There are many sites around the world contaminated by radioactive materials. Some sites such as the Hanford Nuclear Reservation in Washington State were dedicated to nuclear weapons production and little regard was given to safely disposing of radioactive materials. Some sites such as the Nevada Test Site were used to test nuclear weapons before a treaty banned above ground and atmospheric tests. Some sites such as Fukushima were contaminated by accidents at nuclear power plants. There are millions of tons of soil around the world contaminated by radioactive materials that can threaten the environment and public health.
Last November, Japan’s Fukushima Prefecture and France’s Alternative Energies and Atomic Energy Commission (CEA) carried out a successful test of a new process for decontaminating radioactive soil.
The French Demeterres project was launched in 2013 for the purpose of developing bio- and eco-technology that could decontaminated soil and effluents for post-nuclear accident remediation. Twenty-three million dollars was allocated for the five-year project involving CEA, Orano, Veolia, the Institute for Radiological Protection and Nuclear Safety (IRSN), the National Institute for Agricultural Research (INRA), and the French Agricultural Research Centre for International Development (CIRAD).
One of the physiochemical processes that was developed by the Demeterres project utilizes particulate floatation foams. Soil contaminated with cesium is mixed with water to create a suspension. This mixture is injected into the middle of a floatation column. Air is pumped into the bottom of the floatation column to create bubbles. The contaminated soil particles adhere to the surface of the bubbles of air which rise to the surface of the column. Uncontaminated soil particles sink to the bottom of the column. The first test of the system took place in 2016 when uncontaminated soil was run through the column to gather data on the process.
After the March 2011 nuclear disaster at Fukushima, about twenty-nine million cubic yards of soil were removed. They wanted evacuees to be able to move back into their homes as quickly as possible. The contaminated soil was placed in huge storage bags and stored at several dedicated sites. The Japanese government is looking for the best way to reduce or remove the radioactivity in the soil.
In April of 2017, Japan's Ministry of the Environment put out a call for demonstrations of decontamination techniques. The froth floatation process was one of ten techniques that were selected for demonstration out of a total of nineteen submissions.
The froth floatation process was tested on about six hundred pounds of contaminated soil at Okuma in Fukushima Prefecture between November 13 and November 17 of 2017. The radioactivity of the soil samples was cut to between one third and one half of the original contamination level. As a result of the tests, pretreatment of soil through drying, crumbling, pre-sifting and/or dispersion in water were suggested to improve the process.
A spokesperson for CEA said, “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 centers.”
