Small Modular Reactors have been widely promoted as a source of low-carbon energy that can provide constant power, whatever the weather, unlike renewables. They are much smaller than a traditional nuclear power station, needing less space, but generating a fifth of the energy. Their modular design means they can be partly prefabricated in a factory making them cheaper to build.

Environmentalists are divided on nuclear energy, weighing up the low-carbon energy against the mining of uranium and the unresolved issue of its radioactive waste. Spent fuel rods are still stored above ground at nuclear reactor sites. Finland is the only country in the world to have started storing its nuclear waste in underground stores, but this is a slow and expensive process. The fuel rods must first be cooled for 40 years above ground and then stored in a geologically stable site for hundreds of thousands of years.

The Institute for Energy Economics & Financial Analysis (IEEFA) has assessed whether SMRs can meet our energy needs. Its answer to this question is pretty much found in the report’s title, ‘Small Modular Reactors: Still Too Expensive, Too Slow, and Too Risky’. It says that a new nuclear plant costs about five times as much as an equivalent new onshore windfarm and takes many more years to build. All four SMRs currently operating in the world, in Russian and China, went way over budget, and SMRs still face decommissioning costs at the end of their lifetime.

No SMRs are expected to be constructed in the UK before 2035, so they will not contribute to the urgent reductions we need to make in carbon emissions from electricity generation. Nuclear is notorious for delays, so it could take a much longer timeframe. Planning delays are also likely, as local communities may be unwilling to host even a small nuclear reactor. SMRs still need water for cooling, so coastlines are the preferred location, although this comes with the risks of rising sea levels.

Any public money spent on SMRs could be directed to other sources of energy that are cleaner, quicker to deploy, and safer. The cost per unit of electricity generated will also be many times more expensive than wind and solar power.

Nuclear reactors can ramp up power at times of high demand but slower than batteries or gas-powered plants. They can help ensure the stability of the electric grid in a system with a higher share of renewables. However, the rapid advances in battery technology and the commercialisation of large grid-scale batteries to store wind and solar power diminishes the argument for nuclear as a constant power source

“The much-hyped resource would be too slow, too expensive and too risky to help in the transition away from fossil fuels” is the conclusion in the IEEFA report. Renewables are the near-term solution. We should invest in technologies to store renewable energy that avoids the need for new nuclear and is cheaper, quicker and safer.