The distribution of the ambient dose equivalent rate (i.e., air dose rate) after a nuclear disaster is crucial for zoning contaminated areas to facilitate authorities’ effective decision making. Several countries are considering a gradual characterization strategy where airborne measurement is performed first followed by ground measurement (i.e., via manborne or carborne surveys). Nonetheless, potential differences might emerge in country-specific air dose rate assessment methods. Explaining these discrepancies can improve and converge existing methodologies. The Japan Atomic Energy Agency (JAEA) and the French Institute for Radiological Protection and Nuclear Safety (IRSN), which are organizations involved in post-nuclear accident crisis management, jointly performed air dose rate measurements in 2019 at contaminated sites around the Fukushima Daiichi Nuclear Power Station. The similarities and differences between the two organizations’ methods and results were quantitatively assessed by comparing the average air dose rates obtained within a grid created with a geographic information system, and the reasons for the differences between the organizations’ results were investigated. The air dose rates obtained by the manborne measurements varied depending on the calibration method. Comparing the air dose rate assessment methods and mapping techniques used in different countries will contribute to developing international guidelines for recommending the best method for determining air dose rates.

1. [1] International Atomic Energy Agency, “Operational Intervention Levels for Reactor Emergencies and Methodology for Their Derivation, Emergency Preparedness and Response,” IAEA, 2017. https://www.iaea.org/publications/11093/operational-intervention-levels-for-reactor-emergencies [Accessed March 12, 2024]
2. [2] A. Malins, M. Okumura, M. Machida, H. Takemiya, and K. Saito, “Fields of view for environmental radioactivity,” Proc. of the 2015 Int. Symp. on Radiological Issues for Fukushima’s Revitalized Future, pp. 28-34, 2015.
3. [3] M. Lowdon, P. G. Marin, M. W. J. Hubbrad, M. P. Taggart, D. T. Connor, Y. Verbelen, P. J. Sellin, and T. B. Scott, “Evaluation of Scintillator Detection Materials for Application within Airborne Environmental Radiation Monitoring,” Sensors, Vol.19, No.18, Article No.3828, 2019. https://doi.org/10.3390/s19183828
4. [4] C. M. Chen, L. E. Sinclair, R. Fortin, M. Coyle, and C. Samson, “In-Flight Performance of the Advanced Radiation Detector for UAV Operations (ARDUO),” Nucl. Inst. Metho. Phys. Res. A, Vol.954, Article No.161609, 2020. https://doi.org/10.1016/j.nima.2018.11.068
5. [5] A. Vargas, D. Costa, M. Macias, P. Royo, E. Pastor, M. Luchkov, S. Neumaier, U. Stöhlker, and R. Luff, “Comparison of airborne radiation detectors carried by rotary-wing unmanned aerial systems.” Rad. Meas., Vol.145, Article No.106595, 2021. https://doi.org/10.1016/j.radmeas.2021.106595
6. [6] X. Jia, G. Qin, F. Li, and G. Zhao, “Design of an Airborne -ray Spectrometry System Based on Unmanned Aerial Vehicle,” J. Phys., Vol.2449, Article No.012043, 2023. https://doi.org/10.1088/1742-6596/2449/1/012043
7. [7] L. E. Sinclair and R. Fortin, “Spatial deconvolution of aerial radiometric survey and its application to the fallout from a rediological dispersal device,” J. Environ. Radioact., Vol.197, pp. 39-47, 2019. https://doi.org/10.1016/j.jenvrad.2018.10.014
8. [8] T. Furutani, K. Uehara, and J. Murai, “A Study on Comminity-Based Reconstruction from Nuclear Power Plant Disaster – A Case Study of Minamisoma Ota Area in Fukushima –,” J. Disaster Res., Vol.7, No.sp, pp. 432-438, 2012. https://doi.org/10.20965/jdr.2012.p0432
9. [9] N. M. Hassan, Y. J. Kim, J. Jang, B. U. Chang, and J. S. Chae, “Comparative study of precise measurements of natural radionuclides and radiation dose using in-situ and laboratory -ray spectroscopy techniques,” Sci. Rep., Vol.8, Article No.14115, 2018. https://doi.org/10.1038/s41598-018-32220-9
10. [10] M. Andoh, S. Mikami, S. Tsuda, T. Yoshida, N. Matsuda, and K. Saito, “Decreasing trend of ambient does equivalent rates over a wide area in eastern Japan until 2016 evaluated by carborne surveys using KURAMA systems,” J. Environ. Radioact., Vol.210, Article No.105813, 2019. https://doi.org/10.1016/j.jenvrad.2018.09.011
11. [11] E. Prieto, E. Jabaloyas, R. Gasanovas, C. Rovira, and M. Salvadó, “Set up of a gamma spectrometry mobile unit equipped with LaBr(Ce) detectors for radioactivity monitoring,” Rad. Phys. Chem., Vol.168, Article No.108600, 2020. https://doi.org/10.1016/j.radphyschem.2019.108600
12. [12] Y.-Y. Ji, K. Ochi, S. B. Hong, S. Nakama, Y. Sanada, and S. Mikami, “Joint Environmental Radiation Survey by JAEA and KAERI Around the Fukushima Daiichi Nuclear Power Plant: Performance of Mobile Gamma-Ray Spectrometry Using Backpack and Carborne Survey Platforms,” Health Phys., Vol.121, No.6, pp. 613-620, 2021. https://doi.org/10.1097/HP.0000000000001471
13. [13] R. Pradana, E. D. Nugraha, W. Wahyudi, U. Untara, M. Wiyono, A. Devriany, S. N. Shilfa, M. Sasaki, H. Prasetio, I. D. Winarni, E. Ekaranti, N. Nuraeni, C. Kranrod, D. Iskandar, G. Suhariyono, H. N. E. Surniyantoro, M. Makhsun, S. Widodo, Y. Omori, E. Hiswara, M. Hosoda, S. Yoshinaga, and S. Tokonami, “Carborne survey and dose assessment from external radiation exposure in Bangka Island,” Environ. Sci. Pollut. Res., Vol.30, pp. 89280-89292, 2023. https://doi.org/10.1007/s11356-023-28640-4
14. [14] F. S. Russel-Pavier, S. Kaluvan, D. Megson-Smith, D. T. Corner, S. J. Fearn, E. L. Connolly, T. B. Scott, and P. G. Martin, “A highly scalable and autonomous spectroscopic radiation mapping system with resilient IoT detector units for dosimetry, safety and security,” J. Radiol. Port., Vol.43, Article No.011503, 2023. https://doi.org/10.1088/1361-6498/acab0b
15. [15] A. J. Cresswell, D. C. W. Sanderson, M. Harrold, B. Kirley, C. Mitchell, and A. Weir, “Demonstration of lightweight gamma spectromety systems in urban environments,” J. Environ. Radioact., Vol.124, pp. 22-28, 2013. https://doi.org/10.1016/j.jenvrad.2013.03.006
16. [16] M. Andoh, H. Yamamoto, T. Kanno, and K. Saito, “Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant Using KURAMA-II until 2016,” J. Environ. Radioact., Vols.190-191, pp. 111-121, 2018. https://doi.org/10.1016/j.jenvrad.2018.04.025
17. [17] P. G. Martin, D. Connor, O. D. Payton, M. Leal-Olloqui, A. C. Keatley, and T. B. Scott, “Development and validation of a high-resolution mapping platform to aid in the public awareness of radiological hazards,” J. Radiol. Prot., Vol.38, No.1, pp. 329-342, 2018. https://doi.org/10.1088/1361-6498/aaa914
18. [18] W. Poltabtim, S. Musikawan, A. Thumwong, Y. Omori, C. Kranrod, M. Hosoda, K. Saenboonruang, and S. Tokonami, “Estimation of Ambient Dose Equivalent Rate Distribution Map Using Walking Survey Technique in Hirosaki City, Aomori, Japan,” Int. J. Environ. Res. Publ. Health, Vol.20, No.3, Article No.2657, 2023. https://doi.org/10.3390/ijerph20032657
19. [19] Group for Fukushima Mapping Project, “Investigations on Distribution of Radioactive Substances Owing to the Fukushima Daiichi Nuclear Power Station Accident in the Fiscal Year 2020 (Contact Research),” JAEA-Technology, 2021-025, 2022 (in Japanese). https://doi.org/10.11484/jaea-technology-2021-025
20. [20] Y. Sanada, Y. Urabe, M. Sasaki, K. Ochi, and T. Torii, “Evaluation of ecological half-life of dose rate based on airborne radiation monitoring following the Fukushima Dai-ichi nuclear power plant accident,” J. Environ. Radioact., Vol.192, pp. 417-425, 2018. https://doi.org/10.1016/j.jenvrad.2018.07.016
21. [21] S. Mikami, T. Maeyama, Y. Hoshide, R. Sakamoto, S. Sato, N. Okuda, T. Sato, H. Takemiya, and K. Saito, “The air dose rate around the Fukushima Dai-ichi Nuclear Power Plant: Its spatial characteristics and temporal changes until December 2012,” J. Environ. Radioact., Vol.139, pp. 250-259, 2015. https://doi.org/10.1016/j.jenvrad.2014.08.020
22. [22] Institut de Radioprotection et de Sûreté Nucléaire. https://sfrp.asso.fr/blog/les-manifestations/fukushima-10-ans-apres/ [Accessed March 14, 2024]
23. [23] G. Steinhauser, A. Brandl, and T. E. Johnson, “Comparison of the Chernobyl and Fukushima nuclear accidents: A review of the environmental impacts,” Sci. Tot. Environ., Vol.470-471, pp. 800-817, 2014. https://doi.org/10.1016/j.scitotenv.2013.10.029
24. [24] International Atomic Energy Agency, “Calibration of Radiation Protection Monitoring Instruments,” Safety Reports Series, No.16, 2000. https://www-pub.iaea.org/MTCD/Publications/PDF/P074_scr.pdf [Accessed March 12, 2024]
25. [25] International Atomic Energy Agency, “Guidelines for Radioelement Mapping Using Gamma Ray Spectrometry Data,” IAEA, IAEA-TECDOC-1363, 2003. https://www-pub.iaea.org/MTCD/Publications/PDF/te_1363_web.pdf [Accessed March 12, 2024]
26. [26] B. Lauritzen, D. W. Sandarson, A. Crosswell, M. Scott, R. Finck, and S. Karlsson, “ECOMAGS: Initial results from the RESUME 2002 Exercise,” NKS, NKS-86, 2002. https://inis.iaea.org/collection/NCLCollectionStore/_Public/34/057/34057813.pdf [Accessed March 12, 2024]
27. [27] D. C. W. Sandarson, A. J. Crosswell, I. M. Anthony, and S. Murphy, “Report on SURRC Participation in the ECCOMAGS Project Resume 2002 Exercise,” Scottish Universities Research and Reactor Centre, 2002. https://eprints.gla.ac.uk/39226/1/39226.pdf [Accessed March 12, 2024]
28. [28] D. C. W. Sandarson, A. J. Crosswell, E. M. Scott, and J. J. Lang, “Demonstrating the European capability for airborne gamma spectrometry: Results from the ECOMAGES exercise,” Rad. Prot. Dos., Vol.109, Nos.1-2, pp. 119-125, 2004. https://doi.org/10.1093/rpd/nch243
29. [29] B.-J. Kim, M. Sasaki, and Y. Sanada, “Comparison of the Fukushima radioactive mapping by two different airborne radiation monitoring system,” Prog. Nucl. Sci. Technol., Vol.6, pp. 130-133, 2019. https://doi.org/10.15669/pnst.6.130
30. [30] Y.-Y. Ji, K. Ochi, S. B. Hong, S. Nakama, Y. Sanada, and S. Mikami, “Performance of in situ gamma-ray spectrometry in the assessment of radioactive cesium deposition around the Fukushima Daiichi nuclear power plant,” Rad. Phys. Chem., Vol.179, Article No.109205, 2021. https://doi.org/10.1016/j.radphyschem.2020.109205
31. [31] K. Ochi, M. Sasaki, M. Ishida, and Y. Sanada, “Comparison of airborne and ground-based tools for used for radiation measurement in the environment,” Prog. Nucl. Sci. Technol., Vol.6, pp. 103-107, 2019. https://doi.org/10.15669/pnst.6.103
32. [32] Y. Sanada, M. Ishida, K. Yoshimura, and S. Mikami, “Comparison of Dose Rates from Four Surveys around the Fukushima Daiichi Nuclear Power Plant for Location Factor Evaluation,” J. Rad. Prot. Res., Vol.46, No.4, pp. 184-193, 2021. https://doi.org/10.14407/jrpr.2021.00171
33. [33] Geospatial Information Authority of Japan, “Latest national pictures (seamless).” https://www.gsi.go.jp/ENGLISH/index.html [Accessed February 27, 2023]
34. [34] H. Kato, Y. Onda, X. Gao, Y. Sanada, and K. Saito, “Reconstruction of a Fukushima accident-derived radiocesium fallout map for environmental transfer studies,” J. Environ. Radioact., Vol.210, Article No.105996, 2019. https://doi.org/10.1016/j.jenvrad.2019.105996
35. [35] Y. Sanada, K. Yoshimura, Y. Urabe, T. Iwai, and E. W. Katengeza, “Distribution map of natural gamma-ray dose rates for studies of the additional exposure dose after the Fukushima Dai-ichi Nuclear Power Station accident,” J. Environ. Radioact., Vols.223-224, Article No.106397, 2020. https://doi.org/10.1016/j.jenvrad.2020.106397
36. [36] S. Tsuda, T. Yoshida, M. Tsutsumi, and K. Saito, “Characteristics and verification of a carborne survey system for dose rates in air: KURAMA-II,” J. Environ. Radioact., Vol.139, pp. 260-265, 2015. https://doi.org/10.1016/j.jenvrad.2014.02.028
37. [37] United Nations Scientific Committee on the Effects of Atomic Radiation, “Levels and effects of radiation exposure due to the accident at the Fukushima Daiichi Nuclear Power Station: Implications of information published since the UNSCEAR 2013 Report,” UNSCEAR 2020/2021 Report, United Nations, 2022. https://www.unscear.org/docs/publications/2020/UNSCEAR_2020_21_Report_Vol.II.pdf [Accessed March 12, 2024]
38. [38] P. Bossew, G. Cinelli, M. Hernández-Ceballos, N. Cernohlawek, V. Gruber, B. Dehandschutter, F. Menneson, M. Bleher, U. Stöhlker, I. Hellmann, F. Weiler, T. Tollefsen, P. V. Tognoli, and M. de Cort, “Estimating the terrestrial gamma dose rate by decomposition of the ambient dose equivalent rate,” J. Environ. Radioact., Vol.166, pp. 296-308, 2017. https://doi.org/10.1016/j.jenvrad.2016.02.013
39. [39] E. Buchanan, A. J. Cresswell, B. Seitz, and D. C. W. Sanderson, “Operator related attenuation effects in radiometric surveys,” Radiation Measurements, Vol.86, pp. 24-31, 2016. https://doi.org/10.1016/j.radmeas.2015.12.029
40. [40] V. Ramzaev, C. Bernhardsson, A. Barkovsky, I. Romanovich, J. Jarneborn, S. Mattsson, A. Dvornik, and S. Gaponenko, “A backpack -spectrometer for measurements of ambient dose equivalent rate, , from 137Cs and from naturally occurring radiation: The importance of operator related attenuation,” Radiation Measurements, Vol.107, pp. 14-22, 2017. https://doi.org/10.1016/j.radmeas.2017.10.002