Crisis continues at Fukushima nuclear plant as fuel rods exposed again
TOKYO, March 15, Kyodo
A crisis continued Tuesday at the troubled No. 2 reactor at the quake-hit Fukushima No. 1 nuclear power plant, as fuel rods became fully exposed again after workers recovered water levels to cover half of them in a bid to prevent overheating.
The plant operator, Tokyo Electric Power Co., said steam vents of the pressure container of the reactor that houses the rods were closed probably due to the battery problem, raising fears that its core will melt at a faster pace.
The firm said it will first lower the pressure of the reactor by releasing radioactive steam and open the vents with new batteries to resume the operation to inject seawater to cool down the reactor.
Earlier, cooling functions of the reactor failed, causing water levels to sharply fall and fully exposing the fuel rods for about 140 minutes. TEPCO said they could not pour water into the reactor soon as it took time for workers to release steam from the reactor to lower its pressure, the government's nuclear safety agency said.
As TEPCO began pouring coolant water into the reactor, water levels went up at one point to cover more than half of the rods that measure about 4 meters.
Prior to the second full exposure of the rods around 11 p.m. Monday, radiation was detected at 9:37 p.m. at a level twice the maximum seen so far -- 3,130 micro sievert per hour -- near the main gate of the No. 1 plant, according to TEPCO.
The radiation amount is equivalent to reach by 20 minutes the permissible level for a person in one year.
To ease concerns, Chief Cabinet Secretary Yukio Edano said he believes the problem at the plant ''will not develop into a situation similar to the (1986 accident at the atomic power reactor in) Chernobyl'' in the Soviet Union, even in the worst case.
Officials of the Nuclear and Industrial Safety Agency also said the worst case scenario will be less destructive than the Chernobyl incident, as TEPCO has depressurized the reactors by releasing radioactive steam.
The utility 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 made 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.
Edano denied the possibility that the No. 2 reactor will follow the same path, as the blast at the No. 3 reactor created a gap in the wall of the building that houses the No. 2 reactor. Hydrogen will be released from the space, he said.
However, TEPCO officials did not completely rule out the possibility that a blast will happen, saying hydrogen may have been accumulating while the fuel rods are exposed.
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 in the explosion.
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.
TEPCO said the No. 1 and No. 2 reactors at its Fukushima No. 2 plant, which is adjacent to the No. 1 plant, have successfully cooled down to exit critical situations.
The government ordered residents within a 20-kilometer radius of the No. 1 plant to evacuate Saturday in the wake of the initial blast at the plant's No. 1 reactor. A total of 354 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.