Analytical methods for the characterization and the leachability evaluation of a solid waste generated in a phosphoric acid production plant

Naturally Occurring Radioactive Materials (NORM) are present in the environment and can be concentrated by technical activities, particularly those involving natural resources. These NORM deposits are highly stable and very insoluble under environmental conditions at the earth's surface. However reducing or oxidant conditions or pH changes may enable a fraction of naturally occurring radionuclides to eventually be released to the environment. In this paper the analytical methods to determine the chemical and radiochemical composition of a solid waste generated in an acid phosphoric production plant was shown. The sample, analysed by gamma spectrometry and radiochemical methods, contained 210Pb and 210Po and a high activity concentration of uranium isotopes but it shows a very low quantity of 226Ra. Also a sequential extraction method consisting of five operationally-defined fractions was used to evaluate the leachability of uranium isotopes, 210Pb and 210Po. The average leaching potential observed in the sample is 97.6% for 238U, 93.2% for 210Pb and 82.4% for 210Po. Moreover the results show that 210Pb and 210Po are leachable under only extreme conditions, whereas uranium is very more soluble.