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.