Critical Reflector Thicknesses for Spherical U²³³ and Pu²³⁹ Systems

The thickness of reflectors required for critical configurations with spheres of U²³³ and Pu²³⁹ have been estimated from multiplication measurements of nearly critical assemblies. Reflector materials employed were uranium enriched in U²³⁵, normal uranium, beryllium, and tungsten alloy. Correction of the experimental data has been attempted to give “idealized” dimensions, i.e., a solid core in intimate contact with its reflector material.