The Natrium Energy Island
A Nuclear Regulatory Commission has given TerraPower’s Gen IV Natrium reactor the green light to begin construction – the first approval of its kind for a reactor in the US in a decade.
Once the world leader in nuclear power, the US created many of the Generation I and Generation II reactor designs on which much of the current nuclear fleet is based.
However, as , in the 1970s, a major change occurred in American civil nuclear policy. Nuclear fuel reprocessing and fast breeder reactor programs were canceled, the environmental movement—largely hostile to nuclear power—gained influence over federal policy, and in 1979 it severely damaged public confidence in nuclear power.
As a result, the Energy Reorganization Act 1974, followed by the Kemeny Commission investigation after the Three Mile Island incident in 1979.
Control of the US civil nuclear program passed from the Atomic Energy Commission to the newly formed Nuclear Regulatory Commission (NRC)whose mandate focused primarily on safety rather than promoting the development of nuclear energy.
A combination of increasingly complex regulationslong approval times, high costs and frequent legal challenges by activist groups drastically slowed down new nuclear projects.
As a result, for decades no new reactors were built in the USA, and the last approval of an application for a new reactor occurred about ten years ago.
Now, the US government seeks to revitalize the nuclear sector with a more simplified regulatory process designed to encourage the construction of new plants while maintaining safety standards.
Paradigm shift
A good example of the paradigm shift is the Natrium Demonstration Projectin Kemmerer, Wyoming.
Participant not Advanced Reactor Demonstration Program (ARDP) of the US Department of Energy, the Construction of the plant’s non-nuclear civil engineering components has been ongoing since 2024.
With NRC approval, the work on the nuclear parts of the facility can now begin.
As a Generation IV reactor, Natrium is notable because it will be the first non-light water-cooled reactor built in the U.S. since the 1980s.
O project progressed at an unusually fast pace for North American nuclear development: the technical design review was completed in less than 18 months, the formal application was accepted in May 2024, the safety assessment was issued in December 2025, and the environmental impact statement was finalized in October.
However, as New Atlas points out, approval for construction is only part of the process. Once the reactor is completed, the operator will still need to apply for a separate operating license before the plant can begin generating power.
What will Natrium bring?
The Natrium reactor represents a significant advance in relation to conventional designs in both its concept and configuration. This is a call fast neutron reactorwhich means it does not slow down neutrons using moderators like water or graphite.
Instead, the neutrons remain at high energieswhich requires the fuel to be enriched to higher levels – up to 19.75% compared to around 5% in typical light water reactors.
A water is replaced by liquid sodium as a coolantwhich melts at about 880 °C and is transparent to neutrons. The sodium circulates around the fuel at near-atmospheric pressure, eliminating the need for the huge high-pressure containment vessels required in traditional light-water reactors.
This configuration enables higher operating temperatures and improves thermal efficiency to approximately 41%compared to around 31% in conventional reactors. It also allows for more complete burning of the fuel and potentially allows certain forms of nuclear waste to be used as fuel.
According to (responsible for construction), the project also offers safety advantages: liquid sodium can circulate naturally through the system even if energy from the pumps is lost, providing passive cooling. Furthermore, if the temperature of the reactor core increases, the fuel expands, automatically reducing the rate of the nuclear reaction.
“This is a historic step forward for advanced nuclear energy in the U.S. and reflects our commitment to providing timely, predictable decisions based on a rigorous and independent safety review,” said NRC Chairman, Ho Niehcited by New Atlas.
