Leachability of naturally occurring radioactive materials

Naturally occuring 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 leachability of Pb-210 and Po-210 was determined in three samples coming from a refractories production plant (dust, sludge, finished product), in one dust sample from a steelwork and in one ash sample coming from an electric power station. A sequential extraction method consisting of five operationally-defined fractions was used. The average leaching potential observed in the samples from the refractory industry is very low (mean values: 5.8% for Pb-210 and 1.7% for Po-210). The Pb-210 and Po-210 leachability increases for the ash sample coming from an electric power plant using carbon (17.8% for Pb-210 and 10.0% for Po-210); for the dust sample coming from a steelwork. the percent soluble fraction is 41.1% for Pb-210 and 8.5% for Po-210. For all samples the results obtained show that Pb-210 is slightly more soluble than Po-210.