High Temperature Interaction Studies for Intermediate Product Characterization and Thermal Decomposition Mechanism

Present studies have been carried out to understand the high temperature interaction behaviour of fuel material and fission product in stoichiometric, hypo stoichiometric and hyper stoichiometric ratios. Measurements have been performed using simultaneous thermogravimetric evolved gas analysis and powder diffraction techniques on various molar mixtures (1:1, 3:1, 6:1, 1:3, 1:6) of uranyl nitrate hexahydrate and gadolinium nitrate hexahydrate respectively and the results are being discussed here. The intermediates and / or end products formed have been identified as (U0.5Gd0.5)O2 , U3O8, GdONO3, (U0.25Gd0.75)O2 for different molar mixtures of the two nitrates. Dissolution of gadolinium in uranium matrix has been indicated besides proposing the thermal decomposition mechanism of these mixtures at elevated temperatures.