カテゴリー media Paper Information Radioisotope Research

Quantitative Analysis Reveals Widespread Dispersion of Radioactive Cesium-Rich Microparticles (CsMPs) Released from the Fukushima Daiichi Nuclear Accident

A research team led by Associate Professor Shinya Yamasaki of the Radioisotope Research Division, CRiES, University of Tsukuba, and Professor Satoshi Utsunomiya of National Taiwan University has published a new study in the Journal of Hazardous Materials. The findings were also featured in a press release issued by the University of Tsukuba.

The study investigated the large-scale distribution and dispersion processes of radioactive cesium-rich microparticles (CsMPs) released during the Fukushima Daiichi Nuclear Power Plant accident. By analyzing soil samples collected from 100 locations across Fukushima Prefecture, the researchers found substantial regional variations in both the abundance of CsMPs and their contribution to total radioactivity. In some areas, more than 60% of the soil radioactivity was attributable to CsMPs.

Comparison with atmospheric dispersion simulations further revealed that large quantities of CsMPs were generated and released during the early hours of March 15, 2011, and subsequently transported over a wide area of Fukushima Prefecture under prevailing meteorological conditions. In contrast, radioactive plumes released after March 16 contained few CsMPs and were dominated by more water-soluble forms of radioactive cesium.

These findings improve our understanding of the environmental behavior of radioactive microparticles released during nuclear accidents and provide valuable information for future environmental risk assessments and dispersion modeling of radioactive contaminants.

Figure 1. Quantification of CsMPs in surface soils collected from 100 locations in Fukushima Prefecture by the summer of 2011
Left: The size of each circle represents the number of CsMPs per gram of surface soil. The color within each circle indicates the fraction of total cesium radioactivity attributable to CsMPs (radioactive fraction).
Right: Estimated distribution of CsMPs in radioactive plumes, expressed as the number of CsMPs per cubic meter of air. The size of each red circle corresponds to the particle concentration and is overlaid on plume dispersion maps for representative times on March 15, 2011.

For further details, please refer to the press release and the original publication below.

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