Japan will on Monday start constructing an underground ice wall at the crippled Fukushima nuclear plant, freezing the soil under broken reactors to slow the build-up of radioactive water, officials said.
The wall is intended to block groundwater from nearby hillsides that has been flowing under the plant and mixing with polluted water already there.
The Nuclear Regulation Authority, the national watchdog, last week gave the go-ahead to beginning the construction of the ice wall at Fukushima Daiichi, owned and operated by Tokyo Electric Power Co (TEPCO).
The government-funded scheme will see pipes laid deep in the soil through which refrigerant will be piped to create the 1.5-kilometre (0.9-mile) frozen wall that will stem the inflow of groundwater.
The idea of freezing a section of the ground, which was proposed for Fukushima last year, has previously been used in the construction of tunnels near watercourses.
However, scientists point out that it has not been done on this scale before nor for the proposed length of time.
Coping with the huge -- and growing -- amount of water at the tsunami-damaged plant is proving to be one of the biggest challenges for TEPCO, as it tries to clean up the mess after the worst nuclear disaster in a generation, in which three reactors went into meltdown.
As well as all the water used to keep broken reactors cool, the utility must also deal with water that makes its way along subterranean watercourses from mountainsides to the sea.
Last month TEPCO began a bypass system that diverts groundwater into the sea to try to reduce the volume of contaminated water.
Full decommissioning of the plant at Fukushima is expected to take several decades. An area around the plant remains out of bounds, and experts warn that some settlements may have to be abandoned because of high levels of radiation.