Traveling Wave Reactor Technology

Creating scalable clean energy

TerraPower was founded to address the urgent need for scalable clean energy around the world.

The company's flagship advanced nuclear reactor concept, the Traveling Wave Reactor (TWR®) design, represents incredible progress in nuclear technology thanks to the power of advanced computer modeling and our dedicated team of scientists and engineers.

Nuclear Engineering

To create the Traveling Wave Reactor (TWR®) design, TerraPower has put together a team that boasts unparalleled expertise in nuclear engineering, simulation and modeling, finance, and nuclear project management. They have previously developed new technologies, built nuclear power plants, and managed the financing and development of large-scale infrastructure projects. TerraPower has the talent and expertise to create advanced reactor technologies, and to bring them to market.

The TWR technology takes leaps forward in cost and safety, while drastically reducing waste and proliferation concerns. Its innovative design will operate with higher thermal efficiency, and consume uranium resources in a more efficient, cleaner, and safer manner than current nuclear technology. And of course, the energy provided by the TWR design will produce zero-carbon emissions.

Fuel assembly
Pin duct interaction machine
Traveling Wave Reactor Technology
Control and Safety Rods are suspended above the reactor core. Control rods can be mechanically inserted into the core, adjusting the rate of the fission reaction. Gravity-activated safety rods can be dropped into the core in case of an emergency, quickly stopping the reaction altogether.
The entire reactor is located below grade, which provides additional layers of safety and security.
The Reactor Vessel and Reactor Guard Vessel contain the reactor core and its components, immersed in liquid sodium. This pool-type configuration has no piping penetrations, eliminating the risk of “loss-of-coolant” accidents.
TerraPower’s approach to decay heat removal, the Direct Reactor Auxiliary Cooling System (DRACS), removes heat if the normal path is unavailable.
TWR uses a Rankine steam cycle to convert heat to electricity. Intermediate Heat Exchangers securely transfer the heat from the primary sodium pool to a secondary sodium loop, which transfers the heat to the steam generators.
The Primary Sodium Pool surrounds the reactor core. TWR leverages the natural laws of physics and the inherent advantages of sodium coolant to improve thermal performance and maintain a higher level of safety.
Periodically, to sustain the fission reaction, the In-Vessel Fuel Handling Machine shuffles the fuel, swapping expired fuel rods from the center of the core for fresh fuel rods from the outer edge.
The Reactor Core is the true innovation of TWR. In the center of the core sit a few rods of enriched uranium (U-235), surrounded by rods of depleted uranium (U-238). The U-235 serves as an initiator, kick starting the traveling wave reaction – a slow-moving chain reaction of concentric waves of fission. The traveling wave reaction will then slowly convert the depleted uranium to plutonium and consume this new fuel.


The Traveling Wave Reactor design also operates at atmospheric pressure, which removes the possibility of a pressure-related destabilizing event. It will be capable of utilizing fuel made from depleted uranium – a waste byproduct of the uranium enrichment process – allowing it to gradually convert the fuel through a nuclear reaction without removing it from the reactor’s core. This eliminates the need for reprocessing while generating heat and electricity over a much longer period of continuous operation. Additionally, eliminating reprocessing reduces proliferation concerns, lowers the overall cost of the nuclear fuel cycle, and helps to protect the environment by making use of a waste byproduct.

To date, TerraPower has achieved significant success in the development of this advanced nuclear reactor design, largely through progress made by leveraging public-private partnerships and forging a new supply chain for fuels and materials. Construction of a TWR concept engineering simulator has also been an important milestone, putting engineers in the control room of a virtual TWR system to prepare for the reactor’s operation from start-up to full power. These achievements have led to the completion of the core concept design for a TWR prototype program.

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