高分辨电感耦合等离子体质谱法测定铀矿石样品中234U/238U、230Th/232Th和228Ra/226Ra同位素比值 

采用氢氟酸-硝酸-盐酸混合酸密闭消解含铀矿石样品,用阴离子交换树脂、阳离子交换树脂和锶特效树脂逐级分离富集铀、钍和镭。使用高分辨电感耦合等离子体质谱(HR-ICPMS)测定分离纯化液中234U/238U2、30Th/232Th和228Ra/226Ra同位素。比值的测量精密度取决于比值的大小和对应核素浓度的大小。对质量浓度为10 ng/mL天然铀测量液,234U/238U的测量精密度优于1.2%;对230Th质量浓度为0.6ng/mL且230Th和232Th质量浓度接近的测量液,230Th/232Th的测量精密度为1.2%;对228Ra质量浓度为0.48 pg/mL且228Ra和226Ra质量浓度接近的测量液,228Ra/226Ra的测量精密度为4.0%。

Determination of 234U/238U、230Th/232Th、228Ra/226Ra Ratios in Uranium Ores by High-resolution Inductively Coupled PlasmaMass 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.