一、前言大量U中测定微量Th首先得除去大量U,文献中介绍的方法主要是溶剂萃取或离子交换。靠溶剂萃取法不易将U分离干净;而离子交换法费时较长所用酸度也比较大(8 M HCl或浓HNO_3)。用光谱法测定的文献不多。由于Th属于难挥发及多谱线元素,故采用事先分离后再用光谱测定的方法。如美国ASTM采用以Y为载体及内标,以HF沉淀将Th及RE与大量U分离,灼烧后以粉末光谱法测定。取样5 g时测定下限 I. INTRODUCTION The determination of trace amounts of U in a large amount of U first removes a large amount of U, and the methods described in the literature are mainly solvent extraction or ion exchange. Solvent extraction method is not easy to separate U clean; and ion-exchange method takes longer time used acidity is relatively large (8 M HCl or concentrated HNO 3). There is not much literature about spectrometry. Since Th is a volatile and multi-line element, it is separated by prior spectrometry. Such as the United States ASTM to Y as a carrier and the internal standard to HF precipitation Th and RE with a large number of U separation, burning after determination by powder spectrometry. Sampling lower limit of 5 g