Nuclear excursions in criticality accidents with fissile solutions

Abstract

An accidental criticality may occur in a solution of fissile material. Since the processing of nuclear materials in solution is prevalent throughout the fuel cycle, it would be judicious to have the capability to predict a possible hazard. In view of this concern, a computer simulation was performed of the Los Alamos accident of December 30, 1958, in which the actuation of an electric stirrer produced a sudden criticality. A complete equation of state for a liquid containing gas bubbles was coupled with the equations of energy, momentum, and space-independent point kinetics. Multiplication calculations, implemented with the Monte Carlo Code for Neutron and Photon Transport (MCNP), were performed on thermally expanding solution geometries, to generate a reactivity feedback representation. With the knowledge of the total energy produced in the accident, the maximum reciprocal period on which the power rose was computed.