Advanced cores and fuel assembly designs have been developed to improve operational flexibility and economic performance and to further enhance safety features of nuclear power plants. The simulation of these new designs, along with strong heterogeneous fuel loading, have brought new challenges to the reactor physics methodologies currently employed in the industrial codes for core analyses. Control rod insertion during normal operation is one operational feature in the AP1000® plant of Westinghouse next-generation pressurized water reactor design. This design improves its operational flexibility and efficiency but significantly challenges the conventional reactor physics methods, especially in pin power calculations. The mixture loading of fuel assemblies with significant neutron spectra causes a strong interaction between different fuel assembly types that is not fully captured with the current core design codes. To overcome the weaknesses of the conventional methods, Westinghouse has developed a state-of-the-art three-dimensional (3-D) pin-by-pin calculation methodology (P3C) and successfully implemented it in the Westinghouse core design code ANC. The new methodology has been qualified and licensed for pin power prediction. The 3-D P3C methodology along with its application and validation are discussed in the paper.