31 Mar (NucNet): Japan's Nuclear Regulation Authority (NRA) has authorised the start of freezing works for a land-side impermeable wall at the Fukushima-Daiichi nuclear station, operator Tokyo Electric Power Company (Tepco) said in a statement.
The 1.5 km wall is intended to prevent groundwater from entering the Pacific Ocean after flowing beneath units 1 to 4 at the station.
The wall consists of cooling pipes driven into the ground and surrounds the Unit 1 to 4 reactor buildings.
A cooling agent will be pumped through the pipes, freezing the soil and forming a barrier around the buildings to block groundwater inflow.
NRA’s approval has been received for activating about 95 percent of the wall, while approval for the remaining portions will be considered after assessing the results of the first stage, Tepco said.
According to Tepco, no firm timetable has been set for the gradual activation of the “frozen wall”, but the process is expected to take months.
Tepco also said they will not be activating the wall at 100 percent from the very start in order to allow for performance testing.
The ice wall is part of a multi-layered strategy to divert, contain, treat, and safely store groundwater and storm water at the Fukushima Daiichi power station, severely damaged by an earthquake and subsequent tsunami in March 2011, Tepco said.
