Summer Quarterly 2018
Scientists using a new method of detecting radioactive particles have warned that there was a significant release during the Fukushima nuclear accident that could pose a risk to humans.[The study was published in Environmental Science & Technology, Feb. 13, 2018.]
The method allows scientists to quickly count the number of cesium-rich micro-particles in Fukushima soils and quantify the amount of radioactivity associated with these particles.
The research, which was carried out by scientists from Kyushu University, Japan, and the University of Manchester, contradicts initial [government and industry] findings in the immediate aftermath of the 2011 Fukushima meltdowns.
It was thought that only volatile, gaseous radionuclides, such as cesium and iodine, were released from the damaged reactors. [*See Nukewatch’s related article Fukushima’s “Hot Particles” Travelled Extreme Distances.] However, it has become apparent that small radioactive particles, termed cesium-rich micro-particles, were also released.
Scientists have shown that these particles … contain significant amounts of radioactive cesium as well as smaller amounts of other radioisotopes, such as uranium and technetium.
The abundance of these micro-particles in Japanese soils and sediments, and their environmental impact, is poorly understood. But the particles are very small and do not dissolve easily, meaning they could pose long-term health risks to humans if inhaled.
At present scientists don’t know how many of the micro-particles are present in Fukushima. The new method makes use of a technique called autoradiography, which uses an imaging plate placed over contaminated soil samples…. The radioactive decay from the soil is recorded on the plate as an image, which is then read onto a computer.
The scientists say radioactive decay from the cesium-rich micro-particles can be differentiated from other forms of cesium contamination in the soil.
The scientists tested the new method on rice-paddy soil samples retrieved from different locations within the Fukushima prefecture. The samples were taken close to and far away from the damaged nuclear reactors, at four kilometers and 40 kilometers. The new method found cesium-rich micro-particles in all of the samples and showed that the amount of cesium associated with the micro-particles in the soil was much larger than expected.
“There is a need for further detailed investigation on Fukushima fuel debris, inside, and potentially outside the nuclear exclusion zone.”
— Dr. Gareth Law, Center for Radiochemistry Research, School of Chemistry, Univ. of Manchester
Dr. Satoshi Utsunomiya, associate professor at Kyushu University, Japan, and the lead author of the study, said: “When we first started to find cesium-rich micro-particles in Fukushima soil samples, we thought they would turn out to be relatively rare. Now, using this method, we find there are lots of cesium-rich micro-particles in exclusion zone soils and also in the soils collected from outside of the exclusion zone.”
“We hope that our method will allow scientists to quickly measure the abundance of cesium-rich micro-particles at other locations and estimate the amount of cesium radioactivity associated with the particles….” Utsunomiya said.
In March 2018, a Greenpeace survey found that even seven years after the catastrophic disaster, the people, towns and villages in the surrounding area are still being exposed to excessive levels of radiation.
Dr. Gareth Law, an analytical radiochemistry lecturer at the Univ. of Manchester in England and one of the paper’s authors, said in a news release, “Our research strongly suggests there is a need for further detailed investigation on Fukushima fuel debris, inside, and potentially outside the nuclear exclusion zone.”