The effect of burnable absorbers (Gd and Eu) on the neutronphysical characteristics of fuel assemblies of VVER-1000 reactors

The problem of the use of burnable absorbers (BAs) in VVER-type reactors is considered to reduce the volume of "liquid" regulation of excess reactivity margin for fuel burnup. As such, natural gadolinium and europium are considered in the form of Gd2O3 and Eu2O3, placed in integrated form with uranium fuel in fuel rods. The ratio of fuel rods with BAs and conventional fuel elements is 1:6. Variants of both the homogeneous location of the BAs and heterogeneous, including for the mixed use of these BAs were considered. The strong influence of the BAs composition and their location in the fuel elements on the dependence of the multiplication factor on fuel burnup is shown.