In nuclear power plants corrosion and activation of structural material and its re-deposition on out-ofcore surfaces is of significance as far as structural integrity and radiation exposure to the employees are concerned. Recently, Indian Pressurized Heavy Water Reactors have faced a typical problem of activation of antimony (Sb) from primary heat transport pump seals containing ~10% Sb. This Sb cannot be removed easily and its deposition mechanism is yet to be clearly understood. This article deals with studies related to the understanding of this process and a solution for the removal of Sb.