nuclear-news

The scale and complexity of the challenge is unprecedented. No nuclear reactor has ever been fully decommissioned in Japan, let alone the four certain to be dismantled at Fukushima, after being flooded with seawater to avert meltdowns, and after suffering explosions and other damage. The final fate of the two other reactors there has not been announced, but they too may need to be decommissioned.

The accident at Three Mile Island in 1979 involved just one reactor, and thought there was a partial meltdown of the nuclear fuel rods, the chamber holding them did not rupture. The cleanup there still took 14 years and cost about $1 billion. (Two reactors that continue to operate at the site are set to be decommissioned in 2014.)

Recovery from the disaster at Cherynobyl in 1986, meanwhile, is an example engineers are not eager to study. Following the multiple explosions and fire that sent huge radioactive plumes into the atmosphere, workers covered the remains of the reactor with sand, lead and eventually entombed it with concrete to halt the release of radiation. The concrete coffin still remains at Chernobyl, and the area remains uninhabitable……

serious challenges that remain, including what Japan’s nuclear regulator said Thursday were rising temperatures at one of the units , as well as a series of strong aftershocks. Later, Hidehiko Nishiyama, the deputy director-general of Japan’s Nuclear and Industrial Safety Agency, said the situation at the plant remained “difficult.”……

Tetsuo Matsumoto, a professor in nuclear engineering at Tokyo City University, said that how long the decommissioning process would take depended heavily on the state of the nuclear fuel.

“Will it still be shaped like rods? Or will it have melted and collapsed into a big mass?” he said. “It could be 10 years or it could be 30. You just won’t know until you open up the reactor.”