Multiplication Factor of Uranium Metal by One-Velocity Monte Carlo Calculations

A method is described for predicting the neutron multiplication factors of geometrically complicated configurations of unreflected unmoderated enriched- uranium metal from the results of two delayed-critical experiments in simple geometry. The method requires two constants characteristic of the metal. These are the total collision cross section (∑_t) and the number of neutrons produced per collision (υ∑f/∑t), which are obtained from the two experiments by using S₁₂ transport-theory calculations with isotropic scattering. These constants, together with the assumption of isotropic scattering, are then used in 05R Monte Carlo neutron-transport calculations to predict the multiplication factors. The method has been tested by predicting the multiplication factors of 21 different delayed-critical assemblies with a wide variety of geometries to within a standard deviation of 1.5%.