Descriptions of High and Low Enriched U235 Critical Experiments in 174-1 Spheres

Abstract~A wide variety of criticality experiments, using different geometries and solutions, was performed at Oak Ridge National Laboratory in the 1950s. Two sets performed in 174-1 spheres are analyzed to provide benchmark descriptions for validation of computational tools used by nuclear criticality specialists. One set was performed in an unreflected sphere and contained a highly enriched uranyl nitrate solution (93.18% U235 ). Three of the four measurements from this set were poisoned with boron. The second set consists of one unreflected and two water-reflected measurements and used low-enriched uranyl fluoride solutions (4.9% U235 ). One of these experiments was critical with the sphere 83% full. An uncertainty in the experimental keff was found by sensitivity studies on reported measurement uncertainties, inconsistencies, and omissions in experimental parameters, Benchmark configurations were found for all experiments. To be functional for all computer codes. one-dimensional configurations were used when possible. The sensitivity study of the experiments was performed using ONEDANT with 27-Group ENDF/B-IV cross sections and MCNP with continuous energy ENDF /B-V cross section data. Keff values for the benchmark configurations were found using MCNP with ENDF;B-V and ENDFjB-VI cross section data, ONEDANT and KENO-Va with Hansen-Roach and 27-group ENDF/B-IV cross sections