2021 Volume 2021 Issue 8 Pages 19-27
Restoration and reconstruction is the greatest and most pressing task following a nuclear accident. In this paper we examined the task of reducing external exposure to radiation from radioactive material that has accumulated in agricultural land or its peripheral areas. We focus on the features of a machine for decontaminating agricultural peripheral areas such as embankments and agricultural roads, and we also report the results of onsite testing. Agricultural tractors with a shielded cabin were developed for decontaminating paddy fields that have been contaminated with radioactive material. The developed machines reduced the radiation dose rate of the interior of the cabin by approximately 50% or less from outside. The dust concentration was also reduced by more than 95%. The performances of the machines and the effects of the removal of surface soil were estimated via a decontamination test in Iitate, Fukushima. To reduce radioactive-cross contamination in rice huskers, we investigated two techniques: “decomposition cleaning of a husker”and the “flushing with unhulled rice.”An examination of the latter technique showed the Cs concentration in brown rice to be reduced by 90% from the early stages of husking. This result was not influenced by any initial contamination of the husker, and the resulting Cs concentration of the brown rice was below the regulation value. For this reason, we concluded that flushing rice huskers with unhulled rice is an easy and effective method for preventing radioactive cross-contamination. However, since the Cs concentration in the residue inside the husker after flushing tends to have a high Cs concentration, to prevent recurrence of crosscontamination it is necessary to remove the residue.
