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We all know spent fuel rods taken out from a reactor core keeps generating tremendous amount of heat and needs to be kept cool by running cool water. It is also known that if cooling system fails water will evaporate quickly leading to a blast and meltdown

If the fuel can still produce so much heat, why isn't it used as heat source for some low temperature systems, e.g. power generation via thermocouples, or home heatings for entire blocks or cities?

Why is all that spent fuel kept as a waste?

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closed as off-topic by ACuriousMind, Kyle Kanos, Ryan Unger, Qmechanic Aug 19 '15 at 7:37

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    $\begingroup$ I don't have the figures but it may be you are overestimating the amount of useful heat generated. According to XKCD, swimming in a spent-fuel pond may be quite comfortable and, radiologically, safer than where you are sitting right now. $\endgroup$ – RedGrittyBrick Aug 18 '15 at 10:56
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    $\begingroup$ If it actually generated a "tremendous" amount of heat, it wouldn't be spent, by definition. Also, nuclear waste explodes less than nuclear power plants, which don't explode at all. $\endgroup$ – user10851 Aug 18 '15 at 13:59
  • $\begingroup$ @ChrisWhite Well, the night shift at Chernobyl managed to produce an explosive steam escape event. And the story of how they managed it would be a comedy of errors if not for the outcome. $\endgroup$ – dmckee Aug 19 '15 at 2:50
  • $\begingroup$ physics.stackexchange.com/questions/229686/… $\endgroup$ – inf3rno Nov 24 '17 at 19:51
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Spent fuel is extremely radioactive, and it will induce radioactivity in anything that is in contact with it such as the cooling water. So you'd need separate primary and secondary cooling circuits to avoid heating your houses with radioactive water. You could do this, but it starts getting expensive.

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  • $\begingroup$ someone's coursework found on google: large.stanford.edu/courses/2012/ph241/tilghman1 on such proposal $$$$ QUOTE "And regarding nuclear waste, you don't want things to break. If the turbine of the bottoming steam cycle, or some other part of the heat exchanging process, were to fail, it would be difficult to repair without getting close to the radioactive waste." $$$$ Just us you won't found anyone near the core of a nuclear power station, you won't want spent fuel waste placed near your home $\endgroup$ – Secret Aug 18 '15 at 6:11
  • $\begingroup$ @john house heating was just a vague idea. what I mean is using it industrially with the safety required to operate it , not some average citizen putting it in his backyard. as per your answer its due to safety concerns which can be fulfilled by industrialising it the way live reactors are $\endgroup$ – user1062760 Aug 18 '15 at 13:58
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John answered it well. Just to add, I beleive that there can always be better design to extract more out of the system and the decision is usually around the trade-offs of the return with the well estabilshed methods at the time of imlementation. In future, we may find a simplistic easy way to extract heat from the waste for useful purposes. Thermocouples sound good but I think the generation efficiency is quite low. If we had to deploy a small propulsion assist reactor on a spacecraft, it may make lot of sense to extract every bit from the system.

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