Oklo's (OKLO) Groves Isotope Test Reactor has achieved first criticality after achieving a controlled, self-sustaining nuclear chain reaction at low power.

Oklo's (OKLO) Groves Isotope Test Reactor has achieved first criticality after achieving a controlled, self-sustaining nuclear chain reaction at low power.

First criticality is a standard, scripted milestone on the reactor development path, the point at which the physics is demonstrated at low power before any power ascension, fuel qualification, or commercial licensing work begins. For pre-revenue advanced nuclear names like Oklo, the equity reaction to such announcements has historically been sentiment-driven and often fades, since the event confirms the design works in principle but does not shorten the multi-stage licensing and construction runway that separates demonstration from generation. The distinction worth drawing is between technical de-risking and regulatory de-risking: criticality addresses the former, while timelines in this space have tended to hinge on the latter, on fuel supply (Oklo's designs run on HALEU, a structurally tight market) and on regulator throughput rather than on physics. Follow-ons that matter are regulator acceptance of test data, progress toward a full operating licence, and fuel procurement arrangements. Small-cap nuclear equities in this cohort have tended to trade as a correlated thematic basket, so a headline on one name often lifts or dents the peer set irrespective of name-specific progress.