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JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2022 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2023-024, 176 Pages, 2024/03

JAEA-Technology-2023-024.pdf:22.16MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2022. Car-borne surveys, a measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create their distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. The range of fluctuation of past tritium concentration data in seawater was determined, and the causes of the fluctuation were discussed. Monitoring data in coastal area performed in 2022 owing to the comprehensive radiation monitoring plan was summarized, and temporal changes in cesium-137 were analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated air dose rate distribution data acquired through surveys such as car-borne and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2022 were published on the "Database for Radioactive Substance Monitoring Data", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

Journal Articles

Preliminary study of the criticality monitoring method based on the simulation for the activity ratio of short half-life noble-gas fission products from fuel debris

Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi; Kanno, Ikuo

Journal of Nuclear Science and Technology, 61(2), p.269 - 276, 2024/02

https://doi.org/10.1080/00223131.2023.2300773

Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2021 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2022-026, 152 Pages, 2023/01

JAEA-Technology-2022-026.pdf:20.14MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2021. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data to create air dose rate distribution maps, and temporal changes of the air dose rates were analyzed. Surveys on depth profile of radiocesium and in-situ measurements as for radiocesium deposition were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. Score maps to classify the importance of the measurement points were created for Fukushima Prefecture and the 80 km zone from the FDNPS, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. Monitoring data in coastal area performed owing to the comprehensive radiation monitoring plan until 2020 was summarized, and temporal changes in cesium-137 were analyzed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained in this project with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2021 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Daiichi Nuclear Power Station Accident in the fiscal year 2020 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2021-025, 159 Pages, 2022/01

JAEA-Technology-2021-025.pdf:46.66MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2020. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of the air dose rates were analyzed. Regarding radiocesium deposition into the ground, surveys on depth profile of radiocesium and in-situ measurements were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. In the examination of scoring for classifying the importance of measurement points, a score map was created for Fukushima Prefecture and the 80 km zone from the FDNPS, and the factors causing changes in the score when monitoring data from multiple years were used were discussed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2020 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

JAEA Reports

Investigations on distribution of radioactive substances owing to the Fukushima Dai-ichi Nuclear Power Station Accident in the fiscal year 2019 (Contract research)

Group for Fukushima Mapping Project

JAEA-Technology 2020-014, 158 Pages, 2020/12

JAEA-Technology-2020-014.pdf:23.82MB

This report presents results of the investigations on the distribution-mapping project of radioactive substances owing to TEPCO Fukushima Daiichi Nuclear Power Station (FDNPS) conducted in FY2019. Car-borne surveys, a flat ground measurement using survey meters, a walk survey and an unmanned helicopter survey were carried out to obtain air dose rate data. Air dose rate distribution maps were created and temporal changes of the air dose rates were analyzed. Regarding radiocesium deposition into the ground, surveys on depth profile of radiocesium and in-situ measurements were performed. Based on these measurement results, effective half-lives of the temporal changes in the air dose rates and the deposition were evaluated. In the examination of scoring to classify the importance of measurement points, we created a score map of Fukushima Prefecture and that within 80 km from the FDNPS based on the "score" method developed in 2018. The way of monitoring radioactive materials in land area was examined and the representativeness of monitoring points was proposed. Using the Bayesian hierarchical modeling approach, we obtained maps that integrated the air dose rate distribution data obtained from aircraft monitoring, car-borne surveys, and walk surveys with respect to the region within 80 km from the FDNPS and Fukushima Prefecture. The measurement results for FY2019 were published on the "Expansion Site of Distribution Map of Radiation Dose", and measurement data were stored as CSV format. Radiation monitoring and analysis of environmental samples owing to the comprehensive radiation monitoring plan were carried out.

Journal Articles

Evaluation of decreasing trend in air dose rate and ecological half-life within an 80 km range from Fukushima Dai-ichi Nuclear Power Plant, using car-borne survey data measured by KURAMA systems up to 2018

Ando, Masaki; Sasaki, Miyuki; Saito, Kimiaki

Journal of Nuclear Science and Technology, 57(12), p.1319 - 1330, 2020/12

https://doi.org/10.1080/00223131.2020.1789008

Times Cited Count：4 Percentile：36.46(Nuclear Science & Technology)

Air dose rates measured by car-borne surveys within 80 km range of Fukushima Dai-ichi Nuclear Power Plant using KURAMA systems from 2011 up to 2018 were analyzed, and decreasing trends and ecological half-life were evaluated. The decreasing speed of air dose rates became 0.08 over a period of seven years, indicating a much more rapid decrease than estimated by the physical decay of radiocesium (0.3). The fast components of the ecological half-lives evaluated in entire the evacuation order area were about 2 to 3 y, and were considerably larger than those outside the evacuation order area (0.4 to 0.5 y). To model the acceleration in the decrease of air dose rates observed in evacuation order areas, we modified the bi-exponential curve formula of ecological half-life and introduced the two-group model. The fast decreasing components of the ecological half-life evaluated using the two-group model after 2013 were 0.5 to 1 y, and were much shorter than those up to 2013, at 2 to 3 y.

JAEA Reports

The Data-base of the radiation monitoring in Fukushima based on the comprehensive radiation monitoring plan

Abe, Tomohisa; Ogiya, Takashi*; Shibata, Katsuya*; Hanawa, Tatsuaki*; Sanada, Yukihisa

JAEA-Data/Code 2020-004, 280 Pages, 2020/08

JAEA-Data-Code-2020-004.pdf:3.91MB

After the accidents at Fukushima Daiichi Nuclear Power Station (FDNPS), Japan Atomic Energy Agency has carried on survey for distribution situation of radiation materials under the direction of the Ministry of Education, Culture, Sports, Science and Technology (later the Nuclear Regulatory Agency) from June 2011 to FY2019. This report is mainly summarized as data-base of air dose rate, integrated dose and radionuclide concentration of some types of environmental sample (airborne dust, soil, pine needles) in the radiation monitoring in Fukushima Prefecture (20 km far from FDNPS). The results of radiation monitoring were analyzed for temporal change at each measurement site under the unification format. Furthermore, the effective half-life and the dispersion at each location and sample were evaluated based on these big data.

Journal Articles

Decreasing trend of ambient dose equivalent rates over a wide area in eastern Japan until 2016 evaluated by car-borne surveys using KURAMA systems

Ando, Masaki; Mikami, Satoshi; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Saito, Kimiaki

Journal of Environmental Radioactivity, 192, p.385 - 398, 2018/12

https://doi.org/10.1016/j.jenvrad.2018.07.009

Times Cited Count：15 Percentile：42.75(Environmental Sciences)

Car-borne surveys using KURAMA systems have been conducted over a wide area in eastern Japan since 2011. The measurement data collected until 2016 was analyzed, and decreasing trend of the dose rates in regions within 80 km of Fukushima Dai-ichi Nuclear Power Plant were examined. The averaged dose rates tended to decrease considerably with respect to the physical decay of radiocaesium, and the ecological half-lives of the fast and slow decay components were estimated. The decrease of the dose rate in the forest was slower than its decrease in other regions, and the decrease of the dose rate in urban area was the fastest. The decrease in the dose rates obtained via the car-borne survey was larger than that obtained on flat ground with few disturbances using survey meters approximately 1.5 y after the accident; hereafter, the decrease in the dose rates obtained via the car-borne survey was same as the latter measurement.

Journal Articles

Measurements and evaluations of air dose rates around Fukushima, 5; Characteristics of air dose rate distribution in the environment around the Fukushima Nuclear Power Plant site

Mikami, Satoshi; Matsuda, Norihiro; Ando, Masaki; Kinase, Sakae; Kitano, Mitsuaki; Kawase, Keiichi; Matsumoto, Shinichiro; Yamamoto, Hideaki; Saito, Kimiaki

Radioisotopes, 64(9), p.589 - 607, 2015/09

https://doi.org/10.3769/radioisotopes.64.589

This article presents the features of regional distributions and temporal changes in air dose rate and radionuclide deposition densities in Fukushima on the basis of analyses on large-scale environmental monitoring results using diverse methods. The continuity of decontamination effects is discussed according to repeated monitoring data after the decontamination model project. Further, some examples are shown on the projection of air dose rates together with the ecological half lives for different land uses.

Journal Articles

Empirical description of -delayed fission partial half-lives

Ghys, L.*; Andreyev, A. N.; Antalic, S.*; Huyse, M.*; Van Duppen, P.*

Physical Review C, 91(4), p.044314_1 - 044314_7, 2015/04

https://doi.org/10.1103/PhysRevC.91.044314

Times Cited Count：12 Percentile：61.15(Physics, Nuclear)

Journal Articles

-decay half-lives of new neutron-rich rare-earth isotopes $^{159}$ Pm, $^{162}$ Sm, and $^{166}$ Gd

Ichikawa, Shinichi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Nagame, Yuichiro; Shibata, Michihiro*; Sakama, Minoru*; Kojima, Yasuaki*

Physical Review C, 71(6), p.067302_1 - 067302_4, 2005/06

https://doi.org/10.1103/PhysRevC.71.067302

Times Cited Count：19 Percentile：74.52(Physics, Nuclear)

The new neutron-rich raer-earth isotopes $^{159}$ Pm, $^{162}$ Sm, and $^{166}$ Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport sysetm. The half-lives of $^{159}$ Pm, $^{162}$ Sm, and $^{166}$ Gd were determined to be 1.50.2s, 2.40.5s, and 4.81.0s, respectively. The partial decay scheme of $^{166}$ Gd wes constructed for - coincidence data. The improved half-life values of 25.62.2s wes obtained for the previously identified isotope $^{166}$ Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by the Audei and Wapstra.

Journal Articles

Identification of the new isotope $^{241}$ Bk

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Toyoshima, Atsushi; Kaneko, Tetsuya*; et al.

European Physical Journal A, 16(1), p.17 - 19, 2003/01

https://doi.org/10.1140/epja/i2002-10112-y

Times Cited Count：8 Percentile：49.79(Physics, Nuclear)

The new isotope $^{241}$ Bk has been identified for the first time using a gas-jet coupled on-line isotope separator at the JAERI tandem accelerator facility. Characteristic X rays and three transitions associated with the EC decay of $^{241}$ Bk have been observed, and the half-life was determined to be 4.6 min. The half-life value and the observed -ray energies and intensities can be consistently explained as a consequence of the allowed EC transition of $pi 7/2^{+}[633]$ $nu 7/2^{+}[624]$ .

Journal Articles

Recent studies of unstable nuclei far from stability with the on-line isotope separators of JAERI

Sekine, Toshiaki; Ichikawa, Shinichi; Osa, Akihiko; Koizumi, Mitsuo; Iimura, Hideki; Tsukada, Kazuaki; Nishinaka, Ichiro; Hatsukawa, Yuichi; Nagame, Yuichiro; Asai, Masato*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 239(1), p.127 - 131, 1999/00

https://doi.org/10.1007/BF02349543

Times Cited Count：2 Percentile：20.96(Chemistry, Analytical)

no abstracts in English

Journal Articles