Fluxes of 238U decay series radionuclides in a dicalcium phosphate industrial plant

The production of dicalcium phosphate (DCP) is part of the phosphate industry, which has been recently included in the positive list of the NORM industries defined in the revised version of the EU-BSS (Euratom 29/96). The objective of the present work is to study specific concentrations and fluxes of 238,234U, 230Th, 226Ra, 210Pb and 210Po at the different stages of the DCP production. Results showed highest activities of 238U and 210Pb were found in DCP (1500-2000 Bq kg−1); 230Th and 210Po were released together with the sludges (1600-2000 Bq kg−1) and 226Ra presented particularly high activities in water (48 × 103 Bq m−3) and in the reactor scales (115 × 103 Bq kg−1). Fluxes of radionuclides showed that 238U outflows were equally distributed between sludges (16 × 103 kBq h−1) and dicalcium phosphate (20 × 103 kBq h−1); 230Th and 210Po were almost entirely released in the sludges (30 × 103 kBq h−1) and the greatest 210Pb outflow was the DCP current (25 × 103 kBq h−1). 226Ra was mainly discharged through the water effluent (12 × 103 kBq h−1). This work highlights the importance of studying the industrial processes involving NORM, as minor changes in the production steps lead to different radionuclide distribution in the process.