Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
-contamination visualization (Contract research); FY2023 Nuclear Energy Science & Technology and Human Resource Development ProjectCollaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2025-021, 63 Pages, 2025/10
JAEA-Review-2025-021.pdf:5.71MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2023. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2022, this report summarizes the research results of the "Development of elemental technologies of hand-foot-cloth monitors for -contamination visualization" conducted in FY2023. The present study aims to develop hand-foot-monitors for -contamination visualization and cloth monitors for /
-contamination visualization consisting of a portable phoswich detector. ZnS(Ag) thick films by AD method and rare earth complexes have been studied for development of -ray scintillator materials. The scintillator properties of the newly prepared ZnS(Ag) thick films were improved from those prepared in 2022. A rare earth complex shows strong emission intensity under -ray irradiation, which was 12.5 times higher than that of a commercially available plastic scintillator (Saint-Gobain, BC400). By optimizing the manufacturing process conditions (molding die, sintering conditions, cutting process, annealing conditions, grinding/polishing processes) for La-GPS polycrystalline thin plates, the preparing process for 50 mm square La-GPS was established. The prepared La-GPS provided excellent performance for -ray scintillators. The cloth monitors for /-contamination visualization were also improved for the reflection of the actual situation. Furthermore, the basic performance of the prototype cloth monitors was evaluated, and alpha-ray energy and position distribution information were obtained. In an evaluation test of the phoswich detector, a precise discrimination between - and -rays was achieved.
Zhang, H.*; Umehara, Yutaro*; Horiguchi, Naoki; Yoshida, Hiroyuki; Eto, Atsuro*; Mori, Shoji*
Energy, 335, p.138090_1 - 138090_18, 2025/10
Nuclear power is a key low-carbon energy source for a carbon-neutral future. In boiling water reactors (BWRs), steam-water annular flow near fuel rods is crucial for reactor safety, but its high-temperature, high-pressure conditions (285
C, 7 MPa) make direct measurement challenges. To address this, we used an HFC134a-ethanol system at lower conditions (40C, 0.7 MPa) to simulate BWR annular flow. Using a high-speed camera and the constant electric current method, we analyzed liquid-film characteristics, wave velocity and frequency. We also examined surface tension and interfacial shear stress effects. Furthermore, we proposed a new correlation for base film thickness.
Otani, Kyohei; Igarashi, Takahiro
Journal of the Electrochemical Society, 172(9), p.091503_1 - 091503_8, 2025/09
Times Cited Count：0 Percentile：0.00Brear, D. J.*; Kondo, Satoru; Sogabe, Joji; Tobita, Yoshiharu*; Kamiyama, Kenji
JAEA-Research 2024-009, 134 Pages, 2024/10
JAEA-Research-2024-009.pdf:2.45MB
The SIMMER-III/SIMMER-IV computer codes are being used for liquid-metal fast reactor (LMFR) core disruptive accident (CDA) analysis. The sequence of events predicted in a CDA is often influenced by the heat exchanges between LMFR materials, which are controlled by heat transfer coefficients (HTCs) in the respective materials. The mass transfer processes of melting and freezing, and vaporization and condensation are also controlled by HTCs. The complexities in determining HTCs in a multi-component and multi-phase system are the number of HTCs to be defined at binary contact areas of a fluid with other fluids and structure surfaces, and the modes of heat transfer taking into account different flow topologies representing flow regimes with and without structure. As a result, dozens of HTCs are evaluated in each mesh cell for the heat and mass transfer calculations. This report describes the role of HTCs in SIMMER-III/SIMMER-IV, the heat transfer correlations implemented and the calculation of HTCs in all topologies in multi-component, multi-phase flows. A complete description of the physical basis of HTCs and available experimental correlations is contained in Appendices to this report. The major achievement of the code assessment program conducted in parallel with code development is summarized with respect to HTC modeling to demonstrate that the coding is reliable and that the model is applicable to various multi-phase problems with and without reactor materials.
Battulga, B.; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Otosaka, Shigeyoshi*; Koarashi, Jun
Environmental Science and Pollution Research, 31, p.60080 - 60092, 2024/10
A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium (
Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan. The radioactivity of plastics was estimated based on the Cs activity concentration of the biofilms and compared seasonally with surrounding environmental samples (i.e., sediment and sand). Cs traces were detected in biofilms with activity concentrations of 21-1300 Bq kg
biofilm (dry weight), corresponding to 0.04-4.5 Bq kg plastic (dry weight). Our results reveal the interaction between Cs and plastics and provide evidence that organic and mineral components in biofilms are essential in Cs retention in environmental plastics.
Battulga, B.; Munkhbat, D.*; Matsueda, Makoto; Atarashi-Andoh, Mariko; Oyuntsetseg, B.*; Koarashi, Jun; Kawahigashi, Masayuki*
Environmental Pollution, 357, p.124427_1 - 124427_10, 2024/09
Times Cited Count：1 Percentile：18.39(Environmental Sciences)The occurrence and characteristics of plastic debris in aquatic and terrestrial environments have been extensively studied. However, there is still limited information on the properties and dynamic behavior of plastic-associated biofilms in the environment. In this study, we collected plastic samples from an inland river system in Mongolia and extracted biofilms from the plastics to uncover the characteristics of the biofilms using analytical, isotopic, and thermogravimetric techniques. Mixtures of organic and mineral particles were detected from extracted biofilms, revealing the plastic as a carrier for exogenous substances including contaminants in the river ecosystem. The present study provides insights into the characteristics and environmental behavior of biofilms which are useful to elucidate the impact of plastic-associated biofilms on organic matter and material cycling in the aquatic ecosystems.
-contamination visualization (Contract research); FY2022 Nuclear Energy Science & Technology and Human Resource Development ProjectCollaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*
JAEA-Review 2024-006, 54 Pages, 2024/06
JAEA-Review-2024-006.pdf:2.21MB
The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2022. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2022, this report summarizes the research results of the "Development of elemental technologies of hand-foot-cloth monitors for -contamination visualization" conducted in FY2022. The present study aims to develop hand-foot-monitors for -contamination visualization and cloth monitors for /-contamination visualization consisting of a portable phoswich detector for measuring /-contamination distribution and energy to ensure the safety and security of workers involved in the decommissioning project of the 1F. The possibility of practical application of new scintillator materials and devices was examined with the goal of developing such new instruments.
Takanashi, Koki; Seki, Takeshi*
Magune, 19(3), p.100 - 106, 2024/06
Perpendicular magnetic anisotropy of thin films currently plays an important role in spintronics as well as magnetic recording. Regarding perpendicular magnetic anisotropy, in this article, the fundamentals, the research history, and the recent research trends are reviewed, showing specific examples with perpendicular magnetization such as magnetic multilayers, ordered alloy films, rare earth-transition metal amorphous alloy films, and inhomogeneous or granular films. The physical origins for perpendicular magnetic anisotropy, including interface anisotropy due to structural symmetry breaking, magnetoelastic anisotropy due to strain, bulk-type magnetocrystalline anisotropy, and directional pair ordering of atoms, are discussed in each example.
Zablackaite, G.; Shiotsu, Hiroyuki; Kido, Kentaro; Sugiyama, Tomoyuki
Nuclear Engineering and Technology, 56(2), p.536 - 545, 2024/02
Times Cited Count：2 Percentile：62.28(Nuclear Science & Technology)Hirota, Noriaki; Nakano, Hiroko; Fujita, Yoshitaka; Takeuchi, Tomoaki; Tsuchiya, Kunihiko; Demura, Masahiko*; Kobayashi, Yoshinao*
The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.030007_1 - 030007_6, 2024/01
Dynamic strain aging (DSA) and intergranular stress corrosion cracking (intragranular SCC) occur in high temperature pressurized water simulating a boiling water reactor environment due to changes in dissolved oxygen (DO) content, respectively. In order to clearly understand the difference between these phenomena, the mechanism of their occurrence was summarized. As a result, it was found that DSA due to intragranular cracking occurred in SUS304 stainless steel at low DO 
1 ppb, while DSA was suppressed at DO 100 to 8500 ppb due to the formation of oxide films on the surface. On the other hand, when DO was increased to 20000 ppb, the film was peeled from the matrix, O element diffused to the grain boundary of the matrix, resulting in intergranular SCC. These results are indicated that the optimum DO concentration must be adjusted to suppress crack initiation due to DSA and intergranular SCC.
Fe
Mn
Si heusler alloy thin filmsNabialek, A.*; Chumak, O.*; Seki, Takeshi*; Takanashi, Koki; Baczewski, L. T.*; Szymczak, H.*
IEEE Transactions on Magnetics, 59(11), p.2501405_1 - 2501405_5, 2023/11
Times Cited Count：2 Percentile：22.67(Engineering, Electrical & Electronic)Hirohata, Atsufumi*; Lloyd, D. C.*; Kubota, Takahide*; Seki, Takeshi*; Takanashi, Koki; Sukegawa, Hiroaki*; Wen, Z.*; Mitani, Seiji*; Koizumi, Hiroki*
IEEE Access, 11, p.117443 - 117459, 2023/10
Times Cited Count：5 Percentile：26.16(Computer Science, Information Systems)Zhang, H.*; Umehara, Yutaro*; Yoshida, Hiroyuki; Mori, Shoji*
International Journal of Heat and Mass Transfer, 211, p.124253_1 - 124253_13, 2023/09
Times Cited Count：13 Percentile：79.87(Thermodynamics)
SnS-based shandite filmsLau, Y.-C.*; Ikeda, Junya*; Fujiwara, Kohei*; Ozawa, Akihiro*; Zheng, J.*; Seki, Takeshi*; Nomura, Kentaro*; Du, L.*; Wu, Q.*; Tsukazaki, Atsushi*; et al.
Physical Review B, 108(6), p.064429_1 - 064429_11, 2023/08
Times Cited Count：13 Percentile：80.59(Materials Science, Multidisciplinary)Zhang, H.*; Mori, Shoji*; Hisano, Tsutomu*; Yoshida, Hiroyuki
International Journal of Multiphase Flow, 159, p.104342_1 - 104342_15, 2023/02
Times Cited Count：13 Percentile：67.18(Mechanics)Battulga, B.; Atarashi-Andoh, Mariko; Nakanishi, Takahiro; Koarashi, Jun
Science of the Total Environment, 849, p.157758_1 - 157758_11, 2022/11
Times Cited Count：11 Percentile：58.25(Environmental Sciences)Characterizing plastic-associated biofilms is key to the better understanding of organic material and mineral cycling in the "Plastisphere"-the thin layer of microbial life on plastics. In this study, we propose a new method to extract biofilms from environmental plastics, in order to evaluate the properties of biofilm-derived organic matter through stable carbon (
C) and nitrogen (
N) isotope signatures and their interactions with radionuclides especially radiocesium (Cs). After ultrasound-assisted separation from the plastics, biofilm samples were successfully collected via a sequence of syringe treatments. Biofilm-derived organic matter samples (14.5-65.4 mg) from four river mouths in Japan showed Cs activity concentrations of 75 to 820 Bq kg biofilm (dw), providing evidence that environmental plastics, mediated by developed biofilms, serve as a carrier for Cs in the coastal environment. Significant differences in the (C and N signatures were also obtained for the biofilms, indicating the different sources, pathways, and development processes of biofilms on plastics.
Ito, Kanae; Yamada, Takeshi*; Shinohara, Akihiro*; Takata, Shinichi; Kawakita, Yukinobu
Journal of Physical Chemistry C, 125(39), p.21645 - 21652, 2021/10
Times Cited Count：9 Percentile：38.94(Chemistry, Physical)Ito, Kanae; Harada, Masashi*; Yamada, Norifumi*; Kudo, Kenji*; Aoki, Hiroyuki; Kanaya, Toshiji*
Langmuir, 36(43), p.12830 - 12837, 2020/11
Times Cited Count：16 Percentile：53.46(Chemistry, Multidisciplinary)Chimi, Yasuhiro; Sato, Kenji*; Kasahara, Shigeki; Umehara, Ryuji*; Hanawa, Satoshi
Proceedings of Contribution of Materials Investigations and Operating Experience to Light Water NPPs' Safety, Performance and Reliability (FONTEVRAUD-9) (Internet), 10 Pages, 2018/09
To investigate the influence of Zinc (Zn) injection on primary water stress corrosion cracking (PWSCC) growth behavior, crack growth tests of 10% cold-worked Alloy 600 were performed in simulated primary water environment of pressurized water reactor (PWR) at 320C with a low-concentration (5-10 ppb) Zn injection under dissolved hydrogen (DH) conditions of 5, 30, and 50 cc/kgHO. As a result of the crack growth tests, DH-dependence of crack growth rate (CGR) showed a similar tendency to the predicted CGR based on the CGR data without Zn injection, indicating almost no effect of a low-concentration Zn injection on the crack growth behavior. Moreover, the microstructural analyses of oxide films formed inside the crack and on the specimen surface were conducted, and the intake of Zn in the oxides was detected on the specimen surface, but not detected inside the crack. This result was considered to be the cause of no Zn injection effect on the crack growth behavior.
Inoue, Rintaro*; Kanaya, Toshiji*; Yamada, Takeshi*; Shibata, Kaoru; Fukao, Koji*
Physical Review E, 97(1), p.012501_1 - 012501_6, 2018/01
Times Cited Count：10 Percentile：59.48(Physics, Fluids & Plasmas)In this study, we investigate the process of a polystyrene thin film using inelastic neutron scattering (INS), dielectric relaxation spectroscopy (DRS), and thermal expansion spectroscopy (TES). The DRS and TES measurements exhibited a decrease in glass transition temperature (
) with film thickness. On the other hand, an increase in was observed in INS studies. In order to interpret this contradiction, we investigated the temperature dependence of the peak frequency (
) of the process probed by DRS and TES. The experiments revealed an increase in the peak frequency () with decreasing film thickness in the frequency region. This observation is consistent with the observed decrease in with thickness. The discrepancy between INS and DRS or TES descriptions of the process is likely to be attributed to a decrease in the apparent activation energy with film thickness and reduced mobility, due to the impenetrable wall effect.
