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 easte rn Irish Sea from the Albright & Wilson phosphoric acid production pla nt between 1954 and 1992. In 1992, operations at the plant changed and crude phosphoric acid rather than phosphate ore became the raw materi al. 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 th e eastern Irish Sea. The phosphate ore mix used at the plant in the pe riod immediately prior to June 1992 contained 1377 +/- 34 Bq kg(-1) U- 238, and lower concentrations of U-235 and Th-232 (56 +/- 4 and 13 +/- 2 Bq kg(-1), respectively). The concentration of Th-230 and Ra-226 we re in slight excess of U-238 but were in equilibrium (1508 +/- 57 and 1477 +/- 36 Bq kg(-1), respectively). Pb-210 and Po-210 were present i n lower concentration than Ra-226 but were in equilibrium with each ot her (837 +/- 55 and 835 +/- 29 Bq kg(-1), respectively). Disequilibriu m between U, Th and Ra was created during the initial production of th e crude phosphoric acid. This paper presents radionuclide data obtaine d from effluent samples collected prior to, and following, modificatio ns at the plant during 1992. These data will be used to estimate the i nventory of radionuclides discharged to the marine environment before and after June 1992.