| First principles models of LWR (Light Water Reactor) 𝑈𝑂2 fuel cracking are being developed for the Bison fuel performance code. Model validation will be accomplished using data from out-of-pile experiments. The objective of work presented in this thesis is to guide design of experiments that will use different methods to create the temperature gradient near the pellet surface that is needed to induce cracking: (1) resistive heating and (2) quenching after bulk pre-heating. To guide (1), a temperature dependent electrical conductivity and resistive heating model was developed and coupled with the model for the thermal-mechanical aspects of fuel behavior. Key variables were the coolant heat transfer coefficient, initial temperature and amount of current. To guide (2), only the thermal-mechanical model was needed and key variables were the temperature difference in salt baths used for heating and cooling, thermal conductance of the gap between pellet and clad, and the coolant heat transfer coefficient. Though the out-pile-experiments will not reproduce volumetric heating like an LWR, the simulated cracking patterns for the experiments agree with those from LWRs.
Keywords: Fuel fracture, Bison, out-of-pile experiments, separate-effects, experiment design. |