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Terasaka, Yuta; Sato, Yuki; Uritani, Akira*
Nuclear Instruments and Methods in Physics Research A, 1062, p.169227_1 - 169227_6, 2024/05
Times Cited Count:1 Percentile:75.38(Instruments & Instrumentation)Machida, Masahiko; Shi, W.*; Yamada, Susumu; Miyamura, Hiroko; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji; Aoki, Yuto; Ito, Rintaro; Yamaguchi, Takashi; et al.
Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02
Simanullang, I. L.*; Nakagawa, Naoki*; Ho, H. Q.; Nagasumi, Satoru; Ishitsuka, Etsuo; Iigaki, Kazuhiko; Fujimoto, Nozomu*
Annals of Nuclear Energy, 177, p.109314_1 - 109314_8, 2022/11
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)Takino, Kazuo; Sugino, Kazuteru; Oki, Shigeo
Annals of Nuclear Energy, 162, p.108454_1 - 108454_7, 2021/11
Times Cited Count:1 Percentile:11.39(Nuclear Science & Technology)Ikeda, Reiji*; Ho, H. Q.; Nagasumi, Satoru; Ishii, Toshiaki; Hamamoto, Shimpei; Nakano, Yumi*; Ishitsuka, Etsuo; Fujimoto, Nozomu*
JAEA-Technology 2021-015, 32 Pages, 2021/09
Burnup calculation of the HTTR considering temperature distribution and detailed burning regions was carried out using MVP-BURN code. The results show that the difference in k, as well as the difference in average density of some main isotopes, is insignificant between the cases of uniform temperature and detailed temperature distribution. However, the difference in local density is noticeable, being 6% and 8% for
U and
Pu, respectively, and even 30% for the burnable poison
B. Regarding the division of burning regions to more detail, the change of k
is also small of 0.6%
k/k or less. The small burning region gives a detailed distribution of isotopes such as
U,
Pu, and
B. As a result, the effect of graphite reflector and the burnup behavior could be evaluated more clearly compared with the previous study.
Abe, Yuta; Tsuchikawa, Yusuke; Kai, Tetsuya; Matsumoto, Yoshihiro*; Parker, J. D.*; Shinohara, Takenao; Oishi, Yuji*; Kamiyama, Takashi*; Nagae, Yuji; Sato, Ikken
JPS Conference Proceedings (Internet), 33, p.011075_1 - 011075_6, 2021/03
Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*
JAEA-Review 2020-063, 44 Pages, 2021/01
JAEA/CLADS had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project in FY2019. Among the adopted proposals in FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted in FY2019.
Okita, Shoichiro; Fukaya, Yuji; Goto, Minoru
Journal of Nuclear Science and Technology, 58(1), p.9 - 16, 2021/01
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)Suppressing the kernel migration rates, which depend on both the fuel temperature and the fuel temperature gradient, under normal operation condition is quite important from the viewpoint of the fuel integrity for High Temperature Gas-cooled Reactors. The presence of the ideal axial power distribution to minimize the maximum kernel migration rate allows us to improve efficiency of design work. Therefore, we propose a new method based on Lagrange multiplier method in consideration of thermohydraulic design in order to obtain the ideal axial power distribution to minimize the maximum kernel migration rate. For one of the existing conceptual designs performed by JAEA, the maximum kernel migration rate for the power distribution to minimize the maximum kernel migration rate proposed in this study is lower by approximately 10% than that for the power distribution as a conventional design target to minimize the maximum fuel temperature.
Malins, A.; Ochi, Kotaro; Machida, Masahiko; Sanada, Yukihisa
Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.147 - 154, 2020/10
Abe, Yuta; Tsuchikawa, Yusuke; Kai, Tetsuya; Matsumoto, Yoshihiro*; Parker, J. D.*; Shinohara, Takenao; Oishi, Yuji*; Kamiyama, Takashi*; Nagae, Yuji; Sato, Ikken
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
Muto, Kotomi; Atarashi-Andoh, Mariko; Matsunaga, Takeshi*; Koarashi, Jun
Journal of Environmental Radioactivity, 208-209, p.106040_1 - 106040_10, 2019/11
Times Cited Count:14 Percentile:45.97(Environmental Sciences)Vertical distributions of Cs in the soil profile were observed at five forest sites with different vegetation types for 4.4 years after the Fukushima Dai-ichi Nuclear Power Plant accident, and
Cs migration in the organic layer and mineral soil was analyzed based on a comparison of models and observations. Cesium-137 migration from the organic layer was faster than that observed in European forests, suggesting that the mobility and bioavailability of
Cs could be suppressed rapidly in Japanese forests. The diffusion coefficients of
Cs in the mineral soil were estimated to be 0.042-0.55 cm
y
, which were roughly comparable with those of European forest soils affected by the Chernobyl Nuclear Power Plant accident. Model predictions indicated
Cs mainly distributed in the surface mineral soil at 10 years after the accident. It suggest that the
Cs deposited onto Japanese forest ecosystems will be retained in the surface layers of mineral soil for a long time.
Yoshimura, Kazuya; Fujiwara, Kenso; Nakama, Shigeo
Radiation Protection Dosimetry, 184(3-4), p.315 - 318, 2019/10
Times Cited Count:2 Percentile:18.62(Environmental Sciences)Yoshizawa, Atsufumi*; Oba, Kyoko; Kitamura, Masaharu*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.55 - 68, 2019/06
This study aims to improve the potential of an emergency response by analyzing the workload management during the accident at the Emergency Response Center (ERC) of TEPCO's Fukushima Daiichi Nuclear Power Plant. Specifically, the research focused on the response of the ERC during the time between the discontinuation of Unit 3 core water injection and its recovery. It identified the different types of workload at the ERC had and how they had been managed based on the record of a TV conference. It also deduced the casual factors of the responses, supplementing the interview record of the director of ERC at the time by applying workload management analysis. On the basis of these findings, lessons to enhance the potential of the on-site emergency response have been obtained for ERC and outside organizations.
Matsumura, Taichi; Nagaishi, Ryuji; Katakura, Junichi*; Suzuki, Masahide*
Nuclear Science and Engineering, 192(1), p.70 - 79, 2018/10
Times Cited Count:1 Percentile:10.33(Nuclear Science & Technology)The gamma-scanning of SDS (submerged demineralizer system) vessel used as a typical vessel for decontamination of radioactive water at Three Mile Island Unit 2 (TMI-2) accident was simulated in the axial and radial directions of real and cylindrical-shaped vessels by using a Monte Carlo calculation code (PHITS) on the basis of the geometrical and compositional information of vessel and gamma-scanning available in the previous reports at the accident. In the axial simulation, the true distribution of radioactive Cs in the zeolite packed bed of vessel was successfully evaluated when a correction function derived from a virtual constant distribution of
Cs was applied to the reported gamma-scanning profile. In the radial simulation, the virtual disk-formed and shell-formed sources of
Cs displaced in the packed bed were clearly observed from the top and bottom views of vessel. This new radial gamma-scanning indicates that the radial localization of
Cs could be well observed by measuring gamma-ray from the top view of vessel during storage. We further examined the radial gamma-scanning from the side view whether the radial localization of
Cs can be confirmed in the normally existing gamma-scanning room or not.
Sanada, Yukihisa; Katata, Genki*; Kaneyasu, Naoki*; Nakanishi, Chika*; Urabe, Yoshimi*; Nishizawa, Yukiyasu*
Science of the Total Environment, 618, p.881 - 890, 2018/03
Times Cited Count:23 Percentile:59.32(Environmental Sciences)Although the reconstruction of atmospheric deposition processes of radiocesium during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident is essential, the whole picture of the deposition mechanism in complex topography has not been well understood yet. To understand atmospheric deposition processes of aerosols over the complex mountainous topography, we analyzed altitudinal characteristics of radiocesium released during the accident. At five selected mountainous areas in the eastern Japan, altitudinal characters of air dose rate observed by our high-resolution airborne surveys after the accident was analyzed based on the results of three typical (dry, wet, and cloud water) deposition obtained from the latest atmospheric dispersion.
Ueki, Taro
Journal of Nuclear Science and Technology, 54(12), p.1310 - 1320, 2017/12
Times Cited Count:6 Percentile:47.60(Nuclear Science & Technology)In Monte Carlo criticality calculation, confidence interval estimation is based on the central limit theorem (CLT) for a series of tallies. A fundamental assertion resulting from CLT is the convergence in distribution (CID) of the interpolated standardized time series (ISTS) of tallies. In this work, the spectral analysis of ISTS has been conducted in order to assess the convergence of tallies in terms of CID. Numerical results indicate that the power spectrum of ISTS is equal to the theoretically predicted power spectrum of Brownian motion for effective neutron multiplication factor; on the other hand, the power spectrum of ISTS for local power fluctuates wildly while maintaining the spectral form of fractional Brownian motion. The latter result is the evidence of a case where a series of tallies is away from CID, while the spectral form supports normality assumption on the sample mean.
Hirouchi, Jun; Takahara, Shogo; Iijima, Masashi; Watanabe, Masatoshi; Munakata, Masahiro
Radiation Physics and Chemistry, 140, p.127 - 131, 2017/11
Times Cited Count:3 Percentile:26.37(Chemistry, Physical)Okumura, Keisuke
JAEA-Conf 2016-004, p.123 - 128, 2016/09
For the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), it is important to know the dose rate distribution in the primary containment vessel (PCV). However the distribution of radiation sources in PCV is not clear yet. There are three kinds of radiation sources in PCV. They are fuel debris, structures in PCV contaminated with Cs emitted at the 1F accident, and activated structures irradiated during normal reactor operating before the accident. In order to establish the evaluation method of the dose rate distribution in PCV, a preliminary calculation was carried out with JENDL-4.0. As a result, the sensitivity of each source to the dose distribution was obtained.
Ohgama, Kazuya; Nakano, Yoshihiro; Oki, Shigeo
Journal of Nuclear Science and Technology, 53(8), p.1155 - 1163, 2016/08
Times Cited Count:1 Percentile:9.82(Nuclear Science & Technology)The power distribution and core characteristics in various configurations of fuel subassemblies with an innerduct structure in the Japan Sodium-cooled Fast Reactor were evaluated using a Monte Carlo code for neutron transport and burnup calculation. The correlation between the fraction of fuel subassemblies facing outward and the degree of power increase at the core center was observed regardless of the compositions. This indicated that the spatial fissile distribution caused by innerduct configurations was the major factor of the difference in the power distribution. A power increase was also found in an off-center region, and it tended to be greater than that at the core center because of the steep gradient of neutron flux intensity. The differences in the worth of control rods caused by innerduct configurations were confirmed.
Konoplev, A.*; Golosov, V.*; Laptev, G.*; Namba, Kenji*; Onda, Yuichi*; Takase, Tsugiko*; Wakiyama, Yoshifumi*; Yoshimura, Kazuya
Journal of Environmental Radioactivity, 151(Part 3), p.568 - 578, 2016/01
Times Cited Count:84 Percentile:91.59(Environmental Sciences)