How the sun went down on UK nuclear

Introduction

The Final Investment Decision for the Sizewell C nuclear power project seemed to mark the end of the government’s large reactor ambitions. Not only is there no follow-on large reactor project but there is not even a process for establishing a new project. Realistically and despite all the empty talk of streamlining and cutting red-tape, this probably takes the date of first power to beyond 2050. The focus of the government’s nuclear ambitions now falls on Small Modular and Advanced Modular Reactors (SMRs and AMRs) with a steady flow of new projects and new technologies aimed at the UK being publicised (see tables 1 and 2 in the Annex at the bottom of the page).

The SMR competition and the Nuclear Roadmap to 2050

The SMR competition

In March 2016, the government announced a competition to select the best SMR design for the UK.¹ In December 2017, the competition was effectively abandoned.² The competition was revived in July 2023 to be run by the newly formed state-owned Great British Energy – Nuclear (GBE-N³) (see Table 3 below). In October 2023, six designs were selected by GBE-N to go forward to the next phase. The six designs were: Rolls Royce SMR, GE Vernova BWRX-300, Holtec SMR300, Westinghouse AP300, NuScale VOYGR and Framatome Nuward. This selection was easy for GBE-N as these represent all the designs that could credibly claim to be close to availability and may even have been the only applicants.

Table 3: The SMR Competition

GBE-N then stated it would announce in spring 2024 which of the six companies it would support with contracts expected to be awarded in summer 2024. It was not till November 2024 that a shortlist of four designs was announced – Rolls Royce, GE Vernova, Holtec and Westinghouse, all likely to exceed the IAEA’s upper bound of 300MW. Again, this was an easy decision because Framatome had abandoned the Nuward design in July 2024¹⁰ and withdrawn it. No explanation was given for the elimination of NuScale although following the termination of its Utah SMR project,¹¹ it had few sales prospects.¹² The next stage was detailed negotiations with the four vendors prior to them submitting a Final Tender. Westinghouse chose not to submit a Final Tender, leaving a choice of three.

In March 2024, GBE-N had bought two sites identified by government as potentially suitable for new reactors from Hitachi: Wylfa and Oldbury.¹³ In January 2024, the Interim Chair of GBE-N had said “I think the optimum number is somewhere between two and three [SMR vendors].” The expectation was that two designs would be chosen with each receiving orders for two reactors to be placed in 2029 and they would use these two sites.

It was a surprise when the Chancellor announced on June 10, 2025, that only one design had been chosen, Rolls Royce, with three reactors to be built and a Final Investment Decision (FID) expected in 2029.¹⁴ The Chancellor announced that £2.5bn would be available to the “overall Small Modular Reactor programme” in the period to the end of fiscal year 2029/30, to just beyond the forecast Final Investment Decision date. No information has been published on what proportion of this budget will go to the Rolls Royce design or what the money will be spent on^1a. Subsequently, it was announced that the reactors would be sited at Wylfa.

GBE-N has missed all its target dates by a substantial margin typically taking twice as long to reach the next step as it forecast. The overall competition took two years compared to the one-year GBN was forecasting in October 2023. The government has made five cash allocations to the Sizewell C project between 2022 and 2025 totalling up to £7bn to keep the project afloat and targets for an FID were repeatedly missed. There can therefore be no confidence that the forecast FID date will be met, nor that further cash injections by government beyond the £2.5bn already committed will not be made if the project runs into difficulties.

“It was a surprise when the Chancellor announced on June 10, 2025, that only one design had been chosen, Rolls Royce, with three reactors to be built and a Final Investment Decision (FID) expected in 2029.”

The Roadmap

As part of the earlier SMR policy from the mid-2010s, the government announced in March 2016 that it would publish an ‘SMR delivery roadmap’ by the end of 2016.¹⁵ This promise was quietly forgotten.

However, in April 2022, Prime Minister Johnson announced a target of up to 24GW of new nuclear to come online by 2050 and that a Roadmap to achieve this would be published.¹⁶ However, the focus in the 2022 statement was very much on large reactor projects and the inclusion of “up to” in the target to complete 24GW of new nuclear meant the target was meaningless. The Roadmap was published in January 2024¹⁷ and all the major short-term targets in it for large reactors have already been missed.

The role of SMRs and AMRs was much more prominent: the Roadmap talked about “deployment of fleets of SMRs in the UK”¹⁸ and “we will need to go further across a wide spectrum of nuclear technologies – from SMRs to large-scale nuclear power stations and emerging AMRs.”¹⁹ However, there were no specific plans for SMRs beyond carrying out the nuclear competition. For AMRs, the Roadmap stated: “We have already committed to research and development investment to deploy an AMR High Temperature Gas Reactor demonstration unit by the early 2030s.”

The Starmer government has been careful not to espouse the Roadmap especially the 24GW target and it appears the details in it are no longer a significant indication of policy. When questioned by the House of Commons Energy Security and Net Zero Committee in February 2026 about future large reactor projects, Ed Miliband said that: “We believe in principle that there is a case for at least another large-scale nuclear power station”,^19b suggesting the government has little ambition for further large reactor projects.

Generic Design Assessment, Site Licence Review and Preliminary Design Review

In 2007, a new option for licensing reactors was introduced, the Generic Design Assessment (GDA), (see Table 1 in the Annex). The objective was that the design would be evaluated in depth in a four-step process expected to last four years, revised to a three-step process in 2019; successful designs would receive a Design Acceptance Confirmation (DAC) and Statement of Design Acceptability (SoDA) allowing the design to be built at any UK location with no further evaluation of the design and subject only to local siting issues. The approval would be valid for ten years.²⁰ Four large reactor designs successfully completed the process between 2012 and 2022.²¹ In May 2021, the government opened the Generic Design Assessment (GDA) process to SMRs and AMRs, and in November 2021 Rolls Royce applied for entry to the GDA process.²²

Companies apply to the government for entry to the Generic Design Assessment (GDA) and designs must pass its ‘readiness’ assessment.²³ Little is known about this process: the government does not announce when it receives applications, the companies do: nor does the government announce the result or publish its assessment: if the application is successful the companies do announce it but if it is not, they do not and the results can only be found by explicit questions to the government.

The first step of the Generic Design Assessment (GDA) is information exchange, the second identifies issues needing resolution and in the third these issues are resolved. Rolls Royce applied to conduct all three steps. It appears its costs were covered by the £210m of public money it was allocated in November 2021 (see Table 5 in the Annex). In 2021, the Future Nuclear Enabling Fund (FNEF) was set up with a budget of £120m. It had a funding window of 1st April 2022 to 31st March 2025.²⁴ However, the Fund closed to new applications in July 2023.²⁵ The Fund paid GE Vernova £33.6m to carry out the first two steps of the Generic Design Assessment (GDA) for its BWRX-300 design in January 2023 and Holtec £30.05m for the first two steps of the GDA in December 2023 for its SMR300 design.²⁶

In December 2025, step two of the GE Vernova GDA was completed successfully and on time:²⁷ it was not GE Vernova’s intention to carry out step three and given it was not selected in the SMR Competition and had no other projects in the UK for its design, it seems unlikely it will complete the third step. The Holtec GDA step two completion was expected in October 2025 but by December 2025, this was not expected until “early 2026”. The announcement of the Cottam project (see below) using this design in September 2025 may mean Holtec will choose to request the third step of the GDA. How far the decisions of Westinghouse (AP300) and NewCleo (LFR200) not to proceed with Generic Design Assessments despite passing the government’s readiness test were due to the cost they would have to pay to have the GDA carried out is not known.

“Companies apply to the government for entry to the Generic Design Assessment (GDA) and designs must pass its ‘readiness’ assessment. Little is known about this process: the government does not announce when it receives applications nor does the government announce the result or publish its assessment.”

Ten SMR designs have applied for entry to the GDA process, three passed the ‘readiness’ assessment and the GDA was started. Two passed the readiness assessment but the vendors chose not to proceed, four failed the readiness test and one was undergoing this assessment in February 2026, so passing this test is not guaranteed.

The Generic Design Assessment (GDA) process is not compulsory, and developers can apply for a site-specific Site Licence Review (SLR) in the way licences were all awarded prior to 2007: this would include an in-depth review of the design. The Office for Nuclear Regulation (ONR) has stated it “will undertake an equivalent assessment [to that in the GDA] of the proposed design”²⁸ so it seems that the Site Licence route will be no quicker than the GDA route. SLR is the option Last Energy has chosen for its four 20MW PWR micro-reactors planned for Llynfi. In January 2025, Last Energy signalled its intention to apply for a site licence and in June 2025, the UK Office of Nuclear Regulation (ONR) reported it had completed a Preliminary Design Review.²⁹ ONR stated that Last Energy’s target of receiving a site licence by December 2027 was “achievable”, but given that Last Energy is not expected to apply for an SLR until June/July 2026, this appears unrealistic. To complete the licensing of the Llynfi project in only 18 months in the same depth as a Generic Design Assessment (GDA) is hard to reconcile with the GDA process of four years. The subsequent announcement of a second Last Energy project, London Gateway, (see below) also raises the question, what will be the process for a design that has already received a site licence for a different site. If the GDA process is to have any meaning, the design for this second project cannot be nodded through without some evaluation.

Ahead of the Generic Design Assessment (GDA), a voluntary process of Preliminary Design Review (PDR) (see Table 4 below) was added in 2024. This is a three-tier process.³⁰ Tier 1 is simply a one-day information session required before the next two steps can be carried out. “Tier 2 is a series of structured engagements on a range of topics” while Tier 3 includes a “technical review of certain aspects of a reactor design.” Only one of the five designs starting the Preliminary Design Review (PDR) has completed it and none has yet gone forward into the Generic Design Assessment (GDA).

Table 4. Preliminary Design Review.

The Rolls Royce design

The Rolls Royce design is a newcomer to the market only being announced in 2016 when the size was said to be in the range 220–440 MW. In 2017, it settled on about 450 MWe with the first demonstration unit operating by 2030.³¹ In May 2021, Rolls Royce announced an increase in size to 470 MW.³²

While its publicity frequently talks about innovative features³³, these seem to be mainly those offered by all SMR designs, including smaller size, albeit the Rolls Royce SMR has the highest electrical output of any design classified as an SMR by a vendor (modular construction of assembly line produced modules). Rolls Royce states “the basic elements of the Rolls-Royce SMR are typical of most PWRs operating today.”³⁴

Rolls Royce received £18m from the British government in July 2019 to subsidise development of the design³⁵ and in November 2021, it received a further £210m of public money via the UK Research & Innovation (UKRI) Challenge Fund³⁶ to be matched by £258m from the Rolls Royce SMR consortium.³⁷ UKRI described the design as “based on established pressurised water reactor technology.”

The key advantage the Rolls Royce design seems to have had in receiving this funding, far more than any other SMR/AMR design, and in the SMR Competition over its rivals, whose designs are more innovative, appears to be that it is the only design offered by a British company and one seen as a ‘national champion’.

Siting

In the early days of nuclear power, the lead time from project announcement to first power was around five years, the plants had design lives of about 30 years, and decommissioning was expected to take a couple of decades making the entire life of the project about 50 years. Today, projects in Europe and North America typically take about 20 years from inception to first power, the vendors claim an operating life of 80 years. In the UK, completion of decommissioning the first UK commercial reactors is not expected until the mid-2050s  making it more than 60 years from last power to completion of site clearance. Completion of decommissioning the Advanced Gas-cooled Reactors, the mainstay of the UK’s nuclear power stations, is expected to take 100 years from plant closure. So, a new nuclear project is likely to have a life of 150 or more years from inception to final site clearance. Given how quickly perceptions of climate change are moving, doubts about our ability to know the political situation in the UK at that time and the fact that new reactor design vulnerabilities are still emerging, siting decisions represent an awesome responsibility and not one we should be seeking to streamline or shortcut.

“In the early days of nuclear power, the lead time from project announcement to first power was around five years. Today, projects in Europe and North America typically take about 20 years from inception to first power.”

The projects

There have been five firm projects for SMRs/AMRs announced (see Table 2 in the Annex).

Wylfa/Rolls Royce

The Wylfa project for three Rolls Royce SMRs appears the most likely to go ahead. The government has not determined who will own the plant, how it will be financed or how the power will be sold. The option of making the three reactors fully state-owned would simplify matters meaning it would not be necessary to produce a financial package that would be attractive enough to bring in private investors. The first test the project must pass is successful completion of the third step of the GDA, forecast for August 2026. In December 2025, it was said that the issuing of a Design Acceptance Certificate (DAC) was not expected until 2027, but this was not on the Wylfa project’s critical path so the delay will not prevent the issuing of a Final Investment Decision in 2029. Experience suggests that the design will be accepted but the issue is what level of safety systems will be required. Will the same requirements be asked for as for large reactors? Rolls Royce only started the US pre-application process for design review in April 2025, so it is several years behind the UK process, and it has no serious potential customers there. Its one serious export prospect is to the Czech Republic where it hopes to win an order for one reactor to be built at the Temelin site on about the same timescale as Wylfa.³⁸ Its Czech partner, the utility CEZ, took an equity stake of about 20% in the Rolls Royce SMR consortium in October 2024.³⁹

“The Wylfa project for three Rolls Royce SMRs appears the most likely to go ahead. The government has not determined who will own the plant, how it will be financed or how the power will be sold.”

The Wylfa site is widely seen as the best one in the UK of those already established and saw significant site characterisation when it was being evaluated for deployment of two large Advanced Boiling Water Reactors (ABWRs) in the mid-2010s. Nevertheless, the Planning Inspectorate recommended against it being used.⁴⁰ Its main concerns were lack of funding for the project, failure to meet some of the UN’s biological safety standards, and concerns about the project’s impact on the local economy, housing stock and the Welsh language⁴¹. Government can overrule the Planning Inspectorate and undoubtedly would have done, as it did with the Sizewell C application.⁴² The output of the proposed station would be significantly more than the retired Magnox station (the largest Magnox station, 1100MW) that operated there until 2015 and more than any completed UK nuclear station. Decommissioning of the old Wylfa station is not expected to be complete until 2080.

Cottam/Holtec

Holtec is a US company with a history of work in clean-up and waste disposal but no prior experience of reactor design. The Cottam project for 1GW of power, three reactors of 300MW, announced in September 2025⁴³, is less advanced than Wylfa.⁴⁴ By February 2026, the Holtec design had not completed step two – identification of design issues – of the Generic Design Assessment (GDA) and Holtec had yet to commit to carrying out the third step of resolving design issues. If it chooses not to go ahead with this option, it could adopt the site license approach, in which the analysis that would have been required to complete step three of the GDA would presumably be carried out. It is hard to see how this would save time or money and completing the GDA seems more sensible. The publicity for the project claims “[t]he UK programme will benefit directly from Holtec’s SMR-300 deployment at Palisades, Michigan – the first SMR-300 plant in the U.S.”⁴⁵ The implication that this project is well-advanced is misleading as it has yet to receive a construction permit from the US safety regulator, NRC, and it will be several years before anything can be learnt from it. The design is in the pre-application phase of the US equivalent of the Generic Design Assessment (GDA) process, some way behind the UK in that respect.⁴⁶

The partners in the project are Holtec, EDF and Tritax. It is not clear whether Holtec would be willing to take a significant ownership stake, EDF’s contribution appears to be ownership of the site while Tritax is an investment manager. The announcement talks about involving GBE-N and the National Wealth Fund, so it would appear they are targeting public funding.

The site has good grid connections from its coal-fired power station, but it has not been planned for use for nuclear power plants. So, the site investigations would have to start from scratch.

Hartlepool/X-Energy

X-Energy is a new company set up in 2009 specifically to develop and sell High Temperature Gas-cooled Reactors (HTGRs) and it remains independent. The Hartlepool project for 12 of the Xe-100 High Temperature Gas-cooled Reactors (HTGRs) of 80MW each is at an early stage. It was announced in March 2023⁴⁷ and then re-announced in July 2025⁴⁸ and is on the site of existing reactors. These started construction in the mid-1960s so it would seem likely to need substantive investigation. If the government retains the Semi-Urban Population Density Criterion (SUPDC) in the final version of its latest nuclear siting planning policy, EN-7,⁴⁹ Hartlepool seems unlikely to be allowed because of its proximity to Hartlepool. The proposed station is about the same size as the existing one so it would by no means be small.

The reactor vendors, X-Energy, applied for a Generic Design Assessment (GDA) in January 2023 but it failed the government’s readiness assessment and was not put forward to the Office for Nuclear Regulation. There have been reports in 2025 that the company would re-apply⁵⁰ and in February 2026 X-Energy said it would apply again for a GDA in spring 2026.

No commercial High Temperature Gas-cooled Reactor (HTGR) has been built. The design appears to be based on the German ‘pebble-bed’ design.⁵¹ A prototype reactor, AVR Juelich (13MW), was operated in Germany from 1969-88 but its operation was problematic leading to a massive decommissioning liability, estimated at €1.5-2.5bn.⁵² A demonstration plant was built using this basic design, THTR-300, but this only generated power for three years up to 1987 before it was abandoned.⁵³ South Africa spent 20 years trying to develop a commercial pebble-bed design but abandoned it in 2010 without a complete design.⁵⁴ China also adopted this design and has completed a demonstration plant but this took 11 years to complete and in its first two years of operation, its load factor was only 20%.⁵⁵ Its main prospects in the USA are for a four-reactor station in Texas⁵⁶ and a 12-reactor station in Washington State,⁵⁷ but these are some way from being firm orders.

X-Energy claims the Xe-100 will have a coolant temperature of 750C, the lowest temperature needed for hydrogen synthesis. One of the main technical problems with the High Temperature Gas-cooled Reactors (HTGRs) that have been built has been achieving operating temperatures of 750C. The Hartlepool project has several substantial financial, planning, regulatory and technological hurdles to clear before it can go ahead.

Llynfi/Last Energy

Last Energy was set up in 2019 to develop PWR micro-reactors. The Llynfi site used to accommodate a coal-fired power station, retired in 1977.⁵⁸ Last Energy claims it will make a site license application in June/July 2026, although authoritative sources suggest the application might not be made before 2027. Last Energy wishes to obtain a site by December 2027 and while the UK nuclear regulator (ONR) does not discount this it appears sceptical.⁵⁹ The ONR’s Preliminary Design Review (PDR), identified two serious issues, albeit diplomatically drafted, that need to be monitored:⁶⁰

• The regulators identified that a suitable disposal route for certain reactor materials will be a key issue for Last Energy to resolve, as some materials may not be compatible with UK nuclear waste repositories.
• ONR advised that it is philosophically possible to rely entirely on two passive safety systems, providing there is adequate defence in depth (multiple independent barriers to fault progression), and a robust body of evidence would be required to substantiate the claims. ONR has identified potential for technical challenges in these areas to be significant but there are grounds to expect that they could be resolved in future.

It was not specified what the problematic reactor materials were and the second point seems to be a warning shot that, despite its small size, the reactor will not be licensed with much less stringent safety requirements than larger ones. ONR has said that as the design has not been assessed by Generic Design Assessment (GDA), it will undertake a fundamental assessment of it of equivalent rigour to the GDA. It is hard to see how this could be completed in time for Last Energy’s target to receive a site license by December 2027 to be met.

London Gateway/Last Energy

This project, to site a single 20MW Last Energy reactor near London as a power supply for the expansion of DP World’s London Gateway port and business park, was announced in September 2025⁶¹ and is at an early stage of development with no specific site found yet. Whether it goes ahead will depend in part on progress with the technology assessment to be carried out for the Llynfi project.⁶² It seems likely if it did proceed, the project would follow the site license process without a Generic Design Assessment (GDA).

Reform of the Planning and Regulatory Processes

A major unknown hanging over the future of the UK nuclear sector is the concrete steps that will be taken to implement the recommendations of the Nuclear Regulatory Taskforce.⁶³ There has been a wide acceptance of the basis for its report, that delay and cost overruns at nuclear power projects are the result of inefficient and overzealous planning and regulatory processes. This is despite the Taskforce (and the government) providing no substantial evidence to back this assumption. The report and publicity by the Taskforce and the government are couched in emotive language designed to generate headlines. For example, the Prime Minister blamed “NIMBYs” and “blockers” while the Taskforce characterised Office for Nuclear Regulation (ONR) as “not fit for purpose”. This contrasts with the Government’s 2024 Roadmap which was complimentary about the ONR. It stated:⁶⁴ “The UK is also a world leader in nuclear safety and security – thanks to our commitment to rigorous regulation and the creation of the internationally recognised Office for Nuclear Regulation (ONR).”

The more plausible explanation for the long lead-times in the UK – given that all the recent nuclear projects in Europe and North America have suffered similar problems to the one UK project, Hinkley Point C – is that the main issue is the technology and the competence of the companies building them, is not acknowledged.

Ruth Wilkinson, Institution of Occupational Safety & Health, contested the claim that relaxing health and safety rules was a good way to speed up UK infrastructure projects: “Stripping back protections in the name of speed is a false economy that risks lives, reputations and resilience. The UK’s health and safety framework is the backbone of safe and sustainable growth.”⁶⁵

“The more plausible explanation for the long lead-times in the UK – given that all the recent nuclear projects in Europe and North America have suffered similar problems to the one UK project, Hinkley Point C – is that the main issue is the technology and the competence of the companies building them; this is not acknowledged in the Nuclear Regulatory Taskforce report.”

Future nuclear projects are expected to have a 150-year life cycle,⁶⁶ climate change and global instability appear to be increasing and vulnerabilities to reactor designs are still emerging. For example, new design issues have been thrown up by the risks to the six Zaporizhia reactors in Ukraine from the fighting at the site. In this context, far from trying to shortcut planning and regulation, the priority would appear to be to make planning and regulatory processes rigorous enough to meet these challenges. In terms of the SMR policy, there will be attempts to shorten the Generic Design Assessment and Site License Review processes, shortcut planning processes and restrict the ability of the public to participate in any of the regulatory and planning processes.

What are the prospects for Small Modular Reactors and Advanced Modular Reactors?

There have been numerous critiques that demonstrate claims for SMRs and AMRs are at best unproven or at worst simply false.⁶⁷ The arguments on this are summarised in ‘Small modular reactors: Game changer or more of the same?’ Policy Brief, January 2026.

The UK government’s record with reactor construction programmes is one of total failure starting with the misguided choice of Advanced Gas-cooled Reactor (AGR) technology in 1965 and the 2022 Johnson target of 24GW of new nuclear capacity by 2050, which it is already clear cannot be achieved.⁶⁸ There can be little confidence the current SMR programme will be any more successful.

An attempt around 2015/16 to launch an SMR programme including the production of a Roadmap and with a budget of £500m did not progress and the budget was unspent. Since 2019, nine reactor designs have received public money. The vendors for two of them, Ultra-Safe Nuclear Corporation and U-Battery (in the UK) collapsed, the Westinghouse LFR design appears to have not been pursued, there is no evidence that funding for the National Nuclear Laboratory for High Temperature Gas-cooled Reactors (HTGR) fuel has led anywhere. The only awards that have produced concrete results are the subsidies to GE Vernova and Holtec to pay for their Generic Design Assessments (GDAs) and to the Rolls Royce SMR. This has received more money than all the other grants put together. Given the government’s evident lack of expertise in reactor design assessment, it is difficult to avoid the conclusion that Rolls Royce’s overwhelming advantage is that it is the only British company involved, one with significant brand value.

In addition to these company awards, there is the cost of setting up and operating GBE-N. In 2023/24, its costs were £22.2m and in 2024/25 they were £31.9m. It is not clear how much of this was spent setting up the company and how much on carrying out the SMR Competition.⁶⁹ For the next five years, it will presumably receive a share of the £2.5bn allocated for SMR/AMR development plus funding for any other tasks it is asked to carry out, for example, on large reactor projects.

Looking beyond the SMR Competition, a lot of publicity was generated by the three projects announced at the time of President Trump’s visit in the summer of 2025 (Table 2 in the Annex). All are at an early stage and the chances of such projects progressing are low. For example, in February 2024, an agreement was announced to build four AP300 reactors at a site in Teesside with a new private company, Community Nuclear Projects.⁷⁰ Nothing has been heard about the project since then.

“Given the government’s evident lack of expertise in reactor design assessment, it is difficult to avoid the conclusion that Rolls Royce’s overwhelming advantage is that it is the only British company involved, one with significant brand value.”

On Advanced Modular Reactors (AMRs), the government’s focus is on High Temperature Gas-cooled Reactors (HTGRs). It awarded a very small subsidy to the only established HTGR vendor, X-Energy, but its design failed its ‘readiness’ assessment for entry into the Generic Design Assessment (GDA). The award to National Nuclear Laboratories and the Japanese organisation JAEA in April 2024 to develop HTGR fuel is hard to understand given that neither entity has a significant record in HTGRs. There has been no report of the work done since it was given.

In terms of the contribution of SMRs and AMRs to meeting emissions targets by 2050, it is difficult to see how they could make a significant contribution. The three Rolls Royce SMRs might come online sometime after 2035 if all goes smoothly. Until we can see whether the costs are competitive and the design effective in operation, it would be reckless to order more of this design, meaning follow-up orders would not be online until well after 2040, long after the electricity generation sector ought to have been decarbonised.

The contrast with offshore wind is stark. By January 2026, there was 16.6GW of offshore wind in operation, 11.7GW under construction and 8.4GW more was contracted in January 2026 at an average cost of £91/MWh (2024 money) with expected completion soon after 2030.⁷¹ By comparison, there is about 6GW of nuclear capacity in operation all but 1.1GW of which will be retired by 2030, 3.2GW under construction and the earliest new capacity likely to be contracted is the Wylfa project in 2029. The one project under construction, Hinkley Point C will produce power at £128.8/MWh (2024 money) when it is completed, currently forecast for 2032 and that will be a loss-maker for the plant owners.

What are the alternatives?

The question always asked of those sceptical about the case for new nuclear is what are the alternatives? This implies nuclear is a viable option. Experience says otherwise. A high proportion of announced projects do not materialise, the lead time from project inception to first power is seldom less than 20 years and the costs are unpredictable. If we project UK nuclear capacity up to 2040 (see Table 6 below) assuming the three Rolls Royce SMRs planned for Wylfa are completed between 2035-40 and that the Sizewell C reactors are completed by the central estimated date of 2039, then by 2040, nuclear capacity will only have returned to 2015 levels.

Table 6. UK Nuclear Capacity.

If as planned, fossil fuel generation is essentially phased out by 2030, the UK system will have to survive for a decade with less nuclear capacity than in 2025. There is no prospect of a large reactor station being completed until well after 2040. Unless the UK takes the reckless step of ordering more Rolls Royce SMRs before the design is proven in construction and operation, Rolls Royce SMRs after the Wylfa project also cannot contribute until well after 2040. The other projects announced are at an early stage and would not contribute a significant amount of capacity even if they went ahead.

There are several viable alternatives, all with much quicker, more certain lead-times and lower costs. Energy efficiency measures are difficult to generalise on and the previous government’s insulation scheme failed badly with 98% of the 23,000 homes fitted with external wall insulation requiring repairs.⁷² It appears that as a result, the Starmer government’s Warm Home Plan⁷³ has very few energy efficiency measures despite the fact that they would not only reduce emissions, they would also help tackle the fuel poverty problem.

“If as planned, fossil fuel generation is essentially phased out by 2030, the UK system will have to survive for a decade with less nuclear capacity than in 2025. There is no prospect of a large reactor station being completed until well after 2040.”

However, the price of large-scale renewables is well-established by the series of seven auctions, Allocation Rounds (AR1-AR7); details of these are set out in Table 7 (below). Under these, developers of renewables, predominantly offshore wind, are invited to bid a fixed real price for sales of power from their facilities for a 15-year period. The amount of capacity that is awarded contracts depends on the successful price bid – the lower the prices bid, the more capacity can be awarded a contract. As with the Hinkley deal, the owner of the facility is responsible for any cost or time overruns. However, whereas with Hinkley, there was no competition, there is a competitive field for the renewables auctions. The Hinkley deal (guaranteeing the price for 35 years) proved unrepeatable because of the heavy losses EDF made on the deal due to the large cost overrun. The Allocation Rounds have proved an effective way of procuring new generation at well below the £128.8 (2024 price) that will be paid to Hinkley.

Table 7: Generation. Allocation Round Auctions for Low Carbon.

As a result about 48GW of capacity has been contracted, almost all of which at a lower kWh price than will be paid to Hinkley. More could have been achieved if there had not been an arbitrary ban on onshore wind and solar from 2015-21 and if government had not set an unrealistically low maximum price for offshore wind in auction round 5 (AR5). The bidding process takes about a year, and winning bids are expected to come online within about four years. The average offshore wind price (excluding the first round) is less than 60% of the price to be paid to Hinkley, a price that is clearly far below the actual price.

The price of power from Sizewell C is unknown, will vary from year to year but despite the large consumer and taxpayer subsidies the deal involves⁷⁴ it is highly likely the price will be higher than that for Hinkley. The only estimates for the price of power from Rolls Royce SMRs are from Rolls Royce and are now old. Given that their purpose was to promote the option, they have no credibility.

The programme instigated by the Blair government in 2006 to complete 15GW will not contribute any new capacity by 2030 whereas the Allocation Round auction system is expected to deliver as much capacity as the 15GW target through AR7 alone. The Hinkley Point C project should have been a salutary lesson in how badly wrong nuclear projects can go, especially those using the EPR technology chosen for Sizewell C. In the Hinkley case some of the burden will fall on EDF, although consumers will still have to bear the cost of waiting seven years longer than forecast for first power. For Sizewell C, the risks borne by EDF for Hinkley will fall squarely on electricity consumers and taxpayers. While the costs of abandoning now will be significant, they will be dwarfed by the costs consumers and taxpayers will have to pay if the project goes ahead.

ANNEX: TABLES 1, 2 & 5.

Table 1. Applications for a Generic Design Assessment.

Table 2. UK SMR Projects.

Table 5.                      SMRs receiving government funding.

ENDNOTES

1a. In February 2026, the government stated ‘we committed…. over £2.5 billion to the Great British Energy – Nuclear (GBE-N) SMR project at Wylfa’ implying all the £2.5bn was for Wylfa. https://assets.publishing.service.gov.uk/media/698483397da3dc19896c7ddc/advanced-nuclear-framework.pdf

1. https://www.gov.uk/government/publications/small-modular-reactors-competition-phase-one

2. https://www.gov.uk/government/publications/small-modular-reactors-competition-phase-one

3. GBE-N was originally to be known as Great British Nuclear but in June 2025, it was renamed GBE-N.

4. https://www.gov.uk/government/news/british-nuclear-revival-to-move-towards-energy-independence

5. https://www.gov.uk/government/news/six-companies-through-to-next-stage-of-nuclear-technology-competition

6. https://www.gov.uk/government/news/negotiations-begin-for-uks-small-modular-reactor-programme

7. https://www.gov.uk/government/news/gbn-at-final-stage-of-small-modular-reactor-selection-process

8. https://www.gov.uk/government/news/rolls-royce-smr-selected-to-build-small-modular-nuclear-reactors

9. https://www.gov.uk/government/news/wylfa-confirmed-as-site-for-uks-first-small-modular-reactor

10. https://www.nucnet.org/news/edf-confirms-nuclear-plant-is-no-longer-part-of-uk-nuclear-reactor-competition-7-2-2024

11. https://www.reuters.com/business/energy/nuscale-power-uamps-agree-terminate-nuclear-project-2023-11-08/

12. NuScale was reported as saying: “the company had been told it did not meet the criteria for the SMR competition as it had already begun production of its reactors and did not need support getting to market.” https://www.neimagazine.com/news/final-smr-tenders-submitted-in-uk-competition/

13. https://www.gov.uk/government/news/great-british-nuclear-to-buy-two-hitachi-sites-for-new-nuclear-development

14. https://www.gov.uk/government/news/rolls-royce-smr-selected-to-build-small-modular-nuclear-reactors

15. https://assets.publishing.service.gov.uk/media/5a7fa2d3ed915d74e33f7a36/SMR_Competition_Phase_1_Guidance.pdf

16. https://www.gov.uk/government/publications/british-energy-security-strategy/british-energy-security-strategy#nuclear

17. https://www.gov.uk/government/publications/civil-nuclear-roadmap-to-2050

18. https://assets.publishing.service.gov.uk/media/65c0e7cac43191000d1a457d/6.8610_DESNZ_Civil_Nuclear_Roadmap_report_Final_Web.pdf p 20

19. https://assets.publishing.service.gov.uk/media/65c0e7cac43191000d1a457d/6.8610_DESNZ_Civil_Nuclear_Roadmap_report_Final_Web.pdf p 17

19b. https://committees.parliament.uk/oralevidence/17188/pdf/

20. https://www.onr.org.uk/generic-design-assessment

21. The Framatome European Pressurised Reactor, the Westinghouse AP1000, the Hitachi-GE ABWR and the China General Nuclear HPR1000. https://www.onr.org.uk/generic-design-assessment/assessment-of-reactors

22. https://www.gov.uk/government/publications/advanced-nuclear-technologies  

23. https://assets.publishing.service.gov.uk/media/64b662db0ea2cb000d15e465/gda-entry-guidance.pdf

24. https://assets.publishing.service.gov.uk/media/6350225dd3bf7f6184a29492/future-nuclear-enabling-fund-clarification-questions.pdf

25. https://www.gov.uk/government/publications/future-nuclear-enabling-fund-fnef

26. https://www.gov.uk/government/publications/future-nuclear-enabling-fund-shortlisted-applications/future-nuclear-enabling-fund-successful-applicant

27. https://www.onr.org.uk/news/all-news/2025/12/ge-vernova-hitachi-bwrx-300-completes-gda

28. Communication from ONR to the author, January 6, 2026.

29. https://www.onr.org.uk/our-work/what-we-regulate/new-reactors/licensing-of-new-reactors and https://www.onr.org.uk/generic-design-assessment/early-regulatory-engagement-on-new-nuclear-projects/last-energy-pdr-summary-report

30. https://www.onr.org.uk/generic-design-assessment/early-regulatory-engagement-on-new-nuclear-projects

31. Rolls Royce (2017) ‘UK SMR: A national endeavour.’ Rolls Royce https://www.uknuclearsmr.org/uk-smr-a-national-endeavour-report/

32. Rolls Royce (2021) More power and updated design revealed as nuclear power team targets first place in the assessment queue in Autumn 2021.’ Press Releases https://www.rolls-royce.com/media/press-releases.aspx

33. Rolls Royce publicity says: “through its innovative approach to modular construction, the UK SMR programme is uniquely placed to avoid the complexities, delays and overspends often associated with infrastructure projects.”  https://www.rolls-royce-smr.com/press/british-small-nuclear-plants-can-deliver-low-cost-low-carbon-electricity

34. https://www.rolls-royce-smr.com/about-the-rolls-royce-smr

35. https://www.rolls-royce-smr.com/press/commitment-to-initial-funding-for-smr-welcomed-by-consortium

36. https://www.ukri.org/publications/low-cost-nuclear-phase-two-grant-award-to-rolls-royce-smr-ltd/low-cost-nuclear-phase-two-grant-award-to-rolls-royce-smr-ltd-information/

37. Rolls-Royce Group, BNF Resources UK Limited and Exelon Generation Limited .

38. https://www.rolls-royce-smr.com/press/rolls-royce-smr-and-cez-sign-early-works-agreement-to-advance-smr-deployment-in-czech-republic

39. https://www.world-nuclear-news.org/articles/cez-takes-rolls-royce-smr-stake-plans-to-deploy-3gw-fleet

40. https://nsip-documents.planninginspectorate.gov.uk/published-documents/EN010007-003948-Recommendation%20Report%20-%20English.pdf

41. https://www.neimagazine.com/news/uk-planning-inspectorate-releases-report-on-wylfa-newydd-8502287/

42. https://www.thetimes.com/business/energy/article/government-gives-go-ahead-for-sizewell-c-nuclear-power-station-d9xnhmddh?gaa_at=eafs&gaa_n=AWEtsqfQGlIJVQ4StNxIiroLrMGM85CupTAQ40TI6Vi4vUWT6GGMM9Z5dQ3kz_xtrkc%3D&gaa_ts=6946cfb9&gaa_sig=EZf_Utl7KCz04j9zaN2gDkvLq7yTxtmzQlOcEcb1dFaD_m6lLlY7SFqNghnYP5MWM5CmYKazDfblpRm-CWzBWA%3D%3D

43. https://www.gov.uk/government/news/golden-age-of-nuclear-delivers-uk-us-deal-on-energy-security

44. https://www.edfenergy.com/media-centre/holtec-international-edf-uk-and-tritax-announce-plans-develop-cottam-site-data-centres-and

45. https://www.edfenergy.com/media-centre/holtec-international-edf-uk-and-tritax-announce-plans-develop-cottam-site-data-centres-and

46. https://www.nrc.gov/reactors/new-reactors/advanced/who-were-working-with/pre-application-activities/holtec/smr300

47. https://x-energy.com/media/news-releases/x-energy-amp-cavendish-nuclear-welcome-hartlepool-extended-life-plans-as-a-bridge-to-the-future

48. https://www.gov.uk/government/news/golden-age-of-nuclear-delivers-uk-us-deal-on-energy-security

49. https://www.gov.uk/government/consultations/draft-national-policy-statement-for-nuclear-energy-generation-en-7/outcome/draft-national-policy-statement-for-nuclear-energy-generation-en-7-government-response-to-consultation-accessible-webpage

50. https://www.neimagazine.com/analysis/what-the-uk-us-nuclear-partnership-means-for-smr-development/?cf-view

51. The fuel, along with the graphite moderator are contained in tennis ball-sized ‘pebbles’.

52. R.Moormann: Decommissioning problems of German pebble bed reactors. NURIS-1, Vienna

53. https://pris.iaea.org/PRIS/home.aspx

54. S D Thomas (2011) ‘The Pebble Bed Modular Reactor: An obituary’ Energy Policy, vol 39, 5, 2431-2440

55. https://pris.iaea.org/PRIS/home.aspx

56. https://www.ans.org/news/2025-03-31/article-6902/xenergy-dow-apply-to-build-an-advanced-reactor-project-in-texas/

57. https://www.nucnet.org/news/amazon-unveils-updated-plans-for-12-small-modular-reactors-in-washington-10-5-2025

58. https://www.cleanenergyllynfi.wales/

59. “ONR noted that Last Energy’s aspiration to receive a nuclear site licence decision by December 2027 could be achieved if Last Energy delivers the necessary submissions to the required standard and according to schedule.” https://www.onr.org.uk/generic-design-assessment/early-regulatory-engagement-on-new-nuclear-projects/last-energy-pdr-summary-report

60. https://www.onr.org.uk/generic-design-assessment/early-regulatory-engagement-on-new-nuclear-projects/last-energy-pdr-summary-report

61. https://www.gov.uk/government/news/golden-age-of-nuclear-delivers-uk-us-deal-on-energy-security

62. https://www.gov.uk/government/news/golden-age-of-nuclear-delivers-uk-us-deal-on-energy-security

63. https://www.gov.uk/government/publications/nuclear-regulatory-taskforce

64. https://assets.publishing.service.gov.uk/media/65c0e7cac43191000d1a457d/6.8610_DESNZ_Civil_Nuclear_Roadmap_report_Final_Web.pdf

65. https://www.theguardian.com/global-development/2025/dec/18/dont-weaken-health-and-safety-rules-in-the-name-of-growth

66. 20 years from project inception to first power, 60-80 years’ operating life and 60 years for decommissioning.

67. S D Thomas & M V Ramana (2022) ‘A hopeless pursuit? National efforts to promote small modular nuclear reactors and revive nuclear power’ WIRES Energy & Environment. https://wires.onlinelibrary.wiley.com/doi/10.1002/wene.429

68. The AGR choice was followed by the SGHWR, a concept that, after 7 years’ effort, had to be abandoned  because a final design could not be produced. This was followed by the Thatcher objective of ordering one reactor per year for 10 years with the first order in 1981. Only one reactor was built, a decade late and well over budget. The programme instigated by Tony Blair in 2006 should have led to construction of six projects, five of which online by 2030. Only one project went ahead, and it will not be on- line by 2030

69. https://www.gov.uk/government/publications/gbe-n-annual-report-and-accounts-2024-to-2025

70. https://info.westinghousenuclear.com/uk/news-insights/westinghouse-and-uks-community-nuclear-power-collaborate-to-deploy-fleet-of-ap300-small-modular-reactors

71. https://www.energy-uk.org.uk/publications/energy-uk-explains-allocation-round-7-offshore-wind-results/ and https://www.bbc.co.uk/news/articles/cn9zyx150xdo

72. https: ( (www.theguardian.com (environment (2025 (oct (14 (external-insulation-previous-government-scheme-repair-replacing-report-finds

73. https: ( (www.gov.uk (government (publications (warm-homes-plan

74. https://policybrief.org/briefs/sizewell-c-the-last-of-its-kind

75. https://world-nuclear-news.org/articles/rolls-royce-smr-progresses-to-final-step-of-uk-ass

76. https://world-nuclear-news.org/articles/rolls-royce-smr-progresses-to-final-step-of-uk-ass

77. https://www.neimagazine.com/news/smr-competition-heats-up-in-the-uk-10456556/ Holtec applied for a Generic Design Assessment (GDA) for their SMR160 design. In 2024, the size of the reactor was doubled to 300MW. Holtec did not announce when and why this change was made.

78. https://www.gevernova.com/news/press-releases/ge-hitachi-submits-generic-design-assessment-application-in-the-uk-for-the-bwrx-300

79. https://www.world-nuclear-news.org/Articles/Westinghouse-begins-UK-licensing-process-for-AP300

80. https://neutronbytes.com/2023/01/08/six-smr-firms-file-for-uk-generic-design-assessment/

81. https://www.newcleo.com/

82. https://www.copenhagenatomics.com/technology/

83. https://neutronbytes.com/2023/01/08/six-smr-firms-file-for-uk-generic-design-assessment/

84. https://www.nucnet.org/news/european-advanced-reactor-startup-applies-for-uk-generic-design-assessment-of-lfr-as-200-design-12-2-2024

85. https://www.nucnet.org/news/european-advanced-reactor-startup-applies-for-uk-generic-design-assessment-of-lfr-as-200-design-12-2-2024

86. https://www.gov.uk/government/news/wylfa-confirmed-as-site-for-uks-first-small-modular-reactor

87. https://www.gov.uk/government/news/rolls-royce-smr-selected-to-build-small-modular-nuclear-reactors

88. https://holtecbritain.com/holtec-international-and-edf-in-the-uk-announce-plans-to-deploy-smr-powered-data-centres-at-cottam-uk/

89. https://www.edfenergy.com/media-centre/holtec-international-edf-uk-and-tritax-announce-plans-develop-cottam-site-data-centres-and

90. https://x-energy.com/media/news-releases/centrica-and-x-energy-sign-joint-development-agreement-to-deploy-uks-first-advanced-modular-reactors

91. https://x-energy.com/media/news-releases/x-energy-amp-cavendish-nuclear-welcome-hartlepool-extended-life-plans-as-a-bridge-to-the-future and https://x-energy.com/media/news-releases/centrica-and-x-energy-sign-joint-development-agreement-to-deploy-uks-first-advanced-modular-reactors

92. https://www.niauk.org/last-energy-announces-project-in-south-wales-to-build-four-micro-nuclear-plants/

93. https://www.gov.uk/government/news/golden-age-of-nuclear-delivers-uk-us-deal-on-energy-security

94. https://www.neimagazine.com/news/uk-government-announces-support-for-nuclear-innovation-5999434/?cf-view

95. https://www.neimagazine.com/news/uk-government-announces-support-for-nuclear-innovation-5999434/?cf-view

96. https://www.nucnet.org/news/uk-announces-gbp40-million-funding-for-reactor-projects-7-1-2020

97.https://www.rolls-royce.com/media/press-releases/2021/08-11-2021-rr-announces-funding-secured-for-small-modular-reactors.aspx

98. https://info.westinghousenuclear.com/uk/news-insights/westinghouse-program-awarded-10m-from-uk-government-advanced-modular-reactor-project

99. https://www.gov.uk/government/news/british-nuclear-revival-to-move-towards-energy-independence

100. https://x-energy.com/media/news-releases/uk-government-selects-x-energy-and-cavendish-nuclear-for-first-advanced-modular-reactor-award-from-future-nuclear-enabling-fund

Sources for Table 7.

AR1: https://assets.publishing.service.gov.uk/media/5a7ffb0ee5274a2e8ab4d776/Contracts_for_Difference_-_Auction_Results_-_Official_Statistics.pdf

AR2: https://assets.publishing.service.gov.uk/media/5a82efe7e5274a2e8ab5a1bb/CFD_allocation_round_2_outcome_FINAL.pdf

AR3: https://assets.publishing.service.gov.uk/media/5f566aff8fa8f5107025c055/cfd-ar3-results-corrected-111019.pdf

AR4: https://www.gov.uk/government/collections/contracts-for-difference-cfd-allocation-round-4#auction-results

AR5: https://assets.publishing.service.gov.uk/media/64fa0473fdc5d10014fce820/cfd-ar5-results.pdf

AR6: https://assets.publishing.service.gov.uk/media/66d6ad7c6eb664e57141db4b/Contracts_for_Difference_Allocation_Round_6_results.pdf AR7: https://assets.publishing.service.gov.uk/media/6966861de8c04eb2919f773a/contracts-for-difference-allocation-round-7-results-.pdf

AR7: https://assets.publishing.service.gov.uk/media/6966861de8c04eb2919f773a/contracts-for-difference-allocation-round-7-results-.pdf and https://www.gov.uk/government/news/new-auction-delivers-unprecedented-clean-homegrown-power