Critical Experiment Analysis of Neutron Absorbing Nickel-Chromium-Molybdenum-Gadolinium Alloy Being Considered for the Disposal of Spent Nuclear Fuel

A critical experiment was carried out in order to validate, improve, and benchmark a Nickel-Chromium-Molybdenum- Gadolinium alloy that would be used for nuclear criticality control of spent nuclear fuel (SNF). The experiment was performed at the Los Alamos Critical Experiments Facility (LACEF). The intent of the experiment was to provide criticality safety data for spent nuclear fuel surrounded by this alloy. The experiment was fueled with highly enriched uranium (HEU), mixed with the Ni-Cr- Mo-Gd alloy, and moderated and reflected with polyethylene. The arrangement of the experiment consisted of interlacing Ni- Cr-Mo-Gd alloy/fuel/moderator in the thermal energy region. Analysis of the critical experiment consisted of systematically examining the uncertainties associated with the experiment as they affect the calculated multiplication factor (k analysis is separated into uncertainties due to mass measurements, uncertainties due to geometry, and uncertainties due to impurities. Each type of uncertainty is analyzed individually and a total combined uncertainty is derived. The Ni-Cr-Mo-Gd alloy-HEU experiment had an experimental k using Monte Carlo Neutron Partical Transport Code and ENDF/B-VI cross-section data tends to agree with the experimental values. The sensitivity analysis of the critical experiment yielded a total combined uncertainty on the measured k