Oklo clears startup test for Aurora reactor as DOE pilot deadline nears
Oklo's Aurora reactor has cleared initial startup testing, a key step toward commercial operation as the DOE's July 2026 criticality deadline approaches.
Oklo has received approval to begin startup testing of its Aurora reactor, moving the Sam Altman-backed fission startup one step closer to becoming the first advanced reactor to reach commercial operation under the Department of Energy's pilot program. The company said the milestone clears the path for initial criticality testing at its Idaho site, though a specific timeline for fuel loading has not been disclosed.5
The approval matters because it puts Oklo in position to beat a July 2026 deadline set by a March 23, 2025 (2025-03-23) executive order requiring at least three advanced reactors to achieve criticality, part of a broader push to grow US nuclear capacity from roughly 100 GW to 400 GW by 2050.3 With that window now closed, Oklo's progress will be measured against what competitors have already demonstrated.
Two rivals have moved first. Valar Atomics achieved self-sustaining criticality and completed zero-power testing at its Ward 250 reactor in Utah, a TRISO-fueled modular high-temperature gas reactor rated at 100 kWt initial test power and scalable to 5 MWe, with Kiewit Nuclear Solutions serving as engineering, procurement and construction contractor.4 Antares Nuclear also reported initial criticality on a TRISO-fueled microreactor, the first to reach that stage under the Trump administration program.3
Oklo's path to criticality has been shaped by fuel supply constraints as much as regulatory review. The company secured a uranium supply deal in June (2026-06) that resolved a long-standing gap in its fuel pipeline, according to a June 22 (2026-06-22) report from Yahoo Finance.5 The arrangement followed a National Defense Authorization Act of 2024 directive requiring the DOE to help kick-start commercial HALEU enrichment, with Centrus securing a $900 million contract in January to build out domestic capacity.5
The supply chain for high-assay low-enriched uranium remains the sector's binding constraint. HALEU, enriched to between 5% and 20% U-235, is required for most advanced reactor designs, including Oklo's metal-fueled Aurora and the TRISO-based systems from Valar and Antares.5 Without domestic enrichment at commercial scale, even approved designs face fuel delivery delays that push back commercial operation dates.
Market reaction to the supply chain progress has been uneven. Oklo shares rose 4% on Thursday (2026-06-18), while Centrus Energy jumped more than 12% in the same session, a gap that reflects Centrus's position as the near-term HALEU monopoly.5 The uranium ETF URA traded at $39.07 as of Saturday's close (2026-08-01), down 2.01%, and nuclear equities have seen significant volatility in the first half of 2026 after a strong 2025.6 That divergence suggests investors are pricing fuel suppliers ahead of reactor developers.
Oklo has leaned on partnerships to fill technical gaps. Under a March 2026 agreement, Sweden's Blykalla plans to deploy $100-200 million and 30-40 engineers in the US, with joint workstreams supporting Oklo's DOE-authorized reactor pilot project in neutronics and thermohydraulics.1 Blykalla is simultaneously pursuing its own six-reactor SEALER lead-cooled advanced modular reactor project in Sweden's SE3 bidding zone, a combined 330 MWe, in what the company called a historic first for Sweden.1
The DOE's goal of 400 GW of nuclear capacity by 2050 assumes a buildout rate that the industry has never achieved. The United States has accumulated nearly 100,000 metric tons of used nuclear fuel without a permanent geological repository, even as nuclear generates about one-fifth of the nation's electricity, and no long-term waste solution has been resolved for the new designs now approaching criticality.7 The pilot program's three-reactor target was met on paper before the July 2026 deadline, but grid-scale power delivery from any of these designs remains years away.
Oklo has signed partnerships with major AI and data center players, betting that hyperscale electricity demand will create an offtake market before the reactors are ready.2 That ordering of events, demand preceding supply, is the opposite of how nuclear projects have historically deployed, and it means the company's valuation rests on execution risk rather than contracted revenue.
The next signal to watch is fuel load timing at Idaho. Valar and Antares have proven criticality is achievable; Oklo's challenge is to convert regulatory approval into sustained power operations, which requires the HALEU supply chain to deliver on schedule. If the company's fuel deliveries slip, the pilot program's remaining slots will go to competitors that have already demonstrated the physics.4