At Oak Ridge National Laboratory in Tennessee, a half-dozen workers are making what appear to be gray billiard balls. They’re actually manufacturing a more advanced kind of nuclear fuel than that used in today’s nuclear plants. Inside each gray ball are thousands of tiny black spheres that contain a speck of uranium known as high-assay low-enriched. The Department of Energy says the more enriched uranium will allow newer reactors to run longer and more efficiently, sit on smaller footprints and produce less waste than older reactors. The United States is chasing a new age of nuclear power that banks on domestic production of reactor fuel like X-energy is making.