
Table of Contents
Summary
The Government has committed to delivering growth and clean power on a tight budget and tight timeline. To achieve this, they must pluck the lowest hanging fruit. This should include ministers using their existing powers under current legislation, to deliver quick wins.
New nuclear reactor designs, including Small Modular Reactors, can deliver on both growth and clean power. Several companies are ready to invest in building SMRs immediately - creating jobs and opportunities in different parts of the UK.
However, the current interpretation of ‘Regulatory Justification’ assumes that any new nuclear reactor design must be Justified as a ‘New Practice’, despite the fact that nuclear is a recognised and existing technology.
This means each new reactor and vendor has to make a separate application as a ‘New Practice’ in terms of the practice’s benefits and detriments, which takes significant time and money for both the applicant and the government.
Instead, the Environment Secretary should recognise nuclear energy as an ‘Existing Practice’, since nuclear energy is already justified based upon existing operations showing its well-known and rigorously regulated social impact and risks.
This would speed up the development of an essential technology to help the UK, and the world, achieve Net Zero, and support a burgeoning sector in which the UK could be a world-leader.
The Challenge
The UK’s energy costs are among the highest in the world. This is a major constraint on UK growth. There is a growing consensus among economists that high-income, low-energy countries don't exist, and pro-growth economists have overwhelmingly called for boosting energy supply to be one of the top priorities for the new government.
Cheap energy is essential for growth:
Cheap energy reduces costs across all sectors of the economy, including services, but particularly energy-intensive industries such as manufacturing. This increases the profitability of investments and means that firms have more to invest in their workers and capital.
Cheap energy reduces the proportion of household spending on electricity and gas, which means either increased savings (and therefore more investment), or increased spending in the wider economy. Increasing real disposable income is equivalent to boosting wages.
Cheap energy makes the UK a more attractive place to invest. Firms choosing where to base their operations, build data centres or transport infrastructure, are likely to be influenced by the cost of energy.
AI provides a particular opportunity. Training models is hugely energy intensive, but attracting AI investment could have huge productivity spillovers to the wider economy.
Figure 1: The UK has one of the most expensive energy prices in the world

Source: Financial Times, November 2024
However, the UK is in a particularly bad spot when it comes to energy.
On the supply side, the UK is transitioning away from reliance on imported gas and the North Sea. Whilst this is a necessary shift to meet the Government’s Net Zero targets and reduce dependence on Russian gas, the transition does come with the immediate challenge of tighter energy supply and rising costs, as well as integration costs of variable renewable sources and grid development. The situation is further exacerbated by the decommissioning of nuclear power plants and uncertainty surrounding the development of subsea electricity cables in the post-Brexit landscape.
Meanwhile, electricity demand is poised to surge. Policy-driven adoption of electric vehicles and heat pumps will increase household energy consumption, with further demand likely to come from air conditioning with increasing prevalence of heat waves. The expansion of AI data centres, which need large amounts of round-the-clock power, is likely to further add to demand, as is already being witnessed in the United States. For the sake of its economy and Net Zero, the UK desperately needs to produce more cheap, green and reliable energy.
Nuclear: Britain’s energy heritage
The UK used to lead the world in nuclear energy. The UK opened the world's first commercial nuclear power station, Calder Hall, in 1956. This facility marked the UK's leadership in nuclear power during the mid-20th century. By 1965, Britain had more nuclear reactors than the rest of the world combined.
However, the UK has since declined and we have been overtaken by the US, China, France and South Korea in nuclear power generation. The last nuclear power plant built and connected to the UK grid was Sizewell B in 1995. Since then, the UK has decommissioned many of its older reactors, leading to a reduced share of nuclear energy in its electricity generation mix, with further being due to come offline over the next few years.
Despite these challenges, nuclear remains a critical part of the UK’s energy mix and supports jobs and industry across the UK. As highlighted in a recent report from the Tony Blair Institute:
The nuclear industry is already valuable to the UK economy, generating £6.1 billion in GDP for the UK economy in 2021 and employing directly more than 64,000 people. Indeed, relative to other forms of clean energy, investments in nuclear energy may lead to greater employment of both high- and lower-skilled resources for the construction of nuclear reactors, with a multiplier of about four. These jobs are well paid, long term and predominantly local to where construction takes place, helping to drive economic activity in a number of regions. Research comparing power-sector pay in the US in 2017 indicates that nuclear workers receive compensation that is one-third higher than that in the wind and solar sectors, and twice the average for power-sector workers. Oxford Economics has found that in 2021 each nuclear worker in the UK contributed an average of £95,300 in gross value added (GVA) to the economy. Adjusting for full- and part-time work in the civil nuclear sector, this reached £102,300 in GVA per full-time equivalent worker. This is nearly twice as high as the median UK figure.
In 2021, 46 per cent of the jobs in the civil nuclear industry were concentrated in areas deemed by the government to be in the highest need of investment. This demonstrates the potential for the nuclear industry to drive economic development across the whole country and in specific areas in greater need of this development. For instance, the US nuclear-engineering group Holtec recently selected a north of England location as the site for its new SMR factory, representing a £1.5 billion investment and hundreds of skilled jobs. It will produce SMR components for use within the country and the wider region. With a more favourable policy environment, the UK can continue to attract these types of opportunities.
Building nuclear power in the UK has become expensive and onerous due to self-imposed regulations and restrictions. One example of this challenge is the Regulatory Justification process, which has prevented new entrants to the UK market.
We estimate that the immediate financial cost of the current Regulatory Justification process amounts to around £2m per reactor design. This is in addition to the time and financial costs of delaying construction, and the downstream economic impacts of delaying supply of more affordable, abundant energy.
Table 1: Estimates of costs of Regulatory Justification process

The Opportunity
Nuclear energy presents a significant opportunity for the UK. In a poll conducted by UK Day One, pro-growth economists ranked it as the second most important area for the Government to focus its time and political capital, and the top priority for financial investment.
Figure 2: Results from the UK Growth Survey cite nuclear energy as a top priority

There are two main reasons why nuclear power can be so valuable for the UK economy.
First, as has been well-argued elsewhere, nuclear has considerable advantages for the UK over other energy sources. Unlike wind and solar, it can provide a continuous baseload power, making it particularly valuable for industries and energy-intensive facilities like AI data centres that require a reliable and consistent energy supply, regardless of weather conditions. On a whole system basis, nuclear power can be cheaper than other options due to minimal transmission and grid upgrade costs. This means that the actual cost faced by consumers is lower.
Second, there are benefits to industry. The UK has a particular opportunity to become a world leader in the development of small modular reactors (SMRs) and the next generation of nuclear technology.
One of the main reasons why nuclear fell out of favour in the UK was the high capital costs and slow timelines for building new reactors.
Whilst nuclear power is capital intensive and slower than many other generation projects, many of the costs and delays in building new nuclear reactors are self-imposed, stemming from onerous regulations and requirements for bespoke reactor design.
One example of such a regulatory hurdle, that could easily be avoided, is the ‘Regulatory Justification’ requirement.
Under the current system, every new reactor design and vendor is expected to apply for Justification as a ‘New Practice’. This is due to a 2009 interpretation of the Justification of Practices Involving Ionising Radiation Regulations 2004 (JoPIIRR), a statutory instrument. This interpretation of justification specifically stated that technical differences between reactor designs might lead to variations in their benefits and detriments. However, the 2009 decision did not identify any such differences, making this simple speculation. Meanwhile, any differences between reactor designs are already covered by the wider regulatory framework for nuclear reactors.
Application for Justification as a ‘New Practice’ takes two years and is expensive for both the applicant and the government (as outlined in the table above), which then has to make a determination about the overall societal costs and benefits of a reactor design. It is regrettable that this interpretation was made in 2009, and it would be legal and preferable for a different interpretation to be made going forward.
As has been argued elsewhere, a design-specific approach is duplicative of existing regulation as benefits and detriments are already considered comprehensively under the existing regulatory framework for nuclear installations (specifically Nuclear Site Licenses, Environmental Permits, and planning permission). Indeed, previous Regulatory Justification decisions all make reference to and rely upon the existing regulatory regime when making determinations.
There is a significant opportunity to remove the duplicative Regulatory Justification requirement by recognising nuclear as an ‘Existing Practice’.
Nuclear power has a long history in the UK. The technology is well established and understood, and should therefore be recognised as an ‘Existing Practice’. This means that the Government has already recognised that the benefits from nuclear energy significantly outweigh the risks, and this is also reflected in the Government’s position.
In addition to the wider growth benefits arising from nuclear energy, this will save the taxpayer money and free up valuable civil service and regulatory capacity. Reform in this area would also demonstrate this Government’s firm commitment to delivering clean energy, removing unnecessary regulation, and finding efficiencies wherever possible to enable growth.
There is some urgency to these considerations. Rolls Royce has progressed to the final round of the Great British Nuclear SMR procurement competition, completed step two of the Generic Design Assessment from the Office for Nuclear Regulation, and received hundreds of millions of pounds from the Government. Despite these achievements, Rolls Royce SMR only submitted for a Regulatory Justification decision that it is Justified as a ‘New Practice’ in July 2024, and the government – specifically DEFRA – is still processing the application and expects to take two years to finalise the decision. Rolls Royce is the only participant in the GBN procurement process to have submitted for Regulatory Justification – giving some indication of the cost and resources involved in such an application, as well as the fact that it is not considered a priority when progressing through the UK’s nuclear regulatory process.
Running a procurement competition for technologies which, officially, still have to go through a two year process to determine whether the benefits outweigh the detriments is confusing and undermines the government’s policy position as well as investor confidence. Removing the duplicative Regulatory Justification requirement would resolve this and provide certainty for future investors and developers of nuclear technologies.
Plan of Action
The Secretary of State for Environment, Food and Rural Affairs is the Justifying Authority for Nuclear Energy. This means he has the power to issue a Regulation 12 determination of Regulatory Justification, that “the use of ionising radiation for the generation of electricity from nuclear energy using oxide fuel of low enrichment in fissile content in light water cooled, water moderated thermal reactors” is an existing (as opposed to new) practice.
If the minister were to take this route, a three-week consultation with statutory consultees (as detailed in section 18 of JoPIIRR) would be required and the Statutory Instrument would then need to be laid before Parliament. So defined, this Justification determination would enable all of the participants of the GBN process to push ahead with building SMRs. It is as simple as that.
FAQs
Is this Legal?
Mr Stephen Tromans KC has given his legal Opinion on three points and he gave the underwritten answers:
Whether this is an existing practice;
“It would for the reasons above in principle be possible to regard the PWR-20 and other light water fission reactors as belonging to the same existing practice as Sizewell B PWR.”
Whether it would be lawful for Defra to make a determination to that effect;
“such a determination would differ from that made in 2009, but that does not mean it would be unlawful, provided it is properly reasoned and explained why the approach has changed.”
Whether Defra could do this on the basis of either information which has been used in recent applications for regulatory justification and/or other information readily and publicly available to them.
“Defra can rely on the information and reasoning contained in the determinations for the ACR-100, the AP1000, the EPR and the ESBWR … the issue does not materially turn on details of an individual design but rather on generic issues, including the required standards of safety which would apply equally to the PWR-20 and other light fission reactors and should not be affected by the specific design.”
More detail in this article from Herbert Smith Freehills LLP.
Why hasn’t this been done before?
There is a lack of precedent in this space. There has only really been one Regulatory Justification application, which was in 2009, and it was successful. Since the legislation was introduced in 2004, there have only been three proposed nuclear projects: EPRs at Hinkley and Sizewell; and an ABWR at Wylfa (under Horizon, which failed). Both of these designs sought and received regulatory justification.
This application was for a broad definition of nuclear energy and it could have been determined to be an ‘Existing Practice’. Instead the expectation was set that each reactor has to apply anew individually. To quote Stephen Tromans KC “With the benefit of hindsight, it is probably regrettable that the Secretary of State in 2009 took the approach he did.”
Appendix: Legal Framework
Under the Justification of Practices Involving Ionising Radiation Regulations 2004, as amended in 2018 ("JoPIIRR"), such a class or type of practice must be “Justified” to be allowed to take place within the UK. These regulations implement requirements of the Euratom Treaty and the European Directive 2013/59/Euratom (“the 2013 Directive”). The JoPIIRR legislation provides a procedure for the Justifying Authority to make justification decisions determining whether a class or type of practice is justified (reg. 4(3)). The key definitions are:
"Justified":
In relation to a class or type of practice, it means that the individual or societal benefit resulting from the class or type of practice outweighs the health detriment that it may cause (reg. 4(2)).
"Practice":
As per the 2013 Directive, article 4(65), it means “a human activity that can increase the exposure of individuals to radiation from a radiation source and is managed as a planned exposure situation”.
“New” Practice:
By reg. 4(1), a class or type of practice is “new” for the purposes of the 2004 Regulations if either: (a) No practice in that class or type was carried out in the UK before 6 February 2018; or (b) A practice in that class or type was carried out in the UK before 6 February 2018 but was in breach of a requirement not to carry out a practice unless justified, and in either case the class or type of practice has not been found to be justified.
“Existing” Practice:
By reg. 5(3), a class or type of practice is “an existing class or type of practice” if either: (a) A practice in that class or type was carried out in the UK before 6 February 2018 without breaching any requirement not to carry out a practice in that class or type until that class or type had been found to be justified; or (b) It has been found to be justified; or both.
“Class or type” of Practice:
No definition of “class or type” of practice is provided in legislation, guidance, or directives; instead, it falls to the discretion of the relevant Justifying Authority to determine how broadly or narrowly "class or type" should be interpreted in each case of practices involving ionising radiation.
Enforcement
By reg. 4(5), no person shall carry out a practice, resulting in exposure to ionising radiation, belonging to a new class or type of practice. Breach of this provision may be the subject of enforcement procedures by service of a contravention notice under reg. 22, failure to comply with which is a criminal offence under reg. 24.
Comparing Classes
Since 2010, Justification of Practices Involving Ionising Radiation Regulations (JoPIIRR) decisions for nuclear energy generation have been applied on a design-by-design basis. This approach is unique to nuclear energy. In contrast, other justified classes or types of practice adopt a broader scope, as demonstrated by the following examples:
Use of ionising radiation in smoke and fire detectors and other safety instruments, 5th July 2005.
Transport of radioactive material by road and rail in accordance with the regulations concerning carriage of dangerous goods by road (ADR) and rail (RID), 14th February 2007.
The enrichment of uranium by use of the centrifuge process, 14th October 2008.
Use of radiological material for live agent training of at-risk groups, 2nd February 2009.
Deconversion of uranium hexafluoride to uranium oxide for long-term storage, 16th March 2009.
Use of body scanners for the detection of concealed items on the person for security purposes, 21st March 2016.
In comparison, justification decisions specific to nuclear energy have been made for individual designs:
The generation of electricity from nuclear energy using oxide fuel of low enrichment in fissile content in a light water cooled, light water moderated thermal reactor currently known as the EPR, designed by AREVA NP, 18th October 2010.
The generation of electricity from nuclear energy using oxide fuel of low enrichment in fissile content in a light water cooled, light water moderated thermal reactor currently known as the AP1000, designed by Westinghouse Electric Company LLC, 18th October 2010.
The generation of electricity from nuclear energy using oxide fuel of low enrichment in fissile content in a light water cooled, light water moderated thermal reactor currently known as the ABWR, designed by Hitachi-GE Nuclear Energy Ltd, 12th October 2015.
This design-specific approach continues with two pending applications for nuclear energy:
The generation of energy from nuclear fission using mixed oxide fuel in the lead-cooled fast reactor currently known as the LFR-AS-200, designed by newcleo, application received 22nd March 2024.
The generation of power from nuclear energy using oxide fuel of low enrichment in fissile content in a light water cooled, light water moderated thermal reactor currently known as the RR SMR, designed by Rolls-Royce SMR Limited, application received 9th July 2024.
Tone Langengen is a senior policy advisor at the Toby Blair Institute. She is an expert in net-zero policy and strategy. Her work highlights the importance of practical policy solutions that address climate change. Prior to joining TBI, Tone worked in the UK civil service on various net-zero policy areas such as heat-and-transport decarbonisation and green growth. In addition, she worked in the Cabinet Office where she helped deliver the response to the Covid-19 pandemic.
David Lawrence is the co-director of the UK Day One Project. He has worked in Westminster policy for the last decade, including at Chatham House, in Parliament, and as a parliamentary candidate. He holds degrees from the University of Oxford and the London School of Economics.