Bill Gates sponsored a competition a while back for building a better Nuclear Fission Reactor that he would have tested in China if it hadn't been for Trump Trade War and then COVID. I saw it on a show about Bill and Melinda Gates philanthropic foundation on Netflix.

The fuel would be spent waste and it had a elegant cooling system in a fail-safe ecological mode to prevent meltdowns. Since I'm not a science guy I'm not sure if this would work.