By KEITARO FUKUCHI/ Staff Writer
April 15, 2024 at 15:13 JST
The building that houses a common pool cooling nuclear fuel, left foreground, stands against a slope at the Fukushima No. 1 nuclear power plant. (Asahi Shimbun file photo)
Tokyo Electric Power Co. plans to excavate a massive slope that looms over a pool cooling nuclear fuel at the crippled Fukushima No. 1 nuclear plant to avert the danger of a landslide.
The move comes after the Nuclear Regulation Authority called on the utility to deal with the 24-meter-high slope of soft ground that is vulnerable in the event of an earthquake.
The common pool, where 5,197 spent and unused fuel assembly units were being cooled in water as of March, is expected to hold them for a prolonged period.
TEPCO is expected to remove about 100,000 cubic meters of soil from the slope in an approximately 10-year project, company officials said.
A boring survey by the utility identified a weak layer that can easily crumble over a wide area within the plant premises.
Akira Ishiwatari, a geologist and an NRA commissioner, said a landslide can occur on the slope in question if a minor earthquake strikes or even without any tremor.
TEPCO said a landslide would not affect the safety functions of the nuclear fuel pool.
But the NRA is concerned that if sediment from a landside flows into the pool, nuclear fuel may not remain cooled and, in the worst-case scenario, eventually melt.
About 4,000 fuel assembly units being kept in the buildings that house the No. 1 to No. 6 reactors are scheduled to be moved to the common pool by 2031.
TEPCO plans to transfer fuel assembly units to a different storage facility within the plant premises after they are sufficiently cooled in the nuclear fuel pool.
But the company has been unable to decide when the last fuel assembly units can be transported out of the common pool.
TEPCO plans to complete the design work and obtain approval for the excavation project over one to two years from fiscal 2024, dismantle and relocate steel towers and other obstacles in the next five years and remove the soil over about three years, officials said.
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