Topics

Aiming to Reduce Exposure Dose During Decontamination and House Demolition
−Data Analysis of Exposure Dose During Demolition Work in a Hard-To-Return Zone−


Fig.1 Data acquisition and prediction accuracy indices

Fig. 1 Data acquisition and prediction accuracy indices

Fig.2 Accumulated exposure dose in workers involved in the target work

Fig. 2 Accumulated exposure dose in workers involved in the target work

Fig.3 Comparison of planned and measured values before the work

Fig. 3 Comparison of planned and measured values before the work

Fig.4 Accuracy index of planned values by work type

Fig. 4 Accuracy index of planned values by work type


 Decontamination works to restore difficult-to-return zones around the TEPCO’s Fukushima Daiichi Nuclear Power Station are being conducted based on the guidelines of the Ministry of the Environment. In this study, the external cumulative exposure doses of all workers were obtained during the work associated with dose reduction measures such as house demolition and soil surface covering in five areas Fukushima Prefecture from July 2020 to March 2021. Furthermore, the behavioral histories of some workers in the area was recorded using GPS location information recording equipment (Fig. 1). The maximum integrated dose for each worker measured in this work was 1.1 mSv (Fig. 2). The relative deviation (RD), an indicator of the accuracy of the planned values, was calculated for each work area using the measured exposure dose data and planned exposure dose values. These planned values were calculated on the basis of the air dose rate recommended in the decontamination guidelines, etc., based on the obtained GPS data. The RD distribution peaked at 1.4, implying that the planned value is 2.4 times the measured value. Negative values, indicating that the planned value has underestimated the measured value, accounted for approximately 9 % of the RD values (Fig. 3). Moreover, the planned values of the decontamination workers were closer to the actual measured values than those of other workers (Fig. 4).
 The results of this study not only contribute to enabling radiation protection for decontamination workers but also alleviate the concerns of residents regarding radiation exposure, who will return to their homes in the future.


Acknowledgements

This achievement is part of the results of the "FY2021 Demonstration Project to Evaluate the Effectiveness of Dose Reduction Measures in Areas Other than Specific Reconstruction and Regeneration Zones" organized by the Cabinet Office, Government of Japan.


Author (Researcher) Information

Name | Yukihisa Sanada
Environmental Monitoring Research Group, Collaborative Laboratories for Advanced Decommissioning Science, Fukushima Research and Engineering Institute

Reference

Sanada, Y. et al., Evaluation of External Dose Exposure of Workers During House Demolition and Dose Reduction Work in a Difficult-To-Return Zone, Transactions of the Atomic Energy Society of Japan, vol.22, issue 2, 2023, p.87–96 (in Japanese).

Paper URL: https://doi.org/10.3327/taesj.j22.011

January 7, 2025

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