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Old 2017-03-20, 21:58   #7
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"Victor de Hollander"
Aug 2011
the Netherlands

100100110002 Posts

Originally Posted by Dr Sardonicus View Post
Spent reactor fuel is a witches' brew of radioisotopes, some of them fission fragments with relatively short half-lives. Spent fuel rods are often kept at the bottom of large pools of water in part to dissipate the heat they generate. There are also isotopes of uranium in spent fuel that "crap up" the reactor. In theory, spent fuel could be "reprocessed," but in practice this would (as I understand it) create its own set of very nasty problems.
Spent fuel rods need active cooling because there is so much radioactive decay that generates heat that it can burn/melt the rods if not kept in check. The Fukushima disaster demonstrated the problems decay heat can give. 3 reactors (partly) melted and the water in the spent fuel pools heated up/ evaporated to dangerous levels).

There is such a reprocessing site in France (La Hague) and there is controversy about how much radiation it releases.

A much "hotter" but non-fissile isotope, Pu-238, is used as a heat source to generate power on space probes.
Very little Pu-238 is available and NASA might not get enough for its planned deep space missions.
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