Small modular reactors may have climate benefits, but they can also be climate-vulnerable.

Sipri, 26 January 2024, Vitaly Fedchenko

“……………………………… large nuclear power plants have almost exclusively been built in industrialized countries.

More recently, a new class of small modular reactors (SMRs) for power generation have been gaining in popularity and are supposedly better suited for use in developing countries. SMRs hold the promise of driving progress towards universal access to modern energy sources and several other Sustainable Development Goals in a climate-friendly way. However, while they may not have a negative impact on future climate change, SMRs are not immune to the direct and indirect impacts of an already changing climate.

………………………….. dozens of states have expressed interest in building an SMR of some kind. According to data from the OECD’s Nuclear Energy Agency and the World Nuclear Association, at least 40 states are taking steps towards building an SMR on their territories.

The IAEA has counted at least 80 SMR designs. Most are intended to produce electricity for 60 years or more. With the time allowed for construction, decommissioning and potential extensions of operating life, it is conceivable that the lifetimes of future SMRs may approach 100 years or more.

The other side of the coin: SMRs and climate risks

A century is a long time. At any given location, political and societal changes are inevitable, many impossible to predict. …………………………………

Climate change and its direct and indirect effects, including on politics and security, also pose risks for nuclear power plants and other critical infrastructure. Direct effects include rapid-onset extreme weather events (such as storms and storm surges, heatwaves and flash floods) as well as slower-onset phenomena (such as sea-level rise, water scarcity, changes to rainfall or average temperatures). All of this can undermine the safe and secure functioning of nuclear facilities. For instance, drought—especially compounded by competing demands for water—could disrupt the cooling water supply to a reactor, potentially necessitating a shutdown, while floods or storms could damage critical systems.

A 2021 analysis of nuclear power plants’ vulnerability to such climate-linked effects is full of important insights. The study shows that the average frequency of climate-linked power outages at nuclear power plants globally has dramatically increased—from 0.2 outages per reactor-year in the 1990s to about 0.82 in 2000s, to 1.5 in 2010–19. It projects that energy losses due to climate change will continue to rise among the world’s nuclear power plants.

That study’s findings for the period 2010–19 suggest that, after hurricanes and typhoons (in the United States, South and South East Asia), the second largest climate-linked contributor to outages was increased ambient temperatures. Higher ambient temperatures can affect nuclear power plants in a variety of ways. For example, warmer temperatures can foster the rapid growth of algae or other biological material, which can in turn clog cooling water intakes, reducing production and even requiring the plant to shut down, particularly in warmer areas or reactors using seawater for cooling. High ambient temperatures can also make power generation less efficient. Many of the developing countries where electricity access is currently lowest (and thus where SMRs might have the greatest value in promoting development) already have relatively high ambient temperatures, which are likely to increase further.

… some of the states that have already announced interest in building SMRs are in areas highly exposed to the physical effects of climate change, including lower-middle income countries. Although the accident at the Fukushima Daiichi nuclear power plant in 2011 was caused by a natural disaster unrelated to climate change, it demonstrated that even in a wealthy, industrialized country like Japan, nuclear facilities can be vulnerable to extreme natural events.