（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。
Fri, 20 Feb 2026 20:32:04 UTC (381 KB)
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In 2020 China planted a flag on the Moon on its Chang'e-5 mission
Some say the technology is devaluing their work, while others reckon it is not yet – and might never be – good enough to replace them entirely