Japan raises accident severity level to 5 in nuclear crisis
TOKYO, March 19, Kyodo
Japan raised the severity level of crisis-hit reactors at the Fukushima Daiichi nuclear power plant from 4 to 5 on an international scale of 7, the same level as the Three Mile Island accident in the United States in 1979, Japan's nuclear safety agency said Friday.
The provisional evaluation stands at level 5 on the International Nuclear and Radiological Event Scale for the plant's No. 1, No. 2 and No. 3 reactors as their cores are believed to have partially melted and radiation leaks are continuing, the Nuclear and Industrial Safety Agency said.
While efforts to cool down the overheating reactors and spent fuel continued a week after the plant was crippled by a massive earthquake and tsunami, Tokyo also reiterated its resolve to do everything to control the situation as International Atomic Energy Agency chief Yukiya Amano made an emergency visit to Tokyo.
''This is the biggest crisis for Japan,'' Prime Minister Naoto Kan told Amano as they met at the premier's office. ''Every organization (of the government)...is making all-out efforts to deal with the problem,'' he said.
The premier also pledged to disclose more information to the international community with ''maximum transparency.''
The nuclear agency put the severity level at 3 for the Fukushima Daiichi plant's No. 4 reactor, where an overheating spent fuel pool is also posing risks, and three reactors at the Fukushima Daini plant that have been controlled. The highest level of 7 has only been applied to the 1986 Chernobyl catastrophe.
An unprecedented cooling mission, which was launched Thursday by the Self-Defense Forces' spraying of tons of water over the Daiichi plant's No. 3 reactor building, was bolstered on the second day with more pumps. Efforts to restore power to some of the reactors' cooling systems also continued, the agency said.
Though it may be a stopgap measure until the cooling systems are restored, SDF fire trucks and a high-pressure water cannon truck provided by the U.S. military directed 50 tons of water at the spent fuel pool of the No. 3 reactor.
The operation followed the dropping of up to 104 tons of water on the pool Thursday, in which two SDF choppers and a police water cannon truck were deployed.
The Tokyo Fire Department also prepared to join the operation, likely at the plant's No. 1 reactor, with 30 trucks capable of discharging massive amounts of water to high places and some 140 disaster relief specialists of its ''hyper rescue'' team.
Radiation readings at the disaster-hit nuclear plant have declined a little, but plant operator Tokyo Electric Power Co. stopped short of calling the move a downward trend.
The latest radiation levels are below 500 microsievert per hour, the threshold beyond which the operator is required to report an emergency to the government.
It also fell below 0.1 microsievert per hour to levels below those seen before the crisis in the Kanto region surrounding Tokyo, except in Ibaraki, Tochigi, Gunma and Saitama prefectures, which still recorded higher figures, and Miyagi from which no data were reported, the science and technology ministry said.
Edano said radiation amounts near the Fukushima Daiichi plant ''do not pose immediate adverse effects to the human body,'' after the nuclear agency released data collected by Tokyo Electric, known as TEPCO.
Agency spokesman Hidehiko Nishiyama noted the difficulty in properly assessing the effects of the water-pouring mission from the radiation data. ''We need to observe the situation a little more to determine whether the mission was a success or not,'' he told reporters.
TEPCO accelerated efforts to recover lost cooling function by reconnecting electricity to the plant through outside power lines, with workers trying to restore power to the plant's No. 1 and No. 2 reactors on Saturday and at the No. 3 and No. 4 reactors by Sunday, according to Nishiyama.
Some of the power distribution boards at the plant are covered with water following the quake-triggered tsunami and TEPCO will use makeshift replacement equipment, he added. Even with electricity restored, it is unlikely devices will be reactivated at least until Saturday as equipment needs to be checked, the utility said.
The agency spokesman said applying sand and concrete to bury the troubled reactors to prevent the release of massive radioactive fallout is ''not a realistic choice right now.''
''What we need to do now is to cool the reactors' cores, make sure that electricity will be restored and reestablish the cooling functions'' at the plant, Nishiyama said. Japanese authorities consider the methods used to solve the Chernobyl crisis ''a historic lesson,'' he added.
The spent fuel pools at the power station lost their cooling functions in the wake of the March 11 killer quake and tsunami. It is also no longer possible to monitor the water levels and temperatures of the pools in the No. 1 to No. 4 reactor buildings.
Plumes of smoke or steam have been seen rising from three of the buildings but not the No. 1 unit, Nishiyama said, suggesting their pools situated outside reactor containment vessels are boiling.
A rise in water temperature, usually at 40 C, causes the water level to fall and exposes the spent nuclear fuel rods, which could heat up further, melt and discharge highly radioactive materials in the worst case scenario, experts say.
Among the six reactors at the Fukushima Daiichi Nuclear Power Station, the No. 1, No. 2 and No. 3 reactors that were operating at the time of the magnitude 9.0 quake halted automatically, but the cores are believed to have partially melted as they lost their cooling functions after the quake.
The buildings housing the No. 1, No. 3 and No. 4 reactors have been severely damaged, leaving fuel pools there uncovered, and the No. 2 reactor's containment vessel suffered damage to its pressure-suppression chamber at the bottom.
The government has set an exclusion zone covering areas within a 20-kilometer radius of the plant and has urged people within 20 to 30 km to stay indoors.