Pebbles’ Life Cycle Analysis in Salt-Cooled Pebble Bed Reactor for Enhanced Fuel Performance Assessment

This study explores the lifecycle of fuel pebbles in salt-cooled pebble bed reactors (PBRs), focusing on key parameters such as temperature profiles, fast fluence, and critical isotope concentrations. By employing hyper-fidelity simulation tools (HxF), the analysis provides detailed, pebble-specific histories and identifies potential outlier behaviors for the gFHR, a benchmark salt-cooled PBR. A complementary investigation examines how the diversity in pebble histories influences the diffusion of hazardous fission products under normal operating conditions. To evaluate the impact of these histories, a 1D spherical geometry diffusion solver is employed as a fuel performance model. This solver uses the pebble-wise histories as boundary conditions to simulate a representative TRISO for each pebble, enabling detailed analysis of fission product release rates. The results demonstrate the importance of accounting for time-dependent temperature and burnup histories, as the trajectory and unique conditions experienced by each pebble significantly influence the release rate of fission products from the TRISO’s kernel. This diversity in pebble histories cannot be captured by a single representative pebble model relying on core-averaged values.