Small modular reactors (SMRs) potentially offer significant opportunities to manufacturers. If the UK can take an international lead in technology development, the UK supply chain could produce SMRs for the global market.

Small modular reactors (SMRs) are advanced reactors that can be largely built in factories as modules to minimise costly on-site construction. The International Atomic Energy Agency defines SMRs as producing up to 300MW of electric power, but the term is applied to some larger designs – though all are smaller than the current generation of gigawatt-scale reactors.

SMRs are generally based on Gen III+ technologies which are relatively close to commercial readiness. The term advanced modular reactor (AMR) usually refers to a variety of Generation IV reactor technologies which are at an earlier stage of development.

Initial cost modelling suggests that SMRs will not be significantly cheaper, in terms of capital cost per megawatt output, than the current generation of gigawatt-scale reactors once financing costs are taken into account. The UK SMR consortium, of which the Nuclear AMRC is part, is now targeting a delivery price of £40–60/MWh for its power station, a similar price to offshore wind generation.

SMRs should be much more affordable to build, by avoiding the huge upfront costs and decade-long development times of current reactors. An initial SMR power station would be a fraction of the cost of a gigawatt-scale new build, could be built in four or five years and, once operational, will generate revenue to help finance additional units.

Because SMRs are designed to be largely made in factories, manufacturers will be able to use lessons learned from other sectors such as aerospace to drive down costs, and exploit new manufacturing techniques which aren’t approved for current reactor designs.

With the UK’s net-zero commitments likely to require a quadrupling of low-carbon electricity generation by 2050, SMRs have a vital role to play in the energy mix. They are intended to complement the current generation of gigawatt-scale reactors, rather than be a substitute.

UK government support

The UK government expressed support for domestic SMR development in the 2016 Budget, and launched a competition to identify the best-value design for the UK. The competition considered SMR designs which generate up to 300MWe, and which are able to achieve in-factory production of modular components or systems amounting to a minimum of 40 per cent of the total plant cost. That competition was closed in December 2017, with the publication of a series of techno-economic assessments of SMRs. The government also commissioned an Expert Finance Working Group on Small Reactors which published its final report in July 2018.

In November 2019, the government confirmed that it is investing £18 million match funding in the UK SMR consortium led by Rolls-Royce through the Industrial Strategy Challenge Fund.

The government is also offering a range of targeted support for advanced nuclear technologies, including small and advanced reactors, as part of the Nuclear Sector Deal. In July 2020, BEIS confirmed funding from its AMR competition of £10 million each for three reactor developers: Westinghouse, for its lead-cooled fast reactor; Urenco’s U-Battery; and fusion developer Tokamak Energy.

UK SMR consortium


The UK SMR is a compact power station design, producing 470MWe from a Gen III+ pressurised water reactor (PWR).

The consortium includes Assystem, Atkins, BAM Nuttall, Jacobs, Laing O’Rourke, the National Nuclear Laboratory (NNL), the Nuclear AMRC, Rolls-Royce and TWI.

The entire plant is being designed as a number of modular sub-assemblies which will be manufactured in factories then transported to site for rapid assembly inside a weatherproof canopy. That will cut costs and project risks by avoiding weather disruption, and also secure efficiency savings by using streamlined and standardised manufacturing processes for all its components.

The consortium aims to have its first power station in operation around 2030, with the development programme creating around 6,000 jobs by 2025. Up to 80 per cent by value of the power station components will be made in factories in the Midlands and North of England.

By 2050, a full UK programme of up to 16 of these power stations could create up to 40,000 jobs and £52 billion of value to the UK economy. Developing an SMR in the UK could also create an estimated £250 billion of exports.

Other developers

More than 70 designs of small modular reactor are in development in 18 countries, according to the IAEA. The following developers have expressed interest in UK development, and released information about their proposals.

Westinghouse is developing a 225MWe pressurised water reactor, largely based on technologies deployed in its AP1000 design. The Nuclear AMRC is engaged with Westinghouse on potential UK development, and has completed a manufacturability study which showed that the UK supply chain has the capabilities to effectively manufacture the reactor pressure vessel. The study determined that Westinghouse’s use of UK advanced manufacturing techniques offers a potential 50 per cent reduction in delivery lead times and offers substantial cost savings to SMR manufacturing.

NuScale Power is developing the Power Module, a 50MWe pressurised water reactor and generator, designed to be deployed in clusters of up to 12 per site. US-based NuScale is working with the Nuclear AMRC to collaborate on UK development, and is actively seeking potential UK suppliers. In July 2016, the Nuclear AMRC hosted NuScale’s UK suppliers day. NuScale has launched a supplier registration page at

Urenco is leading development of an ultra-small design called U-Battery. Based on pebble bed technology, each reactor will produce just 4MWe plus 10MWt. Target markets include back-up power, desalination plants and smart cities. Urenco is working with the Nuclear AMRC to support development.

China National Nuclear Corporation (CNNC) is also adapting Westinghouse AP1000 technology for its ACP100 SMR, with an output of 100MWe plus 310MW thermal power which can be used in district heating schemes. CNNC is preparing a demonstration site with two units in Fujian province, and is engaged with the Nuclear AMRC on potential UK development.

Moltex Energy, a privately-held UK company, is developing a 150MWe stable salt reactor, designed for modular deployment in clusters of up to 10 units per site. It is engaged with the Nuclear AMRC on potential development.

GF Nuclear is an independent power generation company which aims to develop the South Korean 100MWe Smart reactor in the UK. GF Nuclear says it will give UK engineering firms every opportunity to supply elements of the reactor’s core and other critical nuclear systems.

Key manufacturing technologies

Driving down production costs is the key to making SMRs economically viable. SMRs offer the nuclear industry the opportunity to become more like other high-value low-volume manufacturing sectors such as aerospace or oil and gas, where the UK has proven expertise. To achieve this, the SMR design must allow economies of volume when making 50 or 100 units, and manufacturers will need to demonstrate high learning rates as production ramps up.

UK manufacturers in other high-value sectors already use a range of processes which have not yet been approved by the UK nuclear regulator. By working with manufacturers, technology providers and researchers, SMR developers will be able to include new processes into the safety case for their new designs, and use techniques such as design for manufacturing and modularisation to build in production efficiencies.

Manufacturing processes which could be exploited for SMRs include a range of machining techniques such as robotic machining, single-platform machining and cryogenic cooling, as well as supporting technologies such as intelligent fixturing and on-machine inspection. Advanced joining and near-net shape manufacturing processes such as electron beam welding, diode laser cladding, automated arc welding, bulk additive manufacturing and hot isostatic pressing also offer significant savings in cost and lead time.

Many of these technologies are already being developed for civil nuclear applications by the Nuclear AMRC. The centre’s advanced machine tools and fabrication cells have been specified to work on representative-size parts for gigawatt-scale reactors, which means that they could also produce full-size prototypes for SMRs.

Since 2017, the Nuclear AMRC has worked with the US-based Electric Power Research Institute (EPRI) to develop new manufacturing and fabrication methods for SMR pressure vessels. The project aims to reduce the total time needed to produce a vessel, based on NuScale’s Power Module design, from three to four years to less than 12 months. The project is funded by the US Department of Energy, and involves industrial partners on both sides of the Atlantic including Sheffield Forgemasters.