The Fukushima Daiichi Nuclear Power Plant accident resulted in a large quantity of radioactivity microparticles that were disbursed into the environment. Understanding the number of these microparticles, the source and movement in the environment had been difficult since the accident in 2011.
Now scientists from Japan, Finland, France and the U.S. led by Dr. Satoshi Utsunomiya, Ryohei Ikehara, and Kazuya Morooka of Kyushu University developed a way to quantify the number of radioactive microparticles in the soil and sediment samples. The method was developed in 2018 and the scientists have now found a way to apply it to a range of soil samples from within and outside of the Fukushima Daiichi nuclear exclusion zone. The research was published in the journal Chemosphere.
Scientists able to determine cesium-rich microparticles in a wide range of locations
"Using our method, we have determined the number and amount of cesium-rich microparticles in surface soils from a wide range of locations up to 60 km from the Fukushima Daiichi site," said Dr. Utsunomiya in a press release highlighting the work. "Our work reveals three regions of particular interest. In two regions to the northwest of the damaged nuclear reactors, the number of cesium-rich microparticles per gram of soil ranged between 22 and 101, and the amount of total soil cesium radioactivity associated with the microparticles ranged from 15-37%. In another region to the southwest of the nuclear reactors, 1-8 cesium-rich microparticles were found per gram of soil, and these microparticles accounted for 27-80% of the total soil cesium radioactivity."
The scientists found that the cesium-rich microparticles were distributed in the same trajectories of the plumes released at the site. That could indicate that microparticles formed only during that short period from the late afternoon of 14 March 2011 to the late afternoon of 15 March 2011.
The scientists said the data and the method they developed could help inform clean up efforts that are still ongoing eight years later. The work "provides important understanding on cesium-rich microparticle dispersion dynamics, which can be used to assess risks and environmental impacts in inhabited regions," said Utsunomiya in the press release.