Dose Estimation in Recycling of Decontamination Soil Resulting From The Fukushima NPS Accident For Road Embankments.

Since the Fukushima nuclear power station accident, large quantities of radiocesium-contaminated soil generated from decontamination activities have been stored in Fukushima prefecture. To complete the final disposal of decontamination soil, reducing the disposal volume through recycling can prove effective. The Ministry of the Environment of Japan has developed a policy of handling low-activity decontamination soil as recycled materials under the management of public authority. The recycling is limited to civil engineering structures in public projects, such as road embankments and coastal levees. However, there has been no practical review or safety assessment of decontamination soil recycling. In this study, to contribute to guideline development for decontamination soil recycling by the Ministry of the Environment, dose estimation was considered as a way of ensuring that the use of recycled decontamination soil for road embankments was safe. First, based on Japanese construction standards, additional doses to workers and the public in construction and service (e.g., use of a road embankment) scenarios were evaluated. From the result, the radioactive cesium concentration level of recycled materials that would result in all additional doses meeting the radiation criterion of 1 mSv y was derived to be 6,000 Bq kg. Then, construction conditions were reviewed to reduce additional doses to the public in a service scenario. To confine doses to the public to below 10 μSv y based on the derived radioactivity level, an additional layer of soil slope protection of 40 cm or more was needed. Finally, additional doses expected in a disaster scenario were confirmed to be below 1 mSv y based on the derived radioactivity level, an additional layer of soil slope protection of 40 cm or more was needed. Finally, additional doses expected in a disaster scenario were confirmed to be below 1 mSv y based on the derived radioactivity level.