（八）放射源，是指除研究堆和动力堆核燃料循环范畴的材料以外，永久密封在容器中或者有严密包层的放射性材料。
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Ian YoungsCulture reporter
Фото: Алексей Майшев / РИА Новости
"To properly advance this critical technology to be able to support a future lunar economy, high power energy generation on Mars, and to strengthen our national security in space, it is imperative the agency move quickly," US transport secretary Sean Duffy, who was appointed temporary head of Nasa by President Donald Trump, wrote to Nasa, according to the New York Times.