Nuclear energy is a vital source of energy that can assist us in meeting our expanding energy needs. Nuclear energy has a significant advantage over traditional energy generation sources. It is not harmful to the environment and could help in the advancement of sustainable energy. In this respect, small modular reactors (SMRs), a relatively new type of modern reactor, are gaining popularity due to their small size and high efficiency. They provide a more straightforward, standardized, and safer modular design owing to initial capital investment and shorter construction periods.
Image Credit: TonyV3112/Shutterstock.com
A Brief Overview of Small Modular Reactors (SMRs)
Small modular reactors (SMRs) can generate significant amounts of low-carbon electricity for domestic and industrial usage while physically occupying much less space as compared to conventional nuclear energy generation plants. The major innovation these reactors introduced was the modular design. The components of these reactors, after manufacturing, could be assembled in the factory, and then the whole unit could be transported to the selected site.
In the 1950s, naval forces utilized small-sized nuclear reactors for powering naval ships. Since then, numerous countries have been consistently engaged in the ongoing development of small modular reactors.
SMR designs can be categorized into three main groups. The first group is based on the design principles of well-established and widely used light water reactors, particularly pressurized water reactors (PWRs). The second group comprises gas-cooled SMRs. The third advanced SMR group features coolants such as liquid metal or liquid salt.
Safety and Reliability Improvements
Currently, there are over 70 SMR concepts in development, with each design equipped with novel technological approaches and levels of maturity. These SMRs are believed to offer significant safety advantages by incorporating advanced smart technologies and inherent safety features.
SMRs utilize passive cooling systems that do not rely on the availability of electric power. This is a significant advantage in numerous accident scenarios.
An article published in Annals of Nuclear Energy discusses the passive safety systems (PSS) incorporated in these modular reactors. The PSS consists of several units, including the condensation heat exchanger, safety injection system, and residual heat removal system (RHRS) as main components.
PSS enhances plant safety even in adverse conditions. The use of passive safety systems eliminates the need for active safety systems and reduces the associated costs, which include various pumps and electrical power supplies from different sources.
The researchers explained the safety system of the multi-application small light water reactor (MASLWR) which is a type of SMR utilized for electric energy production and district heating.
It employs a passive safety system based on sump natural circulation to manage the removal of reactor decay heat during transients. This system establishes natural circulation between the reactor vessel and the high-pressure containment using ADS vent and sump recirculation valves. This type of passive safety system falls into category 'D,' where fluid energy or batteries activate various components of the passive safety system.
SCK CEN, a global leader in nuclear sciences, has been granted authorization by the Belgian government to commercialize a novel SMR using fast neutrons and lead as a coolant.
The MYRRHA project will prove to be a groundbreaking research reactor, being the first in the world to be powered by a particle accelerator. It will utilize liquid lead-bismuth as a coolant. This metal alloy shares similarities with the one used in lead-cooled reactors.
Innovative technology-based reactors generate higher exhaust temperatures compared to their conventional water-cooled counterparts. This creates new possibilities for various applications, including hydrogen production and providing heat for industrial processes.
Applications of Small Modular Reactors
SMRs are useful for electricity generation and for various industrial processes.
They can supply heat for district heating systems, serving residential, commercial, and industrial areas for space heating and hot water. Some SMR designs are also well-suited for seawater desalination.
The residual heat produced by SMRs can be harnessed for various industrial purposes, including chemical reactions, oil refining, and hydrogen production. Hydrogen is typically generated through high-temperature electrolysis or thermochemical methods, offering a clean fuel source for transportation, heating, and industrial applications.
A recent article published in Renewable and Sustainable Energy Reviews provides an overview regarding the integration of SMRs in microgrids. SMRs are a strong complement to renewable resources within microgrids as they enhance the resilience of power systems and reduce their carbon emissions.
Emerging SMR technologies replace traditional diesel generators with cleaner alternatives. These new reactors are equipped with passive safety systems, extended refueling intervals, and load-following capabilities, allowing them to work alongside renewable sources. They provide a reliable, safe, and low-carbon solution for both electricity generation and district or process heat production.
Environmental Benefits and Carbon Reduction
The main reason for the interest in SMR technology worldwide is sustainable green energy production.
SMRs can be paired with renewable energy sources like wind energy and solar energy to enhance their efficiency within a hybrid energy system. These hybrid systems position SMRs as pivotal components in the transition to clean energy, aiding countries in addressing Sustainable Development Goals.
By offering a clean and steady energy supply, SMRs can significantly reduce carbon dioxide and other greenhouse gas emissions. Furthermore, their compact design and higher efficiency reduce nuclear waste. Less nuclear fuel, such as uranium, is required for their operation, and less fuel quantity leads to less nuclear waste production.
SMRs can significantly reduce air pollution. Conventional fossil fuel energy generation methods release harmful gases into the environment. These gases are responsible for global warming and can be harmful to humans. Since SMR energy production involves no greenhouse gas emissions, these reactors will surely reduce the concentration of pollutants in the air.
Recent reports have confirmed that the market for SMRs is thriving worldwide. The United States Department of Energy is hopeful that US companies will be the front runners in the SMR market and will help the United States in establishing its position in the global nuclear energy market.
Future Prospects of Small Modular Reactors
As per recent forecasting reports, SMRs will be responsible for approximately 25-30% of electricity generation using nuclear resources. Several registered startups are starting to invest and provide services for this particular technology.
One of the pioneering companies in the early stages of SMR development is NuScale Power.
NuScale is the first SMR company to obtain Standard Design Approval from the U.S. nuclear regulatory authority. Its approach involves reducing the size of pressurized water reactors (PWRs) and utilizing six of them in their VOYGR-6 design, which collectively provides an electrical capacity of 462 MW.
Several countries, like Estonia and Luxembourg, are investing in this technology. In some countries, SMRs are generating electricity and powering domestic areas.
The recent interest from the higher authorities to include nuclear energy and SMRs in sustainable energy plans ensures that SMR-based nuclear energy generation will play a vital role in the future.
Continue Reading: Advantages and Disadvantages of Nuclear Power Stations
References and Further Reading
Liou, J., 2023. What are Small Modular Reactors (SMRs)?. [Online] Available at: https://www.iaea.org/newscenter/news/what-are-small-modular-reactors-smrs [Accessed 14 October 2023].
SCK CEN, 2022. Progressing towards the first lead-cooled SMR demonstration model. [Online] Available at: https://www.sckcen.be/en/about-sck-cen/annual-reports/highlights-2022/highlights-2022-innovatieve-nucleaire-systemen/progressing-towards-first-lead-cooled-smr-demonstration-model [Accessed 15 October 2023].
Office of Nuclear Energy, 2023. Benefits of Small Modular Reactors (SMRs). [Online] Available at: https://www.energy.gov/ne/benefits-small-modular-reactors-smrs [Accessed 16 October 2023].
Butt, H. et al. (2016). Assessment of passive safety system of a Small Modular Reactor (SMR). Annals of Nuclear Energy. 98. 191-199. Available at: https://doi.org/10.1016/j.anucene.2016.07.018
Michaelson, D., & Jiang, J. (2021). Review of integration of small modular reactors in renewable energy microgrids. Renewable and Sustainable Energy Reviews, 152, 111638. Available at: https://doi.org/10.1016/j.rser.2021.111638
Dale, S., (2023). The Future of Nuclear SMRs: Will Start-ups Disrupt Established Players? [Online] Available at: https://www.idtechex.com/en/research-article/the-future-of-nuclear-smrs-will-start-ups-disrupt-established-players/29374 [Accessed 16 October 2023].
Frąckiewicz, M. (2023). The Advantages of Small Modular Reactors for Environmental Sustainability and Biodiversity. [Online]
Available at: https://ts2.space/en/the-advantages-of-small-modular-reactors-for-environmental-sustainability-and-biodiversity [Accessed 17 October 2023].