Small Modular Reactors: Pros and cons

Small scale nuclear power plants offer a potential zero emissions energy solution for Taiwan but there are numerous challenges that would have to be overcome before they can be seriously considered.

By Bart Linssen
 

The growing demand for electricity, particularly from energy-intensive sectors like AI datacentres, necessitates a rapid expansion of power generation capacity. This pressing need has rekindled interest in nuclear power, with Small Modular Reactors (SMRs) emerging as a potential solution. Recently, industry leaders such as Google and Amazon have invested in SMR pilot projects, signalling a potential shift in the energy landscape. This article examines SMR technology, exploring its potential advantages and disadvantages, and evaluating its viability as a contributor to Taiwan's net zero ambitions.

Understanding SMRs
It is crucial to clarify what SMRs are not. They are not merely scaled-down versions of conventional nuclear power plants, easily transportable and ready for immediate operation. Instead, SMRs are complete nuclear facilities that leverage a modular reactor design to streamline and accelerate the building process. This modular approach can significantly reduce construction time from the typical seven or more years required for traditional nuclear power plants to 3-5 years.

Size, capacity, and global landscape
SMRs distinguish themselves from traditional nuclear reactors through their smaller size and reduced generating capacity. With a power output of up to 300 megawatts (MW) per unit, SMRs possess approximately one-third the generating capacity of their conventional counterparts. The global presence of operational SMR plants is currently limited, with only three completed facilities: two in China and one in Russia. However, there is a growing wave of SMR development projects underway, fuelled by investments from tech giants and energy companies. Notably, Google's first SMR, purchased from Kairos Power, is expected to be operational by 2030, while Amazon and Dow have partnered with X-energy to develop a 320MW SMR, also slated for completion by 2030. Standard Power has placed an order for 24 SMRs from NuScale, totalling 2GW of capacity, with plans for operation by the end of the decade. Currently, only NuScale has obtained regulatory approval in the United States.

Key components of SMRs
Despite their smaller scale, SMRs share the same fundamental components as traditional nuclear reactors. These essential elements work together to harness nuclear energy for electricity generation.

• Reactor module: The heart of the SMR, the reactor module houses the nuclear reactor core. It contains fuel assemblies, which hold the nuclear fuel, control rods to regulate the nuclear reaction, and coolant systems to maintain safe operating temperatures. The design often incorporates passive safety features, enhancing the reactor's ability to manage potential emergencies.
• Containment vessel: Providing an additional layer of safety, the containment vessel encases the reactor module. It serves as a robust barrier designed to contain any radioactive material that might be released in the event of an accident. The containment vessel's construction enables it to withstand both external and internal pressures, ensuring the integrity of the reactor system.
• Steam generator: This critical component facilitates the conversion of heat generated by nuclear reactions into steam. The steam, carrying the energy released from the nuclear process, is then directed to drive turbines for electricity generation.
• Turbine generator: The turbine generator acts as the energy converter, transforming the steam's energy into electrical energy. The high-pressure steam from the steam generator spins the turbines, which are connected to generators that produce electricity.
• Cooling system: Maintaining a safe operating temperature for the reactor is paramount, and the cooling system plays a vital role in achieving this. Many SMR designs employ passive cooling systems that rely on natural convection and gravity-driven flow to circulate coolant, reducing the dependence on external power sources and enhancing safety.
• Control room: Serving as the operational hub of the SMR, the control room provides a centralised location for monitoring and controlling all aspects of the reactor's activities. Advanced monitoring systems and automation technologies are integrated into the control room, ensuring safe and efficient operations.
• Spent fuel pool: After their operational life in the reactor core, used nuclear fuel rods, known as spent fuel, are transferred to the spent fuel pool. This secure storage area is designed to safely contain and cool the spent fuel, mitigating the risks associated with radioactive decay.
• Auxiliary systems: A range of auxiliary systems support the operation of the SMR, including emergency power supplies to ensure functionality during unexpected outages, water treatment facilities to manage water used in various processes, and waste management systems for safe handling and disposal of radioactive waste generated during operations.

Design variations and safety considerations
Several companies are currently developing SMR solutions, and a key distinction among them lies in the method employed for transferring heat from the nuclear reactor to the power generation unit. Common designs include light-water reactors, boiling water reactors, sodium-cooled reactors, and molten salt reactors. A notable emphasis in many SMR designs is the incorporation of passive safety systems, which aim to reduce reliance on active controls and potentially enhance overall safety by leveraging natural forces like gravity and convection to mitigate potential accidents.

Potential advantages of SMRs
Advocates for SMR technology highlight several potential advantages that position them as a promising energy solution:

• Enhanced safety: SMRs often incorporate advanced safety features, such as passive cooling systems, which can function without human intervention or external power sources, enhancing the reactor's ability to manage emergencies and prevent meltdowns.
• Scalable deployment: The modular nature of SMRs allows utilities to incrementally expand their power generation capacity to match evolving energy demands. This flexibility offers a significant advantage over traditional nuclear power plants, which require large upfront investments and lengthy construction times.
• Siting flexibility: SMRs can be deployed in locations that may not be suitable for larger reactors due to space constraints or environmental sensitivities. This siting flexibility opens up new possibilities for deploying nuclear power closer to consumers, reducing transmission losses and enhancing grid resilience.
• Reduced environmental impact: Compared to traditional nuclear power plants, SMRs have a smaller physical footprint, minimizing land use requirements and reducing environmental disruption during construction and integration into existing energy infrastructure.