June 2, 2016

TEPCO to extend frozen soil walls to block water leakages at Fukushima plant

http://mainichi.jp/english/articles/20160602/p2a/00m/0na/011000c

The Nuclear Regulation Authority approved on June 2 a plan submitted by Tokyo Electric Power Co. (TEPCO) to extend frozen soil walls at the Fukushima No. 1 Nuclear Power Plant to around virtually the whole plant to block ground water leakages.

• 【Revised】NRA approves TEPCO's plan to freeze underground walls of soil at Fukushima plant

The plan is to gradually extend the walls, made by freezing underground earth, to surround the crippled plant. TEPCO also revealed plans to pour in cement to supplement parts of the existing walls that are not fully frozen.

In March this year TEPCO began freezing 820 meters of wall, or about 55 percent of the total planned length. There are fears that if the plant is completely surrounded by frozen walls, the underground water level at the plant will drop and highly-radioactive water within the reactor buildings might leak out. For this reason the company was freezing the walls gradually and keeping an eye on conditions, but due to a lack of any major problems so far they decided to extend the walls.

The frozen walls -- together with other measures like a "subdrain plan" to dig wells around the plant and drain out contaminated water -- are at the center of TEPCO's strategies to contain contaminated water leaks. A total of 1,568 pipes are to be driven into the ground and have minus 30 degrees Celsius coolant poured into them to create a "wall of ice" 30 meters deep. When completed, the wall is expected to cut daily underwater inflow from around 200 metric tons to less than 100 tons, but there is no definite proof of this. A date for when the wall will be completed has not been decided.