HYDROGEN DESORPTION PROPERTIES OF HYDROGENATED U-TH-ZR ALLOYS

Hydrogen desorption properties of hydrogenated U-Th-Zr alloys of varie d compositions were investigated using a hydrogen absorption-desorptio n experimental system, TG-DTA and DSC analyzers. Isothermal desorption at 900 degrees C of elemental ratio U:Th:Zr:H = 1:1:4:9.5 exhibited t hat there were two distinct plateau regions identified as ZrH1.4-ZrH a nd ThZr2H7-x-ThZr2 systems. TG-DTA and DSC measurements under the temp erature range from room temperature to 1000 degrees C have shown that there were three endothermic peaks identified as dehydrogenation react ions of ZrH2-x-ZrH and ThZr2H7-x. The DTA curve identified the first p eak area as the ZrH1.4-ZrH system, while the DSC curves identified tha t the second peak is the decomposition of ZrH and the third peak is th e decomposition of ThZr2H7-x. It was also shown that both ZrH2-x and T hZr2H7-x are more stable in the alloy than the pure ones. Measured ent halpy changes during decomposition of the hydrogenated U-Tn-Zr alloy a re similar to the theoretical calculation. Oxidation during measuremen t of the U:Th:Zr:H = 2:1:6:13.1 resulted in a different measured entha lpy change and calculation. Isothermal decomposition of the U:Th:Zr:H = 1:1:4:9.5 without any disintegration indicates stability of the allo y against powdering on hydriding-dehy driding cycles. Stability of the samples at high temperature similar to that of U-ZrH1.6 for TRIGA fue l can be maintained after the first decomposition. (C) 1997 Elsevier S cience B.V.