“Small” Nuclear Reactors

One option being considered for the future of nuclear energy is the use of smaller nuclear reactors. Manufactured in factories and assembled on site, they would be 10 to 20 times less powerful than current models but easier to use and requiring less investment outlay. Around 50 small modular reactor (SMR) projects are currently being developed worldwide, and the International Atomic Energy Agency (IAEA) estimates that they could come onto the market between 2025 and 2030.

Image of the Akademik Lomonosov, a Russian ship with two nuclear reactors, moored in the port of Murmansk in May 2018.
The Akademik Lomonosov, a Russian ship with two nuclear reactors, moored in the port of Murmansk in May 2018 to be loaded with nuclear fuel. It should eventually dock at the port of Pevek in eastern Siberia. ©ALEXANDER NEMENOV / AFP

A Long History

Small nuclear reactors have been used since the 1960s to powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... ships, which they give greater range by freeing them from the need to frequently refuel with petroleum.

Less than 300 MW: The capacity of SMRs currently under development (versus 900 to 1,600 megawatts for conventional reactors).


Around 400 nuclear-powered watercraft have been built around the world, almost all of them military vessels. The most common variety are nuclear submarines, which can stay underwater for several months, whereas conventional models have to come up to the surface every few days to run their dieselDiesel is the name of an internal combustion engine that works by compression-ignition... engines and thereby recharge their electric batteries. Some aircraft carriers are also equipped with nuclear reactors1. Since they do not need to carry fuelFuel is any solid, liquid or gaseous substance or material that can be combined with an oxidant... on board, this frees up space for aircraft and ammunition. The number of accompanying tankersVessel used to transport bulk liquids in huge tanks. The best-known tankers are oil tankers, which carry crude oil. is also reduced.

Russia is the only country to have nuclear-powered vessels in civilian use, with half a dozen icebreakers. Since 2016, it has been commissioning a new, more powerful generation of icebreaker able to navigate through ice up to three meters thick, clearing the way year-round for Russian tankers exporting liquefied natural gas (LNG)LNG is composed almost entirely of methane. Liquefying the gas reduces its initial volume by a factor of around 600... to Asia.

Uses for SMRs

SMRs are intended to perform completely different functions from the nuclear reactors on ships. Essentially, SMRs would be used to generate electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... in hard-to-reach or remote areas, such as islands or coastal regions. They could also be useful on industrial sites that need a lot of electricity or heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter..., or to power energy-intensive seawater desalination plants or oil platforms. In other words, SMRs are not designed to replace conventional power plants that continuously provide energy to large central grids.

According to criteria from the IAEAThe IAEA was set up in 1957 within the United Nations family. It works for the safe, secure and peaceful uses of nuclear energy..., SMRs are nuclear reactors with a capacity of less than 300 megawatts, whereas conventional facilities generally fall somewhere between 900 and 1,600 megawatts. The capacity of most of the currently planned SMRs is less than 100 megawatts.

Some small nuclear reactors currently being developed may measure less than 3 meters in diameter and 20 meters in height.


SMRs are set to feature some new, specific characteristics:

  • As their name suggests, they would be made from modules manufactured in factories, transported by ship or truck and assembled on site. They could also be connected to one another.
  • They would be small (for example, U.S. company NuScale plans to release units measuring less than three meters in diameter and 20 meters in height, weighing 600 metric tons).
  • They should entail less investment outlay and require a smaller specialized labor pool for maintenance than conventional nuclear reactors.
  • They would only need to be refueled every three to five years.
  • They would be much more flexible than conventional reactors, since they could be started up or shut down in a matter of minutes.

However, their safety is already the subject of debate. Greenpeace is concerned that, since SMRs would not be housed in concrete containment buildings, the risks of proliferation would be greater. But companies designing SMRs argue that their small size makes them easier to contain. For example, they could be submerged in pools or installed underground, which is not possible for large power plants. Keeping them cool would also be more straightforward. On the other hand, the issues surrounding waste management would be the same as for conventional nuclear reactors.

SMR Projects Around the World

According to the IAEA, some 50 projects are being examined in around ten countries worldwide2.

Russia – Drawing on its expertise in nuclear marine propulsion, Russia is at the forefront of SMR technology. In the summer of 2018, Rosatom launched the Akademik Lomonosov, a ship carrying two 35-megawatt reactors similar to those used on icebreakers. If all goes to plan, it will dock at the port of Pevek in eastern Siberia in 2019.

China – State-owned CNNC has been working on the Linglong One since 2010. According to CNNC, the reactor has passed the IAEA’s safety review and could be ready as a demonstrator by 2022. IAEA approval is an important step before developing SMRs on an industrial scale, and is intended to prevent proliferation without safeguards in place. However, in practice, the decision to install SMRs will most probably come down to the government of each country.

The United States, Canada, South Korea, the United Kingdom and Argentina also have plans for SMRs in the gas pipelinePipeline used to transport gas over a long distance, either on land or on the seabed.. In France, Naval Group (formerly DCNS) has developed a project for a small underwater reactor, Flexblue, for use near coastlines. The project has been on stand-by since 2014, but plans for a new 150 to 170 megawatt reactor are currently underway.




(1) France’s Charles de Gaulle aircraft carrier, for example, has two 150-megawatt reactors.