Neutronic simulation of the CEFR experiments with the nodal diffusion code system RAST-F

CEFR is a small core-size sodium-cooled fast reactor (SFR) using high enrichment fuel with stainless-steel reflectors, which brings significant challenge to the deterministic methodologies due strong spectral effect. The neutronic simulation of start-up experiments conducted at have been performed code system RAST-F, based on two-step approach that couples multi-group cross-section generation Monte-Carlo (MC) and nodal diffusion solver. RAST-F results were compared against measurement data. Moreover, characteristic neutron spectrum in rings, adjacent reflectors was evaluated different models for accurate nuclear libraries. numerical solution verified full core MC MCS all control rods fully inserted withdrawn states. A good agreement between solutions observed less than 120 pcm discrepancies 1.2% root-mean-square error terms keff power distribution, respectively. Meanwhile, result agreed well experimental values within two-sigma uncertainty. these indicating can be used steady-state simulations SFR, challenged system.