[ RadSafe ] Fukushima decommissioning will take at least three decades
sperle at mirion.com
Tue Nov 1 17:55:53 CDT 2011
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Fukushima decommissioning will take at least three decades
October 29, 2011
A draft road map outlining the more than 30-year process of decommissioning and dismantling the crippled reactors at the Fukushima No. 1 nuclear power plant was published by the Japan Atomic Energy Commission (AEC) on Oct. 28.
The extraction of fuel rods in the storage pools at the reactors will begin around 2014, according to the plan, and removal of melted fuel rods within the reactors is expected to start around 2021.
The whole decommissioning process could be finished by 2041, but the authors of the draft report warn that significant delays are possible because they have not had access to full details of the extent of damage to the nuclear reactors and fuel rods.
Tokyo Electric Power Co. (TEPCO), the plant operator, will draw up detailed plans on the basis of the final report, due to be finalized by the end of the year, and will set about the decommissioning process as soon as a "cold shutdown" of the reactors is achieved, officials said. A cold shutdown is a state in which a nuclear reactor is kept at low temperature on a sustained basis.
A total of 1,496 fuel rods are held in the damaged No. 1, No. 2, No. 3 and No. 4 reactors, and a further 3,108 fuel rods are stored in the spent fuel storage pools at those four reactors. Melted fuel rods are thought to have fallen to the bottom of the pressure vessels causing some leakage into containment vessels at the No. 1 through No. 3 reactors, which were operating when the tsunami hit the plant on March 11.
The decommissioning process at the Three Mile Island nuclear power plant in the United States, where a core meltdown occurred in 1979, was a key reference point for report's authors.
The draft says decommissioning at Fukushima will begin with decontamination of the interiors of the reactor buildings, repairs to the damaged containment vessels, and refilling containment vessels with water.
Equipment to remove melted fuel rods will be inserted into the reactors and extraction will start around 2021. The extraction of fuel from the interior of the reactors is expected to be completed around 2026, although the report does not give a precise date.
The cranes that would normally be used to extract spent fuel rods were broken by the hydrogen explosions that ripped through the No. 1, No. 3 and No. 4 reactor buildings following the tsunami. New cranes will be installed to replace them, and the extraction of fuel from the spent fuel storage pools is expected to begin around 2014.
The draft report says that the government, research institutions, TEPCO and manufacturers will set up a research and development headquarters and work closely with overseas bodies.
"We envision that the extraction of fuel rods will be completed in about five years," said Hajimu Yamana, professor at the Kyoto University Research Reactor Institute who led the committee that drew up the draft report. "We hope to complete the decommissioning process in about the same time that it usually takes to decommission typical nuclear reactors, but we may need longer."
Sander C. Perle
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