The Infinite Unknown

Summary

TerraPower is a Bellevue, Washington nuclear technology company founded in 2008 by Bill Gates and Nathan Myhrvold. Its Natrium reactor is a 345 MW sodium-cooled fast reactor coupled with a 500 MWh molten salt thermal storage system — enabling the facility to dispatch up to 500 MW for short periods to meet peak demand, or hold output steady at 345 MW for baseload. The NRC completed its final safety evaluation for the Kemmerer, Wyoming construction permit in December 2025 and issued the construction permit; non-nuclear site construction is already underway. The training center at the Kemmerer site began construction in August 2025. Commercial operation is targeted for 2030. If it reaches commercial operation on schedule, Kemmerer Unit 1 will be the first utility-scale advanced nuclear power plant in the United States — a major milestone for the entire sector.

Key Facts

• Founded: 2008
• HQ: Bellevue, WA
• Type: Private
• Key backers: Bill Gates (co-founder, primary funder); Berkshire Hathaway Energy; DOE Advanced Reactor Demonstration Program (ARDP) — $2B award (50/50 cost share with TerraPower)
• Reactor design: Natrium — sodium-cooled fast reactor (SFR) with integrated molten salt thermal energy storage
• Reactor output: 345 MW electric (baseload); up to 500 MW during peak discharge from thermal storage
• Thermal storage: 500 MWh molten salt tank — stores heat during low-demand periods; dispatches extra power during peak demand (4–5.5 hours at 500 MW)
• Coolant: Liquid sodium metal; operates at low pressure and ~500°C
• Site: Kemmerer Power Station Unit 1, Kemmerer, Wyoming (adjacent to retiring Naughton coal plant — reuses transmission and workforce)
• NRC status: Construction permit issued (late 2025); NRC final safety evaluation completed December 2025 ahead of accelerated schedule
• Non-nuclear construction: Underway at Kemmerer site
• Training center: Kemmerer Training Center construction commenced August 2025 (30,000 sqft)
• Commercial operation target: 2030
• Construction workforce peak: ~1,600 workers
• Fuel type: Metallic sodium-bonded uranium-zirconium alloy fuel; not TRISO; not HALEU (uses low-enriched uranium)
• EPC contractor: Bechtel (teamed with TerraPower for Natrium plant)

What It Is / How It Works

Sodium fast reactor (SFR) fundamentals: The Natrium reactor uses liquid sodium metal as the primary coolant instead of water. Sodium has excellent heat transfer properties and boils at 883°C (far above the reactor’s ~500°C operating temperature), so the primary coolant loop operates at near-atmospheric pressure — eliminating the high-pressure loss-of-coolant accident risk of LWRs. Sodium also doesn’t slow down (moderate) neutrons, so Natrium operates as a “fast” reactor — neutrons remain at high energy, enabling more efficient fuel use and the ability to “breed” additional fuel or transmute long-lived nuclear waste.

The molten salt storage integration: This is Natrium’s key commercial differentiator. Conventional nuclear plants are poor at load-following — they run best at constant full power. The Natrium design diverts a portion of the sodium coolant heat to charge a large tank of molten nitrate salt (the same technology used in concentrated solar plants for thermal storage). The salt stores heat at ~550°C. When the grid needs extra power — during peak demand when electricity prices are highest — the stored heat is discharged through a steam generator to produce additional electricity. This allows Natrium to: (1) produce constant 345 MW of nuclear heat 24/7, (2) sell 500 MW during peak hours when prices are highest, (3) sell as little as ~100 MW during off-peak hours while charging storage, and (4) arbitrage wholesale electricity prices in a way no other baseload generator can. For Wyoming (a Western Energy Imbalance Market participant), this dispatchability is highly valuable.

Kemmerer coal plant synergy: The Natrium plant is sited adjacent to PacifiCorp’s retiring Naughton coal plant. This enables reuse of: existing high-voltage transmission interconnect (avoiding years of new interconnect queue delays), cooling water infrastructure, some buildings, and critically — the existing workforce community in a coal-dependent area. The “coal-to-nuclear” workforce transition is both economically and politically significant for Wyoming.

The HALEU non-dependency: Unlike most Gen IV designs, Natrium uses standard low-enriched uranium (LEU) metallic fuel — not HALEU. This avoids the HALEU supply chain constraint that affects Oklo, X-energy, and others. TerraPower’s fuel is manufactured through established fuel fabrication pathways.

Notable Developments

• 2025-12: NRC completes final safety evaluation for Kemmerer Unit 1 construction permit — ahead of accelerated schedule; no safety issues identified precluding construction permit. (Wyoming Public Media; World Nuclear News)
• Late 2025: NRC issues construction permit for Kemmerer Power Station Unit 1. (ConstructConnect)
• 2025-08: Groundbreaking on Kemmerer Training Center (KTC) — 30,000 sqft operator training facility at the Kemmerer site. (TerraPower)
• 2025 (ongoing): Non-nuclear site construction underway at Kemmerer.
• 2023: TerraPower awarded pivotal state permit for Natrium plant by Wyoming.
• 2022: DOE ARDP $2B cost-share award announced; construction begins at Wyoming site on non-nuclear elements.
• 2021: Kemmerer, WY announced as site for first Natrium plant.
• 2015: TerraPower and China National Nuclear Corporation (CNNC) begin collaborative work on traveling wave reactor (predecessor concept); collaboration suspended 2019 due to US export control restrictions.
• 2008: Founded by Bill Gates and Nathan Myhrvold.

Key People

Bill Gates — Co-Founder and Chairman

• LinkedIn: Public figure; no profile needed
• Role: Co-founder and primary financial backer; provides strategic direction and high-profile advocacy for advanced nuclear
• Background: Microsoft co-founder; has written extensively about the need for advanced nuclear as part of climate solution (see How to Avoid a Climate Disaster, 2021)
• Notes: Gates’s involvement gives TerraPower unique access to DOE relationships, capital, and public credibility — but also creates a profile that attracts scrutiny of every milestone

Chris Levesque — President and CEO

• LinkedIn: Search “Chris Levesque TerraPower”
• Role: President and CEO; operational leader
• Background: Nuclear industry executive; joined TerraPower to lead commercialization; manages DOE ARDP relationship and NRC licensing

People — Last Reviewed: 2026-03-25

Supply Chain Position

⚑ Sodium system fabrication expertise: Sodium-cooled fast reactors have a limited operational history in the US (EBR-II at INL; FFTF at Hanford, both decommissioned). Sodium is reactive with water and air — requiring specialized handling systems, inert gas cover gas, and sodium-compatible materials. The number of qualified fabricators and construction firms with sodium system experience is small. Bechtel has nuclear construction experience but limited sodium fast reactor specific experience. This is the key execution risk vs. LWR-based designs.

⚑ DOE cost-share dependency: The $2B DOE ARDP award is a 50/50 cost share — TerraPower must match DOE dollar-for-dollar. Total project cost estimates for Kemmerer Unit 1 are in the $4–6B range. If construction costs escalate above the matched amount, TerraPower must find additional private capital. Berkshire Hathaway Energy (PacifiCorp parent) is also a project participant and likely backstop.

Claim Verification

Claim: Natrium can deliver up to 500 MW during peak demand from a 345 MW reactor

Status: Engineering design verified; thermal storage dispatch capability is proven technology (molten salt storage is commercial at concentrated solar plants); integration with fast reactor cooling is novel but physically sound

Supporting:

• Molten nitrate salt thermal storage is commercially deployed at multiple CSP plants (e.g., Crescent Dunes, Noor III); the physics are well understood
• The 500 MWh storage buffer with a 155 MW discharge increment above baseload for 4–5.5 hours is consistent with the energy balance
• Idaho National Laboratory (INL) is TerraPower’s technical partner and has validated aspects of the thermal integration design

Refuting / questioning:

• Integration of sodium-to-salt heat exchange in a nuclear environment is novel; the specific thermal interface between the secondary sodium loop and the molten salt has not been built at commercial scale
• The dispatchability value depends on electricity market conditions in Wyoming; if wholesale prices flatten (due to renewable overbuild), the storage premium narrows

Summary: The 500 MW peak dispatch claim is physically credible and the storage technology is proven in adjacent applications. The integrated sodium-to-salt-to-steam system is novel at commercial scale; Kemmerer Unit 1 will validate it.

Claim: Commercial operation by 2030

Status: Targeted; NRC construction permit received; on track as of Q1 2026

Supporting: NRC construction permit issued; non-nuclear construction already underway; Bechtel is a credible EPC; DOE ARDP provides funding backstop

Refuting / questioning: Five-year construction for a first-of-a-kind advanced reactor is very tight; Vogtle Units 3 & 4 (LWR, proven technology) took 9 years; even optimistic SMR/advanced reactor timelines have historically slipped

Summary: 2030 is achievable if construction proceeds without major issues; 2032–2033 is the more conservative realistic expectation for a first-of-kind. The NRC permit milestone makes 2030 at least possible.

Sources

• TerraPower — terrapower.com
• NRC Issues Construction Permit for Kemmerer — ConstructConnect
• NRC Final Safety Evaluation Completed — Wyoming Public Media (Dec 2025)
• NRC Final Safety Evaluation — World Nuclear News
• TerraPower Begins Construction in Wyoming — TerraPower
• Training Center Construction Begins — TerraPower
• NRC TerraPower Applicant Page