Evaluation of burnable absorber rods effect on neutronic performance in fuel assembly of WWER-1000 reactor

In pressurized water reactors dissolving a soluble neutron absorber in the moderator and varying its concentration with time serves to compensate for excess reactivity. Burnable poisons embedded in the fuel or other core constituents offer an additional means for limiting excess reactivity as well as mitigating localized power peaking. Indeed, burnable absorber rods are one of the most important control elements in with respect to the nuclear reactor safety. We investigated the burnup characteristics of a fuel assembly by varying the concentration of burnable poison in a fuel rod, and the number of burnable poison rods in an assembly. Furthermore, examined the burnable poison distribution pattern and the influence of changing poison material on the main neutronic parameters of the fuel assembly. The performance of chromium diboride and gadolinium oxide was also analyzed in this study. The WWER-1000 reactor was used as our test case.