SMR Q3 2026 Update
IPO CLUB Research · The Criticality Window
SMR and microreactor update 2026: four reactors reach criticality in thirty days
Between 4 June and 4 July 2026, four privately developed advanced reactors sustained a chain reaction under US Department of Energy authorisation. Capital repriced the sector within weeks. This is what that proves, and what it does not.
The window · 4 June to 4 July 2026
Reactors critical
4
Elapsed window
30 days
Required by EO 14301
3
SMRs selling power
0
Criticality dates confirmed by the US Department of Energy and contemporaneous trade reporting. No small modular reactor was operating commercially anywhere in the world as of mid-2026.
Key facts
- Executive Order 14301, signed 23 May 2025, directed the Department of Energy to bring at least three advanced reactors to criticality by 4 July 2026. Eleven projects across ten companies were named in August 2025.
- Antares Nuclear's Mark-0 went critical on 4 June 2026 at Idaho National Laboratory, the first privately developed non-light-water reactor to do so in the United States in more than four decades.
- Valar Atomics' Ward 250 went critical on 18 June 2026 in Emery County, Utah, the first DOE-authorised reactor built and operated entirely outside the national laboratory system.
- Deployable Energy's Unity went critical on 30 June 2026 at Idaho National Laboratory, satisfying the executive order.
- Aalo Atomics' Critical Test Reactor went critical on 4 July 2026, the date of the deadline itself.
- X-energy began trading on Nasdaq under XE on 24 April 2026, priced at $23 per Class A share.
- Valar Atomics raised $1 billion at a $6 billion valuation on 3 August 2026, led by Sequoia Capital.
- Antares Nuclear raised $470 million in equity and debt on 27 July 2026, taking total backing above $600 million.
- newcleo agreed a Nasdaq listing via NewHold Investment Corp III on 26 May 2026 at approximately $2.4 billion pre-money.
Four reactors, thirty days
A regulatory pathway that had produced nothing for four decades produced four demonstrations in a single month. IPO CLUB has tracked each of the eleven pilot projects since the programme was announced. The four that made it, in sequence:
4 June 2026
Antares Nuclear · Mark-0
Idaho National Laboratory, with the DOE, INL and BWX Technologies, and integration and observation support from the US Army. First of the four.
18 June 2026
Valar Atomics · Ward 250
Utah San Rafael Energy Laboratory, Emery County. Confirmed by the DOE Office of Nuclear Energy. The first outside the national laboratory system.
30 June 2026
Deployable Energy · Unity
Idaho National Laboratory, under the Nuclear Energy Launch Pad initiative managed by the National Reactor Innovation Center. The one that met the order.
4 July 2026
Aalo Atomics · Critical Test Reactor
On the deadline itself, roughly eight months from groundbreaking. A second reactor is under construction beside it, intended to power an on-site data centre.
Still pending: Radiant's Kaleidos. First TRISO fuel was delivered to the DOME facility in early July, ahead of a five-phase campaign running from zero-power criticality to a 150-hour continuous full-power run without operator intervention.
The capital response
Capital moved within weeks of each milestone, and at a scale the sector has not previously seen.
X-energy went public
An upsized initial public offering of 44,254,659 Class A shares priced at $23 on 23 April 2026, trading on Nasdaq under XE from 24 April, with J.P. Morgan, Morgan Stanley, Jefferies and Moelis & Company leading. X-energy is the first sizable advanced reactor company to take the traditional IPO route. Oklo and NuScale both reached the public markets by SPAC.
Valar raised $1B at $6B
Announced 3 August, led by Sequoia Capital, with Sequoia partner Shaun Maguire joining the board, alongside a $200 million credit facility led by Erebor Bank. The valuation triples the $2 billion Valar carried after its April round. Between criticality on 18 June and the round announcement, Valar used reactor-generated electricity to run an Nvidia Blackwell-architecture machine in a live demonstration, and announced a joint feasibility study with Nvidia for a 30-megawatt facility.
Antares raised $470M
Announced 27 July, in equity and debt, taking total backing above $600 million. The company holds US Air Force contracts under the Advanced Nuclear Power for Installations initiative and is building toward a directive to operate a reactor at a domestic military installation by 30 September 2028.
newcleo agreed to go public
A business combination with NewHold Investment Corp III, announced 26 May 2026, valuing newcleo at approximately $2.4 billion pre-money, with up to $429 million in gross proceeds from a $220 million PIPE committed at $10.00 per share and up to $209 million held in trust. The combined company is expected to trade on Nasdaq under NWCL, with closing anticipated in the second half of 2026. Existing shareholders roll over 100% of their equity.
Four financings across roughly fifteen weeks, in companies that reached the same technical milestone in the same month. IPO CLUB does not read that as coincidence. Criticality converted a category of company from pre-technical-risk to post-technical-risk, and the capital markets repriced accordingly.
Reference table · output, reactor type and fuel
These are the structural facts that do not move quarter to quarter. IPO CLUB states units explicitly, because thermal and electric output are not interchangeable and are routinely conflated in coverage of this sector.
| Company | Output | Reactor | Fuel |
|---|---|---|---|
| TerraPower | 345 MWe | Sodium-cooled fast reactor (Natrium), with integrated molten salt storage | HALEU metallic fuel (U-10Zr alloy) |
| newcleoPortfolio · public pending, Nasdaq NWCL | 200 MWe | Lead-cooled fast reactor (LFR-AS-200), atmospheric pressure | MOX (mixed uranium-plutonium oxides) |
| X-energyPublic · Nasdaq XE | 80 MWe per unit | High-temperature gas-cooled pebble bed (Xe-100), helium cooling | TRISO-X (HALEU) |
| Kairos Power | 35 MWt | Fluoride salt-cooled high-temperature reactor (KP-FHR). Hermes 1 is non-power | TRISO in pebble form |
| Last Energy | 20 MWe | Pressurized water reactor (PWR-20) | Standard low-enriched uranium |
| Aalo Atomics | 10 MWe | Sodium-cooled, graphite-moderated microreactor (Aalo-X) | Low-enriched uranium dioxide, under 5% U-235, under 8% for LEU+ |
| Valar Atomics | 5 MWe design | High-temperature gas-cooled (Ward 250), helium cooling, graphite moderator. 100 kWt as built | TRISO |
| Radiant | 1 MWe | High-temperature gas-cooled (Kaleidos), helium cooling, prismatic graphite. Plus 1.9 MW thermal | TRISO (HALEU) |
| Antares Nuclear | 100 kW to 1 MW | Sodium heat-pipe cooled microreactor (Mark-0) | TRISO (HALEU) |
Specification figures are as stated by developers and regulators and have not been independently verified by IPO CLUB. Output figures for reactors that have not operated at power are design targets, not demonstrated performance.
What criticality proves, and what it does not
This matters more than the milestones, and it is where most coverage of the summer has been careless. IPO CLUB draws four distinctions.
Zero-power criticality is not power generation
Every one of the four demonstrations was a zero-power fuelled criticality. The reactor sustains a chain reaction; it does not deliver meaningful electricity. Valar's Ward 250 was at roughly 100 kilowatts thermal when it powered a desktop machine, which the company itself put at 37% of intended output. Aalo's Critical Test Reactor operates at near-zero power by design, built to validate reactor physics and control systems. These are physics validations, and they are genuine, but the distance from a validated core to a delivered megawatt-hour is measured in years of engineering.
DOE authorisation is not an NRC licence
The Reactor Pilot Program is an expedited authorisation covering a specific test reactor at a specific site under a Documented Safety Analysis. Selling a commercial kilowatt-hour on civilian land requires the Nuclear Regulatory Commission. These are separate regimes with separate evidentiary burdens, and the second has not been cleared by any company in this cohort. Several are pursuing both pathways in parallel, which is the correct strategy and also an admission that the first does not substitute for the second.
No advanced reactor in this group is operating commercially
As of mid-2026, no small modular reactor was operating commercially anywhere in the world. The demonstrations are firsts within a national programme, not first revenue.
Manufacturing is the unsolved problem
Every company in the cohort has now stated some version of the same next objective: move from building one reactor to building fleets. That transition is where hardware companies historically fail, and none of these has completed it. Valar's own framing is that it took two years to complete its first core and seven months to take Ward 250 critical, with the implication that the interval keeps compressing. That is a hypothesis, not yet a demonstrated manufacturing curve.
The IPO CLUB summary is that the sector has retired a specific and important technical risk, on an accelerated regulatory pathway, and has been repriced as though it retired regulatory and manufacturing risk at the same time. It did not. Current valuations embed execution that has yet to occur.
The position · newcleo
newcleo is the advanced nuclear position held in America 2030, and it is differentiated from the cohort above on two axes.
Fuel cycle rather than reactor alone
The LFR-AS-200 is a 200 MWe lead-cooled fast reactor designed to run on newcleo's proprietary MOX fuel, produced from recovered or surplus nuclear materials. Pairing a fast-neutron spectrum with MOX allows the conversion of legacy nuclear materials and spent fuel into energy while reducing the final volume and radiotoxicity of what remains. Where most of the cohort designs a reactor and sources fuel externally, newcleo is licensing the reactor and a MOX fabrication facility together, aiming at a closed domestic fuel loop.
European origin, American market
newcleo submitted a Regulatory Engagement Plan to the NRC for the LFR-AS-200 on 14 July 2026, following a letter of intent in February and pre-application engagement through the spring. A separate submission covers the MOX fuel fabrication facility. The LFR-AS-200 was accepted into the UK's Generic Design Assessment in June 2025.
Timelines are long and stated plainly by the company: the LFR-AS-30 prototype in the 2030s, the commercial LFR-AS-200 later still. This is not a near-term revenue thesis. It is a position on the fuel cycle at a moment when the rest of the sector is competing on speed to criticality and has not yet resolved where its fuel comes from at scale. The pending Nasdaq listing under NWCL is a liquidity event, not a validation event, and IPO CLUB treats it as such.
Frequently asked questions
How many advanced nuclear reactors reached criticality in 2026?
Four, between 4 June and 4 July 2026, all under US Department of Energy authorisation: Antares Nuclear's Mark-0 on 4 June, Valar Atomics' Ward 250 on 18 June, Deployable Energy's Unity on 30 June, and Aalo Atomics' Critical Test Reactor on 4 July. Executive Order 14301 had asked for three by 4 July.
Is X-energy publicly traded?
Yes. X-energy priced an upsized initial public offering at $23 per Class A share on 23 April 2026 and began trading on Nasdaq under the ticker XE on 24 April 2026. It is the first sizable advanced reactor company to go public via a traditional IPO rather than a SPAC.
Is any small modular reactor selling commercial power?
No. As of mid-2026 no small modular reactor was operating commercially anywhere in the world. The 2026 criticalities were zero-power fuelled demonstrations, which validate reactor physics rather than generate saleable electricity.
Does DOE authorisation mean a reactor is NRC licensed?
No. The DOE Reactor Pilot Program authorises a specific test reactor at a specific site under a Documented Safety Analysis. Selling commercial power on civilian land requires a separate Nuclear Regulatory Commission licence, which no company in the 2026 cohort has obtained.
Is newcleo going public?
newcleo announced a business combination with NewHold Investment Corp III on 26 May 2026, valuing the company at approximately $2.4 billion pre-money. The combined entity is expected to trade on Nasdaq under NWCL, with closing anticipated in the second half of 2026.
What is the difference between an SMR and a microreactor?
Small modular reactors are typically sized from about 20 MWe to several hundred MWe and target utility-scale generation. Microreactors are smaller, usually below 20 MWe and commonly 1 to 10 MWe, and are designed for remote, military, industrial or specialised commercial deployment with greater portability and faster installation.
Method and sources
Figures are drawn from primary sources. Where a company has not publicly announced a financing, this report does not reference it, including where a round is understood to be in market.
- US Department of Energy, Reactor Pilot Program, and the DOE announcement of the third advanced reactor criticality.
- Antares Nuclear, initial criticality announcement of 4 June 2026, and Series C announcement of 27 July 2026.
- NucNet and POWER, Valar Atomics Ward 250 criticality, June 2026.
- American Nuclear Society, Deployable Energy criticality at Idaho National Laboratory, and Reactor Pilot Program deadline review.
- Nuclear Engineering International, Aalo Critical Test Reactor.
- World Nuclear News, TRISO fuel delivery for the Kaleidos reactor experiment, and newcleo US licensing plan.
- newcleo, Regulatory Engagement Plan submission to the US NRC, 14 July 2026.
- US Nuclear Regulatory Commission, advanced reactor pre-application activities.
This report is a full rewrite. It supersedes and replaces the June 2025, August 2025 and October 2025 nuclear updates previously published by IPO CLUB, which have been removed. Figures in those updates should be treated as withdrawn.
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