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The conclusion of the Great British Energy – Nuclear’s (GBE-N) SMR competition and selection of Rolls-Royce SMR’s reactor design has brought delivery of the novel nuclear technology into focus.

In addition to the GBE-N competition, other SMR and advanced modular reactor (AMR) developers are pushing ahead with privately financed plans to deploy power plants without needing to rely on support from the taxpayer.

Attention now needs to turn to planning and building SMRs in a practical rather than hypothetical way.

The draft National Policy Statement for nuclear energy generation (EN-7), published in February, potentially opens up a wider range of types of locations for SMRs to be built, which could previously not have been considered for nuclear development.

EN-7 means that there are new challenges for clients to consider, like proximity to non-nuclear activities such as data centres and steel works, and access to water and grid electricity.

Site identification

Traditional large reactors are generally built miles from residential neighbourhoods, often on the coast and surrounded by countryside. EN-7 and tech giants’ desires to co-locate SMRs with data centres mean developers may be looking at greenfield sites with no history of nuclear activity.

Greenfield versus brownfield is a well-established dichotomy in the world of planning and development, with costs and benefits associated with each. For nuclear deployment, the contrasting options for types of land available for development can be even more extreme.

For example, SMR developers may be comparing greenfield sites with no history of nuclear activities, to brownfield sites with nuclear histories, such as Sellafield and Wylfa.

Jacobs global executive programme director James Hampson says that despite brownfield sites with histories of nuclear activities being assumed as low-hanging fruit for SMR developers, potential costs associated with land remediation can make them on par with non-nuclear greenfield in terms of business case suitability.

Access to significant volumes of water was a key parameter in site location for traditional nuclear reactors. However, Mott MacDonald project director for nuclear (defence and civils) Lewis McVey points out that “many of the reactors now are making safety arguments to say that they can dramatically reduce that volume, or that they don’t need the water at all.”

He explains that if SMRs and AMRs require less water for their operation, “it opens up vast swaths of land that had previously been unviable for these kinds of projects”.

Hampson says the process for identifying suitable SMR sites would start with desktop studies to examine the location holistically, evaluating parameters such as remedial work requirements and proximity to water. This would enable the creation of a business case, which would form the basis of the next step of site development.

A preliminary in situ site assessment would follow, Hampson adds, highlighting that assessments would progressively get more complicated, with cost-benefit analysis used to narrow down possible site locations.

Three or four sites would be selected to be developed in parallel, as a form of risk mitigation against potential issues being discovered at a later stage at any of the sites, Hampson says.

A rendered image of an SMR (Image credit: Rolls-Royce SMR)

Groundwork

McVey says the start of main civil works is dictated by how quickly site characterisation, planning consent and environmental permitting can be carried out.

Hampson echoes McVey, highlighting that SMRs would be major and “very complex” projects.

A significant proportion of the process for delivering an SMR would be administrative tasks like permitting, DCO applications, regulatory approvals, geotechnical work and flood assessment, before workers are able to put shovels in the ground.

“There’s a hugely complex element of non-nuclear work that is required before you even start to look at the actual ground works,” he says.

Site characterisation is an area where particular attention would be paid pre-construction, according to the experts.

Hampson says for sites of former nuclear facilities there is a lot of relevant site characterisation data “that will enable them to move faster compared to a completely greenfield site”.

However, if an SMR developer chooses a greenfield site, extensive ground investigations need to be carried out to determine whether ground stabilisation would be required.

“There might be some strengthening and compression required to give more stability,” says Hampson.

“The civil engineering that you require on a modular reactor in an established site is going to be pretty similar to what it is on a new site,” Balfour Beatty nuclear director Iain Wilson says.

“You still have to put in the deep holes and heavy foundations that are seismically qualified. The only difference might be that on an established site, the geology is proven. If you looked at one of the potential new sites, Wylfa in Anglesey is a hard rock site, so it’s proven to offer resilience to seismic activity. They’ve already built nuclear there, so it’s proven.”

Enhanced protection

Apart from seismic activity, the SMR facility would have to be protected against flooding and potential attacks.

Flood risk mitigation is a critical aspect of nuclear power station design. A nuclear power plant can be in operation for decades, plus the potentially extreme impacts of any incidents or accidents, and the long-term legacy of the site, mean that they must be designed to withstand 1 in 10,000-year extreme weather events.

“The extent of flood defences required to protect an SMR up to the 1 in 10,000 annual chance event depends on the local site topography, the future climate change scenario that is considered in the assessment, and the lifetime of the SMR, including its decommissioning,” Hampson says.

“For any given potential site, if the footprint of an SMR is smaller than a typical nuclear power station, then of course there are advantages with the SMR in terms of the smaller flood defence extent that may be required.”

“However, with nuclear safety cases – as with general planning for infrastructure – there is always an underlying precautionary principle to be followed.”

The push for SMRs to be co-located with energy-intensive industries means the interface between nuclear and non-nuclear activities could be much closer than at present, whereas gigawatt-scale reactors tend to be located in remote corners of the country.

SMR site designers will need to consider how to build those flood ,defences which can withstand 1 in 10,000-year events, and whether they are able to also offer protection to neighbouring properties like data centres.

Hampson adds that the designers of flood defences for SMRs will need to consider which climate breakdown pathway is most relevant and the uncertainty within the calculation which predicts the magnitude of a 1 in 10,000-year event.

He also says floods and other risks which are flood-related but not floods themselves must be factored in, such as “landslides, mudflows and debris in the form of large boulders, trees and motor vehicles, none of which are represented in models.

“In any siting studies, it’s vital to ensure all of these considerations are fully accounted for, balancing all the complex safety, technical, social, sustainability and economic factors, and making sure that flood risk informs the siting.”

Weather events are not the only risk to the SMR facilities as they could also be the targets of attacks.

Nuclear material needs a high level of protection, given the harm it can cause in the wrong hands. Nuclear fuel and irradiated materials need to be kept safe on site and prevented from leaving via unauthorised routes.

A significant proportion of security risk mitigation involves civil engineering, such as earthworks to prevent vehicle attacks, and roads or paths for security patrols.

The physical security of SMRs has been the focus of much debate. In November 2024, King’s College London Centre for Science & Security Studies research fellow Ross Peel told NCE that plans for the physical security, as opposed to cyber-security, of SMRs were “not where they should be”.

Gigawatt-scale reactors are built like modern military fortresses, with armed police officers and significant distances between neighbours and the site ,perimeter, enabling long sight lines to spot threats long before they arrive.

McVey says SMRs will be “likely to require something similar” in terms of a perimeter road which can handle security patrols.

“The circumference of the road [for an SMR] will be much smaller, but overall, you are still likely to need that access road around it,” McVey says.

He adds that for SMRs to take proper account of physical security mitigations, “It’s likely to be more earthwork required. If you look at a lot of the designs of the SMRs, the mounds are there to try to and make it look nice and provide some biodiversity, but the fundamental reason for a lot of them is to stop someone breaking in at high speed with a vehicle,” he says.

A rendered image of an SMR (Image credit: Rolls-Royce SMR)

Transport and grid connections

Moving away from the site and beyond any security fences and flood defences, SMRs will need strong connections to transport and utility networks.

Links to the existing road network will be key for the construction of these reactors, but also for their whole lifecycle, in order to facilitate the movement of workforce and nuclear materials.

“In most cases, there will be large parts of the facility required to be transported to the site. It will require HGVs, which will require sturdy access roads”, McVey says.

“As these [SMRs] are not going to be in highly developed areas where there’s big motorway infrastructure already, bigger access roads and bypasses around villages will be needed.”

McVey says the extent of infrastructure development would depend on the location and the technology. He highlights that the creation of these new roads for SMRs will also benefit local communities through improved connectivity.

Hampson says one of the biggest challenges for the deployment of SMRs is logistics. “We work with micro reactors as well, which are generally in about the 5MW range, and they come on the back of a truck but they are 200t-300t,” he says. “If you’re trying to drive the nuclear battery or reactor down minor roads, they are not geared up for 300t [loads].”

One of the unique selling points of SMRs is their modularity, which can either mean that whole reactors could be modular with one another, allowing them to be stacked next to each other in one location, and/or they could be constructed using modules to build a single reactor. Those reactor modules are likely to be extremely heavy.

Wilson says unusual and heavy loads get moved around the UK “with great frequency”, but specifies that some routes have more capacity to convey heavy loads than others. He adds that for certain loads, some actions may need to be taken such as to “upgrade bridges, take lamp posts down or only move them at night”.

Hampson says it would “definitely” make it easier if SMRs have access to rail. Sizewell C’s plans to extend a rail link out to the planned 3.2GW site will have had a very strong business case. Rail can be expensive to deliver, but Sizewell’s contribution to Great Britain’s energy mix helps justify it.

It is unclear whether SMRs will be profitable enough to warrant the necessary investment to allow for rail network extensions.

McVey says electricity grid connections would likely be a requirement for SMRs because of the need for most of them to export to the grid. Some, however, intend to export their generated electricity to private customers without a need for a grid connection. “You could almost see the formation of local networks, which would be an interesting development,” says McVey.

Hampson echoes McVey and says that SMRs will need a grid connection and will potentially require upgraded access to water.

Last Energy UK says it plans to deliver the UK’s first SMR with its micro-reactor design in South Wales by 2027, far earlier than the plans for SMRs in GBE-N’s programme, so it may be the case that a privately financed project is the first to navigate the complex process of delivering the first-of-a-kind technology.

However, there is a wide range of technologies being considered by established industrial actors like GE-Hitachi and Holtec, alongside entrepreneurial start-ups like newcleo, and it remains to be seen how the process for delivering the civil engineering for an SMR will be carried out in practice.

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