24 Octobre 2016
FUKUSHIMA -- It may be impossible to measure the radioactive contaminant concentrations of water leeching from soil and other waste produced by the Fukushima nuclear disaster cleanup at 31 temporary waste storage sites in Fukushima Prefecture due to a planning flaw, a Board of Audit inspection has found.
The cleanup waste is put in bags, put in piles and covered with a waterproof tarp at the temporary disposal sites. These piles are built atop a low convex mound of earth, which is also covered with a tarp and is supposed to funnel the water leeching out of the waste into underground tanks. Contaminant concentration measurements are then taken from these tanks.
However, though many temporary disposal sites have been built on soft ground such as agricultural land, apparently no provisions were made for land subsidence -- the earth being pushed down by the pressure of the waste bags -- during planning.
The Board of Audit chose 34 of the 106 disposal sites in the prefecture for inspection. The 34 sites were spread across five municipalities, had waste piles five to six bags (or about 5 meters) high, and had been established in the four years up to fiscal 2015. Of these, the earth beneath the waste stack had subsided -- going from convex to concave -- at 31 sites, meaning contaminated water was also not flowing into the storage tanks. It is possible the water is collecting in the tarps.
There are 15 such sites in the Fukushima Prefecture town of Kawamata, five in the town of Namie, four each in the city of Tamura and the village of Iitate, and three in the town of Naraha. The subsidence of the earth bases hasn't been confirmed, but the Board of Audit has pointed out that if contaminated water is pooling in the tarps, it could impact future operations to move the waste to a mid-term storage site. It has also called on the Environment Ministry, which operates the sites, to take necessary measures to rectify the problem.
The ministry told the Mainichi Shimbun, "The stacks are designed so that contaminated water won't escape even if the land underneath subsides, and no harm has been done by the treatment of the water. The waste bags themselves have been replaced with waterproof versions, but we would still like to consider ways to reinforce the ground (under the piles), such as by using sand in the middle."