Analysis on ohe Change in Neutronic Parameters due to Mispositioning of Fuel in ihe Ap1000 Core:

Abstract

AP1000 on the first cycle operation uses three types of UO2 fuel enrichments that are 2.35 w/o, 3.40 w/o and 4.50 w/o. To compensate excess reactivity, AP1000 uses an Integrated Fuel Burnable Absorber (IFBA) and a PYREX absorber as additional compensator to the boric solution in the moderator. IFBA is a burnable absorber made from ZrB2 which is integrated into the UO2 fuel. Human errors, such as fuel misposition, could happen when operators load fuel assemblies into the reactor core. For evaluating the design performance of AP1000, analysis on the change of neutronic parameters due to this fuel mispositioning need to be done. Analysis was performed on the reactor at hot zero power condition (HZP), beginning of cycle (BOC), and zero xenon condition with several cases of mispositioning between two adjacent fuels. Neutronic parameters, mainly the k-eff and power factor distribution will be derived from SRAC2006 computer code module of CITATION. One of the inputs required is fuel lattice macroscopic cross-section data, which are generated by PIJ module. These calculations performed condensation energy group of 107 into 10 groups with JENDL - 3.3 library cross section data. From the analysis, it can be concluded that misposition of the fuel in the first cycle of AP1000 core will result in very small change to the neutronic parameters. This very small change can not reduce the performance of the core.