As the world races to reduce greenhouse gas emissions and meet climate goals, every low-carbon energy source comes under scrutiny. Nuclear energy offers one way to generate large amounts of electricity with very low direct CO₂ emissions. But “low carbon” is not the same as “sustainable”. While nuclear energy is a significant source of power in several EU countries, and accounts for 11% of the total global electricity generation, there are many issues to consider such as radioactive waste, safety, cost, and resource constraints that all complicate the picture and contribute to whether nuclear energy really is ‘green’.
In this post, we’ll objectively summarise what the scientific literature says about nuclear energy. We’ll briefly explain what nuclear energy is, highlight the strengths of nuclear energy, its challenges, and where nuclear fits (or doesn’t) in a sustainable energy future. Let’s dive in!
First: a quick summary on what nuclear energy is. Nuclear energy is generated from the cores of atoms, the nucleus, which consists of protons and neutrons. There are two ways that atoms can generate nuclear energy.
The first one is based on nuclear fission, which is when a heavy nucleus of an atom splits into different parts. The second one is based on nuclear fusion which is when two light nuclei of different atoms fuse together. Only the first one, fission, is used in the world today to create nuclear energy, and the second one is still being extensively researched.
To generate this nuclear power, no greenhouse gas emissions are created during operation and low emissions are created during the full life cycle. The stages for the largest emissions are during processing, such as exploration and processing of the uranium ore, and downstream from the plant when the fuel is reprocessed and stored. Different forms of waste are created during operation and maintenance, such as solid and liquid waste.
When you account for everything — mining, construction, operation, decommissioning — nuclear power tends to emit only a few grams to tens of grams CO₂-equivalent per kWh. That is comparable to renewables, and a lot lower than fossil fuels. Technology keeps refining the reactors, and newer designs (e.g. HPR1000) have been estimated at ~10 g CO₂e/kWh in full life cycle studies.
Nuclear plants can produce steady, continuous electricity from a small land footprint, which is an advantage in systems where space is limited or energy demand is constant. It is therefore not dependent on e.g. the weather (as with solar and wind) and helps grid stability. Compared to other sustainable energy resources, nuclear power plants require less land to produce energy. A report from the US found that wind farms require 360 times more land area compared to nuclear facilities.
Spent nuclear fuel and other high-level wastes contain radionuclides that stay hazardous for thousands to millions of years. The most often used solution is to dispose the waste deep in the ground, but this is not always accepted by the public or regulations. Recent scientific reviews on deep geological disposal point out continued uncertainties in canister corrosion, host rock interactions, and long-term performance models. Even if the volume of the waste is relatively small, their harmful impact on health and the environment is a lot larger than many other wastes.
Although the risk might be relatively small, accidents can and have happened causing radiation in the environment. The most famous catastrophic accidents, such as in Chernobyl and Fukushima, are rare but have a high-impact on the people living close by and the ecosystem. Scientific evidence is not conclusive whether long-term radiation has a negative or neutral effect on the wildlife populations, or even positive as many mammal numbers have increased in e.g. Chernobyl. The severity of consequences depends heavily on containment design, emergency response, human factors, and governance.
Building a new large nuclear plant usually requires heavy upfront investments, regulatory approval burdens, and sometimes decades of construction. This delay reduces its value in urgent climate mitigation scenarios. To significantly decrease greenhouse gas emissions, a huge number of nuclear power plants will need to be produced, which will cost a lot of money and will take time, and such capacity is not always realistic. Plus, the costs of building nuclear power plants have often be underestimated by far, and the realised building costs were way higher than the estimated costs.
If nuclear capacity expanded a lot, the supply will equally increase and this might become problematic. The supplies might become a constraint, such as uranium mining, enrichment, and fabrication. All these factors have a negative environmental impact too.
Trust, governance, liability allocation, regulatory oversight, waste consent from communities, and transparency are not technical but essential elements. A sound safety case (for waste or reactors) must integrate science, uncertainty, and societal confidence. As of now, nuclear energy fails to meet the social criteria of sustainability, which is safety, decentralization and civil engagement.
There are other safety concerns beyond those that can be more easily measured. Nuclear plants will be easy targets for terrorism, cyberattacks or acts of war. They are vulnerable and a unique hazard, and need to be kept on a tight leash at all times, because an attack could be disastrous.
Nuclear energy isn’t a silver bullet because it carries great responsibility. But dismissing it outright may be unwise in certain situations. Green parties often emphasise the high upfront cost as well as high continued costs for nuclear waste management, the slow speed at which the plants can be built, the emissions generated when extracting, transporting and processing uranium, and the high level of risk – factors that make it unrealistic that we can address the climate crisis fast enough with nuclear energy.
Ultimately, the sustainability of nuclear energy depends not just on physics, but on people and institutions.
Beresford and Copplestone about the effect of nuclear power plant accidents and the environment (2011). https://doi.org/10.1002/ieam.238 [scientific paper]
Deryabina and colleagues about the effect of Chernobyl on wildlife (2015). https://doi.org/10.1016/j.cub.2015.08.017 [scientific paper]
Greenpeace about why nuclear power is not green. https://www.greenpeace.org/international/story/52758/reasons-why-nuclear-energy-not-way-green-and-peaceful-world/ [blog post]
Matthew about the sustainability of nuclear energy (2022). https://doi.org/10.1016/j.pnucene.2021.104080 [scientific paper]
Liu and colleagues critically reviewed nuclear power plant carbon emissions https://doi.org/10.3389/fenrg.2023.1147016 [scientific paper]
Pieńkowski about how the Polish nuclear energy program is an example of greenwashing. https://doi.org/10.1016/j.esd.2024.101376 [scientific paper]
Yue and colleagues about the role of nuclear energy in sustainable development in island economies (2022). https://doi.org/10.1016/j.renene.2022.05.017 [scientific paper]
Image source: Freepik
