Determination of ~(234)U/~(238)U,~(230)Th/~(232)Th,~(228)Ra/~(226)Ra Ratios in Uranium Ores by High-resolution Inductively Coupled Plasma-Mass Spectrometry

Uranium ore samples are decomposed with HF-HNO3-HCl in sealed vessels.Anion exchange resin is used to separate U from Th and Ra,Th from Ra.Sr-specific resin is applied to separate Ra from Ba and other elements.Purified U,Th and Ra(solutions) are used for measurement of 234U/238U,230Th/232Th and 228Ra/226Ra by HR-ICPMS.The precision of the isotopic ratio measurements for 234U/238U,230Th/232Th and 228Ra/226Ra depends on their isotopic ratios and the concentration of relative nuclides.For a 10 ng/mL natural uranium solution,the isotopic ratio measurement precision for 234U/238U is better than 1.2%RSD,for a solution with 0.6 ng/mL of 230Th and nearly equal concentration of 230Th and 232Th,the measurement precision for 230Th/232Th is 1.2%RSD and for a solution with 0.48 pg/mL of 228Ra and nearly equal concentration of 228Ra and 226Ra,the measurement precision for 228Ra/226Ra is 4.0%RSD.