It's literally swords into plowshares, what's the problem other than the fact that the word "Plutonium" gives people hives?
2) You can make nuclear bombs out of it. If it's too diluted, you can purify it with normal chemical processes and then make your bombs. It's not like uranium where you need a monstrously expensive isotope separation process to get the fissionables out.
3) Even if ransomware gangs don't get their hands on the Pu, billionaire tech bros with nukes sounds dystopian enough in its own right.
4) Even ignoring the weapons proliferation aspect, startups building Pu-fueled power reactors seems like a dumb idea. Thorium-molten salt may be a little harder but holds lots of promise. It's being built in China now.
While technically it is possible to separate plutonium out chemically, it is extremely difficult to do in practice. Plutonium separation plants are more expensive than uranium enrichment plants, and that's the reason states pursuing clandestine nuclear weapons programs choose uranium enrichment over plutonium. Uranium enrichment was much more expensive in the 40s and 50s when the US built up its plutonium production infrastructure, all of which was shut down in the 80s. Modern centrifuges make uranium enrichment cheap and simple, and the only economical source of plutonium is dismantled nuclear weapons.
Mix some weapons grade and reactor grade plutonium and end up with reactor grade that can't be used. Reactor grade plutonium already gets used in reactors.
So yes there certainly are downsides to anything involving nuclear energy, just like there are downsides to fossil fuels, or the toxic heavy metals so often involved in "green" energy. The upside of nuclear energy is a lack of emissions after the initial construction, minimal mining to support it compared to other options, long working lifetimes and high efficiency.
But people love to focus on Hollywood inspired nightmare scenarios.
Bzzzt...…