The Nuclear Regulation Authority has decided to allow Tokyo Electric Power Co. to begin building an underground ice wall at the wrecked Fukushima No. 1 nuclear power plant in June as planned, despite safety concerns about the move.
The frozen wall, to be set up around the buildings housing reactors 1 through 4, is viewed as an important step in addressing the buildup of radioactive water at the complex. The project is being funded by the government and is expected to cost ¥32 billion.
The NRA has been wary that building the ice wall could cause the ground to sink around the reactor and adjacent turbine buildings. But on Monday the agency accepted Tepco’s explanation that any sinking would not be significant enough to put safety at risk.
A Tepco official told NRA members and experts that the ground may sink up to 16 mm in some spots, but that the utility believes it won’t pose a problem to the stability of the ground.
“I think we have been able to confirm today the scale of ground sinking, which is what we have most feared as side effects of building the wall,” NRA Commissioner Toyoshi Fuketa said after hearing Tepco’s explanation:
But he noted that other issues concerning the project must still be discussed, including ways to accurately measure the level of radioactive water accumulating inside the reactor buildings.
The 1.5-km frozen wall will be built by inserting a line of pipes into the ground that circulates a liquid cold enough to cause the earth around it to freeze.
The wall is expected to help prevent a large volume of groundwater from flowing into the basements of the reactor buildings and mixing with highly radioactive water already accumulating there.
Impermeable walls of this nature are used in civil engineering projects such as subway construction but have never been created on such a large scale for a prolonged period.
Also as part of addressing the toxic water buildup, Tepco has been discharging groundwater that has accumulated at the site into the sea.
The release uses the so-called groundwater bypass system, in which water is pumped out through wells before it flows into the reactor buildings.