الفهرس 
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Abstract
Energy demand is increasing to support the growing populations and economics. Nuclear power, as an economical, safe and clean energy source, is one promising option capable of large scale and short term deployment. Pressurized Water Reactor (PWR), that represents the largest part of the world power plants, will produce the major part of the nuclear electricity during the current century. Thus, the continue deployment of PWR with its low uranium utilization leads to design alternative concepts. The strategies that have been proposed to improve nuclear fuel utilization can be summarized in two main goals: first, converting fertile materials to fissile materials and second increasing the core average discharge burnup.
A typical PWR is simulated using the Monte Carlo MCNP5 code to study the impact of using BeO, as a reflector on the power peaking factor, core average discharge burnup and the core operating cycle. Three cases with different fuel enrichments, different soluble boron concentrations and different uniform distribution of burnable poisons concentrations are studied. The calculations showed that a 20 cm BeO reflector with a combination of an optimized three batch cores would ideally lead to a perfect flattening of the power distribution. Many trails are carried out to optimize the core map and fuel enrichments. Assembly peaking factors less than 1.08 are obtained for the three cases which increase the core average discharge burnup to about 92% from the optimum or licensing limits. Also a fairly flat distribution of plutonium formation throughout the core is obtained which helps in keeping the flattening of the power distribution throughout the core life. With this flattening of the burnup distribution, all assemblies will be loaded once and there is no shuffling needed. This increases the operating cycles and reduces the outage frequency and increasing the capacity factor. All of these will improve the uranium utilization and reduce the operating costs of the nuclear power plant.
The simulated PWR is used also to study the use of thorium as nuclear fuel in PWR. We focused on the improvement of the conversion ratio for thorium based fuel PWR when it is loaded in a fuel assembly to partly replace U-238. Also we compared between traditional PWR fueled with U-235 as fissile nuclide and U-238 as fertile material and a proposed PWR fueled with U-233 as fissile nuclide and Th-232 as fertile materia!. Five homogeneous thorium-uranium fuel cases are studied.