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Yuguchi, Takashi*; Sasao, Eiji; Hibara, Ryoko*; Murakami, Hiroaki; Ozaki, Yusuke
Heliyon (Internet), 10(17), p.e37417_1 - e37417_17, 2024/09
Times Cited Count：0 Percentile：0.00(Multidisciplinary Sciences)Understanding the mass transfer characteristics of matrix diffusion and sorption is important in geological disposal of high-level radioactive waste in crystalline rock. We present a comparative discussion of the effective diffusion coefficient (De), porosity, and petrological data for rock samples collected from the Toki Granite in central Japan, to evaluate the role of micropores within minerals in retardation by matrix diffusion and sorption in granitic rocks. De was derived from the through-diffusion experiments. Petrological data consist of the fracture frequency, the extent of hydrothermal alteration in the minerals, the micropore volume in the minerals, and the three-dimensional modal mineralogy for the target rock samples. The relationship between the De, porosity, and petrological data has the following implications: 1) Micropores act as storage pores that contribute to retardation; 2) Once the uranine, cations, and anion penetrate the micropores in the minerals through matrix diffusion, the cations are sorbed on the micropore surfaces; 3) Regions with a high fracture frequency are associated with not only active advection-dispersion through fractures, but also retardation due to matrix diffusion and sorption.
Okafuji, Takashi*; Miura, Kazuhiro*; Sago, Hiromi*; Murakami, Hisatomo*; Watakabe, Tomoyoshi; Ando, Masanori; Miyazaki, Masashi
Proceedings of ASME 2024 Pressure Vessels & Piping Conference (PVP 2024) (Internet), 8 Pages, 2024/07
We have developed the buckling strength equations of vessels for fast reactors with seismic isolation system. The applicability of the buckling equations was confirmed by a series of buckling tests and analyses under monotonic or cyclic axial compressive load accompanied with constant horizontal load in the previous reports. In this report, we proposed a correction factor to reduce the buckling strength calculated by the buckling equations for large initial imperfections. A series of elastic-plastic buckling analyses considering large displacement and large strain theories was conducted to Grade 91 steel and austenitic stainless steel vessels which has a wide range of dimensions, initial imperfection amplitude, and vertical/horizontal load ratio. The simulation results showed that the correction factor generally shows a reduction tendency of buckling strength corresponding to initial imperfection amplitude, and the modified buckling equations are applicable to the vessels in fast reactors even for large initial imperfection amplitude which exceeds half the wall thickness.
CNguyen, B. V. C.*; Murakami, Kenta*; Chena, L.*; Phongsakorn, P. T.*; Chen, X.*; Hashimoto, Takashi; Hwang, T.*; Furusawa, Akinori; Suzuki, Tatsuya*
Nuclear Materials and Energy (Internet), 39, p.101639_1 - 101639_9, 2024/06
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Murakami, Kenta*; Arai, Taku*; Yamada, Koji*; Momma, Kensuke*; Tsuji, Takashi*; Nakagawa, Nobuyuki*; Onizawa, Kunio
Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 3 Pages, 2024/03
This paper studied the future vision of codes and standards in Japan by systematically comparing Japanese regulatory rules, standards, and industry guides related to long term operation with international safety standards, and confirmed that the Japanese standard system generally meets their recommendations. The recommendation for the future improvements of Japanese codes and standards were summarized into five items.
Lu, K.; Takamizawa, Hisashi; Li, Y.; Masaki, Koichi*; Takagoshi, Daiki*; Nagai, Masaki*; Nannichi, Takashi*; Murakami, Kenta*; Kanto, Yasuhiro*; Yashirodai, Kenji*; et al.
Mechanical Engineering Journal (Internet), 10(4), p.22-00484_1 - 22-00484_13, 2023/08
OKondo, Yosuke*; Achouri, N. L.*; Al Falou, H.*; Atar, L.*; Aumann, T.*; Baba, Hidetada*; Boretzky, K.*; Caesar, C.*; Calvet, D.*; Chae, H.*; et al.
Nature, 620(7976), p.965 - 970, 2023/08
Times Cited Count：18 Percentile：95.53(Multidisciplinary Sciences)no abstracts in English
Doda, Norihiro; Igawa, Kenichi*; Iwasaki, Takashi*; Murakami, Satoshi*; Tanaka, Masaaki
Nuclear Engineering and Design, 410, p.112377_1 - 112377_15, 2023/08
Times Cited Count：1 Percentile：41.04(Nuclear Science & Technology)To enhance the safety of sodium-cooled fast reactors, the decay heat in the core must be removed by natural circulation even if the AC power supply to the forced circulation equipment is lost. Under natural circulation conditions, sodium flow is driven by buoyancy, and flow velocity and temperature distribution influence each other. Thus, it is difficult to evaluate the core hot spot temperature by deterministically considering the uncertainties affecting flow and heat. In this study, a statistical evaluation method is developed for the core hot spot temperature by using Monte Carlo sampling methods. The applicability of the core hotspot evaluation method was confirmed in three representative events during natural circulation decay heat removal operations in loop-type sodium-cooled fast reactors.
Ne at the transition into the island of inversion; Detailed structure study of NeWang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.
Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08
Times Cited Count：3 Percentile：75.57(Astronomy & Astrophysics)Detailed 
-ray spectroscopy of the exotic neon isotope Ne has been performed using the one-neutron removal reaction from Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.
Okafuji, Takashi*; Miura, Kazuhiro*; Sago, Hiromi*; Murakami, Hisatomo*; Ando, Masanori; Okajima, Satoshi
Proceedings of ASME 2023 Pressure Vessels and Piping Conference (PVP 2023) (Internet), 8 Pages, 2023/07
Buckling evaluation methods capable of evaluating elasto-plastic buckling under axial compression, bending, and shear loads are required for cylindrical vessels of fast reactors to cope with thinning due to increasing diameter and application to the seismic isolation design against huge seismic ground motion. In this study, in order to confirm the applicability of the proposal evaluation method, several buckling tests and FE analyses were carried out using the specimens made of Gr.91 and austenitic stainless steel. The buckling modes and strength data in the load region where the interaction of cyclic axial compression, bending and shear buckling could occur were examined. As a result, it was confirmed that the proposal evaluation method estimated the buckling load in the tests conservatively.
dynamics in the H conductors LaH
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Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.
Physical Review B, 107(18), p.184114_1 - 184114_8, 2023/05
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Okafuji, Takashi*; Miura, Kazuhiro*; Sago, Hiromi*; Murakami, Hisatomo*; Ando, Masanori; Okajima, Satoshi
Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 9 Pages, 2022/07
Buckling evaluation methods capable of evaluating elasto-plastic buckling under axial compression, bending, and shear loads are required for cylindrical vessels of fast reactors to cope with thinning due to increasing diameter and application to the seismic isolation design against huge seismic ground motion. In this study, in order to confirm the applicability of the proposal evaluation method, several buckling tests and FE analyses were carried out using the specimens made of austenitic stainless steel. The buckling modes and strength data in the load region where the interaction of cyclic axial compression, bending and shear buckling could occur were examined. As a result, it was confirmed that the proposal evaluation method estimated the buckling load in the tests conservatively. Moreover, a series of finite element analyzes to confirm the applicability of the evaluation method in 2.25Cr-1Mo steel and up to 650 C were conducted.
Doda, Norihiro; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iwasaki, Takashi*; Murakami, Satoshi*; Tanaka, Masaaki
Keisan Kogaku Koenkai Rombunshu (CD-ROM), 27, 6 Pages, 2022/06
As a part of the development of the "Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)" to automatically optimize the life cycle of innovative nuclear reactors including fast reactors, ARKADIA-design is being developed to support the optimization of fast reactor design in the conceptual stage. ARKADIA-Design consists of three systems (Virtual plant Life System (VLS), Evaluation assistance and Application System (EAS), and Knowledge Management System (KMS)). A design optimization framework controls the cooperation between the three systems through the interfaces in each system. This paper reports on the development status of the "VLS interface," which has a control function of coupling analysis codes in VLS.
Okafuji, Takashi*; Miura, Kazuhiro*; Sago, Hiromi*; Murakami, Hisatomo*; Ando, Masanori; Miyazaki, Masashi
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 9 Pages, 2021/07
Buckling evaluation methods capable of evaluating elasto-plastic buckling under axial compression, bending, and shear loads are required for cylindrical vessels of fast reactors to cope with thinning due to increasing diameter and application to the seismic isolation design against huge seismic ground motion. In this study, in order to confirm the applicability of the proposal evaluation method, several buckling tests and FE analyses were carried out using the specimens made of Modified 9Cr-1Mo steel. The buckling modes and strength data in the load region where the interaction of cyclic axial compression, bending and shear buckling could occur were examined. As a result, it was confirmed that the proposal evaluation method estimated the buckling load in the tests conservatively. Moreover, a series of finite element analyzes using a model with residual stress due to welding revealed that the effect of residual stress on buckling strength is negligible in the evaluation method.
Takahashi, Atsushi*; Chiba, Mirei*; Tanahara, Akira*; Aida, Jun*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Murakami, Shinobu*; Koarai, Kazuma; Ono, Takumi*; Oka, Toshitaka; et al.
Scientific Reports (Internet), 11(1), p.10355_1 - 10355_11, 2021/05
Times Cited Count：9 Percentile：47.19(Multidisciplinary Sciences)Okafuji, Takashi*; Miura, Kazuhiro*; Sago, Hiromi*; Murakami, Hisatomo*; Ando, Masanori; Miyazaki, Masashi
Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 9 Pages, 2020/08
Buckling evaluation methods capable of evaluating elasto-plastic buckling under axial compression, bending, and shear loads are required for cylindrical vessels of fast reactors to cope with thinning due to increasing diameter and application to the seismic isolation design against huge seismic ground motion. In this study, in order to confirm the applicability of the proposal evaluation method, several buckling tests and FE analyses were carried out using the specimens made of Modified 9Cr-1Mo steel. The buckling modes and strength data in the load region where the interaction of axial compression, bending and shear buckling could occur were examined. As a result, it was confirmed that the proposal evaluation method estimated the buckling load in the tests conservatively. In addition, buckling strength evaluated by elasto-plastic buckling analysis had good accuracy compared to each test result by considering the stress-strain relationship and imperfection of test specimen.
Suzuki, Masahide*; Murakami, Kenta*; Suzuki, Takashi*; Okayama, Ryuta*; Katsuyama, Jinya; Li, Y.
E-Journal of Advanced Maintenance (Internet), 11(4), p.172 - 178, 2020/02
no abstracts in English
Yamashita, Shinichiro; Ioka, Ikuo; Nemoto, Yoshiyuki; Kawanishi, Tomohiro; Kurata, Masaki; Kaji, Yoshiyuki; Fukahori, Tokio; Nozawa, Takashi*; Sato, Daiki*; Murakami, Nozomu*; et al.
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.206 - 216, 2019/09
After the nuclear accident at Fukushima Daiichi Power Plant, research and development (R&D) program for establishing technical basis of accident-tolerant fuel (ATF) started from 2015 in Japan. Since then, both experimental and analytical studies necessary for designing a new light water reactor (LWR) core with ATF candidate materials are being conducted within the Japanese ATF R&D Consortium for implementing ATF to the existing LWRs, accompanying with various technological developments required. Until now, we have accumulated experimental data of the candidate materials by out-of-pile tests, developed fuel evaluation codes to apply to the ATF candidate materials, and evaluated fuel behavior simulating operational and accidental conditions by the developed codes. In this paper, the R&D progresses of the ATF candidate materials considered in Japan are reviewed based on the information available such as proceedings of international conference and academic papers, providing an overview of ATF program in Japan.
D
measured with inelastic neutron spectroscopyYamaura, Junichi*; Hiraka, Haruhiro*; Iimura, Soshi*; Muraba, Yoshinori*; Bang, J.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Honda, Takashi*; Hiraishi, Masatoshi*; et al.
Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06
Times Cited Count：4 Percentile：19.74(Materials Science, Multidisciplinary)Inelastic neutron scattering was performed for an iron-based superconductor, where most of D (deuterium) replaces oxygen, while a tiny amount goes into interstitial sites. By first-principle calculation, we characterize the interstitial sites for D (and for H slightly mixed) with four equivalent potential minima. Below the superconducting transition temperature Tc = 26 K, new excitations emerge in the range 5-15 meV, while they are absent in the reference system LaFeAsOF. The strong excitations at 14.5 meV and 11.1 meV broaden rapidly around 15 K and 20 K, respectively, where each energy becomes comparable to twice of the superconducting gap. The strong excitations are ascribed to a quantum rattling, or a band motion of hydrogen, which arises only if the number of potential minima is larger than two.
Yokoyama, Tatsunori; Kimura, Junichi*; Mitsuguchi, Takehiro; Danhara, Toru*; Hirata, Takafumi*; Sakata, Shuhei*; Iwano, Hideki*; Maruyama, Seiji*; Chang, Q.*; Miyazaki, Takashi*; et al.
Geochemical Journal, 52(6), p.531 - 540, 2018/12
Times Cited Count：17 Percentile：62.05(Geochemistry & Geophysics)Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Shintaku, Yohei*; Li, T.*; Murakami, Kazuya*; Kanomata, Kenichi*; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi; et al.
Journal of Nuclear Materials, 506, p.3 - 11, 2018/08
Times Cited Count：4 Percentile：35.54(Materials Science, Multidisciplinary)The mercury target vessel is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. In order to estimate the structural integrity of the vessel, it is important to measure the defects in welding accurately. For nondestructive tests of the welding, radiographic testing is applicable but it is difficult to detect for some defect shapes. Therefore it is effective to do ultrasonic testing together with it. Because ultrasonic methods prescribed in JIS inspect on the plate with more than 6 mm in thickness, these methods couldn't be applied as the inspection on the vessel with thin walls. In order to develop effective method, we carried out measurements using some testing method on samples with small defect whose size is specified. In the case of the latest phased array method, measured value agreed with actual size. It was found that this method was applicable to detect defects in the thin-walled structure for which accurate inspection was difficult so far.
