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Rizaal, M.; Nakajima, Kunihisa; Suzuki, Eriko; Miwa, Shuhei
Annals of Nuclear Energy, 218, p.111433_1 - 111433_10, 2025/08
Times Cited Count:0Soma, Yasutaka; Komatsu, Atsushi; Kaji, Yoshiyuki; Yamamoto, Masahiro*; Igarashi, Takahiro
Corrosion Science, 251, p.112897_1 - 112897_15, 2025/07
Times Cited Count:0Experimental and modeling studies of the oxygen ingression at the crevices of stainless steels were conducted in high-temperature water (288C). The limiting distance of oxygen ingression,
, was defined as the point beyond which the primary surface oxide changed (hematite
magnetite), regardless of crevice gap, oxygen concentration, and time. In situ measurements revealed increased electrical conductivity around the
position indicating ion enrichment due to a differential oxygen concentration cell.
increased with increasing crevice gap, oxygen concentration, and immersion time. Modeling study suggested that oxide layer growth reduced anodic dissolution and slowed oxygen consumption, allowing oxygen ingression with time.
Ogawa, Tatsuhiko
Annals of Nuclear Energy, 216, p.111256_1 - 111256_12, 2025/06
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)A novel robust method has been developed to simulate the performance of composite neutron sources composed of an alpha-emitting actinide and a light nucleus with low neutron separation energy. This method is based on the JENDL-5 cross-section data library and the Monte-Carlo radiation transport code PHITS. In contrast to previously devised methods, this approach can predict various quantities of the sources, such as actinide grain size dependence, absolute neutron emission intensity, energy spectra of neutrons and parasitic photons, neutron multiplicity, and time structure, with little approximation. The accurate calculation of stopping power of alpha rays in actinide grains and light elements, as well as the use of (,n) reaction evaluated cross sections, which is one of the unique features of PHITS Ver.3.34 and its later versions, are the essences of the method. This method allows for the calculation of quantities important for practical applications, such as detection signal frequency, coincidence event rate, and the impact of parasitic gamma-rays.
Katano, Ryota; Abe, Takumi; Cibert, H.*
JAEA-Research 2024-019, 22 Pages, 2025/05
An accelerator-driven system (ADS) dedicated to transmutation of minor actinides (MAs) is driven in subcritical states. It is important for establishment of the subcriticality control of ADS to predict the burnup reactivity. To validate the prediction accuracy, the burnup reactivity, especially at the first cycle, must be measured with sufficient accuracy. In this study, we focus on Current-To-Flux (CTF) method. We have simulated the burnup reactivity monitoring during the ADS normal operation with the CTF method by performing fixed-source-burnup calculations using a continuous energy Monte Carlo code SERPENT2 with some tallies that models in-core fission chambers and have estimated its measurement uncertainty. We have clarified that the 10% biases of measure burnup reactivities appear independently of the burnup duration and their detector position dependence is particularly small in the outer region of the system.
Uesawa, Shinichiro; Ono, Ayako; Nagatake, Taku; Yamashita, Susumu; Yoshida, Hiroyuki
Journal of Nuclear Science and Technology, 62(5), p.432 - 456, 2025/05
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)We performed electrostatic simulations of a wire-mesh sensor (WMS) for a single spherical bubble and bubbly flow to clarify the accuracy of the WMS. The electrostatic simulation for the single bubble showed the electric current density distribution and the electric current path from the excited transmitter to receivers for various bubble locations. It indicated systematic errors based on the nonuniform current density distribution around the WMS. The electrostatic simulation for the bubbly flow calculated by the computational fluid dynamics code, JAEA Utility Program for Interdisciplinary Thermal-hydraulics Engineering and Research (JUPITER), indicated that the WMS had difficulty in quantitatively measuring the intermediate values of the instantaneous void fraction between 0 and 1 because they cannot be estimated by previous transformation methods from the WMS signal to the void fraction, such as linear approximation or Maxwell's equation, and have a significant deviation of the void fraction of 0.2 for the WMS signal. However, the electrostatic simulation indicated that the time-averaged void fractions around the center of the flow channel can be estimated using linear approximation, and the time-averaged void fraction near the wall of the flow channel can be estimated using Maxwell's equation.
Nagano, Hirohiko*; Kanda, Yuki*; Suzuki, Yuri*; Hiradate, Shuntaro*; Koarashi, Jun; Atarashi-Andoh, Mariko; Guo, Z.*
Discover Soil (Internet), 2, p.27_1 - 27_9, 2025/04
Endo, Akira
ESI-News, 43(2), p.37 - 41, 2025/04
The International Commission on Radiation Units and Measurements (ICRU) published ICRU Report 95 in 2020, revising the operational quantities for external exposure. This article provides an overview of the developments in the discussions within the ICRU, the International Commission on Radiological Protection (ICRP), and experts from Japan, and explores the background and process that led the ICRU to revise the operational quantities, as well as future responses and challenges. The article aims to enhance the understanding of the experts of the new operational quantities and to contribute to their smooth implementation in the future.
Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke*; Hirata, Yuho; Tsuchida, Hidetsugu*; Yokoya, Akinari*
Journal of Chemical Physics, 162(15), p.154102_1 - 154102_11, 2025/04
Times Cited Count:0Scientific knowledge of low-energy electrons resulting from water radiolysis is required to estimate radiation DNA damage. However, since the analysis of water radiolysis is very complex, this study focuses on the experimental values of low-energy electrons related to simple water photolysis and those generated by photoirradiation of electrodes in water. Both experimental analyses involve the presence or absence of a Coulomb field in the parent ion. In this study, we analyzed these experimental values using a calculation code that combines Monte Carlo and molecular dynamics methods. As a result, it was shown that the code reproduced the experimental values even under different experimental conditions, and the code was validated. The calculation code will be a powerful tool for analyzing the interaction between low-energy electrons and DNA, and is expected to be applied to elucidate the formation mechanism of radiation DNA damage.
Kamada, So*; Hirao, Yoshihiro*; Suyama, Kenya; Iwamoto, Osamu
Nihon Genshiryoku Gakkai-Shi ATOMO, 67(4), p.238 - 242, 2025/04
no abstracts in English
Koarashi, Jun; Takeuchi, Erina; Kokubu, Yoko; Atarashi-Andoh, Mariko
Radiocarbon, 67(2), p.307 - 317, 2025/04
Times Cited Count:0 Percentile:0.00(Geochemistry & Geophysics)Radiocarbon (C) dating of soil samples by accelerator mass spectrometry has been proven useful for studying carbon (C) cycling in terrestrial ecosystems. There are, however, two main difficulties in sample preparation for this application: contamination of samples with modern C and inhibition of graphite formation due to sulfur (S)-containing impurities. Here we evaluated these effects from three different sample preparation methods, by conducting
C measurements of
C-dead sample and S-rich soil samples. The preparation methods were all successful in graphite formation and
C measurement for soil samples with an organic S content
6.9%. The different methods showed different percent Modern Carbon (pMC) values ranging from 0.19% to 0.64% for
C-dead sample. However, the three methods had little influence on the determination of
C age for samples at least younger than 12,000 yr BP. The methods examined in the present study can be used for
C dating with sufficient accuracy in the application to C cycle studies.
Takeda, Ryoma; Shibata, Hiroshi; Takeuchi, Tomoaki; Nakano, Hiroko; Seki, Misaki; Ide, Hiroshi
JAEA-Testing 2024-007, 33 Pages, 2025/03
Japan Materials Testing Reactor (JMTR) in Oarai Research and Development Institute of the Japan Atomic Energy Agency (JAEA) has been developing various reactor materials, irradiation techniques and instruments for more than 30 years. Among them, the development of self-powered neutron detectors (SPNDs) and gamma detectors (SPGDs) has been carried out, and several research results have been reported. In this report, we compare and verify these test results with the theoretical output results obtained by the calculation code created in the JAEA report (JAEA-Data/Code 2021-018). The comparison was made with the irradiation test results of SPGD, a cobalt-60 gamma irradiation facility. As a result, it was found that the calculation results reproduced the test results well when the emitter diameter was relatively small compared to the range of Compton scattered electrons by the gamma rays. On the other hand, when the emitter diameter is relatively large, the output current in the test results is only about half of the calculated output current. The self-shielding effect of the emitter may be one of the reasons for the difference in the emitter diameter, and a new formulation, such as incorporating the effect of self-shielding caused by a larger emitter diameter or a non-isotropic -ray field as a change in the mean electron range or mean minimum energy in the calculation code, is necessary. The new formulation is necessary.
Meigo, Shinichiro; Iwamoto, Hiroki; Sugihara, Kenta*; Hirano, Yukinori*; Tsutsumi, Kazuyoshi*; Saito, Shigeru; Maekawa, Fujio
JAEA-Technology 2024-026, 123 Pages, 2025/03
Based on the design of the ADS Target Test Facility (TEF-T) at the J-PARC Transmutation Experimental Facility, a conceptual study was conducted on the J-PARC proton beam irradiation facility. This research was carried out based on the recommendations of the Nuclear Transmutation Technology Evaluation Task Force of the MEXT. The recommendations state that it is desirable to consider facility specifications that can make the most of the benefits of using the existing J-PARC proton accelerator while also solving the engineering issues of the ADS. We considered facilities that could respond to a variety of needs while reducing the facilities that were not needed in the TEF-T design. In order to clarify these diverse needs, we investigated the usage status of representative accelerator facilities around the world. As a result, it became clear that the main purposes of these facilities were (1) Material irradiation, (2) Soft error testing of semiconductor devices using spallation neutrons, (3) Production of RI for medical use, and (4) Proton beam use, and we investigated the facilities necessary for these purposes. In considering the facility concept, we assumed a user community in 2022 and reflected user opinions in the facility design. This report summarizes the results of the conceptual study of the proton irradiation facility, various needs and responses to them, the roadmap for facility construction, and future issues.
Emori, Tatsuya; Kitatsuji, Yoshihiro; Ban, Yasutoshi
JAEA-Technology 2024-025, 20 Pages, 2025/03
Radioisotope Thermoelectric Generators (RTGs) using the decay heat of Pu-238 has been applied for outer planet missions far from Jupiter, where solar power is limited. However, no facilities are available to produce Pu-238 for space probes in Japan. Moreover, the use of nuclear materials for the space exploration is difficult in term of the regulation. Thus, we focused on Am-241 whose half-life is around 432 years as an alternative heat source for RTGs. This report describes the procedure of separating Am-241 decayed from Pu-241 in aged plutonium oxide. Two experiments were performed: one using solid-liquid extraction and the other combining liquid-liquid extraction and solid-liquid extraction. Packed columns were used in the experiments, with their number reduced by less than one-fifth in the latter experiment compared to the former. Furthermore, the time required for separation in the latter experiment was less than half that of the former. We performed the separation experiments six times, collecting a total of approximately 0.43 g of Am-241 as an oxalate salt.
Terada, Atsuhiko; Thwe Thwe, A.; Hino, Ryutaro*
JAEA-Review 2024-049, 400 Pages, 2025/03
In the aftermath of the Fukushima Daiichi Nuclear Power Station accident, safety measures against hydrogen in severe accident has been recognized as a serious technical problem in Japan. As one of efforts to form a common knowledge base between nuclear engineers and experts on combustion and explosion, we issued the "Handbook of Advanced Nuclear Hydrogen Safety (1st edition)" in 2017. For improvement of the rational advancement of hydrogen safety measures and further reliability of hydrogen safety evaluation, a CFD analysis is highly expected to produce more precisely and quantitative results. We have been developing an integrated CFD analysis code system which can analyze hydrogen diffusion, explosion-combustion and structural integrity at the severe accident especially for pressurized water reactors (PWRs). We organized the role of LP and the CFD analyses and their utilization examples of hydrogen safety validation. Based on these results, we made the "Handbook of Advanced Nuclear Hydrogen Safety (2nd volume)". The analysis results of real scale PWR described in 2nd volume are confirmed by cross-analysis models and existing data obtained through representative small, medium and large-scale tests.
Nemoto, Yoshiyuki
JAEA-Research 2024-018, 16 Pages, 2025/03
The author aimed to contribute to the analysis of the accident behavior of coated cladding with improved oxidation resistance by chromium (Cr) coating on the outer surface of conventional zirconium alloy fuel cladding, and investigated dependence of the oxidation behavior of Cr on the steam flow rate and on temperature. Coated cladding is being developed as one of the Accident Tolerant Fuel (ATF) claddings, and it is important to analyze the behavior of coated cladding under accidental conditions with high accuracy in the purpose of safety evaluation, for which the oxidation kinetics of Cr in high temperature steam is necessary. In this study, based on the results of oxidation tests in high temperature steam using a thermobalance, an oxidation kinetics for Cr in the temperature range and steam flow rate that encompass the conditions of considerable accident was proposed. The results can be used for future analyses in analysis codes such as SAMPSON, thereby contributing to the development of coated cladding.
Urashima, Shuhei; Kusaka, Ryoji
Analyst, 150(5), p.819 - 826, 2025/03
Times Cited Count:0 Percentile:0.00(Chemistry, Analytical)elik, Y.*; Stankovskiy, A.*; Iwamoto, Hiroki; Iwamoto, Yosuke; Van den Eynde, G.*
Annals of Nuclear Energy, 212, p.111048_1 - 111048_12, 2025/03
Times Cited Count:1 Percentile:62.55(Nuclear Science & Technology)Otsuka, Naohiko*; Tada, Kenichi; Cabellos, O.*; Iwamoto, Osamu
Annals of Nuclear Energy, 212, p.110977_1 - 110977_9, 2025/03
Times Cited Count:0 Percentile:0.00(Nuclear Science & Technology)The uranium-233 neutron capture cross section between 3 keV and 1 MeV was evaluated considering the recent new alpha-value measurement performed at the Los Alamos National Laboratory LANCE facility. The obtained capture cross section is systematically lower than the capture cross section in the JENDL-5 library and the reduction is close to 50% around 20 keV. The newly evaluated cross section was validated against 166 criticality experiments chosen from the ICSBEP handbook by performing Monte Carlo neutron transport calculation with the JENDL-5 library, and slight reduction of the chi-square value was achieved by adoption of the newly evaluated capture cross section.
Kai, Takeshi; Toigawa, Tomohiro; Matsuya, Yusuke*; Hirata, Yuho; Tsuchida, Hidetsugu*; Ito, Yuma*; Yokoya, Akinari*
Communications Chemistry (Internet), 8, p.60_1 - 60_9, 2025/03
Times Cited Count:1 Percentile:0.00(Chemistry, Multidisciplinary)Radiation DNA damage is formed from direct and indirect effects. The direct effect is the interaction between DNA and a radiation, while the indirect effect is the chemical reaction between DNA and radiolytic chemical species. We believed that when the direct effect is induced, multiple lesions are formed within 10 base pairs (about 3.4 nm) of DNA. The damage reduces repair efficiency and induces biological effects. In this study, DNA damage induced by only indirect effects was quantitatively evaluated. Our results indicated that the multiple damage is formed when only 10s of eV energy is deposited to water in the vicinity of DNA, although its formation probability is less than 1%. In other words, the possibility of late biological effects cannot be excluded simply by imparting energy to water in the extreme vicinity of DNA without direct interaction between radiation and DNA. Our results are one of the most important findings for understanding low-dose radiation risk.
Chong, Y.*; Tsuru, Tomohito; Mitsuhara, Masatoshi*; Guo, B.*; Gholizadeh, R.*; Inoue, Koji*; Godfrey, A.*; Tsuji, Nobuhiro*
Communications Materials (Internet), 6, p.50_1 - 50_11, 2025/03
Strain-induced martensitic phase transformation (SIMT) critically affects the mechanical properties of metastable
titanium alloys. In this study, the effects of
grain size and oxygen content on SIMT in a Ti-12wt.%Mo alloy were systematically investigated. It is found that SIMT is promoted by a decrease in grain size and in oxygen content. The mechanistic origins of the anomalous grain size dependency and the acute oxygen content dependency of SIMT are discussed based on multi-scale microstructural characterization and state-of-the-art simulations. Grain refinement does not raise the energy barrier for SIMT but rather provides more nucleation sites for strain-induced
martensite, thereby promoting SIMT in fine-grained Ti-12wt.%Mo alloy. In contrast, for the Ti-12wt.%Mo-0.3 wt.%O alloy, oxygen atoms substantially increase the energy barrier for SIMT, due to a change in the local configuration of oxygen atoms during the phase transformation. In addition, atomprobe tomography reveals for the first time that oxygen atoms segregate at
phase boundaries, thereby further restricting the growth of
martensite.