A Calculational Study of Benchmark Critical Experiments on High-Enriched Uranyl Nitrate Solution Systems

Criticality calculations on minimally reflected, concrete-reflected, and plastic-reflected single tanks and on arrays of cylinders reflected by concrete and plastic have been performed using the KENO-IV code with 16-group Hansen-Roach neutron cross sections. The fissile material was high-enriched (93.17% ²³⁵U) uranyl nitrate [UO₂(NO₃)₂] solution. Calculated results are compared with those from a benchmark critical experiments program to provide the best possible verification of the calculational technique. The calculated k_eff’s underestimate the critical condition by an average of 1.28% for the minimally reflected single tanks, 1.09% for the concrete-re-flected single tanks, 0.60% for the plastic-reflected single tanks, 0.75% for the concrete-reflected arrays of cylinders, and 0.51% for the plastic-reflected arrays of cylinders. More than half of the present comparisons were within 1% of the experimental values, and the worst calculational and experimental discrepancy was 2.3% in k_eff for the KENO calculations.