Japan is considering pouring concrete into its crippled Fukushima atomic plant as the United Nations’s nuclear watchdog agency warned that a potential uncontrolled chain reaction could cause further radiation leaks.

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 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 UN’s International Atomic Energy Agency, said at a press conference in Vienna.
‘Localized Criticality’

Nuclear experts call these reactions ‘localized criticality,’ which will increase radiation and hamper the […]