TOKYO, Sept. 2 (Xinhua) -- The frozen soil wall built around the crippled Fukushima No.1 nuclear plant have melted in two places following recent powerful typhoons, local media reported Friday, raising concerns over effect of the approach adopted by Tokyo Electric Power Co.(TEPCO) to reduce the massive volume of radioactive water.
The 1.5-km-long frozen soil wall, also known as the "ice wall," which was partly put into use in March, melted in two places following Powerful Lionrock, the tenth of the season, battered the region, with temperature of the melting parts rising above zero centigrade, Japan's Asahi Shimbun reported.
The melting was probably caused by lashing of large amount of groundwater as a result of recent powerful typhoons and heavy rainfall, said local reports.
Groundwater flowing under the nuclear plant is leaking through the melted parts of the wall to outside and TEPCO is trying to refreeze the parts by injecting special chemicals to the wall, said the reports.
The ice wall construction was finished in February after two years of work involving driving over 1,500 steel pipes with 30 meters into the soil around the perimeter surrounding the No. 1 to 4 reactors at the troubled plant.
Liquid calcium chloride at minus 40 degrees Celsius was then pumped into the pipes to freeze the surrounding soil, which, in theory, would prevent groundwater from flowing into the facilities and getting contaminated when it comes into contact with melted nuclear fuel.
However, reports showed that there still remained unfrozen parts as of mid-August, and TEPCO revealed plans to take additional steps such as injecting cement into the parts of the wall that are not fully frozen.
The ice wall, costing tax payers some 35 billion yen (336 million U.S. dollars), met with doubts and criticisms from experts from the very beginning, with the technique having been used previously in engineering projects, but not on a scale of the Fukushima plant or for the expected duration.
Some experts believe that capping the reactors in concrete, as was the case following the 1986 Chernobyl disaster, would be a more effective means of dealing with the ongoing crisis.
The project was considered failed by some outside experts at an earlier meeting called by the Nuclear Regulation Authority to assess the effectiveness of the approach.