LAUSR

Abstract This paper represents the neutronic characteristics and feasibility of using Gadolinia and Erbia in integral burnable absorber (IBA) rods for the proposed MOX fuel assembly of VVER-1000 reactor by Nuclear Energy Agency (NEA). For comparison the 4.0% Gd2O3 IBA is considered as a reference. The assembly was burned to 40 GWd/t, and by neutronic calculation, the optimum percentage of Gd2O3 and Er2O3 was determined using SRAC-2006 code and JEFF-3.1 data library. The burnup dependent reactivity of a MOX assembly containing 12 UO2-Gd2O3-Er2O3 (U-Gd-Er) IBA rods with 0.9% Gd2O3, and 5.0% Er2O3 was found almost identical to the reference assembly with 4.0% Gd2O3 in IBA rods. However, the assembly with U-Gd-Er IBA rods has a flatter pin-wise power distribution and lower power peaking factor (PPF). Long-lived fission products, poisons, and minor actinides are also investigated for choosing Gd2O3 and Er2O3 as IBA over only Gd2O3 for the VVER-1000 MOX fuel assembly.