Total submersion of the Fukushima nuclear reactor building is considered

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IWAKI, Fukushima Prefecture – A government-licensed company said it plans to submerge the No. 3 reactor building of the Fukushima No. 1 nuclear power plant to recover molten nuclear fuel debris from the reactor.

The Nuclear Damage Compensation and Decommissioning Facilitation Corp. (NDF) said Sept. 3 that the entire reactor building would be wrapped in a steel structure before being submerged in water, according to the proposal.

“No radioactive material would swirl underwater, so there would be almost no impact on the outside,” NDF chairman Hajimu Yamana said.

High radiation levels in the reactor building prevent safe human access.

The method of total submersion, which has no precedent, would contribute to reducing the exposure of workers to radiation because water constitutes an effective shield against it.

NDF officials said they would also investigate other methods before narrowing down feasible options.

The NDF’s proposal to submerge the entire reactor building was presented at a government meeting held in Iwaki, Fukushima Prefecture.

Yamana said the NDF will study the feasibility of the proposed works and consider the alternative option of collecting the fuel debris from the top or side of the containment vessel without filling the vessel with water.

“I can’t say anything for sure yet (about the feasibility of the total submersion method),” Yamana told the Asahi Shimbun after the meeting. “We are still in the very early stages of the concept study. There is still a lot to study as the attempt would be the first of its kind in the world. »

A separate option of filling the containment vessel housed in the reactor building with water was previously considered for the fuel debris recovery process, but the proposal was dropped after it was found that it would be difficult to fill the holes. of the containment tank.

An estimated total of 880 tons of fuel debris is left inside the No. 1, No. 2 and No. 3 reactors of Fukushima Nuclear Power Plant No. 1. Finding a way to recover the debris is the biggest hurdle to dismantling the shackled plant.

Plant operator Tokyo Electric Power Co. originally planned to start recovering fuel debris from the No. 2 reactor on a trial basis before the end of last year.

The utility, however, postponed the planned start date to the second half of fiscal year 2023 in part due to delays in equipment development.

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