Every day, more than 40,000 Americans undergo a diagnostic scan that depends on technetium-99m, a radioactive isotope used to image the heart, spot cancer and check kidney function. Every milligram of the molybdenum-99 that produces it currently arrives in the United States from aging foreign reactors, since the country has no domestic supply of its own. On the evening of August 5, 2026, that changed in a small way. In Lockhart, Texas, just south of Austin, Oklo Inc. announced that its Groves Isotope Test Reactor achieved first criticality, meaning it sustained a controlled nuclear chain reaction on its own for the first time. The reactor was not built to generate electricity. It exists purely to prove that the United States can finally produce its own supply of critical medical isotopes, on a timeline that once seemed impossible for the domestic nuclear industry. If this pace can be replicated at commercial scale, it could mark a genuine turning point for American healthcare infrastructure, finally freeing hospitals from dependence on aging foreign reactors for the medical isotopes millions of patients rely on each year.
Why the Groves reactor near Austin was never meant to power the grid
Groves is a low power test reactor, not a commercial power plant, and Oklo has been clear that it was never designed to feed electricity into the grid. Instead, it exists to prove out the engineering, construction and safety processes that Oklo will need for a future commercial-scale isotope production facility. According to the company, work at Groves has already generated hands-on experience across project engineering, procurement, startup procedures, safety readiness and staff training, all of which is meant to reduce risk and uncertainty across Oklo’s future projects, including its planned power reactors and fuel recycling facilities. Reaching this milestone in under a year is what makes the achievement notable, since building and licensing even a small test reactor in the United States has historically taken years rather than months.
How the Reactor Pilot Program let Groves move from groundbreaking to criticality so fast
Groves reached criticality under the U.S. Department of Energy’s Reactor Pilot Program, a pathway President Trump directed DOE to create via executive order in May 2025 and which DOE formally launched the following month, in June 2025 to let companies advance engineering, construction and operational preparation at the same time as the DOE’s own safety review, rather than waiting for each stage to finish before starting the next. The program’s stated goal was to get at least 3 advanced reactor designs to criticality outside of the national laboratories by July 4, 2026. Groves became the fifth reactor overall to hit that milestone under the program, and the first to do so on privately owned land using a facility built entirely from the ground up. Oklo co-founder and CEO Jacob DeWitte called the pace of the project a new benchmark for the program, noting that his team handled everything in-house, from civil excavation and construction to manufacturing or procuring every reactor component, including the fuel itself.
What comes next for domestic isotope production after the Groves milestone
Groves is only the foundation, not the finished product. Oklo’s broader roadmap for its isotopes business involves a much larger commercial facility planned at Idaho National Laboratory, built around several small reactor units, though that project still needs its own separate licensing approval from the Nuclear Regulatory Commission and has no confirmed production start date yet. For now, Groves will continue startup testing rather than actual isotope production, since the goal at this stage was simply proving the reactor design, construction process and safety systems work as intended. Even so, the milestone matters well beyond one facility in central Texas, since it demonstrates that a domestically built reactor can go from an empty plot of land to a working nuclear facility in under a year, a pace that could eventually let American hospitals rely on isotopes made at home instead of shipped in from reactors overseas.