So if you get an ore of the right type of radioactive element, and you wait millions and millions (or even billions) of years, you make a giant underground store of helium !

所以要是你获得了放射性元素的正确类型矿石后，等上数十亿年（甚至数万亿年）就能获得地下隐藏着的大量氦！

youdao

Planetary scientists can determine a rock's age by calculating how many radioactive "parent" isotopes of a particular element have decayed into "daughter" isotopes.

行星科学家们可以通过计算一个特定元素有多少“母亲”放射性同位素衰变为“女儿”同位素来确定岩石的年龄。

youdao

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

他们当时对一种放射性元素钍很感兴趣，这种元素能驱动核反应堆，却不能制造生产成武器。

youdao

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

World War Two ended. Enrico Fermi had been the first to use a neutron to produce the radioactive change of one element to another.

VOA: special.2009.06.14

When the Sun becomes more active, this isotope becomes more abundant along with beryllium, another radioactive element.

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IAEA-led team was fanning out in western Georgia in search of the remaining two of a batch of eight abandoned devices containing strontium-90, another radioactive element, which had been used in generators for communication stations.

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