DESCRIPTIONS OF HIGH AND LOW ENRICHED U-235 CRITICAL EXPERIMENTS IN 174-1-SPHERES

A wide variety of criticality experiments, using different geometries and solutions, was performed at Oak Ridge National Laboratory in the 1 950s. Two sets performed in 174-1 spheres are analyzed to provide benc hmark descriptions for validation of computational tools used by nucle ar criticality specialists. One set was performed in an unreflected sp here and contained a highly enriched uranyl nitrate solution (93.18% U -235). Three of the four measurements from this set were poisoned with boron. The second set consists of one unreflected and two water-refle cted measurements and used low-enriched uranyl fluoride solutions (4.9 % U-235). One of these experiments was critical with the sphere 83% fu ll. An uncertainty in the experimental k(eff) was found by sensitivity studies on reported measurement uncertainties, inconsistencies, and o missions in experimental parameters. Benchmark configurations were fou nd for all experiments. To be functional for all computer codes, one-d imensional configurations were used when possible. The sensitivity stu dy of the experiments was performed using ONEDANT with 27-Group ENDF/B -IV cross sections and MCNP with continuous energy ENDF/B-V cross sect ion data. K-eff values for the benchmark configurations were found usi ng MCNP with ENDF/B-V and ENDF/B-VI cross section data, ONEDANT and KE NO-Va with Hansen-Roach and 27-group ENDF/B-IV cross sections. (C) 199 7 Elsevier Science Ltd.