Criticality measurements on uranium metal spheres immersed in uranium solution

The results of criticality measurements on enriched (93.16% 235U) uranium metal spheres symmetrically immersed in enriched (93.18% 235U) uranyl nitrate solution cylinders are reported. The solution cylinders are 26.5, 38.4, and 51.1 cm in diameter with heights ranging from 16 to 70 cm. Solution concentrations, expressed in grams of uranium per liter, are 11.47, 12.55, 13.12, 21.25, 24.20, 24.72, 103.0, and 104.8. Twenty-seven critical systems are identified. The experimental critical parameters of each system are compared with computed values obtained by transport (DTF) and Monte Carlo (KENO) methods. Results from neither method exhibit a systematic difference from experimental values; the average difference in the critical radius is 2.5% for DTF and 2.0% for KENO. The effects of experimental perturbations are determined experimentally and calculationally.