Antares Achieves Criticality of Mark-0 Reactor

Antares Industries is a U.S. nuclear startup trying to build a new kind of small, modular reactor. "Criticality" means the reactor has sustained a controlled nuclear chain reaction for the first time — a major engineering milestone, not something that happens daily. Their "Mark-0" is an early prototype, not a commercial product. The company is part of a wave of advanced nuclear ventures (alongside Oklo, NuScale, Kairos Power) that aim to revive atomic energy as a carbon-free power source, after decades of stagnation in the U.S. nuclear industry. Unlike traditional giant plants, these reactors are designed to be smaller, potentially cheaper, and factory-built. Achieving first criticality shows the design works in principle, but years of testing, licensing, and scaling still lie ahead before it could power anything. Interest in such reactors has grown due to AI data centers' enormous electricity demand and climate goals.