Nuclear energy is “green”: now what?

By Manuel Protásio (PhD Candidate at the University of Minho)

In the beginning of July this year, the European Parliament voted in favour of a proposal on labelling natural gas and nuclear power as climate-friendly investments. For the first time, Parliament did not object to the Commission’s Taxonomy Delegated Act to include specific nuclear energy activities, under certain conditions, in the list of environmentally sustainable economic activities covered by the so-called EU Taxonomy. Although it is still early to read anything else besides the actual change in the taxonomy of the European Commission, the truth is that this conceptual change regarding nuclear energy can be seen as a major political statement regarding the future of energy in the European Union.

From a political point of view, it can be argued that this change comes from the urgent and dramatic context we are currently in, due not only to Climate Change but also to the geopolitical shift that has risen from the Russia’s war with Ukraine. Within this new global context, European Union’s political landscape also changed, particularly in what concerns energy policy and I believe this new taxonomy given to nuclear energy is also part of this new political landscape. Nevertheless, it is not our intention to bring forward a political analysis to this shift in European policy regarding nuclear energy, but to give a brief overview of whether nuclear energy should be labelled as a green energy and a climate-friendly investment and if so, how can this change help European Union’s objectives in becoming more self-sustainable in terms of energy production as well as achieving its goals under the Green Deal.

This overview will be based on a comparison between other types of green energy and nuclear energy, while going through certain criteria and requirements used to assess if a certain type of energy is environmentally friendly or not.

So, what can be defined as green energy? We are used to see the concept of green energy connected with renewable energy, but the concept is not exhausted by these types of energy. There are several different criteria used by different institutions and organizations to define something as green or sustainable and we can argue which one is the most suitable, but this article will go through some of them to assess how nuclear energy fits in any of these categories.

Green energy is usually defined as any form of energy produced from natural resources like solar, wind or water. The process through which this energy is generated is also relevant when qualifying any form of energy as green or not. We can generate energy through a totally natural and renewable source but if the process through which we generate that energy is not sustainable, then we can have renewable energy that is not sustainable. An example of that is hydropower, which usually requires a level of industrialisation and deforestation that compromises the sustainability of the process to generate energy from fast flowing water. It can be argued that solar power is also not sustainable since the process to generate energy requires the transformation of heavy metals that are not recyclable, which compromises the sustainability of the process itself.

Here we have examples of forms of energy that are considered to be green because they come from natural and renewable resources, despite the fact that they rely on processes or materials that are not so sustainable. Nuclear energy comes from the power generated by nuclear reactions, which can be obtained through nuclear fission, fusion or decay of certain elements like uranium, which is the most common. Uranium is a very common element in our planet and will not be used up in our lifetime which qualifies as a renewable source of energy. The problem arises with the fact that the fuel used to generate nuclear power is made from uranium U-235, which is a rare isotope of uranium that needs to be gathered through different processes that deem this element as not sustainable. But there are other sources of nuclear power that come from other abundant elements like thorium, which a more environmentally friendly element than uranium. Nuclear energy therefore relies on natural occurring elements that, depending on the processes though which they become nuclear fuel, can be considered sustainable and even renewable.

Another criterion used to assess if a type of energy is “green” or sustainable is its capacity factor which measures the ratio of energy produced in a certain amount of time over the maximum amount of energy that can be produced in that period of time, meaning how often does it run at its full capacity which translates to how reliable is to produce power from this energy source. According with the world nuclear performance report and statistics from Eurostat and the department of energy in the US, the capacity factor of nuclear energy is the highest amongst the other types of energy.[1]

When compared with solar energy or natural gas the numbers are unequivocal: nuclear energy has a capacity factor around 92%, compared with 54% for natural gas, 40% coal and 25% for solar energy. This means that nuclear power plants produce their maximum power more than 92% the time while other types of energy only reach half of that capacity and sometimes only 25% when compared with nuclear energy. This is mainly because the maintenance costs are fixed in nuclear plants, whether the nuclear plant its operating or not and also due to the fact that nuclear plants usually operate for longer periods of time, stopping for refuel only after 1 to 2 years. When compared with renewable energy that usually is very intermittent or coal that requires a lot of refuel and routine maintenance, nuclear energy is very much reliable. Reliability matters if we want to compare different types of energy sources over the same amount of energy produced. If we take, for example, 1 gigawatt of electricity produced by one single nuclear plant, we arrive to the conclusion that the same amount of electricity (1 gigawatt) would require 2 coal units or 3 if we also compare it with solar or wind energy. The level of reliability on producing energy is a key factor to understand the sustainability of a certain energy source and its processes to convert it into power.

Sustainability is of course very relevant if we want to assign the term “green” to anything, but it is not a concept that can be easily defined as it encompasses several different dimensions that overlap each other to reach one fundamental goal, which is to ensure that the needs of one generation do not compromise the ability of future generations to meet theirs. So, sustainability of any energy resource would be related to its capacity to maintain itself for a definable period of time lasting until a generation no longer needs it, at the rate it is being used or expected to be used right now. That’s why renewable energies are considered to be sustainable, due to their capacity of naturally replenishing itself. But even renewable energy can be deemed unsustainable if it is being used at a faster rate than what needs to regenerate.

Nuclear energy, as it stands, is considered to be a sustainable energy source[2] because it is used at a slow rate that still manages to generate power that can last hundreds to thousands of years, overcoming the generational hurdle. Nonetheless, it is not considered renewable because uranium is not a renewable source, but the process to extract uranium in sustainable ways exists[3] and there are other elements like thorium that are much more abundant than uranium and are not under the stigma of nuclear weapons like uranium is. In short nuclear energy is sustainable and it is more sustainable than many other sources of energy, especially comparing with fossil fuels.

We cannot say that nuclear energy is more sustainable than renewable energies but we believe that even for countries like Portugal that have a lot potential for renewable energies, nuclear reactors are still a major investment even to optimize and enhance renewable energy. For countries that go through severe drought like Portugal and Spain, nuclear energy can offer an alternative as a strategy for desalinization of water.[4]

Another major factor that must be considered to consider nuclear energy “green” has to be its environmental impact. This can always be measured by the greenhouse gas emissions, the impact on the landscape, the short term and long-term effects of nuclear accidents, nuclear waste management, among others. This will bring forth the biggest advantage and disadvantage of nuclear energy.

Perhaps the most important factor to assess the impact in the environment, especially if we consider the need to mitigate the effects of climate change, is the carbon footprint. A study published in Nature magazine found that nuclear energy has a CO2 emission footprint of 12 grams(g) per kilowatt of electricity produced, compared with between 25g and 45g (depending on if it is solar power concentrated or a utility or a roof)[5] for solar power, 820g for coal and 490g natural gas.[6]

Nuclear energy is practically a zero-carbon emission compared with other resources, renewable or not and studies have demonstrated that nuclear generated electricity saves our atmosphere from more than 470 million metric tons of carbon dioxide emission that would otherwise come from fossil fuels. The extraction of uranium is the factor that contributes more for indirect emissions of nuclear energy, and it has a big impact on emissions but companies and other countries are already exploring other ways to fuel nuclear plants,[7] through seawater extraction of uranium, or by exploring thorium, the process of extraction and its impact on the environment becomes much more sustainable. The problem arises after, with nuclear waste.

Nuclear waste has always presented itself as one of the main disadvantages and potential hazards in nuclear energy. If we consider the European Union’s standards for nuclear safety,[8] the vast majority are related with nuclear waste and waste-management strategies as well as with potential health hazards, so this is definitely the biggest concern evolving nuclear energy, so it is essential that any current or future investment in nuclear energy is dully supported on all these safety standards. If we look at the data evolving nuclear waste, we see that nuclear waste is considered to be minimal waste since the amount of waste produced over the amount of fuel used is very small due to the density of nuclear energy.

This minimal waste is usually divided into categories depending on their level of radioactivity. The World Nuclear Association indicates three categories (High level; Intermediate level; Low-level waste) and the waste that actually can create a harmful impact is less than 10% of the total waste.[9] If we compare the actual impact on human health in terms of deaths caused by nuclear waste versus fossil fuel waste[10] the numbers are clear – nuclear energy results in 99.9% fewer deaths than brown coal; 99.8% for coal; 99.7% fewer than oil. Nuclear waste presents challenges in storage but there are a lot of safe ways to deal with and some companies and even states are researching and finding new ways to reuse nuclear fuel that would minimize the waste and its dangers.[11] Some scientists even argue that it is easier to recycle nuclear waste than solar waste, which also contains toxic materials like lead or other heavy metals used in panels. So we see from the publicly available data and scientific data that nuclear waste is actually less harmful and easier to deal with it than what the general public perceives, including myself.

This is mainly due to the fact that nuclear energy created throughout time many heuristics and bias in society.[12] Specifically, it falls right in the representativeness and availability heuristic. The first relates with the fact that we perceive nuclear energy as a dangerous and bad type of energy because of highly impactful events like the fear of nuclear war and although nuclear weapons are very different than nuclear power plants, even in the way the nuclear chain reaction happens, people tend to confuse one and the other and that is a heuristic. As it is with the data related with accidents in nuclear power plants. The latest examples we have in our memories are Chernobyl and Fukushima. Because these and other events created a sense of danger and fear towards nuclear energy people tend to think of the frequency that these accidents happen very differently from what happens in reality. A number of studies and reports demonstrate and reinforce the idea that nuclear power plants are safe and the higher the safety standards are, like in the European Union, the less likely it is for these types of accidents to happen.

In the end these heuristics and biases have a huge impact in the regulation of nuclear energy. With this we arrive to one of the most important factors to assess the feasibility of going further with nuclear energy. The economic cost.

It is difficult to assess the economic cost of an energy source without considering many different variables but for the purpose of this article, we will consider the building cost, the impact on employment, among others. It is common knowledge that the investment in building nuclear power plants is usually very high compared to other units that can be built to harness other types of energy, so the cost is always a factor that tends to become a disadvantage compared with other energy sources. Building is not the only high cost in nuclear energy. Maintenance costs both during and after the production of power are very high.

The waste management costs are extremely high compared to other types of energy because nuclear waste is stored underground or in water facilities instead of being released to the environment. But not all is bad, the impact of nuclear energy investment in economies is always very positive not only because of its capacity factor which is crucial to drop the cost to the end consumer but also because it has a major impact on employment since it generates many jobs. In short nuclear energy can have a very meaningful and positive impact on the economy but the end cost of this energy is still high compared with other types of energy because of its building and maintenance costs. Nonetheless, are there any chances of this going down soon? For companies like Copenhagen Atomics[13] this is a certainty that will not take more than 5 years. This company and others have been working on a new model for nuclear reactor that is small and works with thorium and reused uranium which reduces nuclear waste and its radioactivity durability.

These new models are just the beginning of a revolution in nuclear energy that can be led by the Europe Union if this political statement given by the European Parliament becomes a reality. Through regulation and research and development, companies can be incentivized to develop more sustainable ways of dealing with nuclear waste or mining uranium or finding other elements like thorium to create electricity. The potential for nuclear energy is enormous both from a political and socioeconomic point of view as well as in view of the goals of the Green Deal to mitigate climate change effects. Nuclear energy can be essential for Europe to achieve carbon zero emissions and to become completely self-sustainable in terms of energy. It really depends on the political will to incentivize the public and private sector to invest in nuclear energy. For that it will also be essential to change public perception by demystifying certain biases related with hazards and health risks. By doing this and by aligning the future of nuclear energy with the already existing regulation and safety standards in the European Union, there is a bigger chance to overcome the challenges of our time. 


[2] Why nuclear energy is sustainable and has to be part of the energy mix, Barry W.Brook, Agustin Alonso, Daniel A. Meneley, Jozef Misak, Tom Blees, Jan B. van.;

[3] Uranium from seawater – Infinite resource or improbable aspiration?, K.DunganaG.ButleraF.R.LivensaL.M.Warren, 2017,








[11] See Copenhagen Atomics in ref. 10

[12] M. V. Rajeev Gowda. “Heuristics, Biases, and the Regulation of Risk.” Policy Sciences 32, no. 1 (1999): 59–78.


Picture credits: distelAPPArath.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s