Ars Technica, a renowned U.S. technology news outlet, reported that Antares, an American nuclear energy startup, has achieved a significant milestone: its small modular nuclear reactor, dubbed the 'Mark-0', which is installed at the Idaho National Laboratory, has successfully reached criticality in its inaugural test. This achievement stands as the first notable advancement in new reactor design since the Trump administration issued an executive order aimed at expediting nuclear power development.

Criticality, in this context, denotes that the nuclear fission reaction within the reactor core has attained a self-sustaining state, albeit without being linked to the power generation system as of yet. This test not only paves the way for the reactor's subsequent power generation capabilities but also signifies a substantial leap forward in the U.S.'s pursuit of next-generation nuclear energy technology.

The Antares reactor leverages a cutting-edge TRISO fuel system, renowned for its resilience to high temperatures and core meltdown scenarios. It utilizes liquid sodium as its primary coolant, generating electricity through a closed Brayton cycle system. The primary aim of this test was to validate the precision of the company's modeling of the reactor's physical attributes and to amass crucial safety data for forthcoming licensing applications.