The operator of the Fukushima Daiichi nuclear power plant has almost completed work on an ice wall around the reactor buildings to prevent groundwater from flowing into the facilities and becoming contaminated.
This comes one year and 7 months after Tokyo Electric Power Company began the procedure to freeze the 1.5 kilometer-long underground wall.
The last section of the wall on the mountain side of the facility had been purposely left unfrozen as it was thought freezing it could cause a sudden drop in groundwater levels around the buildings, and contaminated water inside the facility could leak out.
In August, workers at the utility started to freeze the remaining 7-meter section by circulating minus 30-degree-Celsius coolant inside underground pipes.
TEPCO officials say underground temperatures went subzero in late October, and the section where work started in August appears to be stably frozen, except for the ground surface.
It is thought some sections where underground equipment and pipes are located are unlikely to be frozen.
TEPCO officials say the ice wall, along with other measures, will reduce the groundwater volume flowing into the facilities to less than 100 tons a day. The volume was 140 tons as of July.
The officials plan to assess how effective the ice wall is in preventing the inflow of groundwater.