Japan will consider pouring concrete into its crippled Fukushima atomic plant to reduce radiation and contain the worst nuclear disaster in 25 years.
Chief Cabinet Secretary Yukio Edano yesterday ruled out the possibility that the two undamaged reactors at Tokyo Electric Power Co.’s six-unit Dai-Ichi plant would be salvaged. Units 1 through 4 suffered from explosions, presumed meltdowns and corrosion from seawater sprayed on radioactive fuel rods after a March 11 earthquake and tsunami cut power to reactor cooling systems.
Workers have averted the threat of a total meltdown by injecting water into the damaged reactors for the past two weeks. The complex’s six units are connected with the power grid and two are using temporary motor-driven pumps. Work to repair the plant’s monitoring and cooling systems has been hampered by discoveries of hazardous radioactive water.
The risk to workers might be greater than previously thought because melted fuel in the No. 1 reactor building may be causing isolated, uncontrolled nuclear chain reactions, Denis Flory, nuclear safety director for the International Atomic Energy Agency, said at a press conference in Vienna.
Radioactive chlorine found March 25 in the Unit 1 turbine building suggests chain reactions continued after the reactor shut down, physicist Ferenc Dalnoki-Veress of the James Martin Center for Nonproliferation Studies in Monterey, California, wrote in a March 28 paper. Radioactive chlorine has a half-life of 37 minutes, according to the report.
Dismantling the Plant
Tokyo Electric mixed boron, an element that absorbs neutrons and hinders nuclear fission, with emergency cooling water to prevent accidental chain reactions, Kathryn Higley, head of nuclear engineering and radiation health physics at Oregon State University in Corvallis, said in an e-mail.Dismantling the plant and decontaminating the site may take 30 years and cost Tokyo Electric more than 1 trillion yen ($12 billion), engineers and analysts said. The government hasn’t ruled out pouring concrete over the whole facility as one way to shut it down, Edano said at a press conference.
Dumping concrete on the plant would serve a second purpose: it would trap contaminated water, said Tony Roulstone, an atomic engineer who directs the University of Cambridge’s masters program in nuclear energy.
Immobilizing the Water
“They need to immobilize this water and they need something to soak it up,” he said. “You don’t want to create another hazard, but you need to get it away from the reactors.”The process will take longer than the 12 years needed to decommission the Three Mile Island reactor in Pennsylvania following a partial meltdown in 1979, said Hironobu Unesaki, a nuclear engineering professor at Kyoto University.
Tokyo Electric’s shareholders may be wiped out by clean-up costs and liabilities stemming from the nuclear accident, the worst since Chernobyl. The company faces claims of as much as 11 trillion yen if the crisis lasts two years and potential takeover by the government, according to a March 29 Bank of America Merrill Lynch report.
Among proposals being considered to contain the disaster, Japan may use a special fabric to cover reactors and curb the spread of airborne radiation. The plant probably is covered by a layer of radioactive dust that may contain plutonium, a radioactive element that can cause cancer when inhaled, Higley said.
Robots
Tokyo Electric said it can’t rule out the possibility that radioactive water may have flowed into the sea from underground trenches outside the reactor buildings.Record levels of contaminated seawater were found near the plant. Radioactive iodine rose to 3,355 times the regulated safety limit yesterday from 2,572 times earlier in the day, said Hidehiko Nishiyama, a spokesman for Japan’s nuclear safety agency. No fishing is occurring nearby so there is no threat, he said.
Work to drain radioactive water from the basement of the Unit 1 reactor turbine building was halted because a storage tank is full, Kazuyo Yamanaka, a manager at the power utility, said yesterday. Tokyo Electric plans to move the contaminated water into a condenser within the same building.
Crews are also considering pumping radioactive water in the reactor buildings to a tanker for safe storage. The U.S. has sent robots to the plant at Japan’s request, Peter Lyons, acting assistant secretary of the U.S. Energy Department, told a congressional panel.
Tokyo Electric Chairman Tsunehisa Katsumata apologized for the nuclear crisis yesterday and said the power company will do all it can to prevent the catastrophe from worsening. Katsumata took charge of the utility after President Masataka Shimizu, 66, was admitted to a hospital for high blood pressure.
The number of dead and missing from the earthquake and tsunami had reached 27,652 as of 9 p.m. yesterday, Japan’s National Police Agency said.
