Once the reactor has shut down, there remains "decay heat" from traces of other radioactive isotopes.

一旦反应堆关闭，它仍热存在有来自其他放射性同位素踪迹的衰变热。

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Unless you have a mechanism to remove that, the heat can build up and can eventually damage the radioactive fuel or the reactor.

除非你有途径将它移除，否则热量将积累并最终破坏放射性燃料或核反应堆。

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RTGs power many space missions — including NASA's Cassini and New Horizons probes — as the slow decay of small pellets of radioactive material produces heat that can be turned into electricity.

RTG已为许多太空任务提供动力，包括美国宇航局的“卡西尼号”和“新视野”探测器。在放射性物质的小球衰退过程中可以产生出热量，从而将其转化为电能。

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Although solar panels will work on spacecraft at that distance, the desire for sufficient energy to drive many instruments means any mission would really need to go with radioisotope thermal generators (RTGs) - solid state electrical generators powered by the heat of radioactive decay.

BBC: NEWS | Science/Nature | Europe tells US: 'Come to Europa'

The enormous heat generated by the radioactive fuel in the reactor core needs a constant flow of cold water.

FORBES: Second Explosion Damages Another Japanese Nuclear Reactor

Once the reactor has shut down, there remains "decay heat" from traces of other radioactive isotopes.

WSJ: William Tucker: Japan Does Not Face Another Chernobyl