Nuclear regulators gave their approval Wednesday to start freezing soil around damaged reactor buildings at the disaster-hit Fukushima No. 1 power plant to prevent groundwater from entering the highly contaminated facilities.

The Nuclear Regulation Authority told Tokyo Electric Power Co., or Tepco, that it could activate the east side coolant-filled wall facing the sea and most of the west side.

The utility plans to bring the wall online in stages.

Tepco started installing the wall and related equipment in June 2014 around the No. 1 through No. 4 reactors at the plant that were crippled by a massive earthquake and tsunami in 2011. It completed the work last month.

The 1.5-kilometer-long wall is designed to block a massive flow of groundwater from entering the basements of the reactor buildings where it mixes with leaked radioactive water. Freezing of the soil is expected to take eight months.

The government provided about ¥35 billion ($309 million) for the project.

The chairman of the NRA, Shunichi Tanaka, said at a regular meeting Wednesday that the ultimate goal is removing the water inside the buildings, not just reducing the volume of groundwater that enters the facilities.

"I hope the necessary data will be collected to show the future path," Tanaka said at the meeting, which was open to the media.

The NRA warned earlier that if the groundwater levels within the walls is reduced excessively by blocking the flow from outside, highly contaminated water within the buildings could seep out as a result.

The wall is expected to reduce the water level around and within the reactor buildings, allowing work to be started to seal reactors and prevent water used to cool melted fuel from leaking out.