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Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.
RIST News, (69), p.2 - 18, 2023/09
The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.
Mori, Hideki*; Tsuru, Tomohito; Okumura, Masahiko; Matsunaka, Daisuke*; Shiihara, Yoshinori*; Itakura, Mitsuhiro
Physical Review Materials (Internet), 7(6), p.063605_1 - 063605_8, 2023/06
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The introduction of obstacles (e.g., precipitates) for controlling dislocation motion in molecular structures is a prevalent method for designing the mechanical strength of metals. Owing to the nanoscale size of the dislocation core (
1 nm), atomic modeling is required to investigate the interactions between the dislocation and obstacles. However, conventional empirical potentials are not adequately accurate, in contrast to the calculations based on density functional theory (DFT). Therefore, the atomic-level details of the interactions between the dislocations and obstacles remain unclarified. To this end, this study applied an artificial neural network (ANN) framework to construct an atomic potential by leveraging the high accuracy of DFT. Using the constructed ANN potential, we investigated the dynamic interaction between the 
edge dislocation and obstacles in BCC iron. When the dislocation crossed the void, an ultrasmooth and symmetric half-loop was observed for the bowing-out dislocation. Except for the screw dislocation, the Peierls stress of all the dislocations predicted using the ANN was less than 100 MPa. More importantly, the results confirmed the formation of an Orowan loop in the interaction between a rigid sphere and dislocation. Furthermore, we discovered a phenomenon in which the Orowan loop disintegrated into two small loops during its interaction with the rigid sphere and dislocation.
Okita, Taira*; Terayama, Satoshi*; Tsugawa, Kiyoto*; Kobayashi, Keita; Okumura, Masahiko; Itakura, Mitsuhiro; Suzuki, Katsuyuki*
Computational Materials Science, 202, p.110865_1 - 110865_9, 2022/02
Times Cited Count：7 Percentile：48.44(Materials Science, Multidisciplinary)Mori, Kazuhiro*; Okumura, Ryo*; Yoshino, Hirofumi*; Kanayama, Masaya*; Sato, Setsuo*; Oba, Yojiro; Iwase, Kenji*; Hiraka, Haruhiro*; Hino, Masahiro*; Sano, Tadafumi*; et al.
JPS Conference Proceedings (Internet), 33, p.011093_1 - 011093_6, 2021/03
no abstracts in English
*(10) dose rates measured in environment contaminated by radioactive caesium; Correction of directional dependence of scintillation detectorsTsuda, Shuichi; Tanigaki, Minoru*; Yoshida, Tadayoshi; Okumura, Ryo*; Saito, Kimiaki
Radiation Protection Dosimetry, 193(3-4), p.228 - 236, 2021/03
Times Cited Count：3 Percentile：31.78(Environmental Sciences)Environmental dose rate monitoring has been performed with various scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident. Gamma-rays from caesium isotopes deposited in soil enter radiation detectors in any direction, but directional dependence of the detectors used for dose rate measurements are not always uniform and the dose rates vary even if measurement takes place at the same place. To investigate the influence of crystal configurations on dose rate, dose rate measurements using several scintillation detectors with different crystal configurations were conducted. By measuring pulse height spectra and multiplying them with spectrum - dose conversion operators (G(E) function), dose rates were deduced and compared. It was found that the dose rates varied within approximately 25% among six detectors. To reduce the differences, the dose rate using G(E) functions determined in rotational geometry were obtained and applied instead. The revised dose rates agreed with one another within uncertainties, but this was not the case of scintillation detector with flat crystal shape, and it means this method could not compensate its strong directional dependence. These experimental results reveal that detectors with superior directional characteristics should be used for environmental dose rate measurement since the compensation of directional dependence using a G(E) function determined in rotational geometry is not always available.
Goto, Minoru; Okumura, Keisuke; Nakagawa, Shigeaki; Inaba, Yoshitomo; Matsuura, Hideaki*; Nakaya, Hiroyuki*; Katayama, Kazunari*
Fusion Engineering and Design, 136(Part A), p.357 - 361, 2018/11
Times Cited Count：6 Percentile：52.79(Nuclear Science & Technology)A High Temperature Gas-cooled Reactor (HTGR) is proposed as a tritium production device, which has the potential to produce a large amount of tritium using 
Li(n,
)T reaction. In the HTGR design, generally, boron is loaded into the core as a burnable poison to suppress excess reactivity. In this study, lithium is loaded into the HTGR core instead of boron and is used as a burnable poison aiming to produce thermal energy and tritium simultaneously. The nuclear characteristics and the fuel temperature were calculated to confirm the feasibility of the lithium-loaded HTGR. It was shown that the calculation results satisfied the design requirements and hence the feasibility was confirmed for the lithium-loaded HTGR, which produce thermal energy and tritium.
Tsuda, Shuichi; Tanigaki, Minoru*; Yoshida, Tadayoshi; Okumura, Ryo*; Saito, Kimiaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 17(1), p.11 - 17, 2018/03
Environmental dose rate monitoring has been performed using scintillation detectors since the Fukushima Dai-ichi Nuclear Power Plant accident happened. After the accident, various scintillation detectors with directional dependence are used in the measurement, though detectors with superior directional dependence are needed because photons come from various direction in the environment. To investigate the influence of crystal configurations on indicated values of dose rates, pulse height spectra were measured using scintillation-based detectors with different crystal configurations and ambient dose rates were obtained using a spectrum - dose conversion operator (G(E) function). It is found that the dose rate for a rectangular-parallelepiped crystal is 
40% than that for a cylindrical one at the maximum. However, the values agreed within 10% among all the detectors irrespective of the crystal shapes, using G(E) functions determined in a rotational irradiation geometry.
Yuyama, Takahiro; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Ishizaka, Tomohisa; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Usui, Aya; Miyawaki, Nobumasa; et al.
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.302 - 304, 2015/09
no abstracts in English
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：52 Percentile：82.76(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.
Miyawaki, Nobumasa; Kurashima, Satoshi; Kashiwagi, Hirotsugu; Okumura, Susumu; Yoshida, Kenichi; Yuri, Yosuke; Yuyama, Takahiro; Ishizaka, Tomohisa; Ishibori, Ikuo; Nara, Takayuki
JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 158, 2014/03
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.
Kurashima, Satoshi; Kashiwagi, Hirotsugu; Miyawaki, Nobumasa; Okumura, Susumu; Yoshida, Kenichi; Yuri, Yosuke; Yuyama, Takahiro; Ishizaka, Tomohisa; Ishibori, Ikuo; Nara, Takayuki
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 154, 2013/01
no abstracts in English
Okumura, Susumu; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Yuyama, Takahiro; Ishizaka, Tomohisa; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Yuri, Yosuke; Nara, Takayuki; et al.
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 172, 2013/01
The AVF cyclotron was operated from May 9th in fiscal 2011 and all the planned experiments on April were cancelled due to scheduled blackouts originated from the Great East Japan Earthquake. The total operation time amounted to 3,038.4 hours. The extended operation from Friday evening to Saturday evening was carried out eight times in order to supply the cancellation on April. The regular yearly overhaul and maintenance were carried out.
Nara, Takayuki; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Yuyama, Takahiro; Ishizaka, Tomohisa; Okumura, Susumu; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Yuri, Yosuke; et al.
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 172, 2012/01
no abstracts in English
Kashiwagi, Hirotsugu; Miyawaki, Nobumasa; Okumura, Susumu; Kurashima, Satoshi; Yoshida, Kenichi; Yuri, Yosuke; Yuyama, Takahiro; Ishizaka, Tomohisa; Ishibori, Ikuo; Nara, Takayuki; et al.
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 157, 2012/01
no abstracts in English
Yuyama, Takahiro; Yuri, Yosuke; Ishizaka, Tomohisa; Kurashima, Satoshi; Ishibori, Ikuo; Okumura, Susumu; Yoshida, Kenichi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Nara, Takayuki; et al.
Proceedings of 19th International Conference on Cyclotrons and their Applications (CYCLOTRONS 2010), p.90 - 92, 2011/12
Okumura, Susumu; Miyawaki, Nobumasa; Yuyama, Takahiro; Ishizaka, Tomohisa; Kurashima, Satoshi; Kashiwagi, Hirotsugu; Yoshida, Kenichi; Ishibori, Ikuo; Yuri, Yosuke; Nara, Takayuki; et al.
Proceedings of 8th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.374 - 376, 2011/12
Reduction of the beam changing time is required to increase the available beam time for users. We are developing a technique for reducing the changing time of the magnetic field of the cyclotron, since it takes a long changing time to form the magnetic field for acceleration. Since the deviation of the magnetic field from the desired value for acceleration in the start-up process of the magnetic field dose not decrease in a short time, a correction system of the cyclotron magnetic field with a bipolar power supply and a 5-turn coil was developed. We confirmed that this system enables the magnetic field to be controlled quickly with a pc-based PID controller.
Osaka, Masahiko; Konashi, Kenji*; Hayashi, Hirokazu; Li, D.*; Homma, Yoshiya*; Yamamura, Tomoo*; Sato, Isamu; Miwa, Shuhei; Sekimoto, Shun*; Kubota, Takumi*; et al.
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Summer schools for future experts have successfully been completed under Japan Actinide Network (J-ACTINET) for the purpose of development of human resources who are expected to be engaged in every areas of actinide-research/engineering. The first summer school was held in Ibaraki-area in August 2009, followed by the second one in Kansai-area in August 2010. Two summer schools have focused on actual experiences of actinides in actinide-research fields for university students and young researchers/engineers as an introductory course of actinide-researches. Several quasi actinide-handling experiences at the actinide-research fields have attracted attentions of participants at the first school in Ibaraki-area. The actual experiments using actinides-containing solutions have been carried out at the second school in Kansai-area. Future summer schools will be held every year for the sustainable human resource development in various actinide-research fields.
Yamada, Keisuke; Nara, Takayuki; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Yuyama, Takahiro; Ishizaka, Tomohisa; Agematsu, Takashi; Uno, Sadanori; Chiba, Atsuya; et al.
Proceedings of 8th Annual Meeting of Particle Accelerator Society of Japan (Internet), 3 Pages, 2011/08
no abstracts in English
