Part3 — The Global SMR Race

There are over 80 SMR designs in development across 18+ countries. Some are genuinely promising. Most are years from deployment. And one — TerraPower’s Natrium reactor in Kemmerer, Wyoming — just became the first commercial non-light-water reactor to receive a U.S. construction permit in more than 40 years. That’s the headline. Let me explain why it matters.

The U.S. and Global SMR Landscape

[ Fig. 4 — The US and Global SMR Landscape ]

The NuScale cancellation in November 2023 deserves a moment of honest reflection. NuScale achieved something genuinely historic — the first SMR to receive full NRC design certification in U.S. history. And then their flagship project in Idaho collapsed because costs had risen from $58/MWh to over $89/MWh, making the power uncompetitive. Regulatory certification does not equal commercial viability. This lesson hangs over every advanced nuclear developer.

The March 2026 milestone for TerraPower is different in character. NRC completed its safety review of Kemmerer Unit 1 in just 18 months — ahead of the 27-month schedule and 11% under budget. This is the first time in more than 40 years the NRC approved a commercial non-light-water reactor for construction. The permit signals not just TerraPower’s progress but the NRC’s growing capability to review genuinely novel reactor designs efficiently.

TerraPower: The Origin and the Mission

In 2006, Bill Gates attended a presentation by physicist Lowell Wood on the Traveling Wave Reactor — a concept for a reactor that could run on depleted uranium (the low-grade ‘waste’ from conventional enrichment plants) for decades without refueling. The idea: make the waste of one reactor the fuel of another.

Gates co-founded TerraPower with a focused mission: design a nuclear reactor that is safe, affordable, runs on abundant fuel, and can scale globally — including in countries with limited uranium enrichment infrastructure. The original Traveling Wave Reactor concept proved too technically challenging at commercial scale. TerraPower pivoted to the Natrium — a more immediately buildable design that preserves the most important innovations.

“TerraPower’s founding insight: the world has enormous stockpiles of depleted uranium sitting in storage as waste. What if that waste could be the fuel of the next generation of reactors?”

The Natrium Reactor — Why It’s Different From Every Other SMR

[ Fig.5 — Natrium System Architecture ]

Natrium is a 345 MWe sodium-cooled fast reactor (SFR) integrated with a molten salt thermal energy storage system (TEGS). That integration is what makes it unique. Every other SMR design separates the nuclear reactor from the grid in a conventional way — heat makes steam, steam makes electricity, done. Natrium decouples electricity generation from reactor output, creating a system that can behave like a flexible, dispatchable power plant while the nuclear core runs at constant, efficient full power.

The Nuclear Island

The reactor core is cooled by liquid sodium at approximately 510°C. Unlike water-cooled reactors that must be pressurized to stay liquid, sodium remains liquid at these temperatures at normal atmospheric pressure. The pool-type vessel design submerges the entire primary circuit — reactor core, pumps, and intermediate heat exchangers — in a single large sodium pool. There are no penetrations in the reactor vessel below the top lid, which physically eliminates the possibility of a loss-of-coolant accident from below.

The Energy Island — Separated and Decoupled

The non-nuclear portion of the plant — the thermal storage tanks, the turbines, the generators — is physically separated from the nuclear island in its own building. This decoupling is architecturally and commercially significant: the energy island does not require nuclear-grade construction standards or NRC oversight, which dramatically reduces its cost and construction timeline. TerraPower calls this the ‘nuclear island / energy island’ design philosophy.

✓ The Commercial Insight Behind Decoupling

By separating nuclear and non-nuclear systems, TerraPower enables the energy island to be built using commercial power plant construction standards — faster, cheaper, and without NRC involvement. The nuclear island can be licensed, the energy island can be built simultaneously on conventional timelines. This parallel construction approach is a genuine cost innovation.

The Kemmerer Project — America’s Most Important Energy Construction Site

TerraPower broke ground on non-nuclear construction in Kemmerer, Wyoming in June 2024. The site is adjacent to a retiring coal plant — a deliberate choice that leverages existing grid infrastructure, skilled energy workforce, and community buy-in from a town whose economic identity had been built on fossil fuel employment.

The U.S. Department of Energy committed $2 billion through the Advanced Reactor Demonstration Program (ARDP) — a 50/50 cost share, meaning TerraPower and its partners are matching the DOE dollar for dollar. In January 2025, Meta announced an agreement to support deployment of up to eight future Natrium reactors, adding another major corporate partner to the project’s backing.

Nuclear island construction is expected to begin in 2026 with commercial operation targeted in 2030. If that timeline holds, Natrium will be the first commercial reactor completed in Wyoming and the first commercial-scale advanced non-LWR nuclear plant in the United States.

In Part 4 — the technical heart of this series — I go deep on what makes Natrium’s engineering so interesting: the CSP-derived storage technology, the natural air draft cooling system, the reduced exclusion zone, and the case for Natrium as a distributed energy resource.