The main purposes of this report are to investigate which parameters that affect the result of weapon-grade plutonium production, and serve as an introduction to nuclear reactor calculations. The report is divided into two parts. Part one consists of a parameter study, and aims to give knowledge about the factors having significance for production of weapon-grade plutonium in nuclear-grade plutonium in nuclear reactors. Properties such as reactor type, fuel composition, and operation have been thoroughly investigated and their effects have been compiled. The second part consists of a guide to depletion and criticality calculations regarding plutonium production. The guide aims to give insight into the calculations that are the foundation of the parameter study, and allow the reader to perform simpler reactor calculations with SCALE and MCNP. All results in this report originate from simulations made with tools intended to be used for depletion and criticality calculations.