uranium 238
uranium-238的词性：
n.（名词）
1. The most common isotope of uranium, having mass number 238 and half-life 4.51 × 109 years, nonfissionable but irradiated with neutrons to produce fissionable plutonium 239.
铀238：铀的最普通的同位素，质量数238，半衰期为4.51×109年，不发生裂变但能用中子照亮以产生裂变钸239