The feasibility of utilizing Thorium-Plutonium Mixed Oxide in the Westinghouse AP1000 Advanced Passive pressurized water reactor is examined under steady-state, beginning of life conditions. Initial core loading of the reactor has three types of UO2 fuel assemblies with the U235 enrichments as: 2.35w/o, 3.40w/o and 4.45w/o. In this paper, one-third of the assemblies are replaced by (Th-Pu)O2 fuel in two arrangements; the first with a blanket of (Th-Pu)O2 fuel replacing the 4.45% enriched UO2 assemblies surrounding the low enriched UO2, and in the second some of the UO2 assemblies are replaced in a way creating a ring of (Th-Pu)O2 fuel in the core. The reactor is modeled using QUARK code. The required cross-section data for QUARK have been generated using WIMSD5. The results of the steady state analysis show that introducing (Th-Pu)O2 fuel into AP1000 would not negatively impact the reactor's safety as the criteria mentioned in design control document are met. For (Th-Pu)O2 blanket and ring loading arrangements, the power peaking factor is less or equal the design limit. Over the length of the hot channel, the MDNBR varies with a minimum above the design limit for blanket and ring loading arrangements. This work provides the basis of the study on fuel behavior and thermal hydraulic analysis of AP1000 to evaluate the safety aspect of various core loading patterns under anticipated and accidental conditions.