Effects of non-decontamination human activities on the reduction of ambient dose equivalent rates in residential areas near the Fukushima Daiichi Nuclear Power Plant

Kim, M.; Yoshimura, Kazuya; Sakuma, Kazuyuki; Malins, A.*; Abe, Tomohisa; Nakama, Shigeo; Machida, Masahiko; Saito, Kimiaki

Journal of Environmental Radioactivity, 294, p.107931_1 - 107931_8, 2026/03

https://doi.org/10.1016/j.jenvrad.2026.107931

This study quantitatively evaluated the effects of non-decontamination human activities, such as traffic, on ambient dose rates in residential areas near the Fukushima Daiichi Nuclear Power Plant through field measurements and simulations. Field surveys showed that areas with higher traffic had greater reductions in Cs deposition, suggesting that vehicular movement may enhance cesium weathering. Monte Carlo simulations using 3D-ADRES confirmed that human activities accelerate the decrease in ambient dose rates on paved surfaces, with reductions of up to approximately 50%. These results indicate that non-decontamination human activities significantly contribute to lowering ambient dose rates.

Isotopic ratios of plutonium in radioactive particles released by the accident of Fukushima Daiichi Nuclear Power Plant

Igarashi, Junya*; Ninomiya, Kazuhiko*; Zheng, J.*; Zhang, Z.*; Fukuda, Miho*; Aono, Tatsuo*; Minowa, Haruka*; Yoshikawa, Hideki*; Sueki, Keisuke*; Satou, Yukihiko; et al.

Journal of Environmental Radioactivity, 291, p.107856_1 - 107856_8, 2026/01

https://doi.org/10.1016/j.jenvrad.2025.107856

no abstracts in English

In situ observation and theoretical study of temporal variations in radon exhalation rates from the gypsum board of a cavity wall; A Comparison with a solid concrete wall

Sakoda, Akihiro; Ishimori, Yuu; Hasan, Md. M.*; Jin, Q.*; Iimoto, Takeshi*

Journal of Environmental Radioactivity, 287, p.107703_1 - 107703_10, 2025/07

https://doi.org/10.1016/j.jenvrad.2025.107703

Building materials are one of the most important indoor radon sources, prompting research into their radon exhalation rate (JRn). Most previous studies examining these rates have relied on laboratory tests using pieces or blocks of materials such as concrete and brick. However, creating samples that mimic real cavity walls, defined as walls with a cavity between the two panels of the associated building material, has been challenging owing to structural complexities. In this study, we conducted the first long-term in situ measurement of JRn from the interior board of a common Japanese cavity wall comprising a thin gypsum board (interior wall), air/insulation, and concrete (exterior wall). Results indicated clear diurnal and seasonal variations in the observed JRn data. In general, the highest and lowest JRn values were observed in summer and winter, respectively, exhibiting the same pattern as that observed for thick solid concrete walls analyzed in our previous in situ study. Interestingly, JRn values increased during the day in summer and at night in winter, contrasting with the constant JRn value observed for the thick solid concrete walls over several days. Theoretical calculations indicated that in this case study, JRn was predominantly driven by diffusion, not by advection. These results could be explained by considering the wall thickness, radon diffusivity, and boundary conditions of radon activity concentrations. Our findings can help the selection and refinement of input parameters for radon sources when modeling the spatiotemporal dynamics of indoor radon in buildings. While this study provides new and interesting insights, it is only the first case study, underscoring the need for future in situ tests and the corresponding theoretical analyses across diverse buildings and environments.

Measurement and analysis of long-term variation of atmospheric Be activity concentrations in Dazaifu (western Japan)

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_10, 2025/04

https://doi.org/10.1016/j.jenvrad.2024.107612

Atmospheric Be activity concentration was continuously measured in Dazaifu, western Japan, from 1999 to 2020, and its variation was analyzed. Daily Be data analysis, encompassing an analysis for 22 years, revealed a concentration range of not detected - 18 mBq/m, characterized by substantial monthly variation and smoothed annual variation. An average daily Be activity concentration of 5.0 2.6 mBq/m was considered to be representative at the ground-surface-level in 30-40N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual Be variabilities. The monthly variability of Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce Be.

Integrated radiation air dose rate maps over the 80 km radius of the Fukushima Daiichi Nuclear Power Plant and the entire Fukushima Prefecture during 2011-2022

Sakuma, Kazuyuki; Kurikami, Hiroshi; Wainwright, Haruko*; Tanimori, Soichiro*; Nagao, Fumiya; Ochi, Kotaro; Sanada, Yukihisa; Saito, Kimiaki

Journal of Environmental Radioactivity, 280, p.107554_1 - 107554_11, 2024/12

https://doi.org/10.1016/j.jenvrad.2024.107554

In this study, we created the integrated radiation air dose rate maps in the Fukushima region during 2011-2022 using multiple types of surveys such as air-borne, car-borne and walk surveys as well as fixed-location measurements. We applied the Bayesian geostatistical method developed by Wainwright et al. (2017, 2019) to the 80 km radius of the Fukushima Daiichi Nuclear Power Plant and the whole of Fukushima Prefecture while considering the history of the lifting of the evacuation zone in Fukushima. The integrated maps fixed the bias to underestimate air dose rates in forest areas, and successfully created more reproducible integrated maps with a wider area and time series than the previous studies. It is highly expected that the results of this study will be used to evaluate detailed exposure doses to the general public.

Seafood dose parameters; Updating Po retention factors for cooking, decay loss and mariculture

Johansen, M. P.*; Carpenter, J. G.*; Charmasson, S.*; Gwynn, J. P.*; McGinnity, P.*; Mori, Airi; Orr, B.*; Simon-Cornu, M.*; Osvath, I.*

Journal of Environmental Radioactivity, 268-269, p.107243_1 - 107243_10, 2023/11

https://doi.org/10.1016/j.jenvrad.2023.107243

Some considerations on the dependence to numerical schemes of Lagrangian radionuclide transport models for the aquatic environment

Periez, R.*; Brovchenko, I.*; Jung, K. T.*; Kim, K. O.*; Liptak, L.*; Little, A.*; Kobayashi, Takuya; Maderich, V.*; Min, B. I.*; Suh, K. S.*

Journal of Environmental Radioactivity, 261, p.107138_1 - 107138_8, 2023/05

https://doi.org/10.1016/j.jenvrad.2023.107138

Lagrangian models present several advantages over Eulerian models to simulate the transport of radionuclides in the aquatic environment in emergency situations. A radionuclide release is simulated as a number of particles whose trajectories are calculated along time and thus these models do not require a spatial discretization. In this paper we investigate the dependence of a Lagrangian model output with the grid spacing which is used to calculate concentrations from the final distribution of particles, with the number of particles in the simulation and with the interpolation schemes which are required because of the discrete nature of the water circulation data used to feed the model.

Third international challenge to model the medium- to long-range transport of radioxenon to four Comprehensive Nuclear-Test-Ban Treaty monitoring stations

Maurer, C.*; Galmarini, S.*; Solazzo, E.*; Kumierczyk-Michulec, J.*; Bar, J.*; Kalinowski, M.*; Schoeppner, M.*; Bourgouin, P.*; Crawford, A.*; Stein, A.*; et al.

Journal of Environmental Radioactivity, 255, p.106968_1 - 106968_27, 2022/12

https://doi.org/10.1016/j.jenvrad.2022.106968

After performing multi-model exercises in 2015 and 2016, a comprehensive Xe-133 atmospheric transport modeling challenge was organized in 2019. For evaluation measured samples for the same time frame were gathered from four International Monitoring System stations located in Europe and North America with overall considerable influence of IRE and/or CNL emissions. As a lesion learnt from the 2nd ATM-Challenge participants were prompted to work with controlled and harmonized model set ups to make runs more comparable, but also to increase diversity. Effects of transport errors, not properly characterized remaining emitters and long IMS sampling times (12 to 24 hours) undoubtedly interfere with the effect of high-quality IRE and CNL stack data. An ensemble based on a few arbitrary submissions is good enough to forecast the Xe-133 background at the stations investigated. The effective ensemble size is below five.

Spatial variations in radiocesium deposition and litter-soil distribution in a mountainous forest catchment affected by the Fukushima nuclear accident

Atarashi-Andoh, Mariko; Koarashi, Jun; Tsuzuki, Katsunori; Takeuchi, Erina; Nishimura, Shusaku; Muto, Kotomi*; Matsunaga, Takeshi*

Journal of Environmental Radioactivity, 238-239, p.106725_1 - 106725_8, 2021/11

https://doi.org/10.1016/j.jenvrad.2021.106725

To understand the spatial variation in soil Cs inventory in complex mountainous topography, a whole-area investigation of Cs deposition in a broad-leaved forest catchment of a mountain stream was conducted using grid sampling. Across the catchment, organic and surface mineral soil layers were collected at 42 locations in 2013 and 6 locations in 2015. Cs deposition on the forest floor exhibited high spatial heterogeneity and altitude-dependent distribution over the catchment. The Cs retention ratio in the organic layer ranged from 6% to 82% in 2013. The Cs retention ratios had positive correlations with the material inventory in the organic layer and the elevation. The Cs retention ratios in the organic layer were less than 20% in 2015, even at the locations where the retention ratio was higher than 55% in 2013. Although there was spatial variation in the migration speed, Cs migration from the organic layer to mineral soil was almost completed within 4 y of the deposition.

Numerical reproduction of dissolved U concentrations in a PO-treated column study of Hanford 300 area sediment using a simple ion exchange and immobile domain model

Saito, Tatsuo; Sato, Kazuhiko; Yamazawa, Hiromi*

Journal of Environmental Radioactivity, 237, p.106708_1 - 106708_9, 2021/10

https://doi.org/10.1016/j.jenvrad.2021.106708

We succeeded at numerical reproduction of dissolved U concentrations from column experiments with PO-treated Hanford 300 Area sediment. The time-series curves of dissolved U concentrations under various Darcy flow rate conditions were reproduced by the numerical model in the present study through optimization of the following parameters:(i) the mass of U in mobile domain (on surface soil connected to the stream) and the rest of the total U left as precipitation in immobile domain (isolated in deep soil);(ii) the mixing ratio between immobile and mobile domains, to fit the final recovering curve of concentration; and (iii) the cation exchange capacity (CEC) and equilibrium constant (k) of the exchange reaction of UO and H on simulated soil surface (), to fit the transient equilibrium concentration, forming the bed of the bathtub curve.