The underground frozen soil wall built around the four crippled Fukushima Daiichi NPP reactors to minimise ground water contamination has melted in two places following recent powerful typhoons, local media reported on 2 September. Japan’s Nuclear Regulation Authority in March approved the use of a massive refrigeration system to install an underground frozen barrier around buildings at the Fukushima nuclear plant in an attempt to contain leaking radioactive water. The 1.5km “ice” wall, which was partly put into use in March, melted in two places after the devastating Lionrock typhoon, the tenth of the season, flooded northern Japan, Asahi Shimbun reported.
Construction of the ice wall construction was completed in February after two years of work involving installation of more than 1,500 steel pipes in the soil around reactors 1-4. Liquid calcium chloride at minus 40 degrees Celsius was then pumped into the pipes to freeze the surrounding soil with the aim of creating a barrier to stop contaminated water from the reactor buildings flowing out into the groundwater. However, even before the typhoon, plant operator Tokyo Electric Power Co (Tepco) admitted parts of the JPY35bn ($336m), wall were not fully frozen and would have to be cemented.