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(Eu) scintillation detector to in-situ gamma-ray spectrometryTakeyasu, Masanori; Mikami, Satoshi; Ando, Masaki; Hokama, Tomonori
JAEA-Testing 2023-005, 17 Pages, 2024/03
JAEA-Testing-2023-005.pdf:1.16MB
As part of the research aimed at developing a detector to easily perform in-situ gamma-ray spectrometry, the applicability of a SrI(Eu) scintillation detector to in-situ gamma-ray spectrometry was investigated. In this study, the characteristics of the SrI(Eu) detector were evaluated for in-situ gamma-ray spectrometry. Intercomparison measurements of in-situ gamma-ray spectrometry using the SrI(Eu) detector and Ge semiconductor detectors were conducted, and the applicability of the SrI(Eu) detector was examined. To characterize the SrI(Eu) detector, the peak efficiency of the SrI(Eu) detector was measured with respect to the change of incident gamma-ray energy. The angular dependence of the peak efficiency of the SrI(Eu) detector was also measured. As the result of the intercomparison measurement of in-situ gamma-ray spectrometry, the radionuclides quantified by Ge detectors were Cs-134, Cs-137, Pb-214, Bi-214, Tl-208, Ac-228 and K-40. On the other hand, those by SrI(Eu) detector were only Cs-137 and K-40 which had relatively high radioactive intensity. The deposition density of Cs-137 and the concentration of K-40 in soil measured by the SrI(Eu) detector showed relatively good agreements with those by Ge detectors. From these results, it was suggested that the in-situ measurement using a SrI(Eu) detector was available for radionuclides which had high radioactive intensity and whose gamma-ray peaks were not interfered by those of other radionuclides in gamma-ray spectrum. During an accident at nuclear power plant, various radionuclides are released into the environment, but radionuclides with short half-life decayed and radionuclides with long half-life only exist at mid-to-long term environmental monitoring situations, when in-situ gamma-ray spectrometry using a SrI(Eu) detector is applicable.
Ando, Masaki; Saito, Kimiaki
JAEA-Technology 2021-032, 66 Pages, 2022/03
JAEA-Technology-2021-032.pdf:3.84MB
Since the occurrence of the accident at the TEPCO Fukushima Daiichi Nuclear Power Station, the Japan Atomic Energy Agency (JAEA) has been conducting a series of car-borne survey over a wide area in the eastern part of Japan using the monitoring system KURAMAII. In this report, outline of the car-borne surveys are summarized and the following characteristics of the temporal changes in each prefecture and region were investigated using the measured data obtained from 2012 to 2019; 1) Average and maximum values for each prefecture for the six years from 2014 to 2019, 2) Average values for each prefecture from 2012 to 2019, 3) Average values for each evacuation order area category, regional category, and northern Soso-area municipality in Fukushima Prefecture from 2012 to 2019, and 4) Average and maximum values for each municipality in each prefecture for four times (at almost two-year intervals) of the measurement results from 2012 to 2018.
Futemma, Akira; Sanada, Yukihisa; Ishizaki, Azusa; Kawasaki, Yoshiharu*; Iwai, Takeyuki*; Hiraga, Shogo*; Sato, Kazuhiko*; Haginoya, Masashi*; Matsunaga, Yuki*; Kikuchi, Hikaru*; et al.
JAEA-Technology 2021-029, 132 Pages, 2022/02
JAEA-Technology-2021-029.pdf:24.58MB
By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the Great East Japan Earthquake and the following tsunami on March 11, 2011, a large amount of radioactive material was released from the FDNPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter has been conducted around FDNPS. The results of the airborne radiation monitoring and the evaluation for temporal change of dose rate in the fiscal 2020 were summarized in this report. Analysis considering topographical effects was applied to the result of the airborne monitoring to improve the accuracy of conventional method. In addition, technique for discriminating gamma rays from the ground and those from the airborne Rn-progenies was also utilized to evaluate their effect on airborne radiation monitoring.
Ando, Masaki; Matsuda, Norihiro; Saito, Kimiaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(1), p.34 - 39, 2021/03
We measured count rates and air dose rates at 11 measurement points where the influence of the Fukushima Dai-ichi Nuclear Power Plant accident could be ignored to obtain parameters for a background equation applying to KURAMA-II loaded with the high sensitivity CsI(Tl) detector, C12137-01. It was found that the sensitivity of KURAMA-II (C12137-01) was about 10 times or more for background measurement, compared with KURAMA-II loaded with the standard type CsI(Tl) detector, C12137. A background equation for the energy range of 1400-2000 keV was determined as, y (
Sv/h)=0.062 x (cps). We evaluated background air dose rates using KURAMA-II (C12137-01) for 71 municipalities and compared them with the previous study using KURAMA-II (C12137). Evaluated background air dose rates in this study were almost equal to those in the previous study. We confirmed that the background equation evaluated in this study was applicable for the KURAMA-II (C12137-01).
Ando, Masaki; Sasaki, Miyuki; Saito, Kimiaki
Journal of Nuclear Science and Technology, 57(12), p.1319 - 1330, 2020/12
Times Cited Count：4 Percentile：44.4(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.
Sato, Tetsuro*; Ando, Masaki; Sato, Masako*; Saito, Kimiaki
Journal of Environmental Radioactivity, 210, p.105973_1 - 105973_7, 2019/12
Times Cited Count：9 Percentile：35.81(Environmental Sciences)A method was devised for estimation of external doses of Fukushima residents expected to return to their homes after evacuation orders are lifted. 211 residents expected to return to six towns and villages were surveyed in FY 2014, FY 2015, and FY2016. Interviewing returning residents about their expected life patterns after returning, air dose rate were measured along the reported personal trails representing their patterns of movement in daily life. Excluding 15 residents from whose homes we were unable to take air dose rate measurements, the maximum external effective dose and the average external effective dose were estimated respectively as 4.9 mSv/y and 0.86 mSv/y. Although the mean values and dispersion of external effective doses differ depending on the evacuation level, for 93.3% of all residents, the estimated external effective doses were less than 2 mSv/y. The average exposure dose at home accounts for 66.8% of the annual exposure dose.
Saito, Kimiaki; Mikami, Satoshi; Ando, Masaki; Matsuda, Norihiro; Kinase, Sakae; Tsuda, Shuichi; Yoshida, Tadayoshi; Sato, Tetsuro*; Seki, Akiyuki; Yamamoto, Hideaki*; et al.
Journal of Environmental Radioactivity, 210, p.105878_1 - 105878_12, 2019/12
Times Cited Count：33 Percentile：80.86(Environmental Sciences)Saito, Kimiaki; Mikami, Satoshi; Ando, Masaki; Matsuda, Norihiro; Kinase, Sakae; Tsuda, Shuichi; Sato, Tetsuro*; Seki, Akiyuki; Sanada, Yukihisa; Wainwright-Murakami, Haruko*; et al.
Journal of Radiation Protection and Research, 44(4), p.128 - 148, 2019/12
Ando, Masaki
Hokeikyo Nyusu, (63), p.2 - 5, 2019/04
This is a commentary on the measurement of air dose rates by walk survey using KURAMA-II within 80 km range from the Fukushima Dai-ichi Nuclear Power Plant, which has been conducted as a commissioned research from the Nuclear Regulation Authority. The outline of KURAMA-II, the distribution map of air dose rates obtained by walk surveys, and the result of analysis concerning the decreasing trend of air dose rates are introduced based on the previous reports and thesis.
Ando, Masaki; Mikami, Satoshi; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Saito, Kimiaki
Journal of Environmental Radioactivity, 192, p.385 - 398, 2018/12
Times Cited Count：14 Percentile：45.18(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.
Ando, Masaki; Yamamoto, Hideaki*; Kanno, Takashi*; Saito, Kimiaki
Journal of Environmental Radioactivity, 190-191, p.111 - 121, 2018/10
Times Cited Count：18 Percentile：52.33(Environmental Sciences)Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 around the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months, which was beyond that attributable to the physical decay. The air dose rates decreased depending on the level of the evacuation areas, and the decrease was slightly larger in populated areas where humans are active. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground. The air dose rates measured by the walk surveys decreased quickly compared with the air dose rate from the flat ground measurement.
Ando, Masaki; Matsuda, Norihiro; Saito, Kimiaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(2), p.63 - 80, 2017/05
In order to discriminate the contribution of radioactive cesium due to the Fukushima Dai-ichi Nuclear Power Plant accident to the air dose rates measured by the car-borne surveys, natural background radiation was evaluated for eastern Japan area as the municipality averaged values. The window count method for distinction between natural and artificial radioactive nuclides was applied to the car-borne surveys using the KURAMA-II. Distribution of the evaluated natural background radiation showed geological feature, and it was found that the radiations measured along paved roads were reflecting the distribution of terrestrial 
-rays. The effect of the radioactive cesium as of 2014 for the municipalities designated as the Intensive Contamination Survey Area was beyond the uncertainty of the natural background radiation. That for the other municipalities, however, was found to be almost negligible.
Ando, Masaki; Kanno, Takashi; Saito, Kimiaki
JAEA-Technology 2015-060, 40 Pages, 2016/03
JAEA-Technology-2015-060.pdf:50.1MB
The ratios of air dose rate averaged in prefecture-wise measured by car borne surveys in wide area has been performed by with the use of the KURAMA and KURAMA-II systems were investigated. The changes in air dose rate from the first (June 2011) car borne survey to the fourth (September 2012) and seventh (November 2013) car borne surveys in Fukushima Prefecture was similar to those in Tochigi Prefecture, and the ratio in Miyagi Prefecture showed quicker decay than those in the other prefectures in the groups of less than 0.5Sv/h. Distribution maps of the ratios of air dose rate obtained in 100m mesh wise in Fukushima, Tochigi and Miyagi prefectures showed that the ratios (i.e. decreasing rates) were depending on the area or road. Further, decreasing in the air dose rate was quicker than the physical decay in the big cities where population is big and the traffic is huge.
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
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.
Tsuda, Shuichi; Yoshida, Tadayoshi; Ando, Masaki; Matsuda, Norihiro; Mikami, Satoshi; Tanigaki, Minoru*; Okumura, Ryo*; Takamiya, Koichi*; Sato, Nobuhiro*; Seki, Akiyuki; et al.
Radioisotopes, 64(4), p.275 - 289, 2015/04
This article provides practically useful information on air dose rate measurements in the environments. The basic requirements for the accurate measurements are described giving actual data. The characteristics and some measured results are shown for reliable methods which are widely used in the environmental radiation measurements. Further, information is given on internet sites where air dose rates and related data obtained by official organizations can be browsed.
Ando, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro*; Tanigaki, Minoru*; et al.
Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01
Times Cited Count：53 Percentile：83(Environmental Sciences)A series of car-borne surveys using the KURAMA and KURAMA-II systems was conducted in a wide area in eastern Japan from June 2011 to December 2012 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant, and to determine the time-dependent trend of decrease in air dose rates. An automated data processing system was established, which enables analyses of large amounts of data obtained with the use of about 100 units of the measurement system in a short time. The initial data for studying the migration status of radioactive cesium was obtained in the first survey, followed by the other car-borne surveys having wider measurement ranges. Comparing the measured air dose rates obtained in each survey, it was found that the decreasing trend of air dose rates measured through car-borne surveys was larger than that expected from the physical decay of radioactive cesium and that measured using NaI (Tl) survey meters around the road.
Tsuda, Shuichi; Yoshida, Tadayoshi; Nakahara, Yukio; Sato, Tetsuro; Seki, Akiyuki; Matsuda, Norihiro; Ando, Masaki; Takemiya, Hiroshi; Tanigaki, Minoru*; Takamiya, Koichi*; et al.
JAEA-Technology 2013-037, 54 Pages, 2013/10
JAEA-Technology-2013-037.pdf:4.94MB
JAEA has been performing dose rate mapping in air using a car-borne survey system KURAMA-II. The KURAMA system is a GPS-aided mobile radiation monitoring system that has been newly developed by Kyoto University Research Reactor Institute in response to the nuclear disaster. The KURAMA system is composed of an energy-compensated scintillation survey meter for measuring dose rate, electric device for controlling both the dose rates and the position data from a GPS module, a computer server for processing and analyzing data from KURAMA, and client PCs for providing for end users. The KURAMA-II has been improved in small-packaging, durability, and automated data transmission. In consequence, dose rate mapping in wide area has become possible in shorter period of time. This report describes the construction of KURAMA-II, its application and a suggestion of how to manage a large number of KURAMA-II.
Fukushima, Masahiro; Kitamura, Yasunori; Ando, Masaki; Kugo, Teruhiko
Journal of Nuclear Science and Technology, 49(10), p.961 - 965, 2012/10
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Ando, Masaki
Nihon Genshiryoku Gakkai Dai-44-Kai Robutsuri Kaki Semina Tekisuto, p.139 - 163, 2012/08
Mock-up experiments for "JOYO" and "MONJU" using FCA and the JUPITER program using ZPPR are introduced. As a validation of the fast reactor analysis method, a process to make a benchmark model, examples of reactivity experiment (Doppler effect and sodium void effect) and benchmark experiments to evaluate nuclear data libraries are described.
Fukushima, Masahiro; Kitamura, Yasunori; Kugo, Teruhiko; Yamane, Tsuyoshi; Ando, Masaki; Chiba, Go; Ishikawa, Makoto; Okajima, Shigeaki
Progress in Nuclear Science and Technology (Internet), 2, p.306 - 311, 2011/10
