Minimum Critical Values Study

This report provides minimum critical values for various 30-cm water-reflected uranium and plutonium oxide and nitrate aqueous mixtures as calculated by the SCALE CSAS1X sequence using the 238-group ENDF/B-V neutron cross-section library. The minimum values were determined through parametric searches in one-dimensional geometry. The calculations have been performed to obtain the minimum values: critical volume and mass for spheres, critical radius for cylinders, critical thickness for slabs, and minimum critical concentration (infinite geometry) for the following homogeneous mixtures: (1) UO2-H2O for 3, 4, 5, 20, and 100 wt % 235U; (2) UNH for 3, 4, 5, 20, and 100 wt % 235U; (3) PuO2-H2O for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of 239Pu/240Pu/241Pu(/242Pu); and (4) PuNH for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of 239Pu/240Pu/241Pu(/242Pu). All bounding surfaces were fully reflected by 30 cm of H2O