Amir Karimi Jafari - Department of Faculty of Engineering Science and Research branch, Islamic Azad University Tehran – Iran

numerous burnable-absorber (BA) types have been used in commercial nuclear fuel assembly designs to suppress initial reactivity. In this study, presents results of calculations for PWR 17 17 fuel assembly with erbium isotopic content by using the DRAGON code simulation. These BAs characteristics are varied in erbium enrichment and number of gadolinia rods in fuel assembly. In order to decrease this parasitic absorption in the end and emphasize the absorption in beginning of the life it is possible to use erbium enriched in Er-167.