Fukushima's Giant Ice Wall Can't Get Cold Enough to Freeze

Remember how Japan decided to build that crazy ice wall to contain the Fukushima nuclear plant's radioactive water leaks? Well, its construction is behind schedule—because its engineers can't achieve temperatures low enough to freeze the ice.

The ice wall was to be constructed by driving vertical pipes, spaced about a meter apart, between 20 and 40 meters into the ground. Then, coolant was to be pumped through them, effectively creating a barrier of permafrost around the affected buildings, keeping the contaminated water in and groundwater out.
But now, the Tokyo Electric Power Co. (TEPCO) has admitted that an initial, smaller inner ice wall—a proof-of-concept, if you like—is proving difficult to construct. A TEPCO spokesperson has explained that:

"We have yet to form the ice stopper because we can't make the temperature low enough to freeze water. We are behind schedule but have already taken additional measures, including putting in more pipes, so that we can remove contaminated water from the trench starting next month."

The engineers involved with the project are using a calcium chloride coolant, chilled down to -30C, or -22F. While that's been enough to create smaller versions of these permafrost walls elsewhere in the past, the same isn't true at Fukushima. Indeed, the project had already been greet with skepticism by some engineers and scientists who—perhaps now correctly—pointed out that the project may struggle to work at such scales and time spans.
The huge amounts of water leaking from the Fukushima site continue to be a real and growing problem, then. Let's hope the engineers can find something more effective than their calcium chloride coolant. [Agence France-Presse via Guardian]