Traveling Wave Reactor Technology

Creating scalable clean energy

Remarkable Progress in Nuclear Technology to Create Scalable Clean Energy

TerraPower's Traveling Wave Reactor (TWR®) design remains an important, long-term goal of the Natrium™ program. A fleet of TWR plants will be able to operate for centuries with unenriched uranium fuel, needing enriched uranium to start only the first reactor in the long chain of plants. The TWR design offers 30 times more efficient use of mined uranium and a factor of five reduction in waste, all based on a once-through fuel cycle without the safety and proliferation concerns of reprocessing used fuel. With its major non-proliferation benefits, it will be an ideal technology for international deployment, as many new countries turn to emissions-free nuclear energy to meet the needs of their citizens and growing economies.

An Innovative Nuclear Technology

The TWR technology takes leaps forward in cost and safety, while dramatically reducing waste and proliferation concerns. Its innovative design will produce zero carbon emissions while operating with higher thermal efficiency and consuming uranium resources in a more efficient, cleaner and safer manner than current nuclear technology.

The reactor core is the true innovation of the TWR design. In the center of the core sit rods of enriched uranium (U-235), surrounded by rods of depleted or natural 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 fissionable plutonium. 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.

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.

Unique Design to Enhance Safety and Support Nonproliferation

The TWR design operates at atmospheric pressure and will be capable of utilizing fuel made from depleted or natural uranium, allowing it to gradually breed fissionable material through a nuclear reaction without removing it from the reactor’s core – an important non-proliferation attribute. This eliminates the need for reprocessing while generating heat and electricity over a much longer period of continuous operation. Unlike previous sodium fast reactor programs, the TWR design eliminates reprocessing, reducing proliferation concerns and lowering overall fuel cycle costs.

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