Types of SMRs
The sudden interest in SMRs has led to resources to put into development of SMRs.
Pressurized Water Reactors
Pressurized Water Reactors (PWRs) are one of the most widely used types of SMRs. These reactors use water as both a coolant and a moderator, maintaining it under high pressure to prevent it from boiling. This design is favored for its safety features, as the pressurized water acts as a stable medium for transferring heat. SMR designs like NuScale’s reactor use PWR technology, emphasizing simplicity and passive safety mechanisms. They are ideal for electricity generation and have been adapted to smaller scales to make them easier to deploy in remote areas or smaller grids.
Boiling Water Reactors
Boiling Water Reactors (BWRs) are another common SMR type, differing from PWRs in how they handle water. In a BWR, water boils directly in the reactor core to produce steam, which then powers turbines to generate electricity. This design eliminates the need for separate steam generators, making the system simpler in some ways. The BWRX-300 from GE Hitachi is a leading example of an SMR using this technology. Its straightforward approach makes it cost-effective and efficient for small-scale electricity needs, especially in areas with limited energy infrastructure.
Molten Salt Reactors
Molten Salt Reactors (MSRs) take a unique approach by using molten salt as both a coolant and a medium for holding the nuclear fuel. This design offers several advantages, including inherent safety features and flexibility in fuel use. If the reactor overheats, the molten salt can naturally cool down without requiring external intervention. MSRs are especially promising for remote regions or countries looking to adopt sustainable and safe nuclear energy. The ThorCon SMR is a notable example of this design in development.
HighTemperature Gas Reactors
High-Temperature Gas-Cooled Reactors (HTGRs) stand out for their ability to produce very high temperatures, which makes them suitable not only for generating electricity but also for industrial processes like hydrogen production. These reactors use gas, typically helium, as a coolant instead of water, which is a key difference. This design allows them to operate at higher temperatures safely. An example is China’s HTR-PM, which showcases the potential of HTGRs to provide both energy and heat for diverse applications, including heavy industries.
Integral Pressurized Water Reactors
Integral Pressurized Water Reactors (iPWRs) are a refined version of traditional PWRs, where the reactor core and steam generators are integrated into a single vessel. This design simplifies construction, reduces the risk of leaks, and enhances safety by minimizing external connections. The SMART reactor from South Korea is an example of an iPWR designed for both electricity and desalination, showcasing its versatility in addressing energy and water needs simultaneously.
Fast Neutron Reactors
Fast Neutron Reactors (FNRs) differ significantly from traditional designs as they use fast neutrons instead of moderated (slower) ones to sustain the nuclear reaction. These reactors are highly efficient at utilizing nuclear fuel and can even recycle spent fuel, making them a sustainable option for reducing nuclear waste. SMRs like the TerraPower Natrium reactor incorporate fast neutron technology and are being developed to balance efficiency with safety in small, modular designs.
