Preliminary model development in support of a new criticality safety benchmark for HEU metal annuli and cylinders with reflectors of three- to nineteen-inch thickness

Between 1963 and 1965, at least 100 experiments utilizing high-enriched uranium (HEU) metal annuli and cylinders with graphite reflectors up to 19 inches in thickness were performed at the Oak Ridge Critical Experiments Facility as the bases of nuclear criticality safety at the Y-12 National Security Complex. A set of 27 of those experiments, with reflectors up to 2 inches, have already been evaluated in HEU-MET-FAST-071 in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. There are 81 remaining experiments featuring reflectors with thicknesses from three to nineteen inches that have not yet been evaluated to benchmark quality, and this project focuses on performing that evaluation. To expedite the process of performing uncertainty quantification on each of the 81 outstanding experiments, the project will incorporate the use of a high-level programming language to automate portions of those calculations. This project presents two areas of great benefit to the nuclear criticality safety community and the greater nuclear industry. First, formulating benchmarks based on these experiments serves to preserve the data contained in the original logbooks without expending the time, effort and cost to execute the experiments again. Second, information regarding the cross sections of ¹²C can be obtained via analysis of the experiments, and can then be used in development of next generation nuclear reactors which utilize graphite as a moderating or reflecting material. The goal of this effort is to have a draft evaluation of the remaining 81 experiments prepared for review by the ICSBEP Technical Review Group by 2025. Here, the development and results of preliminary modeling of one select experiment will be discussed. (author)