My uninitiated mind would think that it would be the other way around.
I was watching a video about nuclear power. The guy being interviewed was wearing safety glasses and nitrile gloves while holding a uranium fuel pellet. Then the camera pans to a screen showing the robot handling spent fuel in the bottom of a 40-foot deep pool of heavy water. The pool is in a room behind a big red door with every “do not enter” warning imaginable. I would think the fuel would be less radioactive coming out than going in.
In: Chemistry
Someone please correct me if I’m wrong, but if I remember right:
Radioactive materials are generally described according to their half-lives–the amount of time it takes for half of the material to undergo radioactive decay, and become something else, releasing radiation in the process. Uranium is one of the more stable radioactive elements, and uranium fuel tends to be a mix of this uranium and its more unstable isotopes.
Through the nuclear reactor setup, a lot of uranium is brought close together, and the radioactive decay process is kicked into high gear, making a *lot* of it decay much quicker, as to release usable energy in high amounts. At the end of this decay, you also get some amount of other, even more unstable (lower half-life) materials. Stuff that is factors higher in danger to handle. So, you pull the fuel out, and this accelerated decay is stopped–but a lot of what remaining, despite being proportionally small, is this significantly more naturally radioactive elements now remaining. Stuff that still has to decay, but is decaying really fast in comparison to uranium (but, might still be many many years). In natural uranium the amount might be so small as to not be of an additional danger. In spent nuclear fuel, for a time it’s going to be *very present* and hazardous to handle, until enough of it decays away.
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