radioactive substance

基本解释

The United Nations agency says they do not protect against external radiation, or against any other radioactive substance.
这个联合国机构表示，这些药片不能防止外部辐射，也不能抵御任何其他的放射性物质。
Alexander Litvinenko, a renegade Russian security officer living in London, was killed by poisoning with polonium, a rare radioactive substance, in 2006.
居住在伦敦的叛逃俄罗斯安全情报官员亚历山大·利特维年科在2006年被一种稀有辐射性物质钚投毒暗杀。
The wife of a Russian spy who was poisoned with a radioactive substance is now tested positive for it.
俄罗斯特工威克多·利特维年科因放射性物质中毒，现在其妻放射性物质测试显阳性。
blog.sina.com.cn

Accordingly, by observing how much of a radioactive substance has decayed, scientists are able to determine how old that substance is.
FORBES: Why Marco Rubio Needs To Know That The Earth Is Billions Of Years Old
Alexander Litvinenko, a renegade Russian security officer living in London, was killed by poisoning with polonium, a rare radioactive substance, in 2006.
ECONOMIST: Assassinations and technology