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Press release | Focus | Radioactivity | Environment
The CEA, Orano and Veolia tested out a radioactive soil decontamination process in Japan between 13 and 17 November 2017. These tests were carried out in Japan on several hundreds of kilograms of soil in the Fukushima region.
In the Fukushima region, around 22 million cubic metres of radioactive soil was removed from the surface of the soil following the nuclear power plant accident with a view to making the zone accessible to its inhabitants as soon as possible. This soil was stored in 'big bags' at several dedicated sites. The Japanese authorities are looking for the best technology to eradicate or reduce the radioactivity from the soil. The aim is to reduce the volume of this waste by concentrating the radioactivity, composed primarily of caesium, into a small volume and recovering the decontaminated part. The specific feature of the process tested by CEA, Orano and Veolia is that it directly separates the soil particles contaminated by the radioactive caesium from the particles that are barely contaminated or not contaminated at all.
In France, the participants in this project, named Demeterres (1), have, since 2013, been developing several innovative remediation technologies for use on contaminated soil and effluents. These technologies, based on biological or physicochemical processes, are designed to decontaminate soil using "eco-compatible" methods with a view to rehabilitating and re-using it.
One of the physicochemical processes developed within the framework of this project by CEA, Orano and Veolia, known as "froth flotation", was tested in Japan during the week of 13 to 17 November 2017. The process entails frothing a soil suspension in a flotation column. First the contaminated soil is mixed with water to form a suspension and a frothing agent is added. The mixture is introduced into the middle of a vertical column, and air is injected into the bottom of the column to produce bubbles. The caesium-charged clay particles attach to the surface of the air bubbles and form a froth, which builds up and is sucked to the top column, producing a concentrate of the radioactive particles. The following is thus recovered:
The flotation tests carried out on two big bags by the teams from the CEA/Orano/Veolia in Japan in November 2017 achieved the objectives set. 70 to 85% of the initial mass of soil was recovered. This mass contained only 33% to 50% of the initial amount of radioactivity.
This decontaminated soil displays a level of radioactivity that complies with the limit value of 8 kBq/kg authorised for potential re-use under Japanese law.
In order to further increase the caesium extraction yield, soil preparation optimisations (drying, crumbling, pre-sifting and dispersion in water) were proposed.
If the technology presented is selected by the Japanese authorities, the next stage will be to develop the process on a larger scale so that it can be used in the Japanese municipalities that house storage centres.
This process is subject to a patent belonging to the CEA and used at "pre-industrial pilot" level by Orano and Veolia.
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.