Monte Carlo calculations of different types of burnable poison rods used in PWR

Abstract

The effect of burnable poisons on neutronic parameters of PWR is an important issue in nuclear fuel design. Burnable poisons are used to control the reactivity of the core and to improve fuel utilization. It classified to Burnable Poison Rods (BPRs) and Integral Burnable Absorbers (IBAs). This work focuses mainly on Burnable Poison Rods. The main purpose with this paper is to study and analyze the effect of different materials of Burnable Poison Rods (BPRs). The investigation was performed using MCNP6 code together with the Evaluated Nuclear Data Files, (ENDF/B)-VII.1. The investigation included study of the effect of: presence of BPRs and the changes of BPRs number. The calculations were carried out for two types of BPRs; Pyrex and WABA rods. The reactivity and radial power distribution and its variations vs. burnup were carried out up to50 Gwd/MTU. The results evidence that at BOC, the Pyrex and WABA have large compensation of reactivity; Pyrex has more negative reactivity than WABA. Lower power is obtained at the pin near the poisons rods due to large absorption cross section of boron material. The maximum pin power was located at the edge of the assembly due to the absorbing effect of BPRs.