What are Small Modular Reactors (SMRs)?

Small Modular Reactors, or SMRs, are nuclear reactors designed to produce less electricity per unit than conventional large nuclear plants. The IAEA commonly uses a limit of up to 300 megawatts of electricity per module, though designs and terminology vary.

“Small” refers to the reactor’s output; “modular” describes the idea of building major components in factories and assembling them at a site. Some designs can be added in stages as electricity demand grows. SMRs may use familiar light-water technology, while others propose different coolants or fuels.

Why consider them?

Supporters expect factory-built reactor modules to make construction more repeatable and allow smaller projects than a traditional nuclear station. Many designs also include passive safety systems, which rely on physical processes such as gravity or natural circulation to help manage heat if power is lost.

Those benefits are not automatic. Costs depend on manufacturing scale, licensing, construction, and financing, and many designs have not yet been proven through large-scale commercial operation. SMRs also raise familiar nuclear questions about spent fuel, waste management, safety, and where plants can be built.

In short, an SMR is a smaller-scale approach to nuclear power, not a single reactor design. Whether it becomes a practical option depends on how reliably and affordably specific projects can be delivered.

Advanced nuclear reactors called small modular reactors (SMRs) have a power capacity of up to 300 MW(e) per unit, which is roughly one-third of the producing capacity of conventional nuclear power reactors. SMRs are able to generate a significant amount of low-carbon electricity.

Physically, it is much smaller than a typical nuclear power reactor. Modularity enables systems and components to be pre-assembled in a factory before being shipped as a whole to a place for installation.
Reactors use heat produced by nuclear fission to produce energy.

The tiny and modular nature of SMRs' design is inextricably related to several of its advantages. SMRs can be placed in regions unsuitable for larger nuclear power facilities due to their reduced footprint. SMRs are less expensive to build than large power reactors because prefabricated units can be produced, shipped, and then installed on site. 

Large power reactors are frequently specially designed for a specific location, which can sometimes cause construction delays. SMRs are more affordable, take less time to build, and may be installed gradually to keep up with rising energy demand.

The development of SMR technology is being aggressively pursued by both governmental and private organisations this decade. Two 35 MW(e) SMRs are used to generate electricity at Russia's Akademik Lomonosov, the first floating nuclear power plant in history to start operating commercially in May 2020. In Argentina, Canada, China, Russia, South Korea, and the United States of America, further SMRs are being built or are awaiting authorization.

Around the world, more than 70 commercial SMR designs are in development. These designs aim to produce a variety of outputs for a variety of applications, including electricity, hybrid energy systems, heating, water desalination, and steam for industrial uses. Even though SMRs offer lower upfront capital costs per unit, their economic viability has yet to be demonstrated once they have been put into use.