A method for the cleanup of ionic species such as cobalt and nickel in nuclear power plant aqueous streams using a sequestration resin material is disclosed herein. The method includes the steps of providing a sequestration resin for removal of radioisotopes of transition metal impurities contained in the plant process streams, and distributing the sequestration resin into the plant process streams such that the sequestration resin interacts with the process streams and removes the transition metal impurities.