Reduction of copper oxide by hydrogen at high temperatures to metallic copper is one of the ways of removing hydrogen gas or its isotopes from its mixture with an inert gas like helium which is the coolant for plasma facing first wall of tritium breeding blanket modules in fusion reactor systems. The kinetics of the reaction of hydrogen with copper oxide was obtained from literature and it was used to model the reduction of a single particle of copper oxide using the well-known shrinking core model along with the pseudo-steady state hypothesis. No controlling regime was assumed a priori and the various interfacial gas concentrations were calculated by an iterative procedure based on the pseudo steady state hypothesis as function of the core radius at any time and for given operating conditions. The time required for complete reaction of the pellet was then calculated by numerical integration. A spherical geometry was considered in this work for the purpose of illustrating the technique, but the method is applicable to any kinetic model and any geometry of the pellets after simple modifications to the governing equations.