12 Décembre 2013
December 11, 2013
The government and Tokyo Electric Power Co. should take more measures to mitigate the radioactive water accumulating at the Fukushima No. 1 plant, including paving the land to block rainwater from seeping into the ground, a new report recommends.
If preventive and multilayer steps can be introduced, most of the risks posed by the tainted water can be taken care of by the end of fiscal 2020, says the report, which a panel submitted to the government Tuesday.
The panel, which consists of experts and Tepco and government officials, stresses the need to come up with additional measures in case steps already planned don’t work.
For instance, the government is planning to create a sunken barrier of frozen soil around the buildings housing the crippled reactors to prevent 400 tons of groundwater from reaching their basements every day. The basements are already flooded with highly radioactive reactor coolant water, with the groundwater seeping in making matters worse.
Tepco also plans to repair wells around the buildings from which the groundwater can be pumped.
“The ice barrier and wells may be highly effective . . . but the level of difficulty to successfully implement them is technically and socially high,” the report says.
Thus, it says, additional measures are necessary and suggests paving the surface and installing another underground wall, but rather than freezing the soil, this one should be constructed with a hard substance.
According to a simulation by the panel, if 1 sq. km of area west of the reactor buildings is paved with asphalt or a similar material, the amount of groundwater seeping into the reactor buildings would be reduced to 300 tons a day.
The amount would be reduced to 170 tons if the additional hard barrier is set up in an area west of the plant, according to the simulation.
Other measures suggested by the panel include preparing bigger and stronger tanks to store the radioactive coolant water and making the water barrier fences around the tank complexes higher.
The report says the tritium in the water will remain a challenge as there is no technology to separate that radioactive isotope out quickly and effectively.
Tepco is test-operating ALPS (advanced liquid processing system), a machine that can remove all radioactive materials except tritium from tainted water.
About 400,000 tons of tainted water is currently stored at the plant and the utility is planning to process all with the ALPS by the end of fiscal 2014.
The panel plans to set up a task force that will focus on the tritium problem. Some 300 to 400 tons of radioactive groundwater meanwhile flows under the plant to the Pacific daily.