A concept which was considered academic only a decade ago is now being considered seriously, according to a new report by the OECD’s NEA, titled SMRs for replacing coal: opportunities and challenges.

Report author Jordan Cox claims: ‘SMRs are no longer a theoretical solution but are rapidly becoming a commercial reality. Many companies are interested in coal-to-nuclear transitions, because nuclear could fill the same role as coal without emissions, and other advantages.’

According to the latest NEA dashboard, 127 SMR designs have been identified globally with 74 under active development, financed from either public or private sources. Last week, the US announced $800mn of funding to develop SMRs at two former nuclear sites.

Since the early 2000s, coal has been losing its dominant position as an energy source because it is no longer the cheapest form of energy production due to environmental regulation and ageing infrastructure. However, the decline of coal for electricity production comes with challenges in terms of loss of baseload energy for reliable, resilient energy systems.

But that does not mean those sites, or the permits they required, are worthless. Cox suggests ‘many of the infrastructures and legal frameworks supporting these coal plants are still valuable, with water cooling systems, grid interconnections and environmental and land-use licences with decades of useable life’.

As coal phase-out continues, other more sustainable resources like nuclear energy could offer viable options. ‘As many countries pursue decarbonisation, coal-to-nuclear replacement could present a unique opportunity to maintain the existing baseload, grid infrastructure and employ workforces, while reducing emissions,’ he says.

SMRs can provide up to 300 MWe. They are designed to be smaller than conventional GW-scale reactors, and utilising modular manufacture offer potential cost savings.

Key benefits
The key benefits for considering nuclear energy as coal plant replacement include emissions reduction, opportunities for workforce transition, baseload replacement where SMRs offer flexible operations, for grid compatibility with accessible grid interconnections and site permits, and for reliable power, as SMRs like other nuclear plant typically operate an 18–24 month refuelling cycle.

There are also opportunities for long-term savings, although the NEA recognises that nuclear energy has high upfront costs, which may be distributed over several decades.

The potential market
The total market for coal replacement by SMRs is estimated to be 2.2 TWe, according to Global Energy Monitor (2023). Of this, 450 GWe of coal capacity could be transitioned from coal to-nuclear technologies by 2050.

The primary regions where this technology transition could occur are North America, Europe and Asia. The NEA suggests that countries can be divided into groups – depending on whether they adhere to International Atomic Energy Agency (IAEA) protocols for developing nuclear technologies under the Non-Proliferation Treaty, lack nuclear phase-out policies, or already have nuclear energy in their energy mix.

What’s more, adoption of net zero policies could accelerate the phase-out of ageing coal units for potential replacement by nuclear energy.

Given a potential market for coal replacement with SMRs of 143 GW by 2035, North America, and the US in particular, has the largest potential for the coal-to-nuclear transition (104 GW), with an ageing nuclear fleet and experience in running coal and nuclear energy assets. The remaining opportunities are spread across Europe (22 GW), led by the UK, South Africa and Asia.

Developments in Asia are led by the Republic of (South) Korea. In December 2024 the Korean government formed the Coal-fired Power Transition Council to minimise the adverse impact of domestic coal-fired plant shutdowns on regional economics and to reuse existing infrastructure such as power generation plants. The newly published Power Plant Transition Roadmap mentions research on converting domestic coal-fired plants to carbon-free energy sources, such as SMRs at smaller sites.

In addition, potential Asian markets include Indonesia, Japan and the Philippines.

In Europe, there are opportunities for coal-to-nuclear in the UK, Poland, France and Czechia.

India’s ambitions
Dr Rahul Tongia, Senior Fellow at the non-profit think tank Centre for Social and Economic Programme (CSEP), spoke at the NEA report launch. He points out that India has ambitious plans for non-fossil generation, primarily wind and solar – aiming to double renewable energy capacity to 450 GW by 2030. Though India had the first nuclear reactor in Asia, the share of electricity from nuclear is only 3%. However, the plan is to grow the capacity from about 8 GW to over 16 GW in a few years, with ambition to reach 100 GW by 2047.

India has used Canadian and Russian reactor designs to date, but has plans for global collaboration, including using SMRs in its Nuclear Energy Mission plan. But this means moving away from incumbents such as public sector enterprise, under the Nuclear Power Corporation of India, towards the private sector ‘which brings money, technology and scale’, he says.

There is also a need for improved regulatory approvals to address land acquisition. ‘SMRs might be more attractive if they can lower the buffer zones because of safety concerns, as well as offering fuel cycle benefits,’ remarks Tongia. Plans are being considered by NTPC, India’s largest coal power company.

From an economic perspective, re-use of buildings and permits can save up to 10% in reconstruction studies, Tongia estimates. Reduction of the heat sink can offer up to 20% capex saving; and up to 35% savings where there is alignment of the Rankine steam cycle in the turbine hall and associated systems.

India’s coal fleet is relatively young, with almost half built between 2011 and 2016, and a sizeable number of older plants at end-of-life. However, the country is behind schedule on adding renewable energy and therefore falls back on its coal power.

‘Moreover, utilities are typically risk averse with capital intensive investments and perceive SMRs as a “not least cost and risky” option from a plant-level perspective,’ notes Tongia.

The NEA report points out that: ‘While many organisations were interested in coal-to-nuclear replacement, they did not want to be “first movers”, due to the risks associated with first-of-a-kind construction.’ This led to a consensus that there was an important role for governments in reducing risk and speeding or demonstrating coal-to-nuclear replacements.

What coal-to-nuclear plant transition involves
Coal-to-nuclear can take three forms:

• Replacement – with re-use of land and permits.
• Repurposing – involving not only re-use of land and associated permits but also grid connections.
• Repowering – which is the most technically challenging, but also yields the most economic benefit by maximising the infrastructure that is re-used, such as using existing grid connections, land permits, auxiliary buildings, cooling systems and the steam cycle (to accommodate new generation technology such as gas or biomass).

In terms of site location, nuclear plants require more stringent site conditions than coal plants. Understandably, they must be more geologically stable, located away from seismic fault lines or flood-prone areas.

Although existing grid connections could often be re-used for nuclear plant when transitioning from a coal plant, further grid infrastructure may be required to build capacity. The cooling infrastructure may need to be augmented or upgraded, with sufficient cooling for waste heat handling. Unlike coal plants, nuclear plants need containment buildings for the reactors, to protect against radiation leaks in an accident scenario. There is also a need for nuclear waste management, with onsite nuclear storage or transport to a centralised repository. Coal infrastructure must also be decommissioned, with dismantling and clean-up of ash ponds.

Furthermore, Cox says: ‘Though some companies are interested in transitioning coal-to-nuclear, there are no SMRs or licensing pathways for this transition.’ Consequently, he sees a role for governments who have gone through the process of pre-licensing and identifying coal sites that may be of interest as nuclear sites.

Increasingly, with SMRs there is a desire to use nuclear as a load following technology – whether as baseload or dispatchable configurations, where there is grid compatibility and reliable power. ‘Since renewables are variable, you need reliable backstop power to meet demand when renewables aren’t available, which opens an opportunity for nuclear replacing coal plants,’ remarks Cox.

A recovery vision
Antonio Vaya Soler, Manager and Strategy Analyst at green consultancy Lucid Catalyst argues that there is an economic case for coal-to-nuclear transition as ‘competitive repowering’. ‘As soon as you can put some carbon price policy incentive in place, things change dramatically… Looking ahead, we can expect to reach some sort of cost parity with a nuclear asset at some point. And if nuclear assets are built better and faster, things will get cheaper, meaning that the level of policy incentives would be lower to bridge the gap.’

He suggests that the ‘Recovery Vision’ of Lucid Catalyst partner Terra Praxis offers cost effective, faster deployment of nuclear power at a former coal plant, with containerised SMRs designed for manufacture and assembly, which could be site independent. (Its Founding Director and co-CEO is Kirsty Gogan FEI.) The systems would feature thermal storage as a buffer that facilitates integration. And potential customers include data centres.

‘Today there are some containerised SMR designs, mostly micro-reactors and molten salt designs, offering flexibility and quick delivery. Using mass manufacturing, with simpler geometry, smaller, low-pressure components and advanced nuclear technology with standardised deployment architecture. These systems are designed to encourage an increased pool of suppliers,’ says Soler.

As mentioned, in the longer term the NEA sees the market for coal replacement could reach 450 GW, which represents more than the current global nuclear capacity today. That’s certainly a big ambition.

• Further reading: ‘World-first for Canada as global interest in SMR surges’. The Western world’s first SMR is being built at Darlington in Canada, spotlighting a global surge in SMR projects fuelled by soaring data centre energy demand. 
• ‘Small is beautiful: UK plans for small modular nuclear reactors’. As momentum gathers under the UK government’s Nuclear Roadmap, what’s on offer and how do the technology options differ here and worldwide?