Aalo Atomics' Critical Test Reactor, known as Project First Light, is a zero-power, graphite-moderated physics reactor using uranium dioxide fuel at Idaho National Laboratory. Aalo unveiled the completed assembly in March 2026, and the reactor reached criticality at 12:20 a.m. MT on 4 July 2026 under the DOE Reactor Pilot Program; DOE announced it on 6 July. It precedes Aalo-X, the company's sodium-cooled demonstration plant at the same laboratory.