Radionuclide fluxes at a plant manufacturing dicalcium phosphate for domestic animals

We have studied a phosphate rock plant which produces dicalcium phosphate ( DCP), used as a source of calcium and phosphorus for domestic animals. A by -product in the manufacturing process is calcium chloride which is used in the oil industry, the food industry and as road-salt. The objectives of our study were to describe the fluxes of radionuclides from the U-238 decay se ries and to estimate the radiation doses to workers at the plant. The radio nuclides in the phosphate rock were found to be in secular radioactive equi librium with U-238, With an average activity concentration of 837 Bq kg(-1) . Separation and concentration processes were observed at different stages in the plant. Most of the Ra-226 was found in the calcium chloride, while t he major part of the U-238, about 950 Bq kg(-1), was found in the dicalcium phosphate. The annual occupational effective dose to the workers was found to be below the 1 mSv limit recommended by ICRP (1991a) for the public. Th is study has shown a good example of an important non-nuclear industry with a high input of natural radionuclides with several conceivable pathways to man. (C) 2001 Elsevier Science Ltd. All rights reserved.