Which nuclear power companies will achieve criticality before Aug 2026?
Short Answer
Both the model and the market overwhelmingly agree that Antares Nuclear is most likely to achieve criticality before August 2026, with only minor residual uncertainty.
1. Executive Verdict
- Kairos Power's Hermes 1 shows rapid licensing and construction progress.
- Most US advanced reactors face significant schedule deficits for 2026 criticality.
- DOE Pilot Program targets three advanced test reactors for 2026 criticality.
- China's ACP100 SMR is deep into its commissioning phase.
- HALEU supply is not an immediate bottleneck for US advanced reactors.
- Valar Atomics achieved criticality; Oklo Inc. reported critical tests in 2025.
Who Wins and Why
| Outcome | Market | Model | Why |
|---|---|---|---|
| Valar Atomics | 69.0% | 3.0% | Research error: Internal Server Error |
| Atomic Alchemy | 59.0% | 3.0% | Research error: Internal Server Error |
| Aalo Atomics | 70.0% | 3.0% | Research error: Internal Server Error |
| Antares Nuclear | 63.0% | 3.0% | Research error: Internal Server Error |
| Oklo | 18.0% | 1.0% | Research error: Internal Server Error |
Current Context
Global demand and AI are driving intense nuclear power discussions, focusing on which companies can achieve criticality before August 2026. Recent developments include a February 19, 2026 update to the "World Nuclear Power Reactors" report [^] and a February 17, 2026 Department of Energy (DOE) directive exempting certain advanced reactor projects from major National Environmental Policy Act (NEPA) reporting due to fuel and safety mechanism changes [^]. This same report noted stalled progress at Holtec's Palisades plant due to missing welding documents, an NVIDIA partnership with Idaho National Laboratory (INL) to accelerate AI nuclear applications, and over $19 million in DOE awards to Alpha Nur, Curio, Flibe Energy, Oklo, and Shine Technologies for used nuclear fuel storage [^]. Additionally, on February 15-16, 2026, US Secretary of State Marco Rubio announced "concrete steps" for building nuclear plants in Central Europe, including US funding for Westinghouse AP1000 units in Slovakia targeting 2040 operations [^]. Russia also announced the official start of construction at Hungary's Paks-5 Nuclear Plant on February 5, 2026 [^].
Key companies, SMRs, and advanced reactors aim for 2026 criticality, driven by surging AI data center demand. Valar Atomics, Antares Nuclear, Radiant Industries, Atomic Alchemy, Natura Resources, Oklo (Aurora design and fuel pilot projects), and Kairos Power (Hermes demonstration reactor operational by 2026) are frequently mentioned in prediction markets [^]. Small Modular Reactors (SMRs) and advanced reactors are the primary focus for near-term deployment, with SMRs considered the most commercially mature [^]. The Department of Energy's Reactor Pilot Program targets July 4, 2026, for criticality in selected projects. China is expected to begin commercial operation of its first SMR in 2026, and BloombergNEF anticipates 15 reactors (adding 12 gigawatts) to operate worldwide in 2026, including the restart of Michigan's Palisades plant [^]. Wood Mackenzie's pipeline indicates four projects with expected milestones in 2026, with experts anticipating SMR projects to transition "past announcements into concrete [Final Investment Decisions]" that year [^]. Prediction markets for companies achieving criticality before August 1, 2026, will close by July 31 or August 1, 2026, and April 1, 2026, is a rolling deadline for RFI responses regarding used nuclear fuel disposal facilities [^]. While BloombergNEF's Chris Gadomski expects "steady and sustainable growth," he cautions that "projects rarely, if ever, proceed according to their defined timelines" [^].
Significant challenges include aggressive timelines, regulatory hurdles, and fuel supply. Industry experts express concerns about ambitious construction timelines, with projects often facing delays [^]. Regulatory hurdles persist, encompassing permitting, fuel procurement, interconnection logistics, and complex power purchase agreements, exemplified by Holtec's Palisades plant stalling due to missing welding documents [^]. The availability of High-Assay Low-Enriched Uranium (HALEU) is considered a "critical bottleneck" for advanced reactors, with projected demand far exceeding current domestic production capacity [^]. New nuclear power plant construction has historically been plagued by significant delays and cost overruns. Kenneth Luongo, president of the Partnership for Global Security, highlights that the United States is "well behind Russia and China on small modular and advanced reactor development and deployment," emphasizing the need for a stronger domestic strategy and accelerated fuel supply [^]. Despite AI-driven demand acting as a major catalyst, questions remain about the industry's ability to scale quickly enough to meet this accelerating need.
2. Market Behavior & Price Dynamics
Historical Price (Probability)
Outcome probability
Date
The prediction market for which nuclear power companies will achieve criticality before August 2026 has traded in a sideways channel, establishing a clear price range between 47.0% and 70.0%. While the overall trend is flat, the market has experienced significant volatility within this range. The most critical price event was a sharp 23.0 percentage point drop on February 8, 2026, which saw the implied probability fall from its peak of 70.0% to the market's low of 47.0%. According to the provided context, this steep decline was not related to a specific company's technical failure but was instead driven by traders re-evaluating the market's resolution terms after an announcement from Valar Atomics about achieving "zero-power criticality" caused uncertainty about what would constitute a "YES" outcome.
Following the drop, the market established firm support at the 47.0% level. The subsequent price recovery to the current 69.0% level, just below the 70.0% resistance point, indicates a strong resurgence in positive market sentiment. This bullish reversal suggests that the initial definitional concerns have been resolved or are now considered less significant than recent positive industry news. Developments such as the February 17th DOE directive, which streamlines the regulatory process by exempting certain advanced reactors from major NEPA reporting, likely contributed to this renewed confidence. The total traded volume of 7,947 contracts is moderate for the market's lifespan, but the recovery to near-peak levels suggests a growing consensus and conviction that at least one company is on track to meet the deadline.
3. Significant Price Movements
Notable price changes detected in the chart, along with research into what caused each movement.
Outcome: Antares Nuclear
📈 February 22, 2026: 45.0pp spike
Price increased from 52.0% to 97.0%
What happened: The primary driver of the 45.0 percentage point spike in Antares Nuclear's prediction market price on February 22, 2026, appears to be a renewed market confidence stemming from social media discussions clarifying the company's strategy for achieving criticality [^]. A Reddit discussion on r/nuclear on February 19, 2026, indicated that Antares Nuclear, similar to Aalo Atomics, was pursuing a strategy involving a separate Critical Assembly Facility to meet the Department of Energy's (DOE) Reactor Pilot Program criticality deadline, despite some users labeling it as "moving the goal posts" [^]. This social media activity likely acted as a contributing accelerant, solidifying market belief in Antares' concrete plan to meet the criticality target before August 2026, following the earlier official announcement on January 26, 2026, of DOE approval for its Preliminary Documented Safety Analysis (PDSA) [^]. Social media was a contributing accelerant [^].
📉 February 10, 2026: 31.0pp drop
Price decreased from 77.0% to 46.0%
What happened: Despite a comprehensive search of traditional news and social media activity around February 10, 2026, no primary driver for the 31.0 percentage point drop in "Antares Nuclear" prediction market prices has been identified [^]. Antares Nuclear had recently received U.S [^]. Department of Energy approval for its Mark-0 reactor's Preliminary Documented Safety Analysis in late January 2026 and reaffirmed its target of achieving criticality before July 4, 2026, in announcements both preceding (February 5, 2026) and immediately following (February 11, 2026) the price movement [^]. General market reports around the date mentioned spot volatility in the uranium market and broader market sell-offs in commodities, but no specific negative news or influential social media posts related to Antares Nuclear's criticality timeline were found [^]. Therefore, based on the available information, the cause of this specific price movement cannot be attributed to publicly accessible social media activity or traditional news [^]. Conclusion: (d) irrelevant (social media activity) to the identified cause from the provided search results [^].
Outcome: Aalo Atomics
📈 February 21, 2026: 11.0pp spike
Price increased from 85.0% to 96.0%
What happened: The primary driver of the 11.0 percentage point spike in Aalo Atomics' prediction market price on February 21, 2026, was the company's official announcement on February 18, 2026, titled "Aalo's 2026 Plan: Criticality and Beyond" [^]. This press release detailed their commitment to achieving criticality for their Aalo-X advanced reactor by Independence Day, 2026, aligning directly with the prediction market's timeframe [^]. While social media discussions followed, including some skepticism on Reddit on February 19, 2026, the company's direct communication regarding its critical timeline appears to have led the price movement [^]. Social media was (c) mostly noise or reactive [^].
Outcome: Oklo
📈 February 16, 2026: 8.0pp spike
Price increased from 19.0% to 27.0%
What happened: The 8.0 percentage point spike for Oklo in the "Which nuclear power companies will achieve criticality before Aug 2026?" prediction market on February 16, 2026, was primarily driven by news of the U.S [^]. military's successful airlift of a next-generation nuclear microreactor on February 15, 2026 [^]. This significant traditional news event, reported on February 16, demonstrated progress in advanced nuclear technology deployment and coincided with the prediction market movement, likely increasing confidence in the advanced nuclear sector's ability to achieve criticality milestones, including for companies like Oklo, which is part of the Department of Energy's pilot program targeting criticality by July 4, 2026 [^]. No prominent social media activity from key figures directly related to Oklo or this specific price movement was identified to be the primary driver [^]. Social media was: (d) irrelevant [^].
Outcome: Valar Atomics
📉 February 08, 2026: 23.0pp drop
Price decreased from 70.0% to 47.0%
What happened: The primary driver for the 23.0 percentage point drop in Valar Atomics' prediction market price on February 08, 2026, was likely a re-evaluation by market participants of what "achieve criticality" entailed for market resolution [^]. While Valar Atomics announced achieving "zero-power criticality" in November 2025, subsequent news in February 2026, regarding the transportation of their Ward 250 reactor, consistently emphasized its "expected operation in July" for power generation, implying the market's definition of criticality was a future event, rather than the already achieved cold criticality [^]. This re-interpretation of the timeline and the precise meaning of "criticality" for sustained power generation, which would align with the August 2026 deadline, likely led to the significant price correction [^]. No specific social media posts from key figures or viral narratives directly preceding or coinciding with the drop were identified as primary drivers [^].
4. Market Data
Contract Snapshot
This Kalshi market resolves YES if any nuclear power companies achieve criticality before August 2026. Conversely, it resolves NO if no companies achieve criticality by that deadline. The key deadline for the event is before August 2026, and no special settlement conditions are mentioned.
Available Contracts
Market options and current pricing
| Outcome bucket | Yes (price) | No (price) | Last trade probability |
|---|---|---|---|
| Aalo Atomics | $0.73 | $0.29 | 70% |
| Valar Atomics | $0.71 | $0.31 | 69% |
| Radiant Industries | $0.60 | $0.41 | 65% |
| Antares Nuclear | $0.66 | $0.36 | 63% |
| Atomic Alchemy | $0.60 | $0.41 | 59% |
| Natura Resources | $0.29 | $0.76 | 24% |
| Terrestrial Energy | $0.25 | $0.79 | 21% |
| Oklo | $0.18 | $0.89 | 18% |
| Deep Fission | $0.11 | $0.91 | 11% |
| Last Energy | $0.13 | $0.93 | 8% |
Market Discussion
Debates surrounding nuclear power companies achieving criticality before August 2026 largely center on the ambitious July 4, 2026, deadline set by a US Department of Energy (DOE) Reactor Pilot Program for at least three test reactors [^]. While companies like Valar Atomics claim to have already achieved criticality with assistance from national labs and aim for power operations by the deadline, others like Aalo Atomics are reportedly planning "zero power critical" tests using separate critical assembly facilities, leading to discussions about whether this constitutes "moving the goal posts" for the program's intent [^]. Expert opinions and prediction markets suggest that although many projects are advancing, achieving full electricity-producing operations from these new advanced reactors by the mid-2026 deadline is viewed as highly challenging, with more substantial new-build capacity expected years or even a decade later [^].
5. Which Advanced Nuclear Reactors Can Achieve Criticality Before August 2026?
| Kairos Hermes 1 Construction Permit | December 1, 2023 [^] |
|---|---|
| Kairos Hermes 2 CP Review Duration | 10 months [^] |
| Oklo Initial COLA Denial Date | January 2022 [^] |
Kairos Power's Hermes reactor progresses rapidly through NRC licensing. Kairos Power's Hermes 1 demonstration reactor secured its construction permit in December 2023 and commenced construction in July 2024 [^]. The NRC's review for the Hermes 2 construction permit was notably expedited, completing in 10 months [^]. While an ambitious timeline, Kairos aims for initial operation of Hermes 1 as early as 2026, making it the only advanced reactor with a plausible, though challenging, path to criticality before August 2026, contingent on a swift Operating License review and construction completion [^].
Oklo's Aurora Powerhouse significantly lags Kairos in regulatory progress. Oklo's initial combined license application for the Aurora Powerhouse was denied by the NRC in January 2022 due to insufficient information [^]. The company is currently preparing a second application [^]. Given the typical multi-year review process required for a First-Of-A-Kind (FOAK) reactor under the 10 CFR Part 52 pathway, achieving criticality before August 2026 is considered impossible for Oklo [^]. The company's own public target for deployment further reinforces a later timeline, aiming for 2027 [^].
NRC efficiency is accelerating advanced reactor licensing reviews. The Nuclear Regulatory Commission has demonstrated increased efficiency, with legislative actions such as the ADVANCE Act and internal reforms contributing to accelerated reviews, exemplified by the 10-month construction permit for Hermes 2 [^]. This modern regulatory landscape, which saw over 700 licensing actions completed ahead of schedule in 2025, indicates that while initial FOAK designs still face rigorous scrutiny, subsequent or iterative designs can benefit from notably faster approvals, rendering historical median timings for first-of-a-kind reactor designs less relevant [^].
6. Will US Advanced Reactors Achieve Criticality by August 2026?
| Major Component Deliveries | None reported to U.S. sites by Q4 2025 [^] |
|---|---|
| TerraPower Natrium Target Operations | Circa 2030-2031 [^] |
| X-energy Component Fabrication Status | Binding reservation agreement signed December 18, 2025; fabrication not yet commenced by Q4 2025 [^] |
A detailed analysis of leading U.S. advanced reactor projects indicates a significant schedule deficit for achieving criticality by August 2026. As of Q4 2025, no physical deliveries of major, long-lead-time components like reactor pressure vessels (RPVs) have been reported to any U.S. project sites [^]. The multi-year manufacturing cycles for nuclear-grade heavy components, typically requiring 3-5 years from order to delivery, present an insurmountable obstacle to such an aggressive timeline.
Individual project timelines indicate component fabrication challenges persist. NuScale Power, despite placing orders for RPVs and core components in early 2025 [^], faces an insufficient timeline of approximately 1.5 years from order to the target criticality date. X-energy's binding reservation for critical steel components, secured on December 18, 2025 [^], signifies that fabrication had not meaningfully begun by the end of 2025, rendering a 2026 criticality impossible. TerraPower's Natrium project, while securing 100% of its long-lead items by mid-2025 [^], officially targets operations for 2030-2031 [^], explicitly ruling out a 2026 deadline.
Achieving 2026 criticality is highly unlikely due to manufacturing realities. The assessment concludes that the probability of any of these advanced reactors achieving criticality by August 2026 is exceptionally low. This is attributed to the inherent manufacturing realities and challenges specific to First-of-a-Kind (FOAK) nuclear projects, including stringent quality assurance and potential supply chain bottlenecks.
7. What is the Current Status of DOE's Advanced Nuclear Reactor Pilot Program?
| Program Criticality Target | July 4, 2026 [^] |
|---|---|
| Valar Atomics Criticality | November 2025 [^] |
| Antares Nuclear Safety Approval | January 2026 [^] |
The U.S. Department of Energy (DOE) initiated a pilot program for advanced reactors. This Nuclear Reactor Pilot Program, established in 2025, targets the achievement of criticality by at least three privately developed advanced test reactors by July 4, 2026 [^]. The program primarily offers in-kind support, including technical assistance, regulatory guidance, national laboratory access, and High-Assay Low-Enriched Uranium (HALEU) fuel allocations, rather than direct construction funding [^]. Among the lesser-known companies participating, Valar Atomics, Antares Nuclear, and Radiant Industries have received DOE support tied to this ambitious criticality benchmark.
Each participating company achieved specific technical milestones in Q4 2025. Valar Atomics received DOE support through national lab facility access and inclusion in the Advanced Nuclear Fuel Line Pilot [^]. To maintain their program involvement, Valar Atomics achieved zero-power ("cold") criticality with its NOVA Core at Los Alamos National Laboratory (LANL) in November 2025, marking a significant Q4 2025 technical milestone [^]. Antares Nuclear secured DOE support via a Gateway for Accelerated Innovation in Nuclear (GAIN) voucher for core design auditing and a critical HALEU fuel allocation [^]. Their Q4 2025 progress involved finalizing work for their Preliminary Documented Safety Analysis (PDSA), which subsequently received DOE approval in January 2026 [^]. Radiant Industries, having received a $5 million DOE award in late 2024 for a test phase [^], marked its primary Q4 2025 milestone by submitting its DOE Authorization Request for Kaleidos (DARK) in November 2025 [^]. These Q4 2025 achievements demonstrate progress towards the July 4, 2026 criticality target.
8. Will China's ACP100 SMR Achieve Criticality Before August 2026?
| Cold Functional Test Completion | October 16, 2025 [^] |
|---|---|
| Non-Nuclear Steam Turbine Tests Completion | December 23, 2025 [^] |
| Official Commercial Operation Target | First half of 2026 [^] |
China's ACP100 SMR is deep into its commissioning phase. Officially known as "Linglong One," this first-of-a-kind commercial Small Modular Reactor (SMR) began with its First Concrete Pour (FCD) on July 13, 2021 [^]. Significant construction milestones include the installation of the integrated Reactor Pressure Vessel (RPV) [^] and the containment dome [^]. As of early 2026, the project has successfully completed cold functional tests on October 16, 2025 [^], and non-nuclear steam turbine tests on December 23, 2025 [^], marking substantial progress into its commissioning stage.
First criticality is projected for late June to early September 2026. Based on historical commissioning timelines for China's First-of-a-Kind (FOAK) reactor designs, the critical Hot Functional Testing (HFT) phase is estimated to conclude around late April to early May 2026. Following HFT, regulatory approvals for fuel loading and the actual fuel loading process will determine the path to first criticality, placing the most probable window between late June and early September 2026. While the project has an official target for commercial operation in the first half of 2026 [^], achieving this would necessitate an even earlier criticality date.
Achieving early criticality depends on an aggressive, problem-free schedule. Attaining first criticality before the August 1, 2026 deadline is plausible but is highly contingent on an aggressive, problem-free commissioning schedule. Key risks include potential technical issues that could arise from the ACP100's integrated, first-of-a-kind design during HFT, and the rigorous regulatory scrutiny by the National Nuclear Safety Administration (NNSA) required for the fuel loading permit. Any unforeseen delays in these final critical stages would likely push the criticality date beyond August 1, 2026, making the timely completion of HFT a crucial indicator.
9. Is HALEU Supply a Bottleneck for Advanced Reactors by Mid-2026?
| Centrus HALEU Production (H1 2026) | 450 kg [^] |
|---|---|
| Unallocated HALEU Inventory (H1 2026) | Zero kg [^] |
| Top 3 Reactor HALEU Demand (H1 2026) | Zero kg [^] |
HALEU supply is not an immediate bottleneck for US advanced reactors. The research indicates that High-Assay Low-Enriched Uranium (HALEU) supply does not pose an immediate bottleneck for leading U.S. advanced reactor candidates in the first half of 2026, or by an August 2026 deadline. The primary constraints on their operational timelines are lengthy construction and licensing processes, rather than near-term fuel availability. The total projected HALEU demand from NuScale Power, X-energy (Xe-100), and TerraPower (Natrium) for initial fuel loading in H1 2026 is zero, as their operational targets are currently set for 2028-2030 [^].
Centrus Energy's HALEU production is fully allocated to the DOE. Centrus Energy is currently the sole licensed domestic HALEU enrichment producer, with its demonstration cascade projected to yield approximately 450 kg of HALEU UF6 in H1 2026 [^]. However, all of Centrus's production, including its cumulative output exceeding 1 metric ton by the end of 2025, is contractually obligated and delivered directly to the U.S. Department of Energy (DOE) for its HALEU Availability Program [^]. Consequently, there is no significant unallocated HALEU inventory available on the commercial market from domestic suppliers in this timeframe [^].
Future HALEU demand highlights a significant strategic supply challenge. While no immediate bottleneck exists for H1 2026, the industry faces a significant strategic challenge for the late 2020s. Centrus's current pilot-scale production of approximately 900 kg per year is vastly insufficient for the multi-metric-ton initial core loadings expected from advanced reactors around 2028-2030 [^]. The DOE's HALEU Availability Program is designed to accumulate a temporary strategic stockpile, bridging the gap until larger commercial-scale enrichment facilities come online. These facilities target 12 metric tons per year by 2029 and up to 50 metric tons per year by 2035 [^].
10. What Could Change the Odds
Key Catalysts
Potential bullish catalysts include specific achievements from companies like Valar Atomics and Oklo Inc., which announced criticality and critical tests respectively in late 2025 [^] . A significant driver will be the U.S [^]. Department of Energy (DOE) Reactor Pilot Program, aiming for at least three advanced test reactors to achieve criticality by July 4, 2026 [^]. Official announcements from participating companies (e.g., Aalo Atomics, Antares Nuclear, Valar Atomics) confirming criticality before this deadline would strongly impact the market [^]. Accelerated regulatory approvals from the DOE or U.S [^]. Nuclear Regulatory Commission (NRC) could also expedite these projects [^]. Conversely, bearish catalysts primarily revolve around potential delays and setbacks [^]. The DOE Reactor Pilot Program faces skepticism regarding its aggressive July 4, 2026, target, and any announcements of delays would be negative [^]. Technical issues during testing, construction, or operational phases, or new safety concerns (e.g., regarding TerraPower's Natrium reactor design), could significantly impede progress [^]. Funding challenges, such as Oklo Inc.'s potential need for additional capital, and persistent shortages of High-Assay Low-Enriched Uranium (HALEU) fuel, essential for many next-generation reactors, also pose significant risks to achieving criticality before the August 2026 deadline [^].
Key Dates & Catalysts
- Expiration: August 08, 2026
- Closes: August 01, 2026
11. Decision-Flipping Events
- Trigger: Potential bullish catalysts include specific achievements from companies like Valar Atomics and Oklo Inc., which announced criticality and critical tests respectively in late 2025 [^] .
- Trigger: A significant driver will be the U.S [^] .
- Trigger: Department of Energy (DOE) Reactor Pilot Program, aiming for at least three advanced test reactors to achieve criticality by July 4, 2026 [^] .
- Trigger: Official announcements from participating companies (e.g., Aalo Atomics, Antares Nuclear, Valar Atomics) confirming criticality before this deadline would strongly impact the market [^] .
13. Historical Resolutions
No historical resolution data available for this series.
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