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2023.07.25
At the 152nd Annual Meeting of The Minerals, Metals & Materials Society (TMS) held in San Diego, California, U.S.A., Tetsuya Hirade of Research Group for Radiation Materials Engineering, the Nuclear Science and Engineering Center received the "AIME Champion H. Mathewson Award" for his joint research with Sophia University. The award-winning paper is "Hydrogen Desorption Spectra from Excess Vacancy-Type Defects Enhanced by Hydrogen in Tempered Martensitic Steel Showing Quasi-cleavage Fracture", Metallurgical and Materials Transactions A, November 2019 (open access due to the editor's pick). TMS is an organization headquartered in the United States and conducts a wide range of activities, from materials and engineering to material processing, basic research, and advanced applied research.
An attempt was made to separate and identify hydrogen peaks desorbed from plastic-strained, hydrogen-enhanced lattice defects from among various trapping sites in tempered martensitic steel showing quasi-cleavage fracture using thermal desorption spectroscopy from a low temperature (L-TDS) and positron annihilation spectroscopy (PAS). The amount of the lattice defects beneath the quasi-cleavage fracture surface was measured by L-TDS. The L-TDS results made it possible to separate two peaks, namely that of the original desorption and also that of new desorption from the steel specimens due to the application of plastic strain in the presence of hydrogen. The PAS results revealed that the new desorption obtained by L-TDS corresponded to vacancy-type defects. Hydrogen and plastic strain noticeably enhanced lattice defects formed within 1.5 mm from the fracture surface, where the average concentration of vacancy-type defects reached approximately 10-5 order in terms of atomic ratio. These results indicate that the accumulation of excess vacancy-type defects enhanced by hydrogen in the local region can lead to nanovoid nucleation and coalescence in plastic deformation, resulting in quasi-cleavage fracture of tempered martensitic steel.
2023.07.10
Dr. Chiaki Kato, Director of the Research Co-ordination and Promotion Office, Nuclear Science and Engineering Center, has received the prize of “2023 Japa Society of Corrosion Engineering Academic Award” in recognition of his contribution to the development of science and technology in the field of corrosion engineering. He has been involved in research and development for nearly 30 years to elucidate the corrosion behavior of nuclear materials such as light water reactor structural materials and reprocessing structural materials, etc. He has conducted research from an academic perspective about extremely difficult special corrosion environments.
2023.03.28
Dr. Hiroki Iwamoto of Research Group for Nuclear Transmutation System, Nuclear Science and Engineering Center, Dr. Shin-ichiro Meigo of Nuclear Transmutation Division, J-PARC Center, Dr. Daiki Satoh and Dr. Yosuke Iwamoto of Research Group for Radiation Transport Analysis, Nuclear Science and Engineering Center received the prize of "55th Atomic Energy Society of Japan Article Award" for the paper entitled "Measurement of 107-MeV proton-induced double-differential thick target neutron yields for Fe, Pb, and Bi using a fixed-field alternating gradient accelerator at Kyoto University" (J. Nucl. Sci. Technol., 60, 435-449, 2023) on March 14, 2023.
Spent fuel from nuclear power plants is radiotoxic for a long period of time, up to tens of thousands of years. The accelerator-driven transmutation system (ADS) is attracting attention as a system to reduce the radiotoxicity. In the design of ADS, it is necessary to accurately predict the number of neutrons (spallation neutrons) emitted in the nuclear reaction between high-energy protons and target materials, as well as their energy and spatial distribution. In this paper, we obtained detailed data on spallation neutrons by irradiating iron (Fe), lead (Pb), and bismuth (Bi), which are important materials in the ADS design, with a proton beam using the FFAG proton accelerator at Kyoto University. Based on the obtained data, we validated the accuracy of the nuclear reaction models used in the design of ADS and obtained knowledge for the advancement of the nuclear reaction models. This achievement and the data obtained in this study are expected to contribute not only to the ADS design but also to the design of many accelerator facilities. This work was supported by "the MEXT Innovative Nuclear Research Development Program: Experimental study of nuclear data for ADS using FFAG proton accelerator".
【Awarded papers】
https://www.tandfonline.com/doi/full/10.1080/00223131.2022.2115423
2023.03.28
Dr. Hiromasa Nakayama of Research Group for Environmental Science, Dr. Daiki Satoh of Research Group for Radiation Transport Analysis at Nuclear Science and Engineering Center and Dr. Naoyuki Onodera of Center for Computational Science and E-Systems received the prize of "55th Atomic Energy Society of Japan Award for Local-scale High-resolution Atmospheric Dispersion and Dose Assessment System (LHADDAS)".
Conventional atmospheric dispersion simulation systems, such as SPEEDI and WSPEEDI developed by JAEA, are targeted at a regional scale of approximately 100 km × 100 km with a grid resolution of several hundred meters. However, they can neither reproduce inhomogeneous distributions of air concentrations, surface deposition of radionuclides, caused by complex wind flow patterns influenced by buildings, nor estimate consequent air dose rates considering the shielding effects of surrounding buildings.
We combined atmospheric dispersion and air dose calculation to develop a new simulation code. Firstly, we utilized the local-scale high-resolution atmospheric dispersion model using large-eddy simulation (LOHDIM-LES). It can perform detailed simulations of complex turbulent flows and plume dispersion with regards to individual buildings that are resolved by a fine grid resolution. Secondly, the dose calculation code powered by lattice dose-response functions (SIBYL), which can quickly estimate air dose rates by a three-dimensional radiation transport scheme, was also used. Furthermore, the real-time dispersion simulation model based on the lattice Boltzmann method (CityLBM) was recently developed. By integrating these calculation codes, LHADDAS has been developed.
LHADDAS can provide a more realistic analysis method than wind tunnel experiments for plume dispersion under the actual meteorological conditions in the safety assessment of nuclear facilities. It is also useful for detailed pre/post-analyses of radiological dose exposures for emergency workers in nuclear accidents, the general public and first responders, in case of terrorist attacks, in urban/central districts. It can also be used for real-time consequence assessment in emergency response to terrorist attacks in urban/central districts.
2023.03.28
Dr. Yuho Hirata of Research Group for Radiation Transport Analysis and others received 2022 AESJ Award for Encouragement for the study entitled "Theoretical and experimental estimation of the relative optically stimulated luminescence efficiency of an optical-fiber-based BaFBr:Eu detector for swift ions" (J. Nucl. Sci. Technol., 59, 915-924, 2022) on March 14, 2023.
An optical stimulated luminescence element of BaFBr:Eu is expected to be used as a small size dosimeter for dose evaluation in the human body during the radiotherapy. However, the luminescence efficiencies of BaFBr:Eu for swift ions are lower than that for photons at the same dose, leading to an underestimation of the evaluated dose. This decrease in luminescence efficiency was thought to be caused by the lack of luminescence centers that can convert electrons into photons, because the swift ions densely deposit energy to generate a large number of secondary electrons locally. In this paper, we predicted the luminescence efficiency of BaFBr:Eu by applying the microdosimetric function of PHITS to calculate the density of energy deposition. The developed prediction method can be used with other luminescence materials and various detectors and is expected to have a ripple effect on the field of radiation measurement.
【Awarded papers】
https://www.tandfonline.com/doi/full/10.1080/00223131.2021.2017372
2023.03.28
Dr. Shinsuke Nakayama of Nuclear Data Center and others received the prize of "The Journal of Nuclear Science and Technology Most Popular Article Award 2022" for the paper entitled "JENDL/DEU-2020: deuteron nuclear data library for design studies of accelerator-based neutron sources" (J. Nucl. Sci. Technol., 58, 805-821, 2021) on March 14, 2023.
In the fields of nuclear physics, medicine, and fusion reactor development, large quantities of neutrons with energies higher than 10 MeV are required. However, conventional neutron sources such as nuclear reactors cannot supply enough neutrons to meet these requirements. Under these circumstances, the nuclear reactions induced by deuterons are attracting attention as a high-energy neutron source. However, it has been difficult to accurately predict the amount of neutrons produced by these reactions. In this paper, they have developed a calculation method to accurately predict the amount of neutrons produced by the nuclear reaction induced by deuterons. They have also developed a nuclear reaction database, JENDL/DEU-2020, based on the calculated results of the method. Using JENDL/DEU-2020, it is possible to design neutron sources employing deuteron with various specifications according to the purpose of use. This is expected to promote the use of neutrons in a wide range of fields, including basic science, medicine, and materials development. This work was partially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant-in-Aid.
【Awarded papers】
https://www.tandfonline.com/doi/full/10.1080/00223131.2020.1870010
2023.03.28
Dr. Ryoji Kusaka of Research Group for Nuclear Chemistry and others received the prize of "The Journal of Nuclear Science and Technology Most Popular Article Award 2022" for the paper entitled "Distribution of studtite and metastudtite generated on the surface of U3O8: application of Raman imaging technique to uranium compound" (J. Nucl. Sci. Technol., 58, 629-634, 2021) on March 14, 2023.
The composition of nuclear fuel debris will be complex. To understand its chemical state will be important for the storage, process, and disposal of nuclear fuel debris. So far, it has been known that uranium dioxide (UO2), which is the main component of nuclear fuel debris, reacts with hydrogen peroxide (H2O2) generated by radiolysis of water to form uranyl peroxide. In this paper, we showed that uranyl peroxide was also generated from U3O8, which will be contained in nuclear fuel debris. Furthermore, it was demonstrated that two uranyl peroxides, studtite and metastudtite, were produced independently on the surface of U3O8. It is expected that this result and the Raman spectroscopic analysis method used in this study will help to better understand the chemical state of fuel debris in the future. This research was supported from "JAEA Nuclear Energy S&T and Human Resource Development Project through Concentrating Wisdom".
【Awarded papers】
https://www.tandfonline.com/doi/full/10.1080/00223131.2020.1854881
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