Tokyo Electric has been struggling to deal with contaminated water both above and below ground at the crippled Fukushima Daiichi nuclear power plant. Tunnels connected to the turbine buildings have provided areas for the accumulation of water, additional routes for the movement of the radioactive water, and have increased the headaches for the utility working to deal with them.
In early 2014, TEPCO will start work to freeze contaminated water in an underground tunnel, in the hopes that it will prevent further movement of radioactive water into the Pacific Ocean. Tokyo Electric has claimed that the water in the tunnel is the primary source of contamination off-site.
The utility plans to freeze the contaminated water in the tunnel into an ice wall that would block the flow of water from the turbine building into the tunnel. According to the proposed plan, TEPCO would be able to start removal of 10,000 tons of contaminated water from the underground tunnel in 2014-2015.
To prepare for this operation, TEPCO engineers conducted a test in August using a mockup of the tunnel. According to the test operation, an ice wall 2 meters high and 2 meters wide formed in a month and a half, but the water did not freeze uniformly. Engineers were able to remove water from the mock tunnel, but the test revealed many problems that will have to be overcome if the real mission is to be a success.
Extra pipes will have to be installed in many places in order to freeze the water uniformly. This is one of the hardest parts of the mission, given that the radiation levels, among other conditions, in the real tunnel will prevent long worker stay times.