Antares Nuclear Inc.’s Mark-0—a sodium heat-pipe-cooled microreactor fueled by high-assay low-enriched uranium (HALEU) tri-structural isotropic (TRISO) fuel compacts—has achieved zero-power criticality at Idaho National Laboratory’s (INL’s) Reactor and Critical Experiment (RACE) facility, becoming the first advanced reactor to reach that milestone under the Department of Energy’s (DOE’s) Reactor P...
The achievement of zero-power criticality by Antares Nuclear Inc.’s Mark-0 reactor is a significant technical milestone, but it also reflects broader patterns in the resurgence of nuclear innovation in the U.S. The strongest version of this narrative highlights a successful public-private partnership, rapid development timelines, and a strategic push to revitalize advanced reactor technology. Antares’ progress is notable for its speed—achieving criticality in just over two years—and its iterativ...