Feasibility Study on Hydrogenated U-Th-Zr Fuel

H. Suwarno, F. Ono*, K. Yamaguchi*, M. Yamawaki
Department of Quantum Engineering and Systems Science
The University of Tokyo
* Nuclear Engineering Research Laboratory
The University of Tokyo

Hydrogen absorption-desorption property of U-Th-Zr was investigated in order to develop a new fuel material based on hydrided uranium-metal alloy. It was found that the U-Th-Zr alloy at varied atomic compositional ratio absorbed hydrogen at high capacity compared to that of the U-Zr fuel widely used in TRIGA reactors. Hydrogen absorption desorption of the alloy after several cycles have been demonstrated without any disintegration of the alloy into powder. Absorption rate was relatively fast, an indication of the stability of the hydrogenated specimen. Microstructural and X-ray diffraction examinations of the alloys exhibited that before hydrogenation it consisted of α-Th and δ-UZr2 with Th in it on hydrogenation. Th and Zr react with hydrogen to form stable ThZr2H7+x (or ThZr2H7-x) and ZrH2 compounds. The U-metal decomposed from the stable δ-UZr2 is distributed finely and homogeneously among the ThZr2H7+x (ThZr2H7-x) and ZrH2. Thermal properties of the hydrogenated U-Th-Zr alloys have been proven to be better than that of U-Zr-H alloy. Post-irradiation experiments revealed that under high neutron fluence, at temperature of about 973 K, the alloys were relatively stable. It has been proven from the microstructural examination that almost no hydrogen desorbed from the alloy.

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  2. T. Yamamoto, H. Suwarno, H. Kayano, M. Yamawaki, "Development of new reactor fuel materials: hydrogenation properties of U-Th-Zr alloys and neutron irradiation effects on their hydrides", J. Nucl. Mater. 247 (1997) 339-344.