samedi 17 mai 2014

experiment to create an underground barrier

Media crews have visited the Fukushima Daiichi nuclear plant to observe an experiment to create an underground barrier around damaged reactor buildings by freezing the ground.The government and Tokyo Electric Power Company plan to freeze soil over a 1.5 kilometer stretch around reactors No.1 through 4. The aim is to hold back groundwater, preventing it from seeping into the structures where it can get contaminated.TEPCO has frozen soil on a smaller scale within the plant premises to test the feasibility of the plan.Media crews observed the test site, where steel pipes have been placed at intervals around an area of 10 square meters. The pipes reach about 30 meters below ground level.TEPCO officials say engineers filled the pipes with minus 30 degrees Celsius coolant. After around one month, the soil around the pipes froze, creating an underground wall.Officials said the frozen wall made for the test is blocking groundwater, even where there are obstacles.TEPCO hopes to begin work around the reactor buildings in June, if the plan is approved by the Nuclear Regulation Authority, or NRA.A panel of NRA experts is asking the utility to assess how the ground structure could be affected, and what may happen if the project fails.An official of TEPCO's in-house unit in charge of decontamination and decommissioning says the experiment has shown that frozen soil can block water.He said the utility plans to offer a detailed briefing to the NRA.

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