Determination of 210Po in the phosphogypsum samples

Environmental increases on radioactivity are normally attributed to uranium mining and milling activities and phosphate ore processing. 222Rn gas emanation in the environment due to uranium processing activities has been considered as one of the largest sources that contribute to the internal dose level; however, one of the more biologically active and radiotoxic products of the 238U decay chain is 210Po ( t1/2 = 138.38 days). This paper describes a simple procedure for 210Po determination in phosphogypsum carried out after a previous sample treatment followed by polonium deposition in a reducing medium. After addition of 209Po tracer, the sample is dissolved with mineral acids or leaching is done with concentrated nitric acid and hydrogen peroxide. A coprecipitation is then performed with iron III hydroxide in order to eliminate interference. After separation and dissolution of the precipitate with HCl, the polonium is deposited at 90 deg C. To optimize 210Po deposition for phosphogypsum samples that have high concentrations of Ca+2 and SO4+2 and to avoid very poor resolution that is linked to appearance of a precipitate and thickness of the deposited material, an excess of sodium citrate was used. Good resolution and deposition efficiency as well as an absence of interference were observed. The procedure was validated by analyzing an IAEA-327 reference soil. (author)