This fallout material decays over a long period of time, and is the main source of residual nuclear radiation.

尘降物需要很长的时间才会衰减，这是核辐射残留的主要来源。

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For human beings, natural radiation is the main source of radiation. It is much more than the radiation exposure from all nuclear facilities for peaceful purposes.

天然辐射是人类所受辐射照射的主要来源，远大于用于和平目的所有核设施带给全世界人口的辐射照射量。

youdao

For human beings, natural radiation is the main source of radiation. It is much more than the radiation exposure from all nuclear facilities for peaceful purposes.

天然辐射是人类所受辐射照射的主要来源，远大于用于和平目的所有核设施带给全世界人口的辐射照射量。

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