All the reactors at Fukushima Daiichi are boiling water reactors (BWR) designed by General Electric. The reactors for Units 1, 2, and 6 reactors were manufactured by General Electric. Toshiba supplied the reactors for Units 3 and 5.  The Unit 4 reactor was manufactured by Hitachi.

April 4 Toshiba with four US firms submitted a proposal for decommissioning the disabled reactors at Daiichi.  April 8 Hitachi with help from General Electric and two other U.S. firms, Exelon Corp. and Bechtel Corp, also submitted a proposal to TEPCO.  Hitachi did not say how long it expects the process to take, but a Hitachi spokeman suggested something on the order of 30 years.

Toshiba’s submission proposes 3 phases over ten years.

Stabilizing reactors

Cooling and stabilizing the reactors and spent fuel pools will take several months. It is intended to do this in a way that will not produce more radioactive water.

Safe removal of nuclear fuel rods

Removing fuel rods from the reactors and spent fuel pools will take 5 years.

Dismantling the reactors

Dismantling the reactors and removing radioactive material from the land will require another 5 years.

Decommissioning Three Mile Island Unit 2

For comparison it is interesting to look at what happened to Three Mile Island Unit 2 (TMI-2), which began operating commercially in December 1978.  TMI-2 experienced an accident March 28, 1979 and since then has been in a non-operating status.  A remote camera inserted in the reactor core about three years after the accident showed that the core had partially melted.  

Defueling the plant was completed in April 1990. TMI-2 has also been decontaminated and the plant is considered to be in a safe and stable condition. The plant shares equipment with Three Mile Island Unit 1, which is a fully operating nuclear power plant owned by Exelon Corp.  First Energy plans to decommission TMI-2 in parallel with the decommissioning of TMI-1.  The estimated cost of radiological decommissioning  is $836.9 million.