This invention generally concerns radioactive decontamination of deposits on components in a nuclear power plant and is specifically concerned with improved systems and methods for disrupting, dissolving, removing and reducing at ambient temperature radionuclides formed on the primary side surfaces of components in a pressurized water reactor and the internal components of a boiling water reactor. The methods include identifying the structure, taking the structure out of operational service, contacting the structure with an aqueous solution (e.g., a recirculating flow or static immersion), and adding an effective amount of elemental metal in solid form to the aqueous solution.