Last week the Nuclear Regulation Authority approved the use of ground freezing at Fukushima Daiichi Nuclear Power Plant, which was damaged in an earthquake in 2011.
Last month Fukushima owner Tokyo Electric Power Co (Tepco) began work on a bypass system to divert groundwater into the sea to try to reduce the contaminated water leaking from the plant.
Tepco has reported that groundwater is leaking in higher volumes and with greater radiation levels than previously thought.
Today work began on the government-funded scheme to use ground freezing techniques to form a 1.5km long wall of ice around the plant to stem the inflow of groundwater.
The ground freezing is part of a wider Y50bn (£260M) publicly funded plan to prevent contaminated water leaking from the site that includes construction of an outer cut-off wall using more conventional combi-wall.
The Japanese government has said that the ground freezing solution, previously used in the construction of tunnels near watercourses, has never been used on this scale for a long-term solution before.