TWR Technology: Preparing Nuclear Energy for Global Growth

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.

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.

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.

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 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.

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.

TerraPower’s approach to decay heat removal, the Direct Reactor Auxiliary Cooling System (DRACS), removes heat if the normal path is unavailable.

Its innovative design results in a reactor that can operate with higher thermal efficiency and consume uranium resources in a more efficient, clean and safe manner than previously possible.

Unlike traditional nuclear reactors, this technology will be capable of utilizing fuel made from depleted uranium, which is currently a waste byproduct of the uranium enrichment process. Its unique design gradually converts the fuel through a nuclear reaction without removing it from the reactor’s core, eliminating the need for reprocessing, generating heat and producing electricity over a much longer period of continuous operation. Additionally, eliminating reprocessing reduces proliferation concerns, lowers the overall cost of the nuclear energy process, and helps to protect the environment by making use of a waste byproduct and reducing the production of greenhouse gases.

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, seeking excellence in commercial partners, and forging a new supply chain for fuels and materials. This has led to the completion of the core concept design for a prototype of the TWR program.

Construction of a TWR engineering simulator is an important milestone, as it puts engineers in the control room of a virtual TWR system to study the reactor’s operation from start-up to full power. By pairing cutting-edge computing power with real-world data, TerraPower continues to improve the TWR design, analyzing it using new seismic, physics and mechanical methodologies. Together, these activities bring the design ever closer to construction of the first TWR technology.

TerraPower aims to achieve startup of its prototype TWR reactor in the mid-2020s, followed by global commercial deployment.


1958

Savelli M. Feinburg proposes the first known proposal for a fast reactor that could sustain a breed-and-burn condition using only natural or depleted uranium as fuel. In his design, unenriched fuel moves around the core to sustain fission.

1958

1979

Brookhaven National Laboratory with Michael J. Driscoll and others at MIT further evaluate breed-burn reactor ideas, exploring the Fast-Mixed Spectrum Reactor (FMSR) concept. This approach pairs a fast reactor core with conventional assemblies and fuel shuffling.

1979

1995

Edward Teller proposes a gas-cooled thorium breed-and-burn reactor. He and others at Lawrence Livermore National Laboratory detail ways to make breed-burn waves travel through a stationary fuel supply.

1995

1997

Georgy Toshinsky develops the concept of a liquid metal fast breeder reactor. His design is similar to the FSMR concept, but lead-cooled.

1997

2000

Hugo van Dam publishes mathematical analyses of waves of fission moving through nuclear fuels.

2000

2001

Hiroshi Sekimoto popularizes breed-burn concepts with the CANDLE (Constant Axial shape of Neutron flux, nuclide number densities and power shape During Life of Energy producing reactor). His CANDLE concept incorporates lead coolant.

2001

2005

Peter Yarsky studies gas-cooled breed-burn fast reactor core concepts.

2005

2006

Intellectual Ventures gathers an invention session to find a solution to global energy issues, decides on the TWR program as the path forward.

2006

2008

TerraPower becomes a private company and begins developing the first practical engineering embodiment of the TWR.

2008