- Advanced Nuclear and Next-Generation Fission 2026
- Executive summary
Executive summary
The edition on a few pages: the abstract, the key messages, the headline finding and what each steward reads in it.
Contents
- ·Edition home
- ·Executive summary
- 1Advanced nuclear is firm infrastructure and a delivery test
- 2Key findings
- 3Systems and sectors at baseline
- 4Risks and capability
- 5Fuel supply gap while first-of-a-kind units are delayed
- 6Readings from the other desks
- 7The 2027 agenda
- 8Systems in depth
- AMethodology
- BData appendix
- CReferences and record
- ·Complete edition, for print
S.1Abstract
Advanced nuclear fission matters to the Nexus programme as firm power infrastructure and as a test of how fast a regulated industry can deliver new designs. The fleet is large and old: 443 operable reactors with 405,667 MWe of net capacity supplied about 9% of world electricity in 2025, and 80 more were under construction1. Next-generation designs are at the demonstration stage. The US Department of Energy reported that four test reactors reached zero-power criticality under its pilot program by 4 July 2026, against a goal of three67. The US Nuclear Regulatory Commission issued a construction permit in March 2026 for a 345 MWe sodium-cooled fast reactor in Wyoming, the first such permit for a commercial non-light-water power reactor89. Policy is moving fast. Executive orders of May 2025 set a goal of 400 GW of US nuclear capacity by 20503, and a final rule for a technology-inclusive licensing framework was published in 202610. The binding inputs are fuel, cost and time. Fuel for many new designs is high-assay low-enriched uranium, and DOE estimates demand could reach 50 tonnes a year by 203511. Recent large reactors ran far over their first estimates1517, and a peer-reviewed study found that none of 15 small reactor concepts competed with existing renewables on its assumptions2526. This baseline sets out what the evidence supports and where it is thin. It forecasts no delivery date and orders no country or vendor.
S.2Key messages
Six readings that frame the advanced nuclear baseline, and the eight questions this edition answers, each with its status and source.
443 operable reactors with 405,667 MWe, about 9% of world electricity, in 2025.1
How large is the nuclear fleet?Reported
Four DOE-authorized test reactors reached zero-power criticality by 4 July 2026; no commercial advanced power reactor was found operating.67
Are advanced reactors operating?Reported
A construction permit for a 345 MWe sodium-cooled reactor in March 2026.89
What did the NRC license?Reported
Part 53, an optional technology-inclusive framework published in 2026.10
What is the new licensing route?Reported
HALEU, enriched to 5% up to less than 20% U-235; DOE sees demand up to 50 tonnes a year by 2035.11
What fuel do many new designs need?Reported
Rosatom held about 42.8% of 2025 capacity; the US bars Russian low-enriched uranium imports from August 2024, with waivers.12
Who supplies enrichment?Reported
Recent large units ran far over first estimates; small-reactor costs are modelled and contested.1525
What do reactors cost?Reported
Whether announced schedules meet delivered units, with fuel supply as the limit. SCN-XT15-FUE-01
What will 2027 test first?Expert input
S.3Headline finding
ReportedEQL 4NRF-XTECH-FISSION-GLOBAL-2026-BASELINE-INF-003
The US NRC issued a construction permit in March 2026 for the Natrium reactor at Kemmerer, Wyoming: a 345 MWe sodium-cooled fast reactor with a molten-salt storage system that can raise output to 500 MW.
| Item | Bar, scaled to the largest value | Value |
|---|---|---|
| Base output (MWe) | 345 | |
| Output with storage (MW) | 500 |
Source: US Department of Energy release of March 20268. The release gives the boosted figure in megawatts, not MWe.
A commercial non-light-water power reactor has passed construction licensing in the United States. The NRC review ran 18 months against an initial 27-month schedule9. The permit does not cover operation: an operating licence application is still needed, and completion is expected in 20309.
S.4At a glance
S.5What each steward reads in it
GCRI · KEY T
Technical Truth
The evidence supports reading advanced nuclear as firm infrastructure at baseline and as a delivery test for the next decade.
GRF · KEY M
Public Meaning
For most people the story arrives as a headline about a test reactor, an executive order or a data-centre deal.
GRA · KEY F
Capital Meaning
Readiness implications only. Recent large units ran far over first estimates, and small-reactor costs are modelled and contested.
NEXUS
Synthesis
Advanced nuclear is well described by permits and announcements and thinly measured as a system.
S.6What this edition is, and is not
What this edition is
A baseline: the 2026 state of advanced nuclear and next-generation fission and the couplings through which it carries risk into other systems. It synthesises published evidence and ranks no country, company or asset.
What it is not
Not a forecast of when any reactor will operate, a technology comparison, an endorsement of any vendor or an assessment of any programme. Licensing, safeguards, fuel policy and funding are decisions of competent authorities.
What comes next
National, regional and sector evidence feeds the 2027 advanced nuclear edition through the federation. Each edition reports what changed against this baseline: observations, source revisions, method changes, scenario updates and corrections.
Notes
Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references
- 1World Nuclear Association (ed.), Nuclear Power in the World Today (information library page; 443 operable reactors, 405,667 MWe net, about 9% of world electricity, 80 under construction with 87,813 MWe gross; electricity data for 2025). World Nuclear Association, London. Observation year 2025. Accessed 2026-11-03.back
- 6American Nuclear Society (ed.), The deadline arrives: checking in on the Reactor Pilot Program (news article, 2 July 2026; criticality by Antares 4 June, Valar 18 June, Deployable Energy 1 July; ten companies selected in August 2025; status of the remaining participants). American Nuclear Society, La Grange Park. Observation year 2026. Accessed 2026-11-03.back
- 7US Department of Energy (ed.), Department of Energy Celebrates Fourth Criticality Ahead of July 4th Goal (press release, 6 July 2026; Aalo-X, Mark-0, Ward 250 and Unity; zero-power fueled criticality; agency announcement). US Department of Energy, Washington. Observation year 2026. Accessed 2026-11-03.back
- 8US Department of Energy, Office of Nuclear Energy (ed.), NRC Issues Construction Permit for TerraPower’s Natrium Advanced Reactor (article, 9 March 2026; 345 MWe sodium-cooled fast reactor, storage lifts output to 500 MW; Kemmerer Unit 1, Wyoming; operating licence separate). US Department of Energy, Washington. Observation year 2026. Accessed 2026-11-03.back
- 9World Nuclear News (ed.), NRC issues construction permit for first Natrium plant (news report, 5 March 2026; 18-month review against 27 months initially; completion expected 2030). World Nuclear Association, London. Observation year 2026. Accessed 2026-11-03.back
- 3The White House (ed.), Ordering the Reform of the Nuclear Regulatory Commission, Executive Order 14300, 23 May 2025 (goal of 400 GW by 2050 from about 100 GW in 2024; 18-month limit for new reactor decisions; 1-year limit for continued operation). The White House, Washington. Observation year 2025. Accessed 2026-11-03.back
- 10US Nuclear Regulatory Commission (ed.), 10 CFR Part 53 rulemaking page (final rule 91 FR 15696; risk-informed, performance-based, technology-inclusive framework; background in NEIMA and the ADVANCE Act). US Nuclear Regulatory Commission, Rockville. Observation year 2026. Accessed 2026-11-03.back
- 11US Department of Energy, Office of Nuclear Energy (ed.), What is high-assay low-enriched uranium (HALEU)? (article of 3 December 2024; enrichment 5% to less than 20% U-235; demand could reach 50 metric tons a year by 2035; Piketon more than 100 kg enriched). US Department of Energy, Washington. Observation year 2024. Accessed 2026-11-03.back
- 15World Nuclear Association (ed.), Nuclear Power in the USA (country profile; 94 operable reactors, 96,952 MWe; Vogtle 3 and 4 cost estimates; Kemmerer permit March 2026; Clinch River construction licence September 2026; Palisades and Crane restart status; page states three reactors critical by July 2026). World Nuclear Association, London. Observation year 2026. Accessed 2026-11-03.back
- 17World Nuclear Association (ed.), Nuclear Power in the United Kingdom (country profile, first 100,000 characters read; Rolls-Royce SMR delivery contract April 2026 for three Wylfa units with up to GBP 599 million loan financing; Hinkley Point C GBP 35 billion in 2015 prices, February 2026; Sizewell C). World Nuclear Association, London. Observation year 2026. Accessed 2026-11-03.back
- 25Steigerwald, B., Weibezahn, J., Slowik, M. and von Hirschhausen, C., Uncertainties in estimating production costs of future nuclear technologies: a model-based analysis of small modular reactors, Energy 281, 128204, 2023 (abstract page read). Elsevier, Amsterdam. Observation year 2023. Accessed 2026-11-03.back
- 26Steigerwald, B. et al., Future nuclear fission reactors: uncertainties, the effect of parameter choice and an application to small modular reactor concepts, Safety of Nuclear Waste Disposal 2, 217, 2023 (abstract page read; 15 concepts; none competes with existing renewables on its assumptions). Copernicus Publications, Gottingen. Observation year 2023. Accessed 2026-11-03.back
- 12World Nuclear Association (ed.), Uranium Enrichment (information library page; capacity table from the WNA Nuclear Fuel Report 2025: 68.076 million SWU in 2025, Rosatom 29.133, Urenco 17.300, CNNC 13.789 estimated, Orano 7.500; US ban on Russian low-enriched uranium from August 2024). World Nuclear Association, London. Observation year 2025. Accessed 2026-11-03.back