TerraPower

Table of Contents

⚠ Disclaimer: This entry may be incomplete, out of date, or inaccurate. It is AI-maintained on a best-effort basis. Do not rely on it as a sole source — verify claims independently using the sources listed below.

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 approved the permit on 2026-03-04, about three months after its own target; nuclear construction began in April 2026, and an operating license is a separate later NRC approval. In September 2026 Bechtel announced it was leaving the project after the parties could not agree on the next phase, and TerraPower plans to rebid the EPC contract. The training center at the Kemmerer site began construction in August 2025. TerraPower says construction completes in 2030 and commercial operation follows in 2031. 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: Final safety evaluation completed December 2025; construction permit approved 2026-03-04; nuclear construction commenced April 2026; a separate Part 50 operating license application is still required
Non-nuclear construction: Underway at Kemmerer site since 2022; no specific construction-progress milestone was published between June and August 2026
UK expansion (NEW): GDA application submitted October 2025; accepted by DESNZ February 2026; TerraPower UK Ltd launched and GDA Step 1 formally commenced June 16, 2026 — TerraPower’s first office outside the US, led by Dr. Ian Hudson. Regulators: ONR, Environment Agency, Natural Resources Wales
Korean supply chain and EPC (NEW):
- HD Hyundai Heavy Industries named preferred manufacturer for Natrium Reactor Enclosure System components, May 20, 2026 — extending a March 2025 strategic manufacturing supply-chain agreement. Unit counts and timelines not disclosed
- Hyundai E&C (HDEC) selected as EPC contractor under a framework agreement covering up to eight future Natrium reactors with completion, price and performance guarantees, for US and select international markets — August 14, 2026
- SK Innovation term sheet to develop Korea’s first commercial Natrium plant, plus digital-twin and AI O&M collaboration — August 14, 2026
Meta agreement: January 9, 2026 — up to eight Natrium units, up to 2.8 GW (4 GW with storage); first two units could come online in 2032 and the full order by 2035; dollar value and first site not disclosed (GeekWire)
TerraPower Isotopes: expanded collaboration with PanTera for Ac-225 production at IRE in Belgium (Aug 2026)
Training center: Kemmerer Training Center construction commenced August 2025 (30,000 sqft)
Schedule: construction completion 2030; commercial operation 2031 (TerraPower statement via POWER Engineering, September 2026)
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 is exiting; TerraPower will rebid the EPC contract for the next phase and has named no successor. Hyundai E&C holds a framework EPC agreement for up to eight future reactors but has not been named for Kemmerer Unit 1

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

2026-09-24: Bechtel exits the Natrium project in Wyoming after the companies could not agree on the next phase; Bechtel stays to finish the sodium test and fill facility and help transition; a Virginia WARN notice covers about 200 jobs from around 2026-11-16; TerraPower says Unit 1 remains on track. (POWER Engineering)
2026-08-14: Following meetings between Bill Gates, CEO Chris Levesque and Korean leaders in Seoul — Hyundai E&C selected as EPC contractor under a framework covering up to eight future Natrium reactors with completion, price and performance guarantees; SK Innovation term sheet to develop Korea’s first commercial Natrium plant. (TerraPower; ANS)
2026-06-16: TerraPower UK Ltd launched — the company’s first office outside the US — and GDA Step 1 formally commences for Natrium with ONR, the Environment Agency and Natural Resources Wales. Head of TerraPower UK: Dr. Ian Hudson. (TerraPower; WNN)
2026-05-20: HD Hyundai Heavy Industries named preferred manufacturer for Natrium Reactor Enclosure System components. (TerraPower; WNN)
2026-03-04: NRC approves the Kemmerer Unit 1 construction permit, about three months past its end-of-2025 target. (ANS)
2026-04: Nuclear construction commences at Kemmerer Unit 1 following NRC construction permit issuance; the plan calls for about 1,600 construction workers and about 250 permanent staff (GeekWire) — the first utility-scale advanced nuclear plant under construction in the US. (ANS; DOE)
2026-02: UK DESNZ accepts the Natrium generic design assessment application (submitted October 2025).
2026-01-09: Meta agreement — up to eight Natrium units and up to 2.8 GW; first two targeted for 2032. (GeekWire) (Utility Dive)
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)
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: 2026-10-26

Supply Chain Position

Layer	Detail
Fuel	Metallic sodium-bonded U-Zr alloy; not HALEU; fabricated by TerraPower’s fuel development partner (specific supplier not named publicly for metallic fuel)
Sodium coolant	Industrial liquid sodium; produced by multiple suppliers; not a constraint
Molten salt storage	Nitrate salt (solar salt — KNO₃/NaNO₃ blend); commodity; multiple suppliers
Reactor vessel / sodium system	Specialized sodium-compatible stainless steel and other alloys; limited fabricators with sodium system experience
EPC contractor	Bechtel exiting (announced 2026-09-24); EPC for next phase to be rebid; Hyundai E&C framework for up to eight future reactors
Turbine-generator	GE Vernova (steam turbine for conventional Rankine cycle at higher temperature)
Power offtake	PacifiCorp (Rocky Mountain Power utility subsidiary of Berkshire Hathaway Energy) — long-term power purchase agreement

⚑ 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. This is the key execution risk vs. LWR-based designs, and the September 2026 Bechtel exit adds a contractor-transition risk to it.

⚑ 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 March 2026; TerraPower says construction completes 2030 and commercial operation is 2031

Supporting: NRC construction permit approved; nuclear construction under way; DOE ARDP provides funding backstop; TerraPower reaffirmed the schedule after Bechtel announced its exit

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 permit milestone makes the schedule possible, and a mid-project EPC change raises the risk of slippage.

The Infinite Unknown