Overview
TerraPower, backed by Bill Gates and founded by John Deutch, is developing the Natrium sodium-cooled fast reactor specifically for industrial and data center power. The key differentiator is integrated molten-salt thermal energy storage—the reactor can dispatch 500+ MW of power for 5+ hours by drawing down heat stored in a molten-salt tank, enabling true load-following without separate battery infrastructure.
| Attribute | Value |
|---|---|
| Technology | Sodium-cooled fast reactor (SFR) |
| Fuel | Low-enriched uranium (LEU) metallic fuel |
| Baseload Capacity | 345 MWe |
| Peak Output (with storage) | 500+ MWe for 5+ hours |
| Thermal Storage | Molten salt (enables load-following) |
| Status | Pre-construction (site prep Wyoming) |
| First Online Target | ~2030 (Kemmerer, Wyoming) |
| Data Center Partnerships | Meta (8 units, 2.76 GW); Sabey Data Centers (MOU) |
Technology: Natrium Reactor + Storage System
Core Reactor Design
The Natrium reactor operates at 545°C in a pool-type configuration with sodium coolant circulating through the core and three independent cooling loops—a design inherited from Integral Fast Reactor (IFR) research and validated across decades of sodium-cooled reactor operation (EBR-II, FFTF, Monju).
Key design features:
- Passive safety: No active cooling required; if all power is lost, natural circulation and thermal conduction safely cool the core
- Compact footprint: Pool design limits external footprint; can be sited on industrial campuses or within large data center sites
- Fuel efficiency: Fast spectrum breeding allows multi-cycle operation on depleted uranium or LEU stockpiles
- Metallurgical fuel: Metallic U-Zr fuel (vs. oxide pellets in light-water reactors); higher density, higher burnup capability
Thermal Energy Storage Integration
The distinguishing feature of Natrium is integrated molten-salt thermal storage. At steady state:
- Reactor operates at 345 MWe baseload output
- Excess heat is directed into a molten-salt storage tank (liquid salt maintained at ~500°C)
- When data center demand spikes, the salt discharges its heat to a steam generator, boosting turbine output to 500+ MW for 5+ hours without reactor power increase
Storage capacity: Approximately 1 GWh thermal energy, enabling realistic data center load-following without external battery hardware.
Advantage over SMRs without storage:
- Oklo Aurora (75 MW) and Kairos Hermes (50 MW) cannot follow variable data center loads; they run flat baseload
- Natrium with storage is truly flexible—can match 24/7 varying compute demand without grid backup
- Eliminates need for 500+ MWh battery systems (cost: $100–300M for equivalent storage)
Data Center Partnerships
Meta: 8-Unit Natrium Fleet (2.76 GW)
Signed: Binding agreement (spring 2025) Capacity: 8 × 345 MW = 2.76 GW baseload + storage-enabled flexibility Locations: Specific Meta data center sites TBD (likely Wyoming + additional locations) Timeline: First unit (Kemmerer) ~2030; subsequent units phased through 2035
Significance:
- Largest SMR data center order to date (by GWh)
- Meta’s diversification strategy: balances Oklo (15 GW LOI), TerraPower (2.76 GW binding), geothermal (Sage, 150 MW), and solar
- Storage feature aligns with Meta’s variable load profile (model training batches + inference peaks)
Sabey Data Centers: Multi-Site MOU
Announced: 2025 Type: Memorandum of Understanding (nonbinding framework) Target: Wide-scale deployment at Sabey facilities nationwide Status: Early-stage; specific site selection and commitment timelines TBD
Context:
- Sabey is a mid-tier colocation/hyperscale data center provider (not Meta/Google/Amazon scale)
- MOU suggests TerraPower exploring sub-hyperscaler customer segment for Natrium units
- Sabey partnership may focus on 1–2 unit deployments at regional data center clusters
First Deployment: Wyoming Kemmerer Site
Site & Regulatory Status
Location: Kemmerer, Wyoming (Sweetwater County) — formerly a coal plant site Site Preparation: Underway (site survey, environmental baseline, infrastructure planning) Expected Permit Status: Construction permit application expected 2026; NRC review 24–36 months nominal Target First Power: ~2030
Advantages of Wyoming:
- Permissive regulatory environment (no state-level SMR size limits or restrictions)
- Industrial precedent (coal generation → power plant workforce transition narrative)
- Proximity to Meta hyperscale demand centers
- Adequate water supply for cooling (Kemmerer site has industrial water access)
Construction & Manufacturing
TerraPower partners with:
- BWXT (Babcock & Wilcox): Reactor vessel fabrication, ASME N stamped components
- Kiewit Corporation: Heavy civil construction (concrete, structural steel, site infrastructure)
- Burnham Industrial: Molten-salt storage tank fabrication and installation
Lead time expectations:
- Permit-to-first-pour: 12–18 months post-license
- First-of-a-kind construction: 36–48 months (Kemmerer likely on higher end due to prototype complexities)
- Subsequent units (units 2–8): 24–36 months per unit (learning curve, pre-fabrication maturity)
Technology Advantages for Data Centers
Load-Following Without External Storage
Unlike Oklo or Kairos (which run constant baseload), Natrium’s integrated storage enables:
- Matched load response: If data center demand drops 30%, reactor can divert heat to storage rather than curtailing power
- Demand peaks: Molten-salt discharge can boost output 45% above baseload for 5+ hours (e.g., training run, model deployment surge)
- Cost savings: No separate 500 MWh battery pack ($100–300M capex) needed for daily load-following
Fuel Supply Advantage
Natrium uses low-enriched uranium (LEU) metallic fuel, not HALEU:
- LEU enrichment (<20% U-235) widely available; no supply bottleneck
- Competing with Oklo (HALEU-dependent), Kairos (TRISO/HALEU-dependent), X-energy (TRISO-dependent)
- TerraPower’s fuel pathway more resilient to supply constraints
Caveat: No commercial metallic-fuel processing in the U.S. yet; terawatt would need pilot-scale fab (currently BWXT can support ~4 GW/year capacity if funded). This is a soft constraint, not a binding limitation like HALEU enrichment.
Competitive Position
vs. Oklo Aurora (75 MW, nonbinding LOIs)
| Factor | TerraPower Natrium | Oklo Aurora |
|---|---|---|
| Capacity | 345 MW + storage | 75 MW baseload only |
| Load-following | Yes (integrated storage) | No (constant output) |
| Fuel supply risk | Low (LEU available) | High (HALEU bottleneck) |
| Data center contracts | 2.76 GW binding (Meta) | 15 GW LOI (~90% nonbinding) |
| First deployment | 2030 (Kemmerer) | 2027–2028 (INL, demo phase) |
vs. Kairos Hermes (50 MW, molten-salt cooled)
| Factor | TerraPower Natrium | Kairos Hermes |
|---|---|---|
| Fuel | LEU metallic | TRISO (HALEU in some contexts) |
| Cooling | Sodium + molten-salt storage | Molten-salt direct coolant |
| Temperature | 545°C | 700+°C (higher efficiency potential) |
| Load flexibility | Integrated thermal storage | None (constant output) |
| Data center contracts | 2.76 GW (Meta, 8 units) | 500 MW (Google, 6–7 units) |
Advantage: TerraPower’s storage + LEU fuel is more flexible and supply-resilient. Disadvantage: Later first deployment (~2030 vs. Kairos 2030).
Regulatory & Permitting Status
NRC Licensing
TerraPower’s Natrium design is undergoing pre-application phase reviews with NRC:
- Design Certification Application (DCA): Expected to be filed 2026–2027 (ahead of specific project COLAs)
- Kemmerer Combined License Application (COLA): Expected 2027–2028
- NRC review timeline: 18–24 months nominal; first-of-a-kind designs often slip to 24–36 months
- Operating License: Earliest issuance ~2029; construction then 36–48 months → first power ~2030–2031
Wyoming State Regulatory
- Air Quality: No major expected opposition; Wyoming Office of Air Quality (air regulator) is pro-business
- Water permits: Adequate industrial water available at Kemmerer site; no expected conflict
- Decommissioning / Financial Assurance: Wyoming requires standard financial assurance for reactor decommissioning; TerraPower is securing DOE backing and commercial financing
Financial & Supply Chain
Capex Estimates
| Component | Estimate (2026$) |
|---|---|
| Reactor vessel + core internals | $200–300M |
| Molten-salt storage system | $100–150M |
| Steam turbine + generator | $80–120M |
| Site, BOP, engineering | $300–500M |
| Contingency (first-of-a-kind) | +30–50% |
| Total capex (unit 1, Kemmerer) | ~$1.0–1.5B |
| Subsequent units (learning curve) | ~$0.8–1.2B |
**$/MW:** ~$2.9–4.3M/MW all-in capex (Kemmerer); ~$2.3–3.5M/MW (units 2–8, learning curve).
Financing
- Bill Gates (TerraPower founder/investor): Committed $1B+ via Breakthrough Energy Ventures
- U.S. DOE: Path to federal loan guarantee or direct investment (advanced reactor program)
- Meta partnership: Potential direct investment or structured PPA financing
- Private equity: Discussions ongoing with infrastructure funds
Supply Chain Partnerships
| Component | Supplier | Lead Time | Risk |
|---|---|---|---|
| Reactor vessel (ASME N) | BWXT | 24–30 months | Medium (first-of-a-kind) |
| Molten-salt storage tank | Burnham Industrial / ITM | 18–24 months | Medium (specialty fabrication) |
| Metallic fuel manufacturing | TBD (BWXT capable) | 12–18 months | Medium (scale-up needed) |
| Turbine/generator | GE or Siemens | 18–24 months | Low (standard LWR heritage) |
| Cooling loops, piping, controls | Multiple (Sensormatic, Emerson, etc.) | 12–18 months | Low (industrial sourcing) |
Key constraint: Metallic-fuel fabrication is not yet commercial in the U.S. BWXT is the leading candidate but would require pilot-scale production facility startup (2026–2027). This is a soft constraint (solvable with capex + time), not a binding supply bottleneck like HALEU enrichment.
Risks & Challenges
⚠️ First-of-a-Kind Construction Complexity
Natrium has never been built at commercial scale:
- Molten-salt storage system: Proven in academic + pilot settings; no full commercial deployment as primary BTM storage
- Sodium reactor construction: Proven design lineage (EBR-II, FFTF), but U.S. regulatory environment for new sodium reactors is untested at commercial scale
- Likelihood: Kemmerer unit 1 is likely 10–30% more expensive and 12–24 months behind schedule relative to plan
Metallic Fuel Supply Ramp
Natrium uses metallic U-Zr fuel, which offers:
- ✅ Higher density than oxide (more burnup per batch)
- ✅ No HALEU enrichment bottleneck
- ⚠️ Manufacturing not yet operational in U.S.; BWXT capable but unfunded
Status: TerraPower is working with DOE on pilot-scale fuel fab funding (expected decisions 2026–2027). If funded, production facility operational by 2028; if delayed, first units may source from foreign facilities (Russia, France, UK have limited capacity) → potential 12–18 month supply delay.
Regulatory Uncertainty
- Molten-salt systems in nuclear plants: NRC has limited precedent for integrated thermal energy storage in reactor designs; review could uncover new safety questions → schedule slippage
- Decommissioning of molten-salt equipment: No established decommissioning precedent for large molten-salt systems; NRC may impose costly monitoring / long-term stewardship requirements
Market Execution Risk
- Meta commitment: 8 units is a binding order, but contract likely includes “development milestones” gates. If Kemmerer unit 1 experiences major cost overruns or schedule delays >24 months, Meta may renegotiate or withdraw
- Sabey MOU: Nonbinding; heavily dependent on Kemmerer success and cost trajectory
2026–2030 Milestones
| Date | Milestone | Probability | Impact |
|---|---|---|---|
| Q2–Q4 2026 | Design Certification Application filing (NRC) | High | Clears regulatory pathway for any COLA |
| 2027 | Kemmerer COLA filed; construction prep begins | High | Site ready for first concrete |
| 2027–2028 | Metallic fuel fab pilot phase funded (DOE decision) | Medium | Resolves fuel supply path for units 2+ |
| Late 2028 | First concrete pour (Kemmerer) | Medium | ~18-month construction phase begins |
| 2029 | Fuel loading (first core assembly) | Medium | Final NRC operating license imminent |
| ~2030 | Critical and first power (Kemmerer unit 1) | Medium–Low | Demonstrates Natrium commercial viability |
| 2031–2032 | Meta unit 2 online (site TBD) | Low–Medium | Parallel construction begins |
| 2033–2035 | Meta units 3–8 online (phased) | Low | If schedule holds and costs acceptable |
Outlook: Why Natrium Matters for Data Centers
Natrium’s integrated molten-salt storage is a genuine competitive advantage over constant-baseload SMRs (Oklo, Kairos, X-energy). Data center power demands are not flat—they vary 2–5x between idle and peak model-training loads. Most SMR developers are ignoring this; Natrium is solving for it.
If Kemmerer unit 1 succeeds (on-time, on-budget), Natrium could capture 5–10% of SMR data center market by 2035. If Kemmerer faces major cost overruns or delays, Meta’s 8-unit commitment likely dissolves or shrinks to 2–3 units; Natrium becomes niche player.
Supply chain and fuel: Advantage over Oklo/Kairos (no HALEU bottleneck), but dependent on metallic-fuel fab capitalization in 2026–2027.
Competitive pressure: Watch for Kairos molten-salt cooled design to offer storage options (different approach from Natrium’s separate storage tank). If Kairos adds storage, it could erode Natrium’s differentiation.
Key watch: Kemmerer site prep and COLA timeline 2026–2027 will determine whether 2030 first-power target is realistic or slips to 2032+.
Key People
Bill Gates — Co-Founder, Principal Investor
- Co-founded TerraPower in 2006 alongside John Deutch; primary private backer
- LinkedIn: public profile available
- Background: Microsoft co-founder; global health/energy philanthropist via Bill & Melinda Gates Foundation; nuclear energy advocate
Chris Levesque — President & CEO
- LinkedIn: TODO: verify slug — note this is the same name as Kairos CEO; these are different people. TODO: find TerraPower’s Chris Levesque LinkedIn.
- Prior: TerraPower COO (pre-CEO); deep advanced reactor operations experience. ⚑ Overlap: TerraPower and Kairos Power are often discussed together in data center nuclear context; the coincidence of the name “Chris Levesque” at both companies requires verification — confirm these are distinct individuals.
People — Last Reviewed: 2026-04-25
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- /research/datacenters/behind-meter-power/kairos-power-btm/ — Kairos Hermes (50 MW molten-salt cooled SMR, Google partnership)
- /research/energy/nuclear/x-energy/ — X-energy Xe-100 (80 MW HTGR, Amazon partnership)
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