But at least some uranium fuel is needed to make thorium atoms split, making it an imperfect replacement. It’s also less well suited for use in the light-water reactors that power the vast majority of commercial nuclear plants worldwide. And in any case, the complex, highly regulated nuclear industry is extremely resistant to change. Clean Core created a new type of fuel that blends thorium with a more concentrated type of uranium called HALEU (high-assay low-enriched uranium). Enriched up to 20%, HALEU allows reactors to extract more of the available energy and thus reduce the volume of waste.