Six small modular reactor (SMR) designs have been selected to progress to the next stage of a UK competition that forms a key part of government ambitions for up to a quarter of the country’s electricity to come from nuclear power by 2050. The designs chosen by Great British Nuclear – the government-backed body driving nuclear projects across the UK – are those considered most able to deliver operating reactors by the mid-2030s and support the UK’s ambitions to reach 24 GW of nuclear capacity by 2050. Gwen Parry-Jones, CEO of Great British Nuclear, explained: “Our priority in this process has been to prioritise reliable and sustainable power to the grid early, and that’s why we have focused our first step on the technologies that we viewed as most likely to meet the objective of a final investment decision in 2029.”

The SMR competition is part of a plan for the UK to develop cutting-edge technologies to rapidly deliver cleaner, cheaper and more secure energy. A nuclear power revival is a central plank of that strategy and the companies through to the next stage will be invited to bid for government contracts later this year. The winning bidders are expected to be announced in spring next year and contracts are due to be awarded in the summer. Announcing the initial tranche of winning entrants, UK Energy Security Secretary Claire Coutinho said: “Small Modular Reactors will help the UK rapidly expand nuclear power and deliver cheaper, cleaner, and more secure energy.”

EDF, GE-Hitachi Nuclear Energy International LLC, Holtec Britain Limited, NuScale Power, Rolls-Royce SMR and Westinghouse Electric Company UK Limited are the companies that have been chosen for the next stage of the process. Key design details and developments are outlined below:


EDF’s NUWARDTM is a Generation III+ pressurised water reactor with an integrated primary loop producing 340 MWe from two independent reactors rated at 170 MWe each or 540 MWth. The two units will be housed in a single building and will share common equipment where possible.

According to EDF, the design is focused on standardisation, modular manufacturing and simplicity for in-factory mass production, and flexibility in the construction and operation phases. Furthermore, the design has been developed to support load following and adapted for non-electric uses. With a design availability of around 90%, the fuel cycle is two years and the service life is 60 years. The core features 76 fuel assemblies.

In March this year, EDF created the NUWARD subsidiary in line with its objective to achieve first nuclear concrete in 2030 for its reference SMR plant in France. After finalising the conceptual design, NUWARD is now shifting to the basic design phase.

The NUWARD subsidiary will continue to work with historic partners CEA, TechnicAtome, Naval Group as well as new partners Framatome and Tractebel who were onboarded last year. Tractebel will be responsible for the civil engineering preliminary studies and the evaluation of costs, for example.

Earlier this year EDF submitted the NUWARD design to France’s Autorité de Sûreté Nucléaire (ASN – Nuclear Safety Authority), marking the start of the pre-licensing process while in June 2022, EDF announced that the design would be the case study for a European early joint regulatory review led by ASN with participation from Finland’s Radiation & Nuclear Safety Authority (STUK) and the Czech State Office for Nuclear Safety (SÚJB).

Renaud Crassous, NUWARD’s President said: “We are committed to increasing the speed of execution to deliver the NUWARDTM SMR design on time to meet market expectations for first nuclear concrete as early as 2030”.

According to EDF’s SMR roadmap, the detailed design and formal application for a new nuclear facility is scheduled to be carried out between 2025 and 2030, during which time the design is expected to be certified and the supply chain developed.

The aim is to achieve first nuclear concrete for its reference plant in France in 2030, after finalising the conceptual design phase of the project. Construction is expected to take three years.

GE Hitachi

GE Hitachi’s BWRX-300 is a 300 MWe SMR generating 870 MWth that is based on a larger BWR that is already licensed and operating. The Economic Simplified Boiling Water Reactor (ESBWR) is a Generation III+ reactor certified by the US Nuclear Regulatory Commission (NRC) in 2014. The SMR version, the BWRX-300, uses natural circulation and passive cooling isolation condenser systems as well as fully passive safety systems. It’s fuel enrichment, averaging 3.81% and with a 4.95% maximum, puts it firmly in the realms of conventional commercially available fuels and it has a design refueling cycle of 12-24 months as well as a 60-year operational design life.

The construction technologies incorporated into the design adopt advanced concrete solutions and innovative techniques that have been proven in the oil and gas, tunneling and power industries. As a result of this approach and using a combination of modular and open-top construction techniques, GE Hitachi suggests the Nth-of-a-kind BWRX-300 can be constructed in as little as 24-36 months while also achieving an approximate 90% volume reduction in plant layout. In addition, reducing the building volume by about 50% per MW it should also account for around half the amount of concrete. As with other SMR designs, the BWRX-300 claims a cost-competitive approach that can be deployed for both electricity generation and industrial applications, including hydrogen production, desalination, and district heating.

An advanced reactor, GE Hitachi says the BWRX-300 sets itself apart from other SMR designs with its proven, less complicated attributes and anticipates the design will be deployable globally as early as 2029 thanks to proven know-how and innovative construction techniques. Launched in 2017, the SMR is the 10th evolution of the BWR light water reactor design from GE.

The design has achieved some notable success. This year the Tennessee Valley Authority (TVA) announced plans to explore the construction of multiple advanced nuclear reactors including proposals for a BWRX-300 at its Clinch River site, starting with a plant design and an NRC license application with a view to potentially getting an operational SMR at the site around 2032. Meanwhile, last year Canada’s Ontario Power Generation (OPG) selected the BWRX-300 for single-unit project that was initially anticipated to begin operating as early as 2028.


Holtec’s SMR-160+ small modular reactor is a PWR that uses low-enriched uranium fuel. The design, which has been in development since 2010, features a reactor core and nuclear steam supply system components that are located underground, as well as a passive cooling system that would be able to operate indefinitely after shutdown. No active components, such as pumps, are needed to run the reactor, which does not need any on-site or off-site power to shut down or dissipate decay heat. A key part of the SMR-160 roll-out as envisioned by Holtec is to deploy the reactor as a replacement for the boilers found in coal-fired power stations and reusing the majority of the existing assets. The use of multi-stage compressors that are capable of uprating SMR-160’s steam (700 psi @ 595 Deg F) to the elevated pressure and superheat needed to run the turbogenerator of a fossil power plant are a critical part of this plan. Furthermore, the ability of the SMR-160 to deliver steam at any desired pressure also opens new development opportunities, such as using high-pressure steam for industrial applications.

Having been shortlisted, the aim is to start construction of the first UK SMR-160 unit as early as 2028 and Holtec intends to deploy 32 SMR-160s in serial production by 2050 across the UK, amounting to 5.1 GW.

This year South Korean national financial institutions K-Sure (Korea Trade Insurance Corporation) and Kexim (Export-Import Bank of Korea) signed agreements with Holtec and Korea’s Hyundai Engineering & Construction to provide financial support for SMR-160 projects around the world.

Holtec has a collaboration agreement with Hyundai E&C from late 2021 that will see Hyundai perform the detailed design of the balance of plant and prepare the full plant construction specification for the SMR-160. Hyundai will also develop the integrated 3D plant model for construction. The reactor will be initially manufactured at Holtec’s Krishna P. Singh Technology Campus in Camden, New Jersey.

The SMR-160 design has completed the first phase of the Canadian Nuclear Safety Commission’s three-phase pre-licensing design review and is undergoing pre-licensing activities with the US Nuclear Regulatory Commission. Holtec has also applied for a Generic Design Assessment of the SMR-160 in the UK.

More recently, Ukraine’s nuclear generating company Energoatom signed a cooperation agreement that envisions implementation of an SMR-160 pilot project with targeted grid connection by March 2029. The deal further contemplates up to 20 additional SMR-160 units in Ukraine and a manufacturing facility.


The NuScale SMR is a PWR dubbed the NuScale Power Module. This a small PWR is designed to generate 77 MWe at 250 MWth and with be deloyed as a series of modules that can be scaled to meet specific demand up to 924 MWe. VOYGRTM SMR plants will feature four six or up to 12 power modules. It will use standard light water reactor fuel and is the only small modular reactor to receive design approval from the US Nuclear Regulatory Commission (NRC). As with other SMR designs, the NuScale Power Module was developed to supply electricity but also potentially generation, district heating, desalination, commercial-scale hydrogen production and other process heat applications. The design features passive operating and safety systems and the modules are submerged in a pool built below ground level.

NuScale SMR projects are already being considered in more than 10 countries and the first project is expected to begin operation in 2029 in Idaho. NuScale has already placed an order for the production of pressure vessel components and, in May, South Korea’s Doosan Enerbility began producing forgings for the first VOYGR-6 power plant to be built for Utah Associated Municipal Power Systems (UAMPS).

Earlier this year Polish metals company KGHM Polska MiedzKGHM received preliminary state approval for a planned SMR which followed on from a 2022 agreement with NuScale to work on deploying a VOYGR plant in Poland by 2029.

A Memorandum of Understanding was also signed this year by Romanian nuclear utility SNN, NuScale, Romanian companies E-INFRA and Nova Power & Gas, US-based Fluor Enterprises and South Korea’s Samsung C&T Corporation to collaborate on the deployment of VOYGR plants in Central and Eastern Europe. Romania aims to be the first country in Europe to deploy a VOYGR SMR and earlier this month Romania’s National Commission for the Control of Nuclear Activities approved the Licensing Basis Document for the NuScale design.

Rolls-Royce SMR

The Rolls-Royce SMR design is one of the larger reactors destined for this market as a three loop PWR with an output of 470 MWe derived from 1,358 MWth. The Rolls-Royce SMR concept is centred on innovative modularisation of reliable and proven technology, allowing maximum use of the factory environment to combine standard components with advanced manufacturing techniques. The factory-built modularisation approach is expected to drastically reduce the amount of on-site construction while its compact footprint and modular design means it can be located alongside energy intensive industrial processes.

Rolls-Royce SMR, which was established in November 2021, suggests the unit will offer availability above 92% for 60 years supplying both on- and off-grid electricity as well supplying industrial applications and sectors such as the production of clean fuels. They add that their low-cost nuclear solution is expected to be competitive with renewable alternatives. The Rolls-Royce SMR design is currently progressing through Generic Design Assessment in the UK where it has completed the first phase and is expected to complete the second step by July 2024.

Commenting on the shortlisting, Chris Cholerton, Rolls-Royce SMR CEO, said: “We have the only SMR technology in a European regulatory approval process, putting us almost two years ahead of any of our competitors. Securing a domestic contract is vitally important to unlock the enormous global export potential of our clean energy technology.”

This year Rolls-Royce SMR and Sumitomo Corporation completed a joint feasibility study which shows the reactor could offer a significant advantage for the production of low-carbon hydrogen when cost, availability and carbon emissions are taken into consideration.

The company has also signed a memorandum of understanding (MOU) with Finnish power company Fortum to explore opportunities for the deployment of SMRs in Finland and Sweden. Last year Fortum began a two-year feasibility study to explore necessary conditions for deployment of SMRs.

A Rolls-Royce-led UK SMR consortium aims to build 16 SMRs and expects to complete its first unit in the early 2030s. Rolls-Royce is also discussing deployment of its SMR with the Czech Republic, Poland, Estonia and the Netherlands.


The Westinghouse AP300TM small modular reactor is currently the only SMR based on a licensed, operating nuclear reactor design. Launched in May this year, the design is derived from the operating AP1000 PWR which makes it unlike every other SMR under development with first-of-a-kind technologies and risks. It is an advanced, Generation III+ single-loop pressurised light water reactor.

It utilises the same engineering, components and supply chain as the AP1000 which Westinghouse says will thus enable streamlined licensing and leveraging of available technical skills. The company adds that the advantageous economics of the AP300 are based on robust analysis and existing project costs from AP1000 reactors already in operation or development. Four AP1000 units are operating in China with a further six under construction and one is operating at Plant Vogtle in Georgia, USA, while a second is nearing completion there. The simplified, modular, ultra-compact nuclear island also reduces construction costs and schedule, Westinghouse says. For these reasons the company argues that it is confident that the first operating unit will be available in the early 2030s.

The AP300 SMR features advanced passive safety systems designed to achieve and maintain safe shutdown condition without operator action, back-up power or pumps and has an output of 300 MWe from 990 MWth.

Commenting, Patrick Fragman, Westinghouse President and CEO said: “We look forward to this opportunity to demonstrate that the AP300 SMR is the best option for the UK.”

Earlier this year Westinghouse Electric Company and Finland’s Fortum signed a Memorandum of Understanding (MoU) to study the possibilities for the development and deployment of AP300 reactor projects in Finland and Sweden. This deal was followed by a similar MoU agreement with Slovak state-owned nuclear company JAVYS and another with Ukraine’s Energoatom.

SMR outlook

The successful development of SMRs could completely transform how nuclear power stations are built and result in billions of pounds of investment in the UK and elsewhere. The flexibility of design means that SMRs could also play a significant role is decarbonising hard-to-reach sectors like chemicals, building materials and other energy-intensive industries. Although six companies’ designs have been shortlisted for the next phase of the UK competition, much will depend on a successful roll out of the winning designs, not just in the UK but much further afield too. SMRs clearly offer much promise but the success of SMRs will also mark a key breakthrough for nuclear technology more broadly.