The natural radioactivity of phosphate ore and associated waste products discharged into the eastern Irish Sea from a phosphoric acid production plant

Large volumes of liquid and solid waste were discharged into the eastern Irish Sea from the Albright & Wilson phosphoric acid production plant between 1954 and 1992. In 1992, operations at the plant changed and crude phosphoric acid rather than phosphate ore became the raw material. These changes resulted in a large reduction in the volume of waste discharged. The discharges are of particular interest since they are a significant local source of natural series radionuclides entering the eastern Irish Sea. The phosphate ore mix used at the plant in the period immediately prior to June 1992 contained 1377 ± 34 Bq kg −1 238U, and lower concentrations of 235U and 232Th (56 ± 4 and 13 ± 2 Bq kg −1, respectively). The concentration of 230Th and 226Ra were in slight excess of 238U but were in equilibrium (1508 ± 57 and 1477 ± 36 Bq kg −1, respectively). 210Pb and 210Po were present in lower concentration than 226Ra but were in equilibrium with each other (837 ± 55 and 835 ± 29 Bq kg −1, respectively). Disequilibrium between U, Th and Ra was created during the initial production of the crude phosphoric acid. This paper presents radionuclide data obtained from effluent samples collected prior to, and following, modifications at the plant during 1992. These data will be used to estimate the inventory of radionuclides discharged to the marine environment before and after June 1992.