The more the fuel is exposed, the closer the reactor comes to a full meltdown.

也就是说燃料棒暴露的越多，那么越容易全部熔化。

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A partial meltdown can occur when radioactive fuel rods, which normally are covered in water, remain partially uncovered for too long.

通常燃料棒处于水中，一旦有部分长时间暴露于水的话，就会熔化。

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If the cores cannot be cooled sufficiently, a total meltdown could ensue, exposing the fuel rods to the outside air and further spreading radiation.

如果内核不能得到充分冷却，恐其随后将完全熔毁，从而使能源棒暴露在空气中导致辐射进一步扩散。

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Officials said they could not rule out the possibility of a meltdown, which occurs when nuclear fuel rods cannot be cooled and melt the steel and concrete structure containing them, at all three troubled reactors at the plant.

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The Japanese government said Monday that the fuel rods in one reactor have fused together in a partial meltdown.

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The fuel, called MOX, takes uranium from spent fuel rods and mixes it with plutonium, creating a less stable fuel, one that is potentially far more dangerous in a meltdown.

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