Conversely, some fission products and actinides produced in nuclear reactors are radiotoxic and have long half-lives. Radionuclides are beneficial in many instances such as power generation, industrial, medical, and geochronological applications. Indeed, biological half- lives of insoluble caesium particles might be much larger than that of soluble caesium".Ĭonference Abstract: Plenary: Monday 27th June 11:45-12:45Ĭhallenging Radionuclides in Environment at the Atomic Scale: Issues in Waste Disposal and Fukushima SATOSHI UTSUNOMIYA They may change our understanding of the mechanism of long range atmospheric mass transfer of radioactive caesium from the reactor accident at Fukushima to Tokyo, but they may also change the way we assess inhalation doses from the caesium microparticles inhaled by humans. "The leading edge observations by nano-science facilities presented here are extremely important. Bernd Grambow, Director of SUBATECH laboratory, Nantes, France and leader of the research group on interfacial reaction field chemistry of the ASRC/JAEA, Tokai, Japan, said: This may mean that our ideas of the health implications should be modified".Ĭommenting, Prof. However, the concentration of radioactive caesium in microparticles means that, at an extremely localised and focused level, the radioactive fallout may have been more (or less) concentrated than anticipated. It looks like the clean-up procedure, which consisted of washing and removal of top soils, was the correct thing to do. The airborne Cs nanoparticles were condensed along with the Fe-Zn nanoparticles and the gas from the molten concrete, to form the SiO2 glass nanoparticles, which were then dispersed.Īnalysis from several air filters collected in Tokyo on 15 March 2011 showed that 89% of the total radioactivity was present as a result of these caesium-rich microparticles, rather than the soluble Cs, as had originally been supposed.Īccording to Dr Satoshi Utsunomiya: "This work changes some of our assumptions about the Fukushima fallout. Nuclear fuel, at temperatures of above 2200 K (about as hot as a blowtorch), melted the reactor pressure vessel resulting in failure of the vessel. Radioactive Cs was released and formed airborne Cs nanoparticles. Because of the high Cs content in the microparticles, the radioactivity per unit mass was as high as ~4.4x10 11 Bq/g, which is between 10 7 and 10 8 times higher than the background Cs radioactivity per unit mass of the typical soils in Fukushima.Ĭloser microparticle structural and geochemical analysis also revealed what happened during the accident at FDNPP. The analysis shows that these particles mainly consist of Fe-Zn-oxides nanoparticles, which, along with the caesium were embedded in Si oxide glass that formed during the molten core-concrete interaction inside the primary containment vessel in the Fukushima reactor units 1 and/or 3. However, analysis with state-of-the-art electron microscopy in conjunction with autoradiography techniques showed that most of the radioactive caesium in fact fell to the ground enclosed in glassy microparticles, formed at the time of the reactor meltdown. As caesium is water-soluble, it had been anticipated that most of the radioactive fallout would have been flushed from the environment by rainwater. Japanese geochemists, headed by Dr Satoshi Utsunomiya (Kyushu University, Japan), analysed samples collected from within an area up to 230 km from the FDNPP. The flooding of the Fukushima Daiichi Nuclear Power Plant (FDNPP) after the disastrous earthquake on Macaused the release of significant amounts of radioactive material, including caesium (Cs) isotopes 134Cs (half-life, 2 years) and 137Cs (half-life, 30 years).
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