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Visualizing the True Distribution of Trace Uranium Using Superconducting Technology – Advancing the Understanding of Trace Elements Migration in the Environment – 

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)

Elucidation of Factors Governing Brittleness and Ductility in Refractory High-Entropy Alloys – Diversity of Elements Opens the Door to Superior Alloys – 

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)