The effect of burn up on the kinetic parameters for a pressurized water reactor fueled by MOX using MCNPX code

Abstract

Reactor kinetic parameters are very important for safety analysis in power reactors. This paper focused on calculations of kinetic parameters such as the effective delayed neutron fraction (β _eff), the neutron generation time (Λ) and the prompt neutron lifetime l _p for PWR. In this paper the burn-up calculations were performed to calculate kinetic parameters as a function of burn-up for a PWR when fueled with standard UO ₂ fuel and MOX (Mixed-Oxide) fuel in order to study the impact of burn-up on these parameters. The calculations were performed using the Monte Carlo code MCNPX. The core chosen for the simulation is based on a 4-loop Westinghouse PWR power plant. The calculations were performed from beginning of the life to the end of life 210 days and compared with safety values taken from the design control document of an AP1000 PWR. The results are in agreement for UO ₂ but not for MOX until end of cycle (EOC).