Small Reactors, Great Potential

Hearing the words ‘nuclear power’ usually conjures up images of huge power plants and cooling towers, but with small modular reactors (SMRs) and microreactors (MRs) starting to become a reality, the face and reach of nuclear power is changing.

“SMRs and MRs provide low carbon energy like large nuclear reactors do, but they are smaller, more flexible and more affordable, so they can be used on smaller power grids and be built in hard-to-reach places where large reactors wouldn’t be practical,” said Frederik Reitsma, Team Leader for SMR Technology at the IAEA. “Many are designed to provide non-electrical services in addition to electricity production, adding to their clean energy benefits and cost-effectiveness.”

SMRs are expected to generate up to 300 megawatts (electrical) (MW(e)) of power and MRs up to 10 MW(e), depending on their designs. In addition to their modularity, some other common features are passive and built-in systems that enhance safety, the ability to efficiently and flexibly generate energy to meet fluctuating demands, and simpler designs that are faster and less complex to construct than current reactors. They also have more factory-based manufacturing possibilities, which can reduce on-site construction time and makes them easier and more cost-effective to reproduce for additional deployment.

“Large nuclear reactors are a major undertaking and require substantial long-term investment, which is feasible and appropriate for some situations. For others, however, SMRs and MRs can be a more realistic and faster approach and sometimes the only way to cost-effectively access nuclear power,” said Reitsma. “When you combine this with effective financing and market policies, it opens up nuclear power to a wider range of users and makes it a more competitive and attractive option on the energy market.” Learn more about financing and market policies in nuclear power here.

The world’s first advanced SMR was connected to the grid in 2019 and started commercial operation in May 2020.

Akademik Lomonosov floating nuclear power plant, located just off Russia’s Arctic coast, houses two 35 MW(e) KLT40S SMR units that are now generating enough energy to power a city of about 100 000 people. The plant also has a heat capacity of 50 gigacalories per hour, and it is used for seawater desalination, producing up to 240 000 cubic metres of fresh drinking water per day.

“With the help of small nuclear reactors, the Arctic can achieve net zero emissions as early as 2040,” said Anton Moskvin, Vice President for Marketing and Business Development at Rusatom Overseas. “Akademik Lomonosov will replace a plant that burns brown coal. Besides contributing to the elimination of harmful emissions in the Arctic ecosystem, it will provide guarantees that the region’s inhabitants will not be left without light and heat in the freezing Far North.”

Other SMRs at the most advanced stage of construction are the 30 MW(e) CAREM reactor in Argentina and the 210 MW(e) HTR–PM in China. Several are also far along in the regulatory process, including the NuScale Power SMR in the United States and several in Canada. In total, there are more than 70 SMR designs worldwide at various stages of development.

The IAEA has several activities related to SMRs to support research and development worldwide. It facilitates cooperation in SMR design, development and deployment and serves as a hub for sharing SMR regulatory knowledge and experience.

While SMR designs are generally based on well-known reactor systems, MRs are the sort of thing you would expect to see in a science fiction movie. They are small enough for the whole plant to be built in a factory and transported by a truck. With self-regulating passive safety systems, they only require a small workforce to run. Operating independently from the electric grid, they can be moved around and used in different locations. They can generate up to 10 MW(e) of power — around 10 years or more of electricity for more than 5 000 homes, 24 hours a day, 7 days a week.

These compact, movable reactors can serve as backup power supplies for places like hospitals, or replace power generators that are often fuelled by diesel and are the only source of electricity for remote communities as well as industrial and mining sites.

More than a dozen MRs are now under development by private companies and research groups worldwide.

One close to deployment is the Aurora 1.5 MW(e) fast spectrum reactor being developed by Oklo, a US-based start-up company. Now going through the regulatory process, Aurora is designed to function and self-regulate primarily using natural physical phenomena, meaning it has very few moving parts, which increases safety. It is also expected to be able to operate for decades without refuelling, using high assay low enriched uranium fuel.

“The fission reaction can be used in many formats: small and large, different fuels, different ways to cool, and enable many different ways for business models and community interaction and ownership,” said Caroline Cochran, Chief Operating Officer of Oklo. “The novel use of fission and the implementation of distributed, smaller plants can enable human development while minimizing resource use.”

Other MRs at advanced stages include a 4 MW(e) reactor developed by U-Battery, a URENCO-led company based in the United Kingdom that is expected to begin operation in 2028.

Despite advances, SMRs and MRs are still far from deployment on a large scale.

“It is a ‘chicken and egg’ situation,” said Reitsma. “On the one hand, investment to develop and deploy SMRs requires a secured market and demand for the product, but on the other, one cannot secure the market without funding to develop and demonstrate, or even to do the necessary research or build test facilities that may be required for licensing. Potential investors are hesitant to invest in new technology if they are unsure about the market risks.”

One of the other major obstacles for deployment is applying regulations to the wide range of SMR and MR designs. The diverse combination of systems, structures and components means standard regulatory approaches, which were set up for conventional nuclear power plants, have to be re-evaluated and eventually adjusted to ensure an adequate level of safety. Learn more about the SMR regulatory process here.

“At this point, many first of a kind advanced SMRs have been going through the regulatory process and, once that’s done, we generally expect at least another four to five years until they are constructed and operating,” Reitsma said. “But as SMRs and MRs become mainstream, we can expect to see this timeline shrink as the deployment processes should become faster, more cost effective and easier.”