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JAEA Reports

Study of the applicability of SrI$$_{2}$$(Eu) scintillation detector to in-situ gamma-ray spectrometry

Takeyasu, 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$$_{2}$$(Eu) scintillation detector to in-situ gamma-ray spectrometry was investigated. In this study, the characteristics of the SrI$$_{2}$$(Eu) detector were evaluated for in-situ gamma-ray spectrometry. Intercomparison measurements of in-situ gamma-ray spectrometry using the SrI$$_{2}$$(Eu) detector and Ge semiconductor detectors were conducted, and the applicability of the SrI$$_{2}$$(Eu) detector was examined. To characterize the SrI$$_{2}$$(Eu) detector, the peak efficiency of the SrI$$_{2}$$(Eu) detector was measured with respect to the change of incident gamma-ray energy. The angular dependence of the peak efficiency of the SrI$$_{2}$$(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$$_{2}$$(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$$_{2}$$(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$$_{2}$$(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$$_{2}$$(Eu) detector is applicable.

Journal Articles

The Role of collision ionization of K-shell ions in nonequilibrium plasmas produced by the action of super strong, ultrashort PW-class laser pulses on micron-scale argon clusters with intensity up to 5 $$times$$ 10$$^{21}$$ W/cm$$^{2}$$

Skobelev, I. Yu.*; Ryazantsev, S. N.*; Kulikov, R. K.*; Sedov, M. V.*; Filippov, E. D.*; Pikuz, S. A.*; Asai, Takafumi*; Kanasaki, Masato*; Yamauchi, Tomoya*; Jinno, Satoshi; et al.

Photonics (Internet), 10(11), p.1250_1 - 1250_11, 2023/11

It is challenging to clearly distinguish the impacts of the optical field and collisional ionization in the evolution of the charge state of a plasma produced when matter interacts with high-intensity laser pulses. In this work, time-dependent calculations of plasma kinetics are used to show that it is possible only when low-density gaseous targets with sufficiently small clusters are used. In the case of Ar plasma, the upper limit of the cluster radius was estimated to be $$R_0 = 0.1 mu$$m.

Journal Articles

Urban factors and mental health symptoms in children of the Tokyo Early Adolescence Survey; Impact of proximity to railway stations

Davies, S. J. C.*; Bolea-Alamanac, B.*; Endo, Kaori*; Yamamoto, Yu*; Yamasaki, Shudo*; Malins, A.; Evans, J.*; Sullivan, S.*; Ando, Shuntaro*; Nishida, Atsushi*; et al.

Journal of Transport & Health, 28, p.101564_1 - 101564_11, 2023/01

Journal Articles

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

JAEA Reports

Result of measurement of the ambient dose equivalent rates by car-borne surveys using KURAMA-II from 2012 until 2019

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.

JAEA Reports

Radiation monitoring using manned helicopter around the Nuclear Power Station in the fiscal year 2020 (Contract research)

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.

Journal Articles

Determination of parameters for an equation to obtain natural background radiation using KURAMA-II loaded with C12137-01 type CsI(Tl) detector

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 ($$mu$$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).

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

 Times Cited Count:4 Percentile:46.37(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.

Journal Articles

Degradation prediction using displacement damage dose method for AlInGaP solar cells by changing displacement threshold energy under irradiation with low-energy electrons

Okuno, Yasuki*; Ishikawa, Norito; Akiyoshi, Masafumi*; Ando, Hirokazu*; Harumoto, Masaki*; Imaizumi, Mitsuru*

Japanese Journal of Applied Physics, 59(7), p.074001_1 - 074001_7, 2020/07

 Times Cited Count:3 Percentile:20(Physics, Applied)

Performance degradation prediction for space solar cells under irradiation with low-energy electrons is greatly affected by displacement threshold energy (Ed) when a displacement damage dose (DDD) model is used. According to recent studies, the Ed of P atoms is much lower than the conventional Ed value in InP-type solar cells irradiated with low-energy electrons. This indicates that the value of Ed typically used in DDD model leads to significant error in performance degradation prediction. In this study, degradation of AlInGaP solar cells is observed after irradiation with 60 keV electrons. The results suggest that the Ed of P atoms in AlInGaP solar cells is much smaller than the conventionally used Ed value. By using the DDD model with the Ed value obtained in this study, we demonstrated that the performance degradation predicted by the DDD model agrees well with the experimental results.

Journal Articles

External dose evaluation based on detailed air dose rate measurements in living environments

Sato, Tetsuro*; Ando, Masaki; Sato, Masako*; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105973_1 - 105973_7, 2019/12

 Times Cited Count:8 Percentile:37.04(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.

Journal Articles

Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident

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:30 Percentile:81.17(Environmental Sciences)

Journal Articles

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident

Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

AA2019-0019.pdf:2.65MB

 Times Cited Count:20 Percentile:67.75(Environmental Sciences)

The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of $$^{134}$$Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of $$^{134}$$Cs and $$^{137}$$Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.

Journal Articles

Temporal change in radiological environments on land after the Fukushima Daiichi Nuclear Power Plant accident

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

Journal Articles

Measurement of air dose rates by walk survey using KURAMA-II within 80 km range from Fukushima Dai-ichi Nuclear Power Plant

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.

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

 Times Cited Count:13 Percentile:46.29(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

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016

Ando, Masaki; Yamamoto, Hideaki*; Kanno, Takashi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 190-191, p.111 - 121, 2018/10

 Times Cited Count:14 Percentile:53.45(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.

Journal Articles

Effect of water for the oxygen adsorption on surface of PtCo catalysts

Cui, Y.-T.*; Harada, Yoshihisa*; Niwa, Hideharu*; Oshima, Masaharu*; Hatanaka, Tatsuya*; Nakamura, Naoki*; Ando, Masaki*; Yoshida, Toshihiko*; Ishii, Kenji*; Matsumura, Daiju

NanotechJapan Bulletin (Internet), 11(4), 6 Pages, 2018/08

no abstracts in English

JAEA Reports

The Annual report on the environmental monitoring around the waste rock sites 2016 Tottori

Ono, Takayuki; Kawasaki, Satoru; Ishimori, Yuu; Ando, Masaki

JAEA-Review 2017-044, 13 Pages, 2018/03

JAEA-Review-2017-044.pdf:1.17MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency performs the environmental monitoring around the Ningyo-toge and the waste rock sites according to the agreements with local governments, Okayama and Tottori prefectures. Each prefectural committee on the environmental monitoring evaluates the monitoring data annually. This report summarized the results of the environmental monitoring in Tottori prefecture in the fiscal year 2016. The results show that the levels of the radiation doses and the radioactive concentrations in the environment were within natural variations, and the waste rock sites have been well maintained. The committee concluded that the environmental impacts from the sites were negligible.

JAEA Reports

The Annual report on the environmental monitoring around the Ningyo-toge 2016; Okayama

Ono, Takayuki; Kawasaki, Satoru; Ishimori, Yuu; Ando, Masaki

JAEA-Review 2017-043, 39 Pages, 2018/03

JAEA-Review-2017-043.pdf:1.92MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency (JAEA Ningyo-toge) performs the environmental monitoring around the Ningyo-toge and the waste rock sites according to the agreements with local governments, Okayama and Tottori prefectures. Environmental monitoring of plutonium has been also performed around the Ningyo-toge regarding the practical application study on the reprocessed uranium conversion, which was carried out from 1994 to 1999 at the Ningyo-toge. Each prefectural committee on the environmental monitoring evaluates the monitoring data annually. This report summarized the results of the environmental monitoring in Okayama prefecture in the fiscal year 2016. The results show that the levels of the radiation doses and the radioactive concentrations in the environment were within natural variations, and the committee concluded that the environmental impacts from the sites were negligible. Therefore, the site of the JAEA Ningyo-toge has been well operated, and the waste rock sites have been well maintained.

Journal Articles

Shell evolution beyond $$Z$$=28 and $$N$$=50; Spectroscopy of $$^{81,82,83,84}$$Zn

Shand, C. M.*; Podoly$'a$k, Zs.*; G$'o$rska, M.*; Doornenbal, P.*; Obertelli, A.*; Nowacki, F.*; Otsuka, T.*; Sieja, K.*; Tostevin, J. A.*; Tsunoda, T.*; et al.

Physics Letters B, 773, p.492 - 497, 2017/10

 Times Cited Count:23 Percentile:87.56(Astronomy & Astrophysics)

555 (Records 1-20 displayed on this page)