This work gives the nuclear operator an integrated insight into the possibility of operating a CANDU reactor with thorium-based fuel types. MCNPX code was used to design 3D model of CANDU bundle. Thorium mixed with 235U, 233U and rgPu were investigated as a fuels in separate fuel cycles and their results were compared with the traditional fuel (UO2). The main neutronic and safety parameters such as infinity multiplication factor (kinf), neutron generation time (Λ), breeding ratio, Doppler reactivity coefficient (DRC), effective delayed neutron fraction (βeff) and moderator temperature coefficient (MTC) have been studied for the investigated fuels. Due to the significant impact of the rgPu and minor actinides (MAs) on the environment, their concentrations have been investigated with burn-up for the proposed fuels to reach the optimum one from the neutronic and economic point of view.