DETERMINATION OF NATURALLY-OCCURRING RADIONUCLIDES IN ULTRAPURE ORGANIC LIQUIDS

For the determination of trace elements in organic liquids radiochemic al neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation param eters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facilit y. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separati on process. The attainable limits of detection are 2.10(-16)g/g for U and Lu, in the 5.10(-15)g/g range for Th and Sm, in the 1.10(-14)g/g r egion for La, 5.10(-13)g/g for Rb, Cd and 2.10(-12)g/g for K and In. A lthough the analysis focused on traces of naturally occurring radioiso topes, results for Cr, Fe, W and Zn are presented as well.