A small modular reactor is a nuclear plant of 50–300 MW that is assembled in a factory and delivered as ready modules. Such a reactor gives light and heat to a village, mine or island where running a power line and shipping in fuel is expensive. The energy flows around the clock for years without new deliveries, and factory assembly is meant to make construction faster and more predictable than for large nuclear plants.
How it works
At its core is uranium fission. A uranium-235 nucleus catches a neutron, splits into two fragments and throws out two or three more neutrons, which split neighboring nuclei. The fragments fly apart at enormous speed and heat the fuel, and the fuel heats the water around it. The pace of the chain reaction is set by rods that absorb excess neutrons: rods deeper — the reaction is weaker; higher — stronger. After that, it is all as in an ordinary plant: heat, steam, turbine, generator.
Small size changes the main thing — cooling. After shutdown the fuel keeps giving off residual heat for a long time, and that heat has to go somewhere. The smaller the core, the easier it is to remove it without pumps: heated water rises, cooled water sinks, and the circulation runs by itself, on physics alone. In many designs the steam generators are built right into the reactor vessel, so there are fewer pipes that could leak.
Factory assembly is closer to shipbuilding than to construction: a module is made in a workshop, tested and shipped to the site by water or by road. Russian reactors of this class grew out of icebreaker reactors. The floating plant Akademik Lomonosov has been operating since 2020, and a land-based small nuclear plant with a RITM-200N reactor is being built in Yakutia — launch is planned for 2028. China’s Linglong One is going through hot testing before connecting to the grid.
Where it already works
- The floating plant Akademik Lomonosov has supplied energy to Chukotka in Russia’s Far East since 2020.
- Yakutia: a land-based small nuclear plant with a RITM-200N reactor, launch planned for 2028.
- China: Linglong One in hot testing, grid connection expected in 2026.
- Remote villages, mines and islands where running power lines and shipping in fuel is expensive.
What to consider
- This is state-run energy: projects go through state companies, licenses and intergovernmental agreements.
- The first units cost more than series ones — the economics work out when reactors are built in series.
- You need a consumer for decades: a plant takes years to build and runs for a very long time.
- Handling fuel and waste is part of the project from day one.