Technology Race: What are the Prospects for Small Modular Reactors in 2024?
More and more countries are supporting the development of small modular reactors (SMRs), as they can be used in remote areas and regions with unstable energy supply for flexible electricity generation and heat supply in countries, as well as for the development of hybrid nuclear and renewable energy systems and hydrogen production.
Among European countries, Poland is the most active in implementing SMR, where a separate company, Orlen Synthos Green Energy, was established to deploy a fleet of small modular reactors. The development of the latest low-carbon energy sources will contribute to the energy autonomy of industrial regions and ensure the country’s energy safety.
Small modular reactors are also suitable for the conversion of coal power plants. According to the report “Can an Advanced Reactor Restore a Coal Country?” prepared by the American independent organization “The Bipartisan Policy Center”, SMRs can reuse electrical equipment of coal power plants, steam cycle components, power transmission lines and administrative buildings. This approach is supported by Nuclearelectrica, Romania’s state-owned nuclear power corporation, which will deploy the first small modular reactors at the site of a coal power plant in Deucesti.
Today, NuScale, Hitachi, Rolls-Royce, Holtec, and Westinghouse are the largest players in the global small modular reactor scene. The reactors of these developers have different modifications and features, which are described in this article.
NuScale
For a long time, NuScale has been the leader in the technology race. On 19 January 2023, the 50 MWe SMR design was certified by the US Nuclear Regulatory Commission, and the company had 19 signed agreements to deploy SMR-based NPPs in 12 different countries, including Poland, Romania, the Czech Republic, and Jordan. In addition, in March 2023, the second application for a 77 MWe SMR of a six-modular power plant configuration was launched.
Despite the continued success, in November 2023, NuScale announced the cancellation of the project to build NuScale small modular reactors in Utah, USA. The reason was a sharp increase in costs and a rise in construction expenses. At first, this led to a drop in NuScale shares and then to a forced reduction in staff. Nevertheless, the Polish copper mining company KGHM Polska Miedz and the Romanian company RoPower do not abandon their intentions to implement NuScale small modular reactors in their countries.
NuScale small modular reactors are designed for flexible, depending on the load power and process heat generation for industrial applications, including cogeneration, the combined generation of electricity and heat.
The NuScale Power Module is a small modular pressurized water reactor with light water as the coolant and is an integral reactor, meaning it can operate as a single unit with an electrical capacity of 50 MW or as a system of up to 12 modules with a total capacity of 600 MW. Each module is autonomous and does not depend on the operation of the other ones.
The NuSale SMR design consists of a containment and a reactor pressure vessel, which integrates two steam generators and a pressurizer, with the core inside. The NuScale plant uses a set of technical passive safety features designed to ensure safe shutdown and self-cooling for an indefinite period of time without the need for operator or computer intervention, AC or DC power, or introduction of water for the first time in light water reactor technology. NuScale Power Module safety critical systems include: emergency core cooling system, containment, residual heat removal system, module protection system, neutron monitoring system, chemical composition and volume monitoring system.
The NuScale SMR power plant consists of a reactor building, a main control room (MCR) building, two turbine generator buildings, a radioactive waste treatment building, forced draft cooling towers, a switchyard, and a dry spent fuel storage area. The main operation center is located in the control room adjacent to the reactor building. All modules are controlled from a single control room. The reactor building houses up to 12 modules, equipment for module assembly/disassembly, fuel transportation equipment, and a spent fuel pool. Each module operates submerged in the common reactor pool in a separate concrete-covered compartment that serves as a biological shield.
GE Hitachi BWRX-300
The leader in the technology race is the BWRX-300 small modular reactor, which is being considered for implementation by most countries: The United States, Canada, the United Kingdom, Poland, Sweden, the Czech Republic, and Estonia.
This is due to the fact that BWRX-300 is a smaller version of the developed ESBWR with a capacity of 1520 MW, which was successfully certified by the US Nuclear Regulatory Commission in 2014, and the letter X in the model name means the tenth generation of GE Hitachi boiling water reactors. In addition, the BWRX-300 SMR is based on a unified approach that reduces construction costs. That is, regulators, utilities, and the technology developer GE Hitachi are striving for a standardized design. If a country chooses this technology and is committed to a standardized SMR design, it can join the BWRX-300 group (countries that have also chosen this technology for implementation) for further cooperation and accelerated project implementation.
This SMR was developed taking into account the IAEA recommendations to simplify licensing in many countries. At the end of 2019, GE Hitachi Nuclear Energy started the licensing process for the BWRX-300 small modular reactor in the United States. The BWRX-300 has passed the pre-licensing process at the UK Nuclear Regulatory Authority, the US Nuclear Regulatory Commission and the Canadian Nuclear Safety Commission. In the United Kingdom, the BWRX-300 was assessed by the UK Department of Business, Energy and Industrial Strategy. In the United States, five topical licensing reports have been submitted and approved for design features and analysis methods that are considered to pose greater regulatory risks.
The BWRX-300 can be used to generate electricity, synthetic hydrogen fuel, produce centralized heating and process heat for industrial applications.
It is a 300 MWe small modular water-cooled, with naturally circulating boiling water reactor. Like most boiling water reactors, the BWRX-300 uses low-pressure water to remove heat from the core. Unlike most nuclear reactors, which require electric pumps to actively pump coolant through the core, this reactor design makes water circulate within the core due to natural circulation.
The BWRX-300 has a passive safety system, meaning that neither off-site power nor operator action is required to maintain a safe state even under extreme conditions. The basic safety design philosophy of the BWRX-300 is based on the use of inherent redundancies (e.g., larger structural volumes and water reserves) to eliminate system problems and can easily adapt to transients. Safety systems based on simple natural phenomena mitigate consequences of accidents without the need for electricity.
The BWRX-300 SMR-based power plant has dimensions of 260×332 m (86,320 m2). The power unit with dimensions of 140×70 m consists of a reactor and turbine buildings, a main control room and a radioactive waste storage building. The control room consists of an operator center, electrical and control equipment. The turbine building houses the turbine, generator, main condenser, condensate and feedwater systems, condensate treatment system, and waste gas system. The reactor building is the only seismic category structure in the BWRX-300. The BWRX-300 primary containment is located below ground level and encloses the reactor vessel, providing radiation protection and acting as a boundary for the release of radioactive substances from the reactor vessel into the environment. It is an integral part of the reactor building and is surrounded by it. A water pool is located above the primary containment.
Rolls Royce
In 2022, the first phase of the UK regulatory review of Rolls-Royce’s small modular reactor design started, and in 2023 the company proceeded to the second phase, a detailed assessment of the design’s technical characteristics by the regulatory authorities. The company plans to start construction of the one-of-a-kind power plant in 2026 and build it by 2030.
The main purpose of Rolls-Royce small modular reactors is to supply electricity, but they can also be used to provide heat, cogeneration, and electric fuel production.
The Rolls-Royce small modular reactor is a monoblock three-circuit pressurized water reactor using an indirect Rankine cycle with a capacity of 470 MW. The design philosophy of the Rolls-Royce SMR is to optimize the cost of electricity and low capital investment. The power output is maximized, providing reliable savings in nuclear power plant investment, and the size of the plant ensures modularity and standardization in all aspects.
The Rolls-Royce Small Modular Reactor design was developed using a combined approach for system engineering and safety assessment. In-depth protection is ensured by multiple levels of protection and a variety of active and passive safety systems with multiple circuits. Passive safety systems are designed to perform safety functions autonomously for 72 hours, minimizing the need for human intervention and electricity.
The power plant, built on the basis of Rolls-Royce SMRs, will cover an area of about 40,000 m2, and its design feature is seismic isolation for key safety zones. The nuclear reactor is located on a reactor island next to the turbine island, behind which a cooling water island will be located. The reactor circuit and other key systems are located inside a steel containment to limit the release of radioactive materials during malfunctions and/or accidents.
The construction and commissioning of such a small modular reactor takes up to 5 years, and the design life of the Rolls-Royce SMR is 60 years.
Holtec
Holtec’s small modular reactor design is at the preliminary licensing phase with the U.S. Nuclear Regulatory Commission. The company has also applied for a General Design Assessment (GDA) of the SMR-300 in the UK. However, it is worth noting that in 2020, the first phase of the three-phase preliminary design review by the Canadian Nuclear Safety Commission was completed before the supplier was licensed. This is an example of early involvement of the regulator in reviewing the safety justification of an SMR design developed according to the rules and regulations of another country.
The main application principle of SMR-300 is electricity generation with additional cogeneration equipment (i.e., hydrogen production, thermal energy storage, centralized heat supply, seawater desalination). SMR-300 small modular reactors, thanks to Holtec International’s patented air-cooled condenser technology, can be deployed in places with water shortages and operate both in “black-start” mode as well as in isolated mode in places with unstable energy grid or in stand-alone operation.
The SMR-300 is a single-circuit pressurized light water reactor that generates 300 MW of electricity. A feature of SMR-300 is the “Walk away safe” safety level: in the event of an accident that occurs for any reason (including sabotage or terrorist attack), the reactor will shut down and enter a safe state without human intervention. Passive and backup safety systems operate by natural circulation and ensure safe shutdown and heat removal for an unlimited period of time without the need for electricity, makeup water or operator action. All safety systems are housed within a robust containment, making them safe and secure from external hazards. All the makeup water required in the event of a postulated loss-of-coolant accident is located inside the containment. Another water reservoir located between the containment and the protective enclosure ensures that the heat sink can be switched to air cooling for an unlimited period after a design basis accident without any operator action or makeup water, ensuring long-term post-accident service life.
The SMR-300 small modular reactor is housed in a containment, which is enclosed by a structure of reinforced concrete walls. These structures, which are half underground, house all safety systems and the spent fuel pool. The containment building is missile resistant and protects the containment and safety systems from the most serious environmental hazards or sabotage. The reactor auxiliary building houses many auxiliary systems of the nuclear power plant, in particular, spent fuel is prepared for dry interim on-site storage in HI-STORM UMAX modules (patented underground dry storage technology). The steam turbine and associated systems are housed in a turbine building at ground level. The electrical power system consists of a main generator, a main transformer, auxiliary transformers, diesel generators and Class 1E batteries.
SMR-300 components are manufactured and assembled prior to arrival at the construction site, which takes 24 months.
Westinghousе
In early May 2023, Westinghouse Electric presented a single small modular reactor that will be constructed basing on the design of the existing AP-1000 reactor. The conceptual design of the reactor was developed back in 2015, and the developer is finalizing the design and preparing to apply for its certification to the US Nuclear Regulatory Commission. It is expected that the design will be certified by 2027, after which site-specific licenses will be obtained and construction of the first unit will start at the end of the decade.
The target application of Westinghouse’s SMR is electricity generation, however, the AP-300 can also be used to provide process heat, centralized heating, and stand-alone applications, including in places of production of liquid transportation fuel, oil shale, and coal liquefaction.
It is an integral pressurized water reactor design with a thermal output of 800 MWe and over 225 MWe, that will use identical AP-1000 technology, including major equipment, structural components, passive safety, proven fuel, and control and monitoring systems. The AP-300 will utilize an established supply chain, rapid load tracking capabilities, and proven operation and maintenance procedures.
The Westinghouse small modular reactor utilizes passive safety systems and proven components implemented in the AP-1000 reactor design and earlier Westinghouse designs. The advanced passive safety system utilizes the natural forces of evaporation, condensation, and gravity to automatically ensure safe shutdown of the reactor without operator action and eliminates the need for an additional power supply and cooling system. The plant is not dependent on power or other auxiliary systems to perform its safety functions.
The AP-300 SMR-based nuclear power plant is stand-alone and has no shared safety systems, which eliminates the vulnerability to failures that cascade from one unit to another in a multi-unit plant. The design provides for an “island mode” capability to control grid disconnection and is capable of providing 100% steam bypass to control turbine shutdown, which prevents the need for emergency reactor decommissioning. The main control room is located entirely underground on the reactor island; in addition, several safety monitoring stations are located in individual sectors. The location of the reactor pressure vessel, containment, and spent fuel pool below ground level provides protection against external and natural hazards.
All components of the small modular reactor can be easily transported by rail, truck or barge. Like the AP-1000, the AP-300 is designed for an 80+ year life cycle.
Summary
To support small modular reactors, the U.S. Department of State initiated the Foundational Infrastructure for Responsible Use of Small Modular Reactor Technology (FIRST) Program in 2021. Thus, countries considering the use of SMRs or other advanced reactors in achieving zero carbon emissions to mitigate climate change can join this Program and share their plans to expand their nuclear energy capacity. Early dialog between U.S. experts and the interested partner country is achieved through trainings, seminars, webinars, and organized study tours.
Other international organizations also promote the development of small modular reactor technologies. The European Commission continues to support research, innovation, education and training in this area for the safety of European SMRs, and the Western European Nuclear Regulators Association (WENRA) is ready for mutual cooperation in assessing the safety of reactor designs. The members of the International Nuclear Regulators Association (INRA) cooperate at the SMR design and licensing phases and support national regulatory reviews in countries that are just starting to implement the latest technologies.
Uatom.org Editorial Board