Fission products chemistry in simulated PWR fuel up to 2100C: Experimental characterisation and TAF-ID modelling
Résumé
The capabilities of the Thermodynamic of Advanced Fuels – International Database (TAF-ID) for reproducing the chemical behaviour of irradiated nuclear fuel in severe accident conditions were studied, by comparing calculation results to experimental observations. SIMFUELs samples containing UO2 + 11 elements (Ba, Ce, La, Mo, Nd, Pd, Rh, Ru, Sr, Y and Zr, in concentration representative of a 76 GWd•tU-1 Burn-up) were submitted to 1327°C in oxidizing conditions, and to 1800, 2000, and 2100°C under reducing ones. Samples were characterized by Electron Probe Micro-Analysis (EPMA), High-Resolution XRD, and X-ray Absorption Spectroscopy (XAS). Thermodynamic calculations reproduced accurately the solubility of fission products in the UO2 matrix, and the type and composition of minor oxide and most metallic phases. Calculations also explain metallic phases microstructure as a result of the progressive solidification of liquids. However, some features such as the U-Pd-Rh association could not be reproduced, due to the lack of a thermodynamic model for this ternary system.