It burned for 10 days and released a cloud of radioactive matter that spread over a wide area of the USSR.

它整整燃烧了10天，产生的放射性物质云笼罩了前苏联的大片地区。

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The positrons, produced by the decay of radioactive sodium, are cooled into a similarly sized cloud of around 1m particles and held in a neighbouring trap.

由放射性钠衰变产生正电子，冷却后形成一个由大约100万个正电子组成的体积同样大小的粒子云团，这团正电子被存放在相邻的一个容器中。

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The fireball and mushroom cloud carry radioactive particles upward, and the wind sends them near and far.

火球和蘑菇云将放射性粒子推到上空，然后风将它们吹送到附近及远处。

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But the disaster sent a cloud of radioactive fallout over hundreds of thousands of square miles of what is now Russia, Belarus and Ukraine that would have an impact on the health of many more.

CNN: 26 years on: helping Chernobyl's children

That is why they drove straight into the radioactive cloud.

ECONOMIST: Banyan

In 1986, the fourth reactor at the Chernobyl nuclear complex in the Ukraine exploded and caught fire, spreading a radioactive cloud across Europe in the world's worst nuclear disaster.

CNN: Saturday,