Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Physics

In The Present Work: the US-APWR core is analyzed with resilient fuel configurations and design. The main neutronic parameters are determined for the fuel assemblies and the reactor core. Moreover, the effect of axial distribution of the gadolinium burnable absorber in the fuel rods is investigated. The reactor core design is based on the Japanese APWR. It consists of 257 mechanically identical 17 x 17 fuel assemblies of 264 fuel rods; it has a thermal output of approximately 4451 MWt. The Monte Carlo code MCNP6 is used to model the fuel assemblies and the initial core. Three models of US-APWR assemblies (A), (B), and (C) are simulated. In the first model, UO2 fuel with enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium enriched uranium 4.15 wt%4.15 wt%4.15 wt%4.15 wt%4.15 wt%4.15 wt% is distributed uniformly in all the fuel rods. In the other two models some of the UO2 fuel rods are replaced by UO2-Gd2O3 rods in part length axial distribution. In one of the Gadolinia models, gadolinium is present in the lower part of the fuel rod. In the other model Gadolinium is present in the central part of the fuel rod. Two gadolinium concentrations (6 and 10 wt %) are used. The main neutronic safety parameters are estimated for the three models: the multiplication factor (K-infinity) as a function of burnup (GWd/MTU), the radial and axial power distributions. The results obtained show that the distribution of the gadolinium absorber in the central region of fuel rod leads to flattening of axial power, which means additional axial power distribution control

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