| environ. |
actinide A group of 15 radioactive elements some of which occur naturally while others are produced in nuclear reactions. They include plutonium, americium and neptunium. The health hazard presented by the actinides, if they are released into the environment, comes from the potency of their radioactive characteristics. They are alpha-emitters, and therefore can cause intense localized damage in tissues if absorbed into the body (一组包含15种放射性元素的化学元素，其中一部分是自然存在，另一部分是在核反应中产生的，包括钚、镅、镎等。如果将锕类释放到环境中，其放射性特性将带来巨大的灾难。这些阿尔法射线一旦被身体吸收，将会给组织带来局部的剧烈损伤。) |
