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2024.10.25
Nuclear Science and Engineering Center (NSEC) has developed new polygon mesh-type human models of adult male (JPM) and female (JPF) for the purpose of evaluating exposure doses that reflect the physical characteristics of standard adult Japanese based on the latest scientific knowledges on radiation protection.
To accurately evaluate exposure doses, it is necessary to take into account the detailed behavior of radiation in the body. Thus, a method for calculation method by combining a Monte Carlo simulation code such as the PHITS code with a human model is very useful for evaluating exposure doses. Based on the latest scientific findings, the ICRP recommended the need to evaluate exposure doses to stem cell regions (lens, skin, etc.), which are radiosensitive and have micro-sized and complicated structures. However, the adult Japanese human models currently used for dose assessments not have defined stem cell regions. Therefore, NSEC has developed newly polygon mesh-type human models (JPM and JPF) that reproduce the shapes of organs and tissues of the whole-body using polygon technique, which can represent object shapes flexibly. By employing polygon technique, we were able to accurately define the micro-sized and complicated structures of stem cell regions within the organs and tissues of JPM and JPF. In addition, JPM and JPF have the standard body sizes and organ masses of adult Japanese people. This will enable us to accurately evaluate the equivalent dose to the lens under various exposure situations, which is necessary for dose control, while taking into account the body size characteristics of the Japanese. Development of the human model deformation technique for changing the postures and body sizes of JPM and JPF is currently underway. In the future, JPM and JPF in combination with the human model deformation technique under development will plan to use to evaluate exposure doses in consideration of posture and body size characteristics of individuals.
The electronic data for the JPM and JPF models will be made publicly available on the GitHub webpage below, and can be downloaded free of charge by accessing the webpage:
URL: https://github.com/JapanesePolygonPhantom/JPM-JPF-Phantom
The results of this study have been published in PLOS ONE on October 24, 2024.
Article information: https://doi.org/10.1371/journal.pone.0309753
JAEA HP Press release (Japanese only)
2024.07.10
The Nuclear Science and Engineering Research Center, in collaboration with the Advanced Science Research Center, the Center for Computational Science and Engineering, and several research institutes including the University of Tokyo, Yamagata University, and Hokkaido University, has conducted a study of the self-assembly action of ceramic particles with the aim of advancing the manufacturing technology for exhaust gas purification catalysts. The research discovered an integration technique that can easily control the size of particles by utilizing the forces acting on their surfaces.
In the catalyst manufacturing process, it is important to control the size of particles uniformly, but it is difficult to do so with ceramic materials used for exhaust gas catalysts. In this study, we focused on "self-assembly," in which ceramic particles spontaneously form a structure, and analyzed the role of particle surfaces in self-assembly using neutron beams, X-rays, and microscopic techniques. We found that the surface properties of the self-assembled particles change depending on the ions attached to the particle surfaces, resulting in significant differences in their structures. Furthermore, we found that when the binding method is controlled by integrated nanotechnology, the secondary particles fold over each other to form a higher order structure. This property makes it possible to easily control the size of ceramic particles, which is expected to be applied to reduce the amount of material used in the production of catalysts for exhaust gas purification and to develop new functional materials.
The research has been published online June 12, 2024 (local time) in Communications Chemistry, an international journal of the Nature Publishing Group.
Article information: https://www.nature.com/articles/s42004-024-01199-y
JAEA HP Press release (Japanese only)
2024.04.11
Nuclear Science and Engineering Center (NSEC) has developed the method for microbeam X-ray analysis using the transition edge sensor. It has succeeded in identifying the distribution of trace uranium (U) in real environmental samples, a feat unachievable with conventional semiconductor detectors under the collaboration with Rikkyo University, the University of Tokyo, Japan Synchrotron Radiation Research Institute (JASRI) and other organizations.
Uranium (U), used as fuel for nuclear power generation globally, is predominantly stored underground when it becomes waste, necessitating research into its migration behavior in subsurface environments. However, in environmental samples containing various elements, conventional semiconductor detectors struggle to resolve the fluorescence X-rays of trace U from those of abundant elements like rubidium (Rb), posing a challenge in accurately understanding U’s distribution and chemical forms. Our focus on Transition Edge Sensors (TES), which offer high energy resolution and detection efficiency, aims to overcome this challenge. Our validation of TES alongside semiconductor detectors (Silicon Drift Detectors: SDD) at SPring-8's Beamline BL37XU showed TES's superior ability to analyze trace amounts of U unachievable with conventional detectors. This has not only enabled the accurate identification of U's distribution but also its chemical state analysis within biotite, indicating some U reduction and immobilization, providing insights into the mechanisms of U retention in minerals. With TES's high energy resolution, its application extends beyond U to other elements within this energy range, promising broader environmental sample analysis applications.
The results of this study have been published in "Analyst," a journal issued by the Royal Society of Chemistry, on April 9, 2024.
Article information: https://doi.org/10.1039/D4AN00059E
JAEA HP Press release (Japanese only)
2024.03.07
Nuclear Science and Engineering Center (NSEC), in collaboration with Kyoto University, has clarified the mechanical properties and mechanisms in refractory high-entropy alloys (RHEA) by experiments and atomistic simulations to develop new refractory and heat-resistant alloys.
While increasing the efficiency of engines and power plants requires higher operating temperatures, the alloys used in turbine blades are reaching the limit of their heat-resistance performance. RHEA with its high melting point is expected to be a new alloy candidate for ultra-high temperature applications. However, most RHEA alloys are brittle at room temperature. Up to now, two representative alloys, TiZrHfNbTa alloy (denoted RHEA-Ti) and VNbMoTaW alloy (denoted RHEA-V), have been widely studied, but the nature of the differences in strength and ductility between two alloys have not been unexplored. In this study, change in properties of RHEAs depending on temperature and its mechanism were examined by both experiments and atomistic simulations. Our careful experiments show RHEA-Ti exhibits excellent strength and ductility even at low temperatures below room temperature, and atomic simulations indicate that the high strength and ductility in RHEA-Ti are due to the addition of Group IV elements on the electronic bonding. The above results are a good example of effectiveness of the element strategy design. Alloy design based on element strategies is expected to lead to the development of new alloys for next-generation high-temperature structural applications.
The results of this study have been published in Nature Communications (https://doi.org/10.1038/s41467-024-45639-8) on Feb. 24, 2024.
JAEA HP Press release (Japanese only)
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