铀是放射性元素。它的一些同位素可以作为核燃料,另一些同位素往往可以作为某些地质作用的指示剂,所以研究天然铀同位素在自然界的分布和变化就具有重要的实际意义和深远的理论意义。 U~(238)、U~(235)、U~(234)和U~(233)是铀的天然同位素,在自然界常常有比较稳定的组成。它们之间的重量比一般为:U~(235)/U~(238)≈0.7205; Uranium is a radioactive element. Some of its isotopes can be used as nuclear fuels, while others can often be used as indicators of some geological processes. Therefore, it is of great practical significance and far-reaching theoretical significance to study the distribution and changes of natural uranium isotopes in nature. U ~ (238), U ~ (235), U ~ (234) and U ~ (233) are the natural isotopes of uranium, which are often stable in nature. The weight ratio between them is generally: U ~ (235) / U ~ (238) ≈ 0.7205;