Applications of Radionuclides Partitioning during Leaching Processes to Follow-up The history of Different Rocks Samples, Sinai, Egypt

Abstract

The distribution of radionuclides in five sedimentary rocks samples representing mudstone (3 samples), shale (one sample) and carbonaceous shale (one sample) were studied to follow the alteration processes affected these rock types. Two samples were selected for leaching process; one mudstone and one shale. The processes carried out include acidic leaching with (different H2SO4 concentrations). Also, studying the radionuclides distribution in the pregnant solutions, residual samples and follow up the leachability of each radionuclide. The radioactivity measurements of the original samples using the HPGe detector indicated that these rocks contain specific activity concentrations of 238U and 235U and its progenies. However, the activity concentrations of 40K and 232Th are relatively low. The results show that the studied samples were categorized into three grades (high, medium and low). The high-grade samples (U10 and U13), medium-grade (U3) and low-grade sample (U1 and U2) were nearly equal to 1600, 600 and 190 ppm, respectively. The different activity ratios of radionuclides were calculated. The mean isotopic activity ratio 238U/235U was found to be around 21.80 in different rock types under investigation with few exceptions. The results obtained that there is slightly equilibrium between 235U and its daughter in all samples except U1. In the 238U series, the activity ratios of 226Ra/238U in different studied samples were approximately unity while there was disequilibrium between 230Th/238U and 234U/238U. The disequilibrium is due to chemical weathering, which affect on the solubility of these radionuclides. This activity ratios used in calculating the radiometric age dating of uranium migration.