When the commonest isotope of iron (56Fe) absorbs a neutron, the result is not radioactive.

当最普通的铁（56Fe）的同位素吸收了一个中子，生成物无放射性。

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One of Marie Curie's outstanding achievements was to have understood the need to accumulate intense radioactive sources, not only to treat illness but also to maintain an abundant supply for research.

居里夫人的一项杰出成就是理解了积累强放射源的必要性，这不仅是为了治疗疾病，而且也是为了保持充足的研究供应。

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Not until the nineteen fifties did scientists, using radioactive dating, place the age of the Earth at over four billion years.

VOA: special.2009.12.01

They had been interested in thorium -- a radioactive element that can fuel nuclear reactors but not be processed into weapons.

VOA: special.2010.10.15

But the acquisition of radioactive material for a so-called 'dirty bomb,' which is radioactive material that is dispersed with a conventional explosive device, that is not that challenging.

VOA: standard.2009.05.01

Humans burning old fossil fuels spew out carbon-12, which is NOT radioactive.

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Quattrone is probably not as radioactive as he appeared to be one or even two years ago.

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What makes helium-3 so attractive as an alternative future fuel source is its environmentally friendly credentials, as it does not produce radioactive waste.

CNN: Mining the moon for a nuclear future