Tokyo Electric Power Company (Tepco) has announced that it will build a 600-metre-long seawall to strengthen protection against tsunami at the Fukushima Daiichi nuclear plant.

The decision was taken at a meeting of the Nuclear Regulation Authority (NRA). The wall will be built to the east of the four reactor buildings at the plant, but details, such as height, construction schedule and costs, have yet to be decided. Tepco built a temporary seawall after the March 2011 earthquake and tsunami caused the triple meltdown at the Fukushima plant, insisting that the temporary wall would provide sufficient protection   from future tsunami.

However, Tepco officials reconsidered the decision after the government’s Headquarters for Earthquake Research Promotion warned that the probability of an extremely powerful earthquake of magnitude 8.8 or higher striking in the Pacific Ocean off Hokkaido within 30 years was 40%, Asahi Chimbun reported.  

The headquarters called for additional safety measures at nuclear plants, saying this would be similar to the magnitude 9.0 earthquake that caused the 2011 tsunami. If another tsunami hits the plant, it could cause tons of radioactive water to flow out and obstruct work to decommission the nuclear reactors. “If another tsunami comes, the measures we have taken for the past seven years will be meaningless,” a Tepco official said.

Work continues to cool the melted nuclear fuel within the heavily damaged reactor buildings at Fukushima Daiichi. This water, coupled with the tons of daily groundwater that becomes contaminated after entering the reactor buildings, has forced the utility to store tons of radioactive water in tanks on the site, which would be at risk from another tsunami. In addition, 1573 nuclear fuel assemblies are stored in pools in the damaged reactor buildings.