SMRs for flexibility

Small modular reactors (SMRs) are increasingly cited as a solution to the grid gridlock and increasing demand for clean energy. The relatively small nuclear plants emit no CO2, can provide both power and process heat, and are flexible and can be deployed locally.On the desk of Dirk Rabelink, director and co-founder of the company ULC-energy, are two Lego structures. One is a model of the Borssele nuclear power plant, which has been in operation since 1973, the other a model of a not-yet-existing SMR(small modular reactor) from the British company Rolls-Royce, known for the aircraft engines and cars it previously made. The Lego constructions are almost the same size. 'And they are on the same scale,' says Rabelink. So the difference between the Borssele power plant and that of Rolls-Royce (now Rolls Royce SMR) is not in the S of small, but in the M of modular.'People often think of an SMR as a small power plant, fitting on a football pitch. But there are different types,' says Rabelink. SMRs, by definition, deliver electrical power of up to five hundred megawatts. Borssele delivers a net 485 megawatts of electrical power, the power plant being developed by Rolls-Royce SMR 470 megawatts. By comparison, the first floating nuclear power plant Akademik Lomonosov, which has been supplying power to Chukotka in Russia's far northeast since 2019, delivers seventy megawatts. The four new, large nuclear power plants that the government plans to build in the Netherlands will each have an electrical capacity of 1,000 to 1,600 megawatts.The innovation of Rolls-Royce SMR's power plant lies in its modular design. The idea is that all parts are made in factories and the SMR is assembled on site, much like a prefab house. For building a whole series of power plants, that is the cheapest way - and that is exactly what Rolls-Royce SMR plans to do. ULC-energy wants to place some of these power plants in the Netherlands.The advantages of nuclear power are its lowCO2 emissions, the limited space it requires compared to solar or wind power, and its constant supply. The advantage of relatively small power plants is that they can be deployed locally, without further burdening the electricity grid. Bij ULC-energy staan LEGO-modellen van de kerncentrale Borssele (rechts) en een toekomstige Rolls-Royce SMR, beide op dezelfde schaal. Foto: De Ingenieur Proven or new'SMR is indeed a catch-all term, covering many types of nuclear power plants,' says Marieke van Gemert, manager of new construction at the nuclear research and advisory group NRG PALLAS, through a tiny screen on my phone - just today the power is out. Broadly speaking, they can be divided into SMRs based on existing technology, which includes Rolls-Royce SMR, and SMRs based on new, advanced technology (see box Techniques). Van Gemert: "That's what they call it, although existing technology is also quite advanced SMRs based on new technology can even be so small that they fit in a shipping container.We speak to each other on 22 April, the day it was announced that the power grid in the Utrecht region is full and will be locked: from 1 July, all new applications for a connection will be put on a waiting list, otherwise grid congestion problems will occur during peak hours. 'Very appropriate,' says Van Gemert. 'Because that is exactly the problem for which SMRs provide part of the solution.'SMRs can be deployed locally, is the thought. By not connecting them to the national grid, they can power data centres, large industries and business parks without further burdening the national grid. They then supply the power or heat directly or via a local grid that operates independently of the national grid. 'Or you do connect them to the national grid and agree that they only supply power when much of it is needed and little available from wind and solar,' says Rabelink. Clean energy clustersRabelink worked on the commercial side of the energy sector for much of his career. He was responsible for global sales of nuclear fuels (mainly uranium) to nuclear power plants from Singapore for Dutch/Australian company BHP Billiton, landed in commercial oil and gas sales in Texas after the Fukushima earthquake, when sentiment towards nuclear power changed, and worked in the Netherlands for a company making blending biofuel from waste fats.In 2022, he founded ULC-energy with a colleague. Rabelink: 'We saw a lack of willingness among project developers to include nuclear energy in their energy mix. That's why we are doing it now.' ULC-energy develops clean energy clusters: energy hubs equipped with an SMR, at locations where the energy is consumed directly. Rabelink: 'Then you don't use the public grid and don't need to build it out.'One of the requirements the founders of ULC-energy have for their SMRs is that they are guaranteed to provide energy 90 to 95 per cent of the time. 'That is why we chose a technology that has already proven itself,' says Rabelink, 'and whose costs are known and whose infrastructure is already in place.' These include supply chain, fuel, licensing requirements and reliability. Rabelink: 'Then you quickly end up with a classic light-water reactor, similar to the one at Borssele. But if new technologies have proven themselves, we are open to that too.'Power and heatAn additional advantage of an SMR close to a major industry is that it can provide not only power, but also heat. Indeed, splitting atomic nuclei of uranium in the reactor vessel releases energy in the form of heat, which converts water into steam. That steam can be used to drive a turbine and generate electricity, but can also be used directly in the industrial process. 'This is a godsend for companies that need a lot of process heat,' says Van Gemert.'Rolls-Royce SMR SMR has the inherent flexibility to supply up to four hundred megawatts of its power thermally in the form of steam,' says Rabelink. 'That's almost a matter of just flipping a switch.' Industrial sectors such as the paper and food industries are particularly well placed to use that. Rabelink: 'Otherwise, they have to burn gas to make that steam.'In other industries, such as Chemelot in South Limburg, an SMR is mainly useful for supplying electricity. Van Gemert: 'If they want to useCO2-free energy there, the alternative is electricity from a wind farm in the North Sea. And that does require substantial investments in the grid.'The idea of putting an energy source next to the user is not new, Rabelink stresses. 'People used to do that too. Coal was in Limburg, industry was built next to it. Only when the coal mines closed did people start bringing energy to that industry.'De werking van een kernreactor met zogeheten ‘bewezen technologie’. DepositphotosTechniquesProven technologySMRs with proven technology use the same principle to generate steam or power as a conventional nuclear power plant. The nuclei of heavy atoms, usually uranium, are bombarded with neutrons, causing them to split. In the process, thermal energy is released and new neutrons shoot off. These in turn hit other atomic nuclei: a chain reaction ensues. This process takes place in water, which heats up quickly as a result. Thanks to a control vessel that maintains the pressure, it does not boil. The water gives off its heat in a heat exchanger, to water in the 'secondary circuit'. That water becomes steam, which is either used immediately or drives a turbine that produces electricity, which is then cooled further.The fuel (nuclear fuel) is in the reactor in the form of rods. Between them are control rods, made of a material that absorbs neutrons. These can be used to slow or stop the chain reaction.High-temperature reactorA high-temperature reactor (HTR) uses pyrolytic graphite as a neutron moderator and an inert (very stable) gas, such as helium, nitrogen gas or carbon dioxide, as a coolant. The temperature in the reactor can reach 1,000 degrees Celsius.The fuel used consists of TRISO (TRI-structural ISOtrope) particles and is shaped like spheres instead of rods. The particles themselves consist of a core of uranium, carbon and oxygen, enveloped by three layers of carbon and ceramic materials that prevent the release of radioactive fission products. A TRISO particle is about the size of a poppy seed and acts as a tiny pressure vessel. The final fuel element is a graphite sphere the size of a billiard ball, into which thousands of those particles are squeezed. Graphite ensures that the chain reaction in the TRISO particles can never get out of control.Tests in the High Flux Reactor at nuclear research institute NRG PALLAS in Petten have shown that a reactor with TRISO fuel can withstand extreme conditions. The reactor regulates itself and remains stable. In case of a failure, the system automatically shuts down and the reactor cools down. The particles do not melt and can withstand much higher temperatures than what current nuclear fuels can withstand.Molten saltThe molten salt reactor is considered a promising technology. In the Netherlands, the company Thorizon is working on it. The reactor Thorizon is making can run on different fuels, including thorium and nuclear waste. The nuclear fuel is mixed with liquid salt, which can reach temperatures between 450 and 750 degrees Celsius. This salt is the material that transfers heat from the nuclear reaction to water. This then turns into steam, for electricity or process heat.Molten salt reactors cannot overheat. The liquid salt is simultaneously a coolant: as the temperature increases, the salt expands and the fission rate decreases sharply. The system runs at low pressure and because temperature escalation is prevented, it remains that way under all conditions. No active safety systems are therefore required.Molten salt reactors have great fuel flexibility. Thorizon works with the company Orano, which can convert the long-lived elements from nuclear waste into a fuel in the form of salt. With this, Thorizon can generate energy, leaving short-lived nuclear waste. The nuclear waste needed by Orano is widely available, which is why Thorizon is only betting on this for now.One of the challenges with the molten salt reactor is finding a suitable material for the reactor vessel. Salt causes corrosion, which corrodes the material.SlowNot everyone is enthusiastic about SMRs. They take too long to get there - because both climate change and grid congestion require action now, one of the common objections. In addition, the cost per megawatt is significantly higher than for larger nuclear plants, and spreading nuclear plants over multiple sites also spreads safety and nuclear waste problems. That it will be some time before the first SMRs will appear in the Netherlands is indeed true. Rabelink thinks ULC-energy could connect the first Rolls-Royce SMR in the Netherlands in ten years' time. 'Faster realisation of a commercial SMR in the Netherlands does not seem possible to me.' SMRs based on existing technology already exist in other countries, such as China and Russia, and a few are being built in Ontario in Canada. The UK and Czech Republic are also a little further ahead than the Netherlands: contracts with Rolls-Royce SMR have already been signed there.Among companies, it is mainly the tech giants that are investing in SMR technology. Google, for instance, has an agreement with nuclear power company Kairos Power, which wants to use TRISO fuel (see box Techniques). Van Gemert: 'And in the Netherlands, too, companies are looking at how they can become more sustainable or more independent of the power grid.' Shipbuilder AllSeas, for instance, hopes to equip its first ships with an SMR in five years' time, of 25 megawatts electric, also with TRISO technology.And yes, that takes time, says Van Gemert. 'But so do other solutions. The grid reinforcements the grid operators are working on won't be ready today or tomorrow either.' Moreover, the current problems will persist for some time, she thinks. 'The entire industry still has to become more sustainable, so energy demand is going to increase substantially in the coming years. I believe in a long-term vision and SMRs can certainly play a role in that.'Een microreactor als aanhanger achter een Tesla? Onzin, veel te zwaar, zegt Rabelink. Beeld: Hadron Energy MoneyThe argument that SMRs are more expensive than large nuclear power plants also cuts to the chase, says Rabelink. 'This works on the principle of economics of scale, which certainly applies to nuclear technologies. Radioactive radiation heats up water in a vessel. The larger such a vessel is, the more energy is generated and it becomes cheaper per megawatt-hour. You lose huge potential if you make the vessel smaller.'In November, a picture circulated on the internet of a microreactor as the trailer of a Tesla cybertruck. 'Nonsense,' says Rabelink, 'because such a container is far too heavy for such a truck. But moreover, we see that any company that starts optimising such a container first makes the design bigger.' This was also noticed by the North Holland municipality of Opmeer, looking for a party that could supply a micro-SMR with an electrical power of twenty megawatts at most. This seemed to succeed for a while, with the company Westinghouse's so-called eVinci, but in the end it turned out to be too expensive. Rabelink: 'Westinghouse even decided to stop this reactor altogether for civilian purposes, because the costs were disproportionate and the eVinci could not be sold commercially.' Now the company is targeting specific audiences with it, such as defence.With SMRs of five hundred megawatts electric, the optimum size has been reached, says Rabelink. 'These are also cheaper than the larger nuclear plants, if you factor in complexity, feasibility and logistics.' What plays into this is how big the components can still be to make them efficiently factory-made and transported to the construction site.Nuclear power in the NetherlandsAfter a long period when the Dutch government wanted to get rid of nuclear power, the tide turned a few years ago. The current government wants to keep the existing nuclear power plant in Borssele open longer and build four new nuclear power plants in the Netherlands, each with a capacity of 1,000 to 1,500 megawatts.Small nuclear reactors can also play an important role in the Netherlands' future energy system, knowledge institute TNO and NRG PALLAS concluded in late 2024 from an analysis of the Dutch energy system. Depending on future industrial activity in the Netherlands, there will be room for two to 13 SMRs, each with an electrical capacity of 150 megawatts, by 2050, according to this study.An energy system without new nuclear plants is 1 to 2.5 per cent more expensive than with new nuclear plants, TNO concluded earlier. While it is true that nuclear power plants are more expensive than wind turbines and solar panels, the flexibility options needed to get through periods when they are not supplying energy, such as energy storage, have relatively high costs.Other sourcesNuclear power is more expensive than energy from solar or wind. Research institute Fraunhofer concludes in a report on levelised cost of electricity (LCEO, which is the total cost over the entire lifetime of the power plant) that solar energy costs between 6 and 22 euro cents per kilowatt-hour, wind energy between 4.3 and 10.3 euro cents, and nuclear energy comes out at between 13.6 and 49 euro cents.But modular construction makes SMRs much cheaper than non-modular ones, says Rabelink, because the parts are standardised and come rolling off the assembly line, so to speak. 'And the fact that SMRs can be deployed locally and therefore do not require grid reinforcement should also be factored into the cost.' The report FIEN, (Financial Impact of Energy Policy for Grid Operators), which came out in March 2026, reports that the total investment task for that grid reinforcement over 2026-2040 will come to 269 billion euros - assuming that the new cabinet will develop ten gigawatts more wind energy than the previous cabinet planned.On safety, both Rabelink and van Gemert are not worried. Van Gemert: 'There are very strict safety requirements, that is absolutely right, and they comply. Everyone has to comply with them, even at smaller power plants.' Rabelink: 'I have seen many energy industries from the inside, and I dare say that no energy industry operates as professionally, sophisticated and responsible as the nuclear power industry.'Other opinionsOlof van der Gaag, director of the Dutch Renewable Energy Association (NVDE), says the NVDE is not specifically concerned with SMRs. 'But in general, it is good to look at the energy system not only centrally, but also decentrally. With local generation, you can counteract local demand congestion. The advantage of SMRs here is that you can locate them where they have added value, for instance at Chemelot industrial cluster'Nuclear physicist Nasser Kalantar, professor at the Energy and Sustainability Research Institute at the University of Groningen, sees nuclear energy as a necessary addition to the mix to meet energy transition targets. 'SMRs are an important component in the new systems, because of the relative ease with which they can be made and the potential placement near large users,' he previously told De Ingenieur - and he says he has not changed his mind. 'The prediction is that the cost will come down.'Kalantar does not see safety and waste issues as insurmountable challenges. 'The regulations for large nuclear plants are strict, it will be no different for SMRs,' he says. 'Of course the safety of each plant has to be properly monitored, but so do other large equipment. And we are lucky that the Netherlands already has a good infrastructure for nuclear power, because we already have a nuclear reactor and other nuclear-related activities.' These include reactors, an enrichment plant (Urenco) and a storage facility (COVRA), as well as regulators and the research and advisory institute NRG.Energy securityThe biggest challenge Rabelink sees for installing SMRs in the Netherlands is not technical. 'Nuclear energy involves emotion, I cannot solve that with a technical-economic story. It is mainly due to the current geopolitical development that opinion is turning. People want clean energy, but also energy security. We think SMRs can help with that, not instead of solar and wind, but as part of the mix. Because we just need a lot of power.'Opening image: Artist impression of a Rolls-Royce SMR. In the foreground a Topsoe Solid Oxide Electrolyser Plant, consisting of elek trolyser cells to make hydrogen. Image: Rolls-Royce SMR

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