Tokyo Electric Power Company Holdings Inc. (Tepco) has decided to move up ongoing work on protective measures at its crippled Fukushima No. 1 nuclear power station, as a precaution against major tsunami from potentially huge earthquakes that could occur along the Kuril-Kamchatka Trench in the Pacific.
The company made the decision after the government’s earthquake research committee said in a report in December last year that the likelihood of a quake of at least magnitude 8.8 occurring at the trench off the coast of Hokkaido within 30 years stands at 7-40 percent.
Such a giant earthquake is considered imminent as about 400 years have passed since the previous earthquake occurred along the trench in the 17th century, it also said.
Tepco will accelerate measures to prevent radiation-contaminated water, accumulated in the basements of some reactor buildings at the power station in Fukushima Prefecture, from overflowing in case the plant is hit by tsunami from a Kuril trench quake.
In the event that a powerful earthquake occurs at the trench tsunami of up to 10.1 meters could reach the plant, and the areas where reactor buildings are located could be flooded to a height of 1.8 meters above the ground, according to the company.
If tsunami water enters damaged reactor buildings through openings such as hatches and staircases, radiation-tainted water could flow out of the basement sections when the tsunami water recedes, Tepco said.
The company has finished sealing about half of a total of 122 openings.
Tepco plans to complete work on 11 openings at the No. 2 and No. 3 reactors in the first half of fiscal 2020. The company had previously planned to end the work by March 2021.
Furthermore, Tepco also plans to close nine openings at the No. 4 reactor.
All of the six reactors at the Fukushima No. 1 plant, including the No. 1, No. 2 and No. 3 units that were heavily damaged in the March 2011 powerful earthquake and tsunami, are set to be scrapped.