After four decades of stagnation, the United States is seeing a resurgence of nuclear technology. At about 4:30 p.m. Thursday afternoon, Valar Atomics' small modular reactor in Orangeville, Utah, reached zero-power fueled criticality.

Nuclear energy in the West took another step forward as the first privately developed, non-light-water reactor to go critical in the United States in more than 40 years reached a major milestone when the Antares Nuclear Mark-0 test reactor came online at Idaho National Laboratory.

Nuclear energy in the West took another step forward as the first privately developed, non-light-water reactor to go critical in the United States in more than 40 years reached a major milestone when the Antares Nuclear Mark-0 test reactor came online at Idaho National Laboratory.

Nuclear energy in the West took another step forward as the first privately developed, non-light-water reactor to go critical in the United States in more than 40 years reached a major milestone when the Antares Nuclear Mark-0 test reactor came online at Idaho National Laboratory.