Compendium

Walkthrough: Design a Modular Nuclear Reactor (300 MWe SMR / NuScale-class)

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Walkthrough: Design a Modular Nuclear Reactor (300 MWe SMR / NuScale-class)

A 300 MWe Small Modular Reactor (SMR) — roughly 1,000 MW thermal, factory-fabricated in transportable modules, then assembled and operated on a small site — is the format the nuclear industry has bet on to break the cost spiral that crushed the Westinghouse AP1000 program (Vogtle 3 & 4 in Georgia eventually entered service 2023-2024 at ~14 billion original budget; V.C. Summer 2 & 3 cancelled in 2017 after 20,139/kWe, putting the project’s offtake price at $119/MWh and losing enough subscribers to make the project unviable. But the design pipeline is now full: NuScale (NRC-certified), GE Hitachi BWRX-300 (OPG Darlington construction underway 2025, first reactor target 2028), X-Energy Xe-100 (Dow Seadrift TX, Amazon-funded), TerraPower Natrium (Kemmerer WY, ~2030 target), Holtec SMR-300, Westinghouse AP300, Rolls-Royce SMR (UK), Kairos KP-FHR (Google offtake), Oklo Aurora (microreactor), and many more.

This walkthrough designs a 300 MWe-class SMR — either a multi-module NuScale-style pressurized water plant or a single-unit BWRX-300 / Holtec-300 plant — and works through the technology choices, licensing path, supply chain, economics, and decarbonization context. The reference case targets a Tennessee Valley Authority (TVA) or Ontario Power Generation (OPG) brownfield site with grid interconnect already present from a retired coal plant.

1. SMR landscape — what we mean by “small”

Industry consensus definitions:

  • Microreactor: 1 to 20 MWe (Oklo Aurora 15 MWe initial then 75 MWe variant, Westinghouse eVinci 5 MWe, BWXT Project Pele 1 to 5 MWe, USNC MMR 5 MWe, Last Energy 20 MWe)
  • Small Modular Reactor (SMR): 50 to 300 MWe (NuScale NPM-77 77 MWe per module, X-Energy Xe-100 80 MWe per reactor, BWRX-300 300 MWe, Holtec SMR-300 300 MWe, Westinghouse AP300 300 MWe, Rolls-Royce SMR 470 MWe — at the edge of “small”)
  • Conventional / Gen III+: 1,000 to 1,700 MWe (Westinghouse AP1000 ~1,100 MWe, EPR2 ~1,650 MWe, VVER-1200 ~1,200 MWe, Hualong One HPR1000 ~1,150 MWe, APR1400 ~1,400 MWe)

Modular = the reactor pressure vessel + steam generator + much of the primary loop is fabricated in a factory, shipped to site by rail or barge, and assembled. The promise: factory production learning curve, parallel module manufacturing while site civil works proceed, reduced field labor, reduced schedule risk. The empirical test of that promise is still ahead of us; Vogtle’s mostly-stick-built AP1000 result was the negative example.

2. Reactor types — which technology

The “SMR” label hides four fundamentally different reactor families competing for the market:

Light Water Reactor (LWR) — PWR and BWR variants

The dominant technology for both Gen III+ and most SMRs in 2026. Water serves as both moderator (slowing neutrons to thermal energies for fission with U-235) and primary coolant. Operating temperature ~325°C on the hot leg; pressure ~15.5 MPa (PWR) or ~7 MPa (BWR). About 85% of operating world fleet are PWRs (PWR primary loop drives a secondary loop through a steam generator; the turbine sees clean, non-radioactive steam) and most of the rest are BWRs (the reactor produces steam directly; turbine sees radioactive steam, simpler but with radioactive secondary).

LWR SMR designs:

  • NuScale Power Module (NPM-77): integral PWR, 77 MWe per module (up from initial 60 MWe design certification). Whole reactor + steam generator + pressurizer in one vessel ~23 m tall. Six or twelve modules per plant (462 or 924 MWe). First and so far only US SMR to receive NRC Standard Design Approval (SDA) — initial 50 MWe variant January 2023; 77 MWe uprate certification in progress 2024-2026. Lead project (UAMPS Carbon Free Power Project, Idaho INL site) cancelled November 2023; NuScale has pivoted to data center co-location offtake (Standard Power Ohio + Pennsylvania commitments, others under negotiation).
  • GE Hitachi BWRX-300: 300 MWe BWR derived from the ESBWR; passive safety; natural-circulation primary; first concrete in 2024 at OPG’s Darlington site Ontario for first reactor in service ~2028 (first commercial Western SMR build). TVA applied for Clinch River TN construction permit 2024 (~800 MWe four-reactor plant). SaskPower (Saskatchewan), Synthos Green Energy (Poland) also commit.
  • Holtec SMR-300: 300 MWe integral PWR; Palisades MI restart site (formerly retired LWR; restart funded $1.5B DOE loan 2024-2025) is adjacent to planned SMR-300 first build.
  • Westinghouse AP300: 300 MWe PWR derived directly from the AP1000 (passive safety systems, modular construction). Pre-application discussions with NRC, early commercial customers TBD.
  • Rolls-Royce SMR: 470 MWe LWR (PWR); UK government-backed selection program; CEZ (Czech Republic) and OEG (Greece) downselected RR-SMR in 2024 commercial decisions.
  • Last Energy 20 MWe: small LWR microreactor (technically “micro” but commercially marketed as SMR); first sales agreements in Wales (4 units) and Poland.

High-Temperature Gas-cooled Reactor (HTGR)

Helium coolant, graphite moderator, TRISO fuel particles. Reactor outlet 700 to 950°C — high-quality heat suitable for industrial process applications (hydrogen production via high-temperature steam electrolysis, chemical industry process heat, thermal storage with very high Carnot efficiency).

  • X-Energy Xe-100: 80 MWe per reactor (200 MW thermal); 4-pack standard plant (320 MWe); pebble-bed (fuel is 60 mm graphite-encased “pebbles” each containing thousands of TRISO particles, continuously cycled through reactor). Dow Chemical Seadrift TX commercial agreement 2023 — co-located with Dow’s existing chemical complex for process heat + electricity; Amazon partnership 2024 ($500M+ commitment, Energy Northwest WA siting). DOE ARDP (Advanced Reactor Demonstration Program) co-funded.
  • Kairos Power KP-FHR: fluoride-salt-cooled (not gas-cooled, but graphite-moderated with TRISO so often grouped with HTGRs); 140 MW thermal Hermes demo reactor under construction at Oak Ridge TN (DOE-funded ARDP project); 75 MWe commercial KP-X follow-on; Google offtake announcement October 2024 (six to seven reactors, 500 MW total, deployment 2030-2035).

Sodium Fast Reactor (SFR)

Liquid sodium coolant, fast neutron spectrum (no water = no moderation), passive safety from sodium’s wide liquid range (97 to 883°C), potential to breed fuel + burn long-lived actinides. Legacy designs: EBR-II (Idaho, 1964-1994), Phénix and Superphénix (France), BN-600 / BN-800 (Russia, BN-800 operating commercially).

  • TerraPower Natrium: 345 MWe net + 100 MWe boost via molten-salt thermal storage. Sodium primary loop → intermediate sodium loop → molten-salt (NaCl + chloride salts) thermal storage → steam generator → turbine. Storage decouples reactor power from grid output — reactor runs steady 345 MW thermal, storage allows 100 to 500 MW dispatch over grid hours. Bill Gates backed. Wyoming Kemmerer site (retired coal plant brownfield); PacifiCorp grid partner; ~$4 billion DOE ARDP funding; first concrete delayed multiple times due to high-assay low-enriched uranium (HALEU) fuel supply chain issues. Operational target slipped from 2028 to Q3 2030.
  • Oklo Aurora: compact sodium-cooled fast reactor, 15 MWe initial design (now 75 MWe Aurora variant pivoted to). NRC license application withdrawn 2022 and resubmitted with additional content 2024. Strong corporate offtake announcements: Diamondback Energy oil & gas operations (West Texas), several data center MOUs (Equinix, Switch, etc.).
  • ARC-100 (Advanced Reactor Concepts): 100 MWe sodium-cooled fast reactor; partnerships with New Brunswick Power Canada and others.

Molten Salt Reactor (MSR)

Fuel dissolved in a fluoride salt (e.g., FLiBe = LiF-BeF2 + UF4 or thorium fluoride). Operating temperature 600 to 700°C at near-atmospheric pressure. The 1960s Oak Ridge MSRE proved the concept. Several modern startups: Terrestrial Energy IMSR-400 (Canada; integral MSR; CNSC vendor design review stage), Thorcon (Indonesia partnership), Moltex (UK / Canada; molten-salt fuel + secondary lead coolant), Copenhagen Atomics (Denmark; thorium MSR breeder). None at construction stage in 2026. ThorCon and Terrestrial Energy continue regulatory progress.

Lead / Lead-Bismuth Fast Reactor (LFR)

Russian SVBR-100 (50 MWe), Westinghouse LFR concept, Newcleo (UK / Italy startup); fast spectrum like SFR but lead coolant (chemically inert with water — no fire risk that sodium has). Still in design phase commercially.

3. TRISO fuel — the critical enabling technology for non-LWR SMRs

TRISO (TRi-structural ISOtropic) fuel particles are the technology that makes high-temperature gas reactors and FHRs viable:

  • Kernel: UCO (uranium oxycarbide, UC0.5O1.5) or UO2, ~500 µm diameter, enriched to 5 to 19.75% U-235 (HALEU — high-assay low-enriched uranium; below 20% so still “low-enriched” by international convention)
  • Buffer layer: porous pyrocarbon, ~95 µm; accommodates fission-gas swelling and recoil damage
  • Inner pyrocarbon (IPyC): dense pyrocarbon, ~40 µm; gas barrier
  • Silicon carbide (SiC): dense β-SiC, ~35 µm; the primary fission-product barrier; intact to >1,600°C
  • Outer pyrocarbon (OPyC): dense pyrocarbon, ~40 µm; protection for SiC during handling and irradiation

Total particle diameter ~0.85 to 1.0 mm. Particles are then assembled into either:

  • Pebbles (Xe-100, German HTR-Modul, Chinese HTR-PM): 60 mm graphite spheres each containing ~15,000 TRISO particles
  • Compacts (Kairos KP-FHR, USNC FCM, Project Pele): cylindrical graphite compacts containing TRISO

Manufacturing capacity is the supply-chain bottleneck. BWXT TRISO-X fuel fabrication plant under construction Oak Ridge TN (DOE-funded $150M+); X-Energy TRISO-X subsidiary (separate facility). Each plant ramps to ~8 tonnes/year HALEU fuel by ~2027 — barely enough for the first wave of advanced reactor demonstrations. HALEU itself is supply-constrained (Centrus Energy American Centrifuge restart, with first kgs delivered 2023; DOE LEU-supplementation; Russian TENEX historically dominant but cut off since 2022).

4. The reference design — assume BWRX-300 LWR architecture for the walkthrough

Picking a single design to design through, the BWRX-300 (300 MWe BWR, GE Hitachi) is the most concrete near-term project: first reactor under construction at OPG Darlington (2024 first concrete, 2028 operation target), TVA Clinch River applied, SaskPower committed.

Primary components

  • Reactor pressure vessel (RPV): ~26 m tall, ~4 m diameter, ~7 MPa operating pressure, ~286°C saturation temperature; carbon-steel forging clad with stainless steel internally; ~600 tonnes; forged by Japan Steel Works (JSW) or Doosan Heavy Korea — only ~5 facilities globally capable of single-piece forgings at this scale
  • Fuel: standard LWR fuel; UO2 pellets in zircaloy-2 cladding (Westinghouse / Framatome / Global Nuclear Fuel) at 4 to 5% U-235 enrichment; 240 fuel assemblies in core; 18 to 24 month refueling cycle
  • Reactor internals: core shroud, steam separators, dryers — passive natural-circulation design (no recirculation pumps, a major BWRX simplification over the older BWR designs)
  • Containment: steel-lined concrete reactor building (small footprint, ~30 m × 30 m × 50 m tall); passive isolation condenser on the outside provides decay heat removal without AC power for at least 7 days

Steam cycle

  • Steam exits RPV at: ~286°C, 7 MPa, ~640 t/h
  • Turbine: ~300 MWe; single high-pressure stage + 2-stage low-pressure (or single LP); ~1500 rpm or 3000 rpm depending on grid frequency; manufactured by Mitsubishi Heavy, Toshiba, GE Power, Siemens Energy
  • Condenser: shell-and-tube, ~2 MW cooling water flow (closed-loop cooling tower preferred for site flexibility, once-through to water body where available)
  • Feedwater system: feedwater heaters, condensate pumps, feed pumps; standard BWR architecture
  • Net electrical output: ~300 MWe to grid (95 to 97% gross-to-net efficiency)

Safety systems

  • Passive isolation condenser: heat sink for >7 days post-LOCA without operator action, AC power, or external water makeup
  • Passive containment cooling: condensation on inside of steel containment vessel; pool above containment for sustained heat rejection
  • Gravity-driven core flood: large overhead pool drains into RPV under loss-of-coolant
  • Standard active safety systems: high-pressure ECCS, low-pressure ECCS, standby liquid control (boron injection)

Site footprint

  • BWRX-300 advertised: 16 hectares (40 acres) total site footprint, including switchyard
  • Emergency Planning Zone (EPZ): historically 10 miles for LWRs under 10 CFR 50.47; SMR vendors and NRC are debating reduced EPZ for SMRs given lower source term and stronger passive safety — proposed 1-mile EPZ for NuScale; precedent will affect siting flexibility

5. The licensing path — how the NRC approves a new reactor

US licensing is the regulatory pacing item. Three paths:

  • 10 CFR Part 50 (two-step): Construction Permit → Operating License. Historically slow, multi-decade legacy from older reactors. Vogtle 3 & 4 used Part 52 path; few new Part 50 applications.
  • 10 CFR Part 52 (one-step): Combined Construction and Operating License (COL). Used for all recent reactor applications. Vendor first secures Standard Design Approval (SDA) or Design Certification, then site-specific COLA references the certified design. NuScale received SDA for 50 MWe Power Module January 2023 — the first SDA for any SMR globally.
  • ADVANCE Act (2024): Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy. Bipartisan legislation that updated NRC missions and timelines, reducing licensing fees for advanced reactors, providing prizes for first-mover deployments, and tasking NRC with reforming application processes. Material acceleration; effects still working through.

Outside US:

  • UK: Office for Nuclear Regulation (ONR) + Environment Agency joint Generic Design Assessment (GDA) — 4 phases over ~5 years. Rolls-Royce SMR in GDA. Hualong One completed GDA 2022. AP1000 completed GDA 2017.
  • Canada: Canadian Nuclear Safety Commission (CNSC) Vendor Design Review (VDR) — multi-phase pre-licensing; BWRX-300 completed Phase 2 VDR 2023; Terrestrial Energy IMSR-400 in Phase 2; Moltex in Phase 1.
  • EU: European Utility Requirements (EUR) industrial body; ENSREG (European Nuclear Safety Regulators Group); each member state retains regulator authority but designs converge on common standards.
  • IAEA: international safety standards baseline; new IAEA Nuclear Harmonization and Standardization Initiative aims to align SMR licensing globally.

Typical SMR licensing timeline:

  • Year 0: vendor begins pre-application engagement with NRC
  • Year 2: Standard Design Approval / Design Certification application submitted
  • Year 4-5: SDA/DC issued
  • Year 5-6: COL application from utility, referencing certified design + site-specific data
  • Year 7-8: COL issued
  • Year 7-9: construction begins
  • Year 11-13: first criticality
  • Year 12-14: commercial operation

Compressed for fast-followers (the 2nd through Nth project per design) to ~Year 7 to Year 10 commercial operation from utility decision.

6. Construction and supply chain

Heavy forgings (the global chokepoint)

Few facilities in the world can produce the steel forgings required for reactor pressure vessels and steam generators. The supply base is approximately:

  • Japan Steel Works (JSW) — Muroran Hokkaido, the historically dominant supplier; capable of single-piece forgings up to ~600 tonnes
  • Doosan Enerbility (formerly Doosan Heavy) — Changwon, Korea; major supplier to Westinghouse AP1000, Korean APR1400
  • Mitsubishi Heavy Industries (MHI) — Kobe, Japan; supplier to European EPR, Japanese designs
  • Le Creusot Forge (Framatome, France) — Le Creusot; supplier to EPR (some quality irregularities identified 2016-2018 affecting Flamanville schedule; remediated)
  • Sheffield Forgemasters (UK; renationalized 2021 to ensure UK defense + civil nuclear supply chain)
  • OMZ Izhora (Russia) — supplier to Russian VVER and Akademik Lomonosov barge reactors
  • CFHI / Shanghai Electric (China) — increasing capability for Chinese fleet
  • Larsen & Toubro (India) — supplier to Indian PHWR and growing capability
  • Walter Tosto (Italy), Sherman Foundry (US, smaller)

Total annual capacity for large reactor forgings globally is ~20 to 40 vessel sets — far less than the 25-nation COP28 nuclear-tripling declaration implies for 2050. This is a serious bottleneck the industry has not yet addressed.

EPC contractors (engineering, procurement, construction)

  • Bechtel — US Vogtle 3 & 4 (with Southern Nuclear); strongest US large-project nuclear EPC
  • Fluor — US, joint venture partner on multiple AP1000 efforts (NuScale UAMPS originally)
  • Sargent & Lundy — engineering and design integrator for utility-led projects
  • Burns & McDonnell — engineering services
  • AECOM, Jacobs, Black & Veatch — engineering and consulting
  • SNC-Lavalin / AtkinsRéalis — Canadian (CANDU heritage)
  • KEPCO E&C (Korea), Doosan E&C (Korea), Toshiba Plant Systems (Japan), Hitachi-GE Nuclear Energy (Japan)
  • EDF + Framatome + EDF Energy (France / UK; EPR builds)
  • CGN, CNNC (China)
  • Rosatom (Russia; Akkuyu Turkey, El Dabaa Egypt, Rooppur Bangladesh, others; international project pipeline strongest of any vendor — overlaid by geopolitical risk post-2022)

Module fabrication facilities

For SMRs specifically: NuScale’s lead module fabricator is Doosan Enerbility (initial order intake 2024); BWRX-300 module fabrication at GE Hitachi Wilmington NC plus partnerships in Canada (Aecon, AtkinsRéalis); X-Energy planning a North American TRISO + fuel + module fabrication facility 2027 commissioning. Holtec building SMR-300 module fab at Camden NJ Holtec advanced manufacturing center.

7. Economics — the unsettled question

Overnight construction cost targets (in 2024 USD per kW electric, “overnight” = excluding financing costs and escalation):

  • Gen III+ first-of-kind: 14,000/kWe (Vogtle 3 & 4 ended ~7,000-$10,000/kWe NOAK target)
  • Gen III+ nth-of-kind (NOAK): 6,000/kWe (Korean APR1400 historical achievement; UAE Barakah ~$5,000/kWe at completion)
  • SMR target (NOAK, advertised): 6,000/kWe
  • SMR FOAK (observed so far): NuScale CFPP ended at 5,000 to $7,000/kWe

The FOAK premium (50 to 100% over NOAK) is the persistent problem. Industries that learned how to deliver costs at scale (commercial aircraft, automotive) did so through tens of identical units produced in sequence; nuclear has been producing one-or-two-of-a-kind plants per decade per design family, with each unit carrying the cost-discovery burden of a near-prototype.

Levelized Cost of Electricity (LCOE) targets:

  • Vogtle 3 & 4 LCOE: ~150/MWh
  • NuScale CFPP original PPA: 119/MWh
  • BWRX-300 OPG target: ~$110/MWh implied
  • Comparison: utility solar + 4-hour storage 2024-2026: 80/MWh; onshore wind: 60/MWh; offshore wind: 150/MWh; combined-cycle gas: 90/MWh with current gas prices

Nuclear has a long lifetime (60 to 80 years), high capacity factor (typically 90%+), and dispatchable / firm capability that compares favorably to variable renewables when total system cost (including transmission, storage, backup generation) is considered. The dispatch + capacity value gets lost in headline LCOE comparisons.

OPEX: 15/MWh fuel + O&M; vs. ~4/MWh for renewable solar / wind; vs. 80/MWh for combined-cycle gas at current European gas prices.

8. Customer drivers (why these get built)

The 2024-2026 SMR procurement wave is dominated by three buyer types:

Tech / hyperscaler

  • Microsoft + Constellation: 20-year PPA to restart Three Mile Island Unit 1 (renamed Crane Clean Energy Center), targeting 2028 startup, ~835 MWe capacity — not technically an SMR but the most consequential commercial deal of 2024.
  • Amazon + Talen Energy (500M+ investment, X-Energy series); + Amazon + Dominion Energy Virginia agreement
  • Google + Kairos Power: October 2024, 6-7 reactors, 500 MW total, deployment 2030-2035; + Google + Intersect Power + others
  • Meta: RFP issued December 2024 for 1 to 4 GW nuclear; selection 2025-2026
  • Oracle: 1 GW nuclear DC campus announced 2024
  • xAI (Memphis Colossus): natural gas + grid + diesel + likely nuclear in future build phases

Industrial process heat

  • Dow Chemical + X-Energy (Seadrift TX): integrated process heat + electricity for Dow’s chemical operations; ARDP-funded
  • Hydrogen production: HTGRs with their 750+°C output are uniquely well-suited to high-temperature steam electrolysis (50% higher efficiency than low-temp electrolysis); Bloom Energy + INL + Idaho Falls demonstration ongoing
  • Steel decarbonization (DRI / direct reduction of iron with hydrogen): future market for high-temperature SMRs

Utility / grid

  • TVA (Tennessee Valley Authority): Clinch River BWRX-300 application; potential up to 4 reactors
  • OPG (Ontario Power Generation): Darlington BWRX-300 build underway; potential expansion to 4 reactors
  • SaskPower: BWRX-300 selection 2022; first reactor 2034 target
  • NextEra, Duke Energy, Southern Company, Constellation, Vistra: various SMR evaluations and pre-commitments
  • CEZ (Czech Republic): Rolls-Royce SMR selection 2024
  • EDF (France) + Belgium + Sweden Vattenfall + Finland + Netherlands: various national programs
  • Korea (KHNP): SMART reactor design, i-SMR for export
  • Japan: post-Fukushima slow restart; SMRs evaluated longer-term
  • India: BSMR and indigenous designs

Military

  • Project Pele (US DOD): 1 to 5 MWe transportable microreactor for forward operating bases; BWXT awarded design contract 2022; first unit prototype 2025; deployment ~2027-2028. The first US new-built reactor since the 1990s and the rare case where cost is not the binding constraint.

9. Safety, waste, and the public-perception overhead

Modern SMR safety arguments (versus large LWR):

  • Passive cooling: NuScale module has no primary pumps — natural circulation throughout. Decay heat removed indefinitely by passive evaporation from the reactor pool, no operator action needed.
  • Small core, low decay heat: 100 MW thermal versus 3,400 MW for AP1000; decay heat absolute magnitude is much lower; passive systems can remove it indefinitely
  • TRISO containment (gas-cooled designs): fuel particle itself is the primary fission-product barrier; rated 1,600°C peak; HTGR cores cannot physically reach those temperatures even in worst loss-of-coolant
  • Walk-away passive: eVinci, Aurora, NuScale all advertise multi-day to indefinite passive safety without AC power or operator action — the post-Fukushima design imperative

Emergency Planning Zone (EPZ) debate: legacy 10-mile EPZ around large LWRs is being challenged for SMRs given the lower source term (smaller core inventory) and stronger passive safety. NRC granted NuScale a smaller EPZ (~0.5 mile) in 2020. EPZ reduction makes industrial / urban co-location feasible (Dow Seadrift TX chemical complex with X-Energy reactors is the test case).

Waste

Spent fuel volumes per MWh are similar between SMR and large LWR (slightly higher per MWh for some SMR designs due to higher enrichment + lower burnup). Dry-cask storage on-site is the universal interim solution. The US still has no permanent geological repository — Yucca Mountain Nevada was cancelled politically in 2010 despite $15B+ sunk; consent-based siting reset 2017+; interim consolidated storage proposed at Andrews TX (Waste Control Specialists / Holtec) and Carlsbad NM (Holtec / private), both contested in court 2024.

Fast reactors (Natrium, Aurora) and MSRs offer the possibility of fissioning long-lived actinides in-core, dramatically reducing the radiotoxicity timescale of final waste from hundreds of thousands of years to hundreds of years. This is a major technology argument for the fast-spectrum SMR programs.

10. International scene

Russia

  • Akademik Lomonosov: barge-mounted twin KLT-40S reactors (2 × 35 MWe), operating commercially Pevek (Russian Far East) since December 2019 — the world’s first floating nuclear power plant. Demonstrates marine-deployable SMR concept.
  • RITM-200: 50 MWe pressurized water reactor variant; deployment in Russian nuclear icebreaker fleet (Project 22220 Arktika-class icebreakers — 5 in service or under construction); land-based variant proposed for remote Siberian sites and export.
  • VVER-TOI / VVER-1000 / VVER-1200: Russian large reactor exports (Akkuyu Turkey, El Dabaa Egypt, Paks II Hungary, Rooppur Bangladesh, Kudankulam India); active and growing export pipeline overlaid with significant geopolitical risk.

China

  • HTR-PM Shidaowan: twin 250 MW thermal HTGR pebble-bed reactors (each driving a single 210 MWe turbine — actually 2×250 MWt → 1 turbine architecture); grid-connected December 2021, commercial operation January 2023 — the world’s first commercial HTGR.
  • Linglong One (ACP100): 125 MWe integral PWR; Hainan island construction started 2021; first concrete poured 2021; first criticality target 2026 — the first commercial land-based onshore SMR connected to grid worldwide on completion.
  • Hualong One (HPR1000): large-reactor Gen III+; dozens under construction domestically + Pakistan (K-2, K-3 operating) + UK Bradwell B (CGN, status uncertain post-2022 geopolitical reset).
  • ACPR50 (CGN): 50 MWe SMR offshore concept; demonstration phase.

Korea

  • APR1400: large reactor; Barakah UAE (4 units in operation 2020-2024) is reference commercial export; Korea Shin Hanul 1 & 2 operating; export discussions with Czech Republic, Poland, Saudi Arabia ongoing.
  • SMART: KAERI 100 MWe integral PWR design; Saudi Arabia co-development partnership for first plant; not yet first commercial build.
  • i-SMR: 170 MWe LWR; KEPCO / KHNP / KAERI consortium; targeting 2028 standard design approval, 2030+ commercial.

Argentina

  • CAREM-25: 25 MWe integral PWR; under construction at Atucha site (intermittent construction since 2014, repeatedly delayed; status as of 2026 still pre-operation).

11. Build-out timeline for a 300 MWe SMR plant

  • Year -3 to 0: utility decision, site selection, vendor selection
  • Year 0: COL application filed (assuming vendor design already certified)
  • Year 0 to 2: site civil works, infrastructure
  • Year 0 to 2: COL review by NRC (parallel)
  • Year 2 to 4: COL issued; site works continue; module fabrication ramps at factory
  • Year 4 to 6: first module shipped to site; on-site assembly; balance-of-plant; transmission interconnect commissioning
  • Year 6 to 7: fuel load, cold + hot functional testing
  • Year 7: low-power testing; first criticality
  • Year 7 to 8: power ascension; grid synchronization; commercial operation

For multi-module plants (NuScale 6-module): module 1 entering commercial operation, modules 2-6 continuing assembly with progressive commissioning — total plant commercial operation Year 9 to 10 for a 6-pack.

12. The big picture — nuclear in 2050

IEA Net Zero Emissions Roadmap (2024 update) projects global nuclear capacity needs to double from ~400 GW (2024) to ~900 GW by 2050 to meet net-zero pathways. The 25-nation COP28 nuclear-tripling declaration (UAE Dubai, December 2023; US, France, UK, Japan, Korea, Canada, Ghana, UAE, etc.) targets tripling 2020 capacity by 2050. SMRs are projected to make up 20 to 30% of new nuclear build by 2050 (~150 to 250 GW of SMR capacity globally) on these scenarios.

Whether the industry delivers depends on:

  • SMR FOAK projects: BWRX-300 Darlington (2028) is the bellwether. If it comes in on schedule and on budget (allowing for unavoidable FOAK premium), the SMR commercial case is validated. If it slips multiple years and overruns severely, the case re-collapses to where it was after NuScale CFPP cancellation.
  • HALEU + TRISO supply chain: bottleneck for X-Energy, Kairos, Natrium, Oklo. Centrus + BWXT TRISO-X + X-Energy TRISO-X production must come online by 2027-2028 or the advanced reactor programs slip.
  • Heavy forging capacity: 20-40 vessel sets/year globally is not enough for the projected build rate. New forging capacity has 10-year lead times.
  • Skilled workforce: US nuclear-construction workforce shrank dramatically after the 1970s-1980s build pause; rebuilding takes years.
  • Public acceptance + permitting + grid interconnect: variable by region; less of an issue in tech-hyperscaler-driven projects (where industrial customer is on-board) but a continuing issue for utility-led grid-scale builds.

13. Adjacent

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