Fission products chemistry in simulated PWR fuel up to 2100?C: Experimental characterisation and TAF-ID modelling

The capabilities of the Thermodynamic of Advanced Fuels - International Database (TAF-ID) for repro-ducing 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 el-ements (Ba, Ce, La, Mo, Nd, Pd, Rh, Ru, Sr, Y and Zr, in concentration representative of a 76 GWd center dot tU -1 Burn-up) were submitted to 1327 degrees C in oxidizing conditions, and to 180 0, 20 0 0, and 210 0 degrees C under re-ducing ones. Samples were characterized by Electron Probe Micro-Analysis (EPMA), High-Resolution XRD, and X-ray Absorption Spectroscopy (XAS). Thermodynamic calculations reproduced accurately the solubil-ity 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 solidifica-tion 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. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The capabilities of the Thermodynamic of Advanced Fuels - International Database (TAF-ID) for reproducing the chemical behavior of irradiated nuclear fuel in severe accident conditions were studied. The study found that the thermodynamic calculations accurately simulated the solubility of fission products in the fuel matrix and the formation process of metallic phases but had limited accuracy in certain cases.