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
It sounds like you expect the uranium to be more dangerous because it has more potential energy that can be used, while the by-products should have less energy. And that is largely correct, uranium does have more stored energy which can be released as it naturally decays into elements with less energy available, until you reach iron and it won’t decay any further.
The difference is that uranium is stable on its own, and only very rarely or slowly breaks down into the next step in the decay chain. That is why it is found in nature- because it is stable and sits around. Once it is put in a reactor the decay happens at a massively faster rate, creating elements that are lower in energy but also less stable.
These unstable by-products then continue to break down on their own after they have been taken out of the reactor. This decay releases energy, which causes harm to the body, and makes them dangerous.
A loose analogy is flowing water. Uranium is like a mountain lake, high in energy but stable, there is little flow of the water. If you are in a boat and paddle out of the lake into a river it is then flowing much more rapidly down the hill, and the rate at which it drops down the mountain in rapids or a waterfall makes it dangerous.
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