After struggling for five years to contain the seepage of groundwater contaminated by radiation, caused by the meltdown of the nuclear cores at Japan’s Fukushima I Nuclear Power Plant in the aftermath of a major earthquake and tsunami in March 2011, the plant’s operator switched on a giant underground refrigeration system Thursday in an attempt to contain the radioactive water.

The “ice wall” is actually made of frozen soil. Several pipes, each about 100 feet long, have been inserted into the ground around the nuclear plant in a mile-long circumference, according to information on the Tokyo Electric Power Company website. A refrigerant that TEPCO claims is environmentally safe will flow through the pipes, “freezing the surrounding soil and forming a barrier around the reactor facilities.”

The company didn’t announce a finite timetable for how long it would take for the entire perimeter to be frozen, but said it would happen “over a period of months.” The soil wall will effectively maintain its frozen state for about two months in the event of loss of power, according to the website.

Construction of the 35 billion yen ($312 million) project was funded by the government and carried out by Kajima Corporation, which has used the same technology in earlier construction projects, such as tunnels.

The wall’s construction was finished on Feb. 9, but it was delayed by about a year from its schedule due to technical uncertainties, the Associated Press reported.

About 800,000 tons of radioactive water has already been reportedly pumped out of the plant’s basement. Large amounts of water is needed to keep cool the cores of nuclear reactors, which had melted down during the accident five years ago.