Benchmark characterization for the diluted highly enriched uranium experiments with waste matrix materials 

Critical experiments are carried out in order to validate, improve, and benchmark the extensive data calculations available. A series of such experiments was performed at the Los Alamos Criticality Experiments Facility (LACEF). These experiments were performed to provide criticality safety data for waste matrix materials. These critical experiments were fueled with highly enriched uranium (HEU), moderated with polyethylene, and mixed with silicon dioxide (SiO₂), aluminum (Al), magnesium oxide (MgO) and gadolinium (Gd). The uncertainties affecting the experiment were divided into three broad categories: mass measurement, geometry, and material composition. Each category is considered in turn and then the total experimental uncertainty is derived. These uncertainties were calculated using neutronic codes (MCNP, KENO, DANTSYS). All four experiments had a measured k_eff of 1.000. The benchmark of these critical experiments yielded uncertainties in the measured k_eff of ± 0.0023 for SiO₂, ± 0.0024 for Al, ± 0.0026 for MgO, and ± 0.0024 for Gd. These experiments were judged to be of benchmark quality. (author)