IMPROVED NEUTRONICS MODEL OF THE HIGH-FLUX ISOTOPE REACTOR

An improved core physics model of the High Flux Isotope Reactor (HFIR) has been developed and evaluated by comparing calculational results with experimental results and also with calculational results obtained with earlier models. Eleven-group and 4-group cross-section libraries that are problem specific, collapsed, and weighted for the HEIR are generated from the 39-group Advanced Neutron Source Reactor cross-section library (ANSL-V general-purpose neutron library), which is based on ENDF/B-V. A diffusion theory-based procedure to analyze the static neutronics of the reactor is developed. Precise cross sections that take fuel loading variations (not considered in previous work) into account are also generated and implemented into an improved R-Z geometry model of the reactor. Point-by-point power densities are calculated using a derailed mesh structure. The results show that the improved model and procedure developed in this work give good agreement with experiments at interior locations with significant deviations at the outer boundary of the reactor core, which is near the control blades. More importantly, the improved model and procedure pro vide better overall agreement with experimental results than earlier models.