In this March 10, 2014 file photo, workers wearing protective gears install a trial model of the underground frozen wall at the Fukushima Dai-ichi nuclear power plant in Okuma, Fukushima prefecture, northeastern Japan in their attempt to stop the leakage of radioactive water that has accumulated at the crippled nuclear power plant. Japanese regulators on Wednesday, March 30, 2016, approved the use of a giant refrigeration system to create an unprecedented underground frozen barrier around buildings at the Fukushima nuclear plant in an attempt to contain leaking radioactive water.