Mott MacDonald supports TerraPower with Natrium reactor development

Mott MacDonald is supporting TerraPower, a nuclear innovation company, on the Generic Design Assessment of its Natrium advanced reactor. Ultimately, the project hopes to advance the UK’s net zero ambitions through innovative low carbon technologies – joining China, Russia, India and the United States in pushing ahead with sodium-cooled fast reactor designs.

A sodium-cooled fast reactor is a fast neutron reactor cooled by liquid sodium, to create energy. The use of sodium as a coolant enables high power density and low-pressure operation, and as such reactors are capable of burning up transuranic waste products in the spent fuel of light-water reactors, they can significantly reduce the quantity and lifetime of radioactive waste typically associated with nuclear power plants.

TerraPower’s Natrium reactor is a 345MW sodium-cooled fast reactor, which possesses gigawatt-scale integrated molten salt energy storage, designed for flexible zero-carbon power generation. Its Generic Design Assessment (GDA) was accepted by the Department for Energy Security and Net Zero and the Office for Nuclear Regulation earlier in 2026.

The GDA represents a critical licensing milestone for new nuclear technologies, aiming to provide confidence that the proposed design is capable of being constructed, operated and decommissioned in accordance with the standards of safety, security and environmental protection. Mott MacDonald worked with TerraPower providing guidance on the UK regulatory system and GDA process.

Moving forward

As the project moves ahead, a team from the global management, engineering and development consultancy will now serve as a delivery partner, to lead on the execution of the core GDA documentation. 

Commenting on the appointment of delivery partner, Ming Tan, global practice lead for nuclear at Mott MacDonald, said, “Supporting TerraPower to acceptance of the GDA application was a great achievement, and we now look forward to delivering. Guiding the Natrium reactor successfully through the UK GDA process will demonstrate the country’s commitment to advancing innovative low carbon technology solutions. We look forward to working closely with TerraPower to achieve this.” 

The beginning of the GDA Step 1 process marks a significant step toward potential Natrium advanced reactor deployment in the UK. According to a release from Mott MacDonald, this also “reflects the nation’s ambition to accelerate innovative, sustainable energy solutions.”

Dr. Ian Hudson, head of TerraPower UK, added, “Starting Step 1 of the GDA process is an important step forward in our efforts to deploy a Natrium plant in the United Kingdom. Entering this phase allows us to further highlight our safe, innovative and zero-carbon technology. We look forward to working with DESNZ, ONR and EA as we move through this important stage of the UK’s rigorous regulatory review.”