The Small Modular Reactor (SMR) competition hosted by Great British Nuclear (GBN) has reached an important phase, narrowing down the list of contenders vying for government contracts to build SMRs, a key component of the UK’s future energy strategy. As the UK aims to expand its nuclear power generation and reduce reliance on fossil fuels, SMRs have become central to filling the country’s energy shortfall, given the scheduled decommissioning of many existing reactors.

Background on the SMR Competition

In April 2023, GBN launched a competition for companies to secure funding for SMR development. The ultimate goal is to select technologies that could make a final investment decision by 2029 and be operational by the mid-2030s. The stakes are high, as the successful deployment of these reactors will ensure stable, low-carbon electricity generation, helping to meet the UK’s future energy needs.

Final Four Contenders

GE-Hitachi Nuclear Energy International LLC

GE-Hitachi BWRX-300 BWR – 300MW

GE-Hitachi are a world leader with over 60 years’ experience providing licencing, fuel, design and manufacturing of their large-scale BWR (boiler water reactor) with 67 of their BWRs licenced globally in 10 countries. Their SMR will provide 300MW of carbon-free power. Its simplified design reduces the amount of concrete and steel needed for construction, therefore reducing cost and time. They estimate an end-to-end construction timeline between 24-36 months. They have passed step 1 of their Generic Design Assessment (GDA) with the Office for Nuclear Regulation (ONR) and starting step 2 shortly.

Holtec Britain Limited

Holtec SMR-300 – 300MW

Holtec International is a global player in nuclear energy and has been advancing its SMR technology since 2011. This compact, cost-effective reactor is designed to be scalable and safe, with a particular emphasis on reducing costs and improving deployment speed. Their SMR is designed for a life span of 80 years plus, based on proven PWR design and uses similar fuel to that at Sizewell B and proposed for Hinkley Point C. In September, Holtec Britain, a wholly owned subsidiary of Holtec International (USA), announced it was investing several hundred million pounds in a new SMR manufacturing complex in South Yorkshire. In March they signed Memorandum of Understanding with Hyundai E&C, Mott McDonald and Balfour Beatty giving them design, engineering and construction expertise. Their step 1 completion of the GDA was the quickest in ONR’s history and are currently in step 2.

Rolls-Royce SMR

Rolls-Royce SMR – 470MW

Rolls-Royce’s Small Modular Reactor (SMR), also known as the UK SMR, leverages proven Pressurized Water Reactor (PWR) technology, the same type used in its submarine reactors. The SMR’s design is highly modular, with about 90% of its components manufactured in factories, which allows for significant cost reductions and faster deployment timelines. By pre-fabricating components and transporting them to the site, Rolls-Royce minimises on-site construction complexities. Additionally, all welding at the installation site will occur in a temporary enclosed environment, avoiding the risks of outdoor welding, which can be susceptible to environmental factors.

Of the SMR technologies under consideration in the UK, Rolls-Royce’s is at the most advanced stage, having completed steps 1 and 2 of the Generic Design Assessment (GDA) process, which is required for licensing nuclear reactors in the country. The company is moving forward into step 3, which involves a detailed assessment of the design.

In July 2024, the Nuclear Industry Association (NIA) applied to the UK government for a “justification decision” for the Rolls-Royce SMR. This legal decision is required for any new nuclear technology to be approved for operation in the UK. It was the first time such a justification application had been made for a UK reactor design, marking a significant step in the potential deployment of SMRs in the country.

Westinghouse Electric Company UK Ltd

Westinghouse AP300 SMR – 300MW

The Westinghouse AP300 Small Modular Reactor (SMR) is distinguished in the UK competition by being based on licensed and operating technology. It shares the same design, licensing framework, equipment, components, and passive safety systems as its larger counterpart, the 3GW AP1000. The AP1000 is the most widely deployed Pressurized Water Reactor (PWR) globally, giving the AP300 a strong foundation of proven technology and supply chain reliability.

The AP300 is also noted for its compact size and minimal operational footprint once built. Westinghouse’s Springfields site near Preston has been manufacturing nuclear fuel since 1946, reinforcing their established role in the nuclear supply chain.

The AP300 is set to begin its Generic Design Assessment (GDA) process with the UK’s Office for Nuclear Regulation (ONR). Due to the similarity between the AP300 and the AP1000, which received GDA approval in 2017, Westinghouse expects to complete steps 1 and 2 of the process quickly, leveraging the prior safety approvals and well-understood components of the AP1000. This could potentially accelerate the path to full regulatory approval and deployment of the AP300.

The De-selected

• NuScale Power was a notable company that had originally been shortlisted but was de-selected after tender submission. Though NuScale is known for its innovative SMR designs, GBN opted not to move forward with them.

• EDF withdrew its Nuward SMR from the competition, citing concerns over the maturity of the design and challenges in meeting GBN’s tight schedules. EDF is now focusing on redesigning their SMR to better align with international market demands. 

What’s next?

GBN has now invited the four remaining companies to enter the negotiation phase. These talks will focus on commercial and technical details to determine which technologies are best suited for deployment in the UK. The outcome of these negotiations will be key in deciding which company or companies will lead the UK’s nuclear revival.

The race for SMR leadership is heating up, and the UK’s decision will have long-term implications not only for its energy security but also for the global nuclear industry.

All four companies have strong cases for selection and each brings unique advantages to the table. With Rolls-Royce SMR leading in terms of maturity in the Generic Design Assessment (GDA) process, Westinghouse leveraging its proven AP1000 technology for the AP300, and the other contenders also pushing forward, the competition is tight.

The final decision by Great British Nuclear (GBN) will be highly anticipated as it will shape the future of the UK’s nuclear energy strategy. The chosen SMR technology/technologies will play a crucial role in meeting the country’s energy demands, reducing carbon emissions and ensuring energy security. The combination of modular design, proven safety systems and cost efficiencies will be central to the decision-making process and the outcome could mark a significant milestone in the adoption of SMRs globally.