Characterisation of components of waste rock piles of future uranium mining activities in Brazil using INAA and statistical data treatment

In a preliminary study performed with the waste rocks from the future urani um mine to be explored in Brazil, 106 samples were taken from the eight mai n lithologies found in the massif and analysed by instrumental neutron acti vation analysis (INAA) for 20 elements. For samples from the same lithology , a high variability in the concentration of most of the elements was found (coefficient of variation larger than 20%), which might be attributed to e ither insufficient homogenisation of minerals or to local variation within lithology. The hypothesis that the variability within the lithology does no t have an influence to the total variability was tested by analysing 5 repl icates of the 5 most contrasting samples from the predominant lithology (pl agioclase-microcline-gneiss), chosen after applying statistical evaluation (principal components and cluster analyses). Results indicated that homogen isation of samples was adequate due to low variation among replicates. The hypothesis tested was rejected with a confidence level higher than 99% for all the elements, corroborating the Large intra-lithology variability.