Crippled Fukushima nuclear reactors declared stable

TOKYO, Dec. 16 (UPI) -- The three earthquake-tsunami-damaged nuclear reactors at Japan's Fukushima Daiichi No. 1 plant no longer leak large amounts of radiation, officials said Friday.

Government and Tokyo Electric Power Co. officials said the plant achieved a stable "cold shutdown," meaning reactor core coolant temperatures are below 200 degrees F, coolant water is not boiling and only small amounts of radioactive material are escaping, the Mainichi Shimbun reported.

Plans made available to the newspaper indicated it would take 30 to 40 years for Tokyo Electric and the government to decommission the crippled reactors at the Fukushima No. 1 plant.

Tokyo Electric, which operates the facility devastated by a March 11 earthquake and tsunami, said the temperature in the lower parts of the containment vessels in reactors 1, 2 and 3 indicated the vessels, the last in a line of defense to contain radioactive materials, were safely cooled by injecting coolant water, The Japan Times reported.

Experts still expressed concern about the long-term stability of the coolant system, given the danger of another major earthquake or tsunami, the Times said.

Tepco experienced a leakage of about 40 gallons of water containing radioactive substances into the Pacific Ocean from a water processing facility earlier in December.

The plan for decommissioning the reactors is set in three phases, the Mainichi Shimbun said. The first phase, to run from 2012-2014, involves emptying a common pool and transferring spent nuclear fuel in pools at each reactor building to the common pool.

During the second phase, the damaged containment vessels will be repaired before being filled with water.

In the third phase, Tepco and the government will use remote-controlled cranes to collect melted fuel rods, a process estimated to take at least 30 years and a maximum of 40 years, the Mainichi Shimbun said.

The March earthquake and tsunami, which killed thousands of people, caused a series of equipment failures, nuclear meltdowns and releases of radioactive materials at the plant. It was the worst nuclear crisis since the 1986 Chernobyl disaster in Ukraine.