Advanced Process Model for Polymer Pyrolysis and Uranium Ceramic Material Processing

Silicon carbide (SiC) based uranium ceramic material can be fabricated as hosts for ultra high temperature applications, such as gas-cooled fast reactor fuels and in-core materials. A pyrolysis-based material processing technique allows for the fabrication of SiC based uranium ceramic materials at a lower temperature compared to sintering route. Modeling of the process is considered important for optimizing the fabrication and producing material with high uniformity. This study presents a process model describing polymer pyrolysis and uranium ceramic material processing, including heat transfer, polymer pyrolysis, SiC crystallization, chemical reactions, and species transport of a porous uranium oxide mixed polymer. Three key reactions for polymer pyrolysis and one key reaction for uranium oxide polymer interaction are established for the processing. Included in the model formulation are the effects of transport processes such as heat-up, polymer decomposition, and volatiles escape. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Processing of a sample with certain geometry is simulated. The effects of heating rate, particle size and volume ratio of uranium oxide and polymer on porosity evolution, species uniformity, reaction rate are investigated.