A comparative study and design optimization of potential cladding materials for gas cooled fast reactor: Neutronics, radiation shielding, and thermal hydraulics analysis

Abstract

This study presents a comparative analysis of potential cladding materials for gas-cooled fast reactors (GFR), evaluating neutronics, radiation shielding, and thermal hydraulics, and includes optimized mixed cladding design to improve neutronics and overall performance. Eight different cladding materials—SiC, HT9, ODS steel, 15-15Ti, SS 316, TZM alloy, Ta alloy, and Zircaloy-4 were studied. SiC cladding achieved the longest cycle length, with Zircaloy-4 following closely, while metallic models generally showed shorter cycles, except for the optimized TZM mixed cladding, which also achieved extended cycle lengths. Though the optimized Ta alloy model did not achieve a longer cycle length, it improved radial neutron flux distribution and reduced radial power peaking factors, with TZM model contributing similarly. The study also found that SiC, TZM, and Ta alloy models produced harder neutron spectra and demonstrated reduced fissile inventory depletion and enhanced minor actinide transmutation. SiC and TZM model had the smallest reactivity swings, with all models except HT9 and ODS steel showing satisfactory beta effective values, and all models except Zircaloy-4 exhibited acceptable negative Doppler constant values. Radiation shielding assessments revealed SiC had the highest HVL, TVL, and MFP, while TZM and Ta alloy had the lowest, indicating better shielding performance. Thermal hydraulics analysis showed that these two materials exhibited lower peak temperatures in both fuel and cladding, along with a more uniform temperature distribution compared to other models. Despite these differences, all models maintained an adequate thermal margin in the cladding region.