Simulation of a liquid metal fast breeder reactor on a hybrid computer

Abstract

A Liquid Metal Fast Breeder Reactor is simulated on a hybrid computer to study the transient behavior of the neutron density during a controlled reactivity input disturbance. The nonlinear partial differential equations of heat flow are reduced by a discrete space-continuous time method to ordinary non- linear differential equations which are readily solved on the analog computer. Use is made of time multiplexing of the analog circuitry in order to reduce the number of components. An open-loop iteration process is employed to solve the closed-loop feedback system. Recently conducted research with the open-loop iteration method has demonstrated that a large number of iterations are required for convergence. An algorithm is developed which gives an improvement in the convergence rate for early values of time. For times greater than two seconds a stability problem with the converged solution was encountered and is discussed with some observations and comments. Innovations are introduced in the simulation of the neutron kinetics equations and in the handling of the nonlinear thermal properties of the uranium oxide fuel.