Natural decay series radionuclides in and around a large metal refinery

A review is presented of the occurrence of natural decay series radionuclides in and around a large tin smelter which operated in northeast England from 1937 to 1992. Natural decay series radionuclides occurred as trace constituents in the raw materials used by the refinery but, with the exception of 210Po, the specific activities were less than the limit of 1.5 × 104 Bq kg−1 for classification as a radioactive substance. Polonium-210 occurred at levels in excess of the limit in some tin concentrates and was also selectively enriched to such levels in a number of factory intermediates and in the waste gas discharged from the refinery. Although specific activities of other natural decay series radionuclides were lower than the limit for classification as a radioactive substance, they were within, or close to, the range that was estimated by the UK National Radiological Protection Board potentially to be capable of giving rise to an occupational exposure of 5 mSv year−1. Insufficient information was available to model accurately the pathways of radionuclides through the refinery or to evaluate the environmental impact of the operation. The review suggests that appropriate radiological assessments and monitoring programmes are required in the metal-refining industry to ensure safe working conditions, waste disposal practices and decommissioning procedures.