. 3 reactors and explosions occurred at both reactors in the process, blowing away the roofs and walls of the buildings that house the reactors.

It is feared that the No. 2 reactor will follow the same path. To prevent a possible hydrogen explosion at the No. 2 reactor, TEPCO said it will look into opening a hole in the wall of the building that houses the reactor to release hydrogen.

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.

With only one fire pump working, 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.

The blast earlier in the day injured 11 people but the reactor’s containment vessel was not damaged, with the government dismissing 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. Of the 11, two were found to have been exposed to radiation and are receiving treatment.

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.

Meanwhile, the U.S. Seventh Fleet said Monday that it has moved its ships and aircraft away from a quake-stricken Japanese nuclear power plant after discovering low-level radioactive contamination. The fleet said that the radiation was from a plume of smoke and steam released from the crippled Fukushima Dai-Ichi Nuclear Power Plant.

The aircraft carrier USS Ronald Reagan was about 160 kilometers offshore when its instruments detected the radiation. But the fleet says the dose of radiation was about the same as one month’s normal exposure to natural background radiation in the environment.