Small modular nuclear reactor reaches criticality in first U.S. test

Nuclear startup Antares announced that its small modular test reactor at Idaho National Laboratory has reached criticality, making it the first new U.S. reactor design to achieve self-sustaining reactions. The milestone comes in response to a Trump administration executive order directing the Department of Energy to advance three reactor designs. The Mark 0 unit uses TRISO fuel pellets encased in ceramic and graphite for inherent safety, and is currently being used to validate modeling and generate licensing data before attempting full power generation next year. The company is also collaborating with the Department of Defense's Project Pele and NASA on mobile and space-related nuclear applications.