Japan considers entombing nuclear plant

March 17, 2011 - 0:0

Japan will consider entombing its crippled atomic plant in concrete as workers grapple to reduce radiation and contain the worst nuclear disaster in 25 years.

Chief Cabinet Secretary Yukio Edano on Wednesday ruled out the possibility that two of the six reactors at the Fukushima Daiichi plant would ever be salvaged.
“Given the whole situation, the objective circumstances, it is obvious,” Edano said when asked about reactors 5 and 6, which were offline at the time of the March 11 earthquake and tsunami and so weren’t rendered inoperable. “The public perception is fairly clear.”
About 600 workers, firefighters and soldiers have averted the threat of a total meltdown by injecting water into damaged reactors for the past two weeks. Engineers have connected the complex’s six units with the power grid and two are using temporary motor-driven pumps. While technicians are trying to repair monitoring and cooling systems, the work has been hampered by discoveries of hazardous radioactive water.
The government hasn’t ruled out pouring concrete over the whole facility as one way to shutting it down, Edano said. 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.
“They need to immobilize this water and they need something to soak it up,” he said by phone. “You don’t want to create another hazard, but you need to get it away from the reactors.”
Toxic water
Record high readings of contaminated sea water were found near the plant. Radioactive iodine rose to 3,355 times the regulated safety limit on Tuesday afternoon 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.
The three reactors all lost their roofs following explosions and fires in the days following the magnitude-9 earthquake and tsunami, which knocked out power and backup systems used to cool nuclear fuel.
Among proposals being considered to contain the disaster, Japan may use a special fabric to cover three reactors to curb the spread of toxic radiation in the air.
Crews are also considering pumping radioactive water in the reactor buildings to a tanker for safe storage. The U.S. has transported robots impervious to radiation and their operators to the plant at Japan’s request, Peter Lyons, acting assistant secretary of the U.S. Energy Department, told a congressional panel Tuesday.
Fukushima plant operator Tokyo Electric Power Co. said it can’t rule out the possibility that water may have flowed into the sea from underground trenches outside the reactor buildings.
Work to drain radioactive water from the basement of the No. 1 reactor turbine building was halted because a storage tank is full, Kazuyo Yamanaka, a manager at the power utility, said. Tokyo Electric plans to move the contaminated water into a condenser within the same building.
The level of contaminated water in the basement of the No. 1 reactor turbine building has been reduced by half to 20 centimeters (7.9 inches), Nishiyama said.
Water in a tunnel outside the No. 2 reactor emitted radiation exceeding 1 sievert an hour, a Tokyo Electric spokesman said. Exposure to that dose for 30 minutes would trigger nausea, and four hours’ exposure might lead to death within two months, according to the U.S. Environmental Protection Agency.
Intolerable conditions
“Workers can’t work near water with radiation levels exceeding 1 sievert per hour, at least not within a few meters,” said Hironobu Unesaki, a professor at Kyoto University’s Research Reactor Institute. “They may need to remotely remove water or rotate workers for very short periods of time.”
Tokyo Electric Chairman Tsunehisa Katsumata apologized for the nuclear crisis 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.
Daiichi reactors 1 to 4 will be decommissioned after they are stabilized, Katsumata said. Edano announced the closure of all six units at the same news conference.
5-year cleanup
Cleanup probably will take at least five years because of the time needed for radioactivity to diminish so experts can assess the damage, Akira Tokuhiro, a professor of mechanical and nuclear engineering at the University of Idaho, said in an interview. That assessment will determine whether the reactors should be entombed or dismantled to eliminate any further radiation risk, he said.
Smoke seen at the No. 1 reactor of the nearby Fukushima nuclear power plant wasn’t caused by a fire but by a minor problem with equipment, a spokesperson for Tokyo Electric Power Co. said, citing the local fire department. The smoke was seen rising near (Source: Bloomberg)