Monte Carlo calculations of time-dependent neptunium-237 and uranium-235 fission rates in a pulsed thorium assembly

Abstract

A series of integral pulsed neutron experiments in a thorium assembly have been performed. Monte Carlo calculations are presented of the 237Np and 235U fission rates as a function of space and time. Calculations assuming spherical symmetry are compared with those which represent the geometry of the experiment nearly exactly, and both are compared with the experimental results. It is shown that the calculations give similar results for the simplified and actual geometries. It is concluded that the observed differences between calculation and experiment are not due to errors in the calculations introduced by the use of simplifying geometric assumptions.