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Small modular reactors: the future of the nuclear energy sector?

Although there has been talk about them for some time in theoretical terms with prefixes such as “mini,” Small Modular Reactors (SMRs) have a very real potential within the energy and industrial sector. With their very small size and simple integration plan, SMRs could replace the electrical power of many coal and gas plants, reducing emissions and reaching hard-to-access or isolated sites. Samantha Larriba del Apio, a member of the Board of Directors of the Nuclear Society for Young People (part of the Spanish Nuclear Society), tells us about what could be the most promising future of the nuclear sector.

The future of the nuclear sector could be written in terms of volumes, and a very clear line of research and innovation is aimed precisely at a reduced and compounded version of traditional power plants: Small Modular Reactors (SMRs). SMRs are considered to generate an electrical power less than or equal to 300 MWe—in comparison with conventional reactors that generate between 1,000 and 1,200 MWe; however, medium-sized ones—between 300 MWe and 700 MWe—are often included in this classification. “Its power allows you to scale the network input needed for each site by choosing whether to install one or more reactors based on demand needs. This characteristic also allows the shutdowns to be alternated for recharging fuel, thus preventing the network from being left without any power in one location at the same time,” explains Samantha Larriba del Apio, a member of the Board of Directors of the Nuclear Society for Young People.

Another of the main advantages that this researcher from the Technical University of Madrid (UPM) points out is precisely its modularity, which is why the reactors can be built outside the site where they will be installed, considerably reducing the difficulty of integration and the activation period, as well as lowering manufacturing costs and mitigating the associated risks. It would also allow these reactors to be installed in hard-to-access or isolated places, where the power supply is limited or nonexistent, operating in island mode—without connection to the national network—or where it is difficult to travel to carry out the construction of a conventional reactor.

The role they can play within the future of the nuclear sector is one of central importance, according to our expert, and it would also cover the whole energy transition process, as it would enhance a heterogeneity in the electricity flow of any country. “It is considered that these reactors could eventually replace the power from coal and gas plants, using the same location and even adapting certain auxiliary systems or the overview of the plant to adapt them to the installation of SMRs. This point allows power to be maintained and contributes to the decrease of greenhouse gas emissions, thanks to the replacement of thermal power plants with nuclear power plants,” she says. For the latter, a scenario of replacing infrastructure that has completed its useful life with several chained reactors is proposed, where “the SMRs present interesting alternatives for new applications (outside of the production of electrical power), advances in safeguarding and emergency systems, as well as, for example, the reduction of exclusion zones (or emergency areas) that would allow for more favorable evaluations in the location selection phase,” she states.

What can small reactors contribute?

This emerging technology could drive economic development in many regions, in addition to being key to their energy strategy. “Cogeneration for heat and electricity production is becoming increasingly relevant worldwide due to the growing demand for energy. The importance of obtaining both heat and electricity is derived from improving fuel efficiency and reducing greenhouse gas emissions,” the UPM researcher explains, adding that the potential of SMRs is not limited to generating electricity because “this new type of reactor offers a wider range of possibilities or alternatives. The nonelectrical applications of SMRs range from support for district heating, in a cogeneration system, to its use for the hydrogen production industry.”

The processes and requirements necessary to install these small reactors are, at the regulatory level, similar to those for conventional nuclear power plants: they must comply with the licensing process stipulated by the competent bodies in the nuclear and radioactive field, both national and international, in addition to providing coverage for constant reviews and safety analyses (such as emergency plans and radiological protection regulations).

Large electricity production plants, such as nuclear or thermal power plants, are the most appropriate option for the installation of this type of modular plant. “However, not all are able to support the same applications; it will depend on the type of technology, the fuel and the temperature required by the cogeneration process,” Larriba notes.

Although discerning the advantages of implementing these reactors in different areas is complicated since it affects things in a structural way, some of the main benefits are outlined by the UPM:

  • As regards the industrial sector: this new type of reactor involves perpetuating the technology and operational experience acquired. Considering one of the coupling alternatives, such as cogeneration, involves the joint implementation of the lines of business of conventional companies with nuclear companies. In addition, it maintains skilled jobs within the industry and supports the creation of new jobs with high added value.
  • For the user: replacing electricity production based on the “burning” of fossil fuels with nuclear energy translates into a decrease in the cost of electricity bills against the currently increasing price of gas. Flexibility in the operation of the power plants would offer advantages in terms of the availability of energy resources.
  • As regards society: benefits are those common to the use of nuclear energy. We can also add the non-emission of greenhouse gases, the basic role of energy within the electrical grid and the contribution to keeping the grid frequency stable at 50 Hz. In particular, SMRs have the advantage of occupying a smaller site area, reducing the nuclear emergency zone.


Future challenges

When we ask the researcher about the issues or risks involved in integrating SMRs into the industrial fabric, she points out those common to the traditional sector: the management of spent fuel (high activity) and the plan of action in the event of a nuclear accident. “Fuel management is an issue that the nuclear industry has never concealed and for which it has been responsible throughout history. Both storage and dismantling solutions are being implemented worldwide, and the constant advances in methods to reduce them (through transmutation or using them as an effective fuel for Generation IV reactors), demonstrate the responsibility and professionalism of the nuclear industry. However, the reduced power of these reactors is associated with a decrease in the volume of this spent fuel,” the expert explains.

In terms of risk prevention, very important steps have also been taken in the implementation of safety precautions, with emergency systems covering increasingly unlikely scenarios. “These are analyzed and investigated on an ongoing basis by both the industry and the centers to reduce the risk of the external release of radionuclides or to attenuate possible damage to the core in extreme situations,” she assures.

Apart from traditional challenges, the Spanish Nuclear Society ensures that there are two additional challenges for the adoption of SMRs: the scarce internal and external operation that forces regulatory bodies to analyze and evaluate the criteria and specifications of the large number of existing models and social acceptance. “The incorporation of nuclear power plants into the classification of the European Union’s Green Taxonomy is a step forward, not only in that nuclear energy can now be recognized as a non-contaminating source of energy, but also due to the possibility of investing through European funds in the construction of new power plants such as Modular Reactors.” In contrast, the positive results would be immediately evident. “The investment necessary for this type of project is considered more attractive for companies due to the possibility of recovering part of the money invested before operating all the modules in the same plant, assuming that several Modular Reactors are installed in the same location. This seeks a faster amortization of capital and a lower initial investment, which implies a considerable decrease of financial risk,” she concludes.


Article Collaborator:

Samantha Larriba del ApioSamantha Larriba del Apio has a bachelor’s degree in Energy Engineering and a master’s degree in Nuclear Science and Technology from the Technical University of Madrid. She is currently a predoctoral researcher in the Ph.D. program for Renewable, Sustainable and Nuclear Energy at the same university. Her lines of research are Small Modular Reactors, thermo-hydraulic simulation and Nuclear Safety. She has been part of the Board of Directors of the Nuclear Society for Young People since 2019.

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