Because you can generate plutonium-239 from uranium-238 in a breeder reactor, and then separate the plutonium-239 from the Uranium simply by using chemistry methods because you've created an element with different valence electrons.
Isn't it somewhat funny that it is easier to purify a synthetic element than a naturally occurring one?
This is the mineral that Pierre and Marie Curie used to discover polonium and radium.
Video 1.
The Most Dangerous Rock in the World by Welch Labs
. Source. OK, the title is quite minimalistic, he goes on to talk about the full early history of nuclear fission!
Produced as part of the thorium fuel cycle.
Glass with Uranium added to it to become fluorescent due to Uranium's chemical properties. This is unrelated to Uranium's nuclear properties.
However it was this fluorescence that led Henri Becquerel to discover radioactivity while studying fluorescence, which led him to have Uranium compounds and photographic material in close proximity. I love science I guess.
https://en.wikipedia.org/wiki/File:Vasline_glass_glowing.jpg

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