A Monte Carlo Fuel Assembly Model Validation Adopting Post Irradiation Experiment Dataset

Abstract

Within a hybrid energy system, it is fundamental to have accurate and reliable computational tools to predict the plants; behaviour under different operating conditions; compared to other energy sources, analysis methods for nuclear systems must provide detailed information on reactor criticality and fuel evolution. Thanks to the advancements in computational hardware, using three-dimensional codes to obtain a local description of the reactor core has now become feasible both for deterministic codes and for Monte Carlo (MC) codes. Those computational methods must be compared with experimental measurements to assess their reliability. For this reason, the 3D MC code SERPENT is currently being validated for Light Water Reactor (LWR) fuel cycle simulations. This work will compare the isotopic concentrations measured in a Post Irradiation Experiment and the results of the MC routine, examining the Takahama-3 assembly test case. From literature reports, roughly 35 nuclide species have been measured at different axial locations by destructive analysis following several radiochemical techniques. A sensitivity analysis to evaluate the impact of design features on the results was carried out investigating the cross-section libraries, the simulation time discretisation and the imposition of an axial time-varying temperature. During the process, systematic sources of geometry-related errors were analysed as well. Overall, the model showed good agreement with the experimental data under an acceptable error threshold. The sensitivity studies also showed how the prediction capability could be increased up to +6%, adopting a realistic temperature mesh for the fuel instead of a uniform temperature approach.