Sequential radioanalytical method for the determination of U and Th isotopes, 226Ra and 210Po using alpha spectrometry in samples of the Brazilian phosphate industry

Abstract

The phosphate rock used for the production of the phosphate fertilizers presents in their composition radionuclides of the U and Th natural series. During the chemical attack of the phosphate rock, the equilibrium is disrupted and the radionuclides are distributed in the process and migrate to intermediate and final products and waste, known as phosphogypsum. A sequential radiochemical procedure was implemented to determine the content of radionuclides alpha emitters (234U, 238U, 230Th, 232Th, 228Th, 226Ra and 210Po) in samples of fertilizers (MAP, DAP, TSP and SSP) and phosphogypsum produced in Brazil. The alpha spectrometry was performed using a surface barrier detector. The results obtained show that the levels of radioactivity present in the fertilizers are of the same order of magnitude of those found in the phosphogypsum, reaching values of 1158 Bq kg-1 for 238U, 1167 Bq kg-1 for 234U, 1169 Bq kg-1 for 230Th, 879 Bq kg-1 for 226Ra, 759 Bq kg-1 for 210Po, 457 Bq kg-1 for 232Th, and 346 Bq kg-1 for 228Th.