Sm synchrotron-radiation-based Mssbauer spectroscopy of Sm-based heavy fermion compounds

Tsutsui, Satoshi; Higashinaka, Ryuji*; Mizumaki, Masaichiro*; Kobayashi, Yoshio*; Nakamura, Jin*; Ito, Takashi; Yoda, Yoshitaka*; Matsuda, Tatsuma*; Aoki, Yuji*; Sato, Hideyuki*

Interactions (Internet), 245(1), p.9_1 - 9_10, 2024/12

https://doi.org/10.1007/s10751-024-01851-y

In-situ measurement of radiation driven back-conversion from para to ortho liquid hydrogen state in cold moderators at J-PARC

Teshigawara, Makoto; Lee, Y.*; Tatsumoto, Hideki*; Hartl, M.*; Aso, Tomokazu; Iverson, E. B.*; Ariyoshi, Gen; Ikeda, Yujiro*; Hasegawa, Takumi*

Nuclear Instruments and Methods in Physics Research B, 557, p.165534_1 - 165534_10, 2024/12

https://doi.org/10.1016/j.nimb.2024.165534

At Japanese Spallation Neutron Source in J-PARC, the para-hydrogen fraction was measured by using Raman spectroscopy in-situ for an integrated beam power of 9.4 MWh at 1 MW operation, to evaluate the functionality of the ferric oxyhydroxide catalyst. This result showed that full functionality of the catalyst was retained up to the 1 MW operation. We attempted to study the effect of neutron scattering driven para to ortho-hydrogen back-conversion rate in the absence of the catalyst effect with a bypass line without catalyst. The measured increase of ortho-hydrogen fraction was 0.44% for an integrated beam power of 2.4 MWh at 500 kW operation, however, which was considered to be due to not only to neutron collisions in cold moderators but also to the high ortho-hydrogen fraction of initially static liquid hydrogen in the bypass line and passive exudation of quasi-static hydrogen in the catalyst vessel to the main loop.

Dynamics and functions of microbial communities in the plastisphere in temperate coastal environments

Battulga, B.; Nakayama, Masataka; Matsuoka, Shunsuke*; Kondo, Toshiaki*; Atarashi-Andoh, Mariko; Koarashi, Jun

Water Research, 264, p.122207_1 - 122207_12, 2024/10

https://doi.org/10.1016/j.watres.2024.122207

Growing attention has been given to microbial attachment and biofilm formation on microplastics (MPs; sizes: 5 mm) in the environment. Here, we explore the microbial communities in the plastisphere to improve our understanding of microbial ecology as well as their impacts on aquatic ecosystems. Using the amplicon sequence of 16S and ITS genes, we identified bacterial and fungal community composition and diversity on MPs, surface waters, bottom sediments, and coastal sands in two contrasting coastal areas of Japan. Significantly different microbial diversity and taxonomic composition were detected depending on sample types and research sites. This research highlights the microbial metabolic functions in MP-associated biofilm, which could be the key to uncovering the true impact of plastic debris on the global ecosystem.

Elasto-plastic mechanical analysis considering thermal and hydraulic effects for the in-situ experiment for full-scale engineered barrier system performance experiment at Horonobe Underground Research Laboratory

Ito, Shinji*; Shimizu, Hiroyuki*; Ono, Shintaro*; Takayama, Yusuke

Doboku Gakkai Rombunshu (Internet), 80(8), p.24-00030_1 - 24-00030_18, 2024/08

https://doi.org/10.2208/jscejj.24-00030

In the design consideration of a geological disposal facility for radioactive waste, it is essential to perform a mechanical evaluation that takes into account phenomena that may occur from construction and operation to post-closure. With this background, we have developed the long-term mechanical analysis system MACBECE. In this research, we have built an analysis system that can consistently evaluate the mechanical behavior considering the thermal and hydraulic evolution after the closure of the repository by incorporating the constitutive model for unsaturated soils and coupling with the thermal-hydraulic analysis. As a validation, a mechanical analysis was conducted for the in-situ experiment for full-scale engineered barrier system performance experiment at Horonobe URL. Despite some discrepancies due to constraints in two-dimensional analysis, the extended functionality of the analysis code was confirmed to effectively repro-duce the measured data.

Giant barocaloric effects in sodium hexafluorophosphate and hexafluoroarsenate

Zhang, Z.*; Hattori, Takanori; Song, R.*; Yu, D.*; Mole, R.*; Chen, J.*; He, L.*; Zhang, Z.*; Li, B.*

Journal of Applied Physics, 136(3), p.035105_1 - 035105_8, 2024/07

https://doi.org/10.1063/5.0211085

Solid-state refrigeration using barocaloric materials is environmentally friendly and highly efficient, making it a subject of global interest over the past decade. Here, we report giant barocaloric effects in sodium hexafluorophosphate (NaPF) and sodium hexafluoroarsenate (NaAsF) that both undergo a cubic-to-rhombohedral phase transition near room temperature. We have determined that the low-temperature phase structure of NaPF is a rhombohedral structure with space group R and NaAsF, i.e., F, E, and A. The phase transition temperature varies with pressure at a rate of dT/dP = 250 and 310 K/GPa for NaPF and NaAsF. The pressure-induced entropy changes of NaPF and NaAsF are determined to be around 45.2 and 35.6J kgK, respectively. The saturation driving pressure is about 40 MPa. The pressure-dependent neutron powder diffraction suggests that the barocaloric effects are related to the pressure-induced cubic-to-rhombohedral phase transitions.

Investigation of adsorption mechanism of Mo(VI) by baker's yeast and applicability to the uranium liquid waste treatment process

Arai, Yoichi; Hasegawa, Kenta; Watanabe, So; Watanabe, Masayuki; Minowa, Kazuki*; Matsuura, Haruaki*; Hagura, Naoto*; Katsuki, Kenta*; Arai, Tsuyoshi*; Konishi, Yasuhiro*

Journal of Radioanalytical and Nuclear Chemistry, 333(7), p.3585 - 3593, 2024/07

https://doi.org/10.1007/s10967-023-09278-5

A Proposed regulatory framework for small modular reactors

Nuclear System Technology Review Committee

JAEA-Review 2024-018, 38 Pages, 2024/06

JAEA-Review-2024-018.pdf:1.46MB

In the R&D activities related to the Ministry of Education, Culture, Sports, Science and Technology's Innovative Nuclear R&D Program, "Development of Integrated Energy System Simulation Method Utilizing Small Modular Reactors for Enhanced System Decarbonization and Resilience," Japan Atomic Energy Agency (JAEA) established the "Nuclear System Technology Review Committee," consisting of experts in the subject areas, to obtain advice on the feasibility of deploying Design-standardized, Factory-built, Site-independent Small Modular Reactors (DFS-SMRs) in Japan and other countries. The Committee met three times during the 2021-2024 project period to discuss proposals for a regulatory framework for the potential commercial deployment of DFS-SMRs in Japan. The starting point for the Committee's discussions was the view that Japan's nuclear regulatory framework, like most other countries with existing commercial nuclear power plants in operation, focuses on large Light Water Reactors. Another consideration was the Committee's view on the basic structure of the regulatory framework, consistent with other regulatory initiatives around the world. Specifically, that the most effective regulatory frameworks need to be less prescriptive, less technology-dependent, and more performance-based. This report focuses on the United States, which has played a leading role in the deployment of SMRs and other advanced reactors, and summarizes the discussions regarding the proposal for a licensing framework for SMRs in Japan, an analysis of the gaps between Japan's current licensing framework and the proposed framework, and specific recommendations for closing the gaps. The Committee is hopeful that the changes to the regulatory framework proposed in this report will become a reality.

Time-dependent change in occurrence rate of steam generator tube leak in sodium-cooled fast reactors; Phenix and BN-600

Kurisaka, Kenichi

Mechanical Engineering Journal (Internet), 11(2), p.23-00377_1 - 23-00377_14, 2024/04

https://doi.org/10.1299/mej.23-00377

This study aims to understand the time-dependent change in the occurrence rate of leak from steam generator (SG) tubes in sodium-cooled fast reactors (SFRs). The target SFRs in the present paper are Phenix in France and BN-600 in Russia. By reviewing publicly available literature that show data from the SFRs, we have investigated the numbers of tube-to-tubeplate welds and tube-to-tube welds, heat transfer areas of tube base metal, operating hours of SGs, dates when SG tube leak occurred, locations of leak, and corrective actions taken after tube leak events, such as replacement of the module, in which a leak occurred. Based on these, we have estimated the time to leak and quantitatively analyzed the time-dependent change of the occurrence rates of SG tube leak for each of the above-mentioned parts by hazard plotting method. The results show that the rates of both Phenix and BN-600 decreased over time. For Phenix, this is probably thanks to improved welding and SG operating conditions. For BN-600, it seems that in many cases, the probable cause of the leak was initial defects that developed to failure during the early stage of reactor operation, and that no special countermeasure was taken in the later stages. Therefore, it would be natural to assume that the rate simply decreased over time. The rate of leak at tube-to-tube welds in Phenix shows significant increase in a short term after a certain period of time. This can be caused by thermal stress repeatedly exerted on the materials.

Assessment of probability of aircraft crashes for Nuclear Science Research Institute

Kamikawa, Yutaka; Suzuki, Makoto; Agake, Toshiki; Murakami, Takahiko; Morita, Yusuke; Shiina, Hidenori; Fukushima, Manabu; Hirane, Nobuhiko; Ouchi, Yasuhiro

JAEA-Technology 2023-030, 57 Pages, 2024/03

JAEA-Technology-2023-030.pdf:1.93MB

Owing to the publication of the latest data about aircraft crashes by Nuclear Regulation Authority (NRA), it was necessary to re-evaluate the probabilities of aircraft crashes for Nuclear Science Research Institute (NSRI). By using of the assessment method provided in "Regulatory Guide of the Assessment Standard for Probability of Airplane Crash on a Nuclear Power Reactor Facility", we re-evaluated the probabilities of aircraft crashes against the nuclear facilities in NSRI. As a result of the evaluations, the sum of the probabilities of aircraft crashes against Waste Treatment Facilities (maximum probability among all nuclear facilities in NSRI) is 5.6810 (times/(reactor year)) which is lower than 10 (times/(reactor year)) that is the assessment criterion whether aircraft crashes is considered to be "anticipated external human induced events" in design basis or not.

Atomic position and the chemical state of an active Sn dopant for Sn-doped -GaO(001)

Tsai, Y. H.*; Kobata, Masaaki; Fukuda, Tatsuo; Tanida, Hajime; Kobayashi, Toru; Yamashita, Yoshiyuki*

Applied Physics Letters, 124(11), p.112105_1 - 112105_5, 2024/03

https://doi.org/10.1063/5.0198160