DEVELOPMENT OF ACTINIDE-HYDRIDE FUEL

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Hydride fuels have been used in research reactors (e.g., TRIGA reactors) for many years. Recently, the transmutation method of nuclear wastes using actinide hydrides has been proposed. One of the most important R＆D items to establish the idea is the development of actinide-hydrides target, which can be safely irradiated up to high burnups. In this study, the U-Th-Zr-H type target material was used, since the hydrogen chemical potential of the hydride is close to that of Np and Am hydrides. The U-Th-Zr-H pellet have been successfully fabricated without large crack by means of a Sieverts apparatus. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses show that the hydride targets consist of actinide metal phase, actinide hydride phase and Zr hydride phase. Thermal conductivity data of actinide-hydrides targets are necessary for the design of the hydride fuel pin. The thermal diffusivity measurements of the U-Th-Zr-H type target material have been performed by means of a laser-flash method. The thermal conductivity was calculated from the relation of the measured thermal diffusivity, the literature data of the density, and the specific heat. The design correlation of the thermal conductivity has been developed as a function of temperature and hydrogen content.