Estimation of some neutron physics characteristics by Monte-Carlo method using the importance function

Abstract The work describes the realization of the method that allows reducing bias of the effective multiplication factor calculation in criticality problems without any changes in simulation and receiving reliable evaluations of its statistical uncertainty. The method is based on the calculation of a discrete adjoint function of a matrix transport equation. It is demonstrated that the use of the discrete adjoint function may improve estimations of neutron generation time and the effective delayed neutron fraction. Calculations have been performed by means of the MCU (Monte Carlo Universal) code. The «Whiteside problem» weakly coupled system and ZR-6 critical benchmark experiment have been used to show the effectiveness of the method.