As we look to find ways to decarbonise our environment and tackle the climate crisis, it is clear that renewable energy has a major part to play. What may be less clear is whether nuclear energy is, in fact, renewable, or how advanced nuclear heat technologies might feature in the solution.

What is renewable energy?

Renewable energy is defined as energy from sources that are naturally replenishing, but flow-limited; renewable resources are virtually inexhaustible in the long term, but limited in the amount of energy that is available per unit of time.1

So nuclear energy is not renewable, strictly speaking. The energy that is produced by nuclear power plants is renewable, but the fuel that is required is not renewable. Uranium is a very common metal, however, that is found all over the world.

Our energy challenge: achieving net zero by 2050

The world is far off track when it comes to meeting the Paris Agreement goals of limiting the global temperature increase to 1.5˚C by 2050.2

Current projections, even those that include vast expansion of renewable energy generation, show that fossil fuels will still make up the majority of world energy use by the middle of this century. This would result in a failure to adequately decarbonise, and put us on course for a high-risk 4˚C outcome, which could lead to substantial areas of the planet becoming uninhabitable. According to the Intergovernmental Panel on Climate Change (IPCC), in order to meet that limit of 1.5˚C, human-generated CO2 emissions must be cut in half by 2030 and reach net zero by 2050. Decarbonising is essential.


If our objective is to replace enough dirty energy with clean energy in time for us to decarbonise and avert the worst consequences of global warming, we need to close down as many dirty energy sources as possible and replace them with clean energy sources. Specifically, we need to decarbonisecoal plants, as at current rates, coal plants will use up all of the available CO2 budget by themselves.3

It is really not a question any more of comparing different types of energy production but, instead, a matter of comparing different portfolios of energy production that are able to produce the energy required with significantly lower carbon emissions, and that can also be implemented quickly enough. The question is whether to do so we need an energy production portfolio without nuclear power, or one that includes nuclear energy. And so, in this case, the question ‘is nuclear energy renewable?’ may be less important than ‘can nuclear power help us tackle the climate crisis?’

You might decide against nuclear power because you believe that all our future energy requirements can be met by renewables; that all the required assets can be delivered in time to decarbonise; and that the overall context and incentives are right for this to happen. And if they are not, you might still judge that the consequences for humanity are not as bad as the risks we would incur by using nuclear energy.

Although some argue that it would be technically possible to meet all of our energy needs using renewable energy sources by 2050,4 it is much harder to argue that it is practically possible to achieve the necessary, aggressive decarbonising of emissions within the next decade. The only countries that have been able to achieve the required rate in carbon emission reductions are those that have been using nuclear power (see figure below).5 Renewables require a lot more land, as well as the installation of additional distribution grid, which takes time and becomes increasingly more difficult and costly, as the obvious and easy places for these technologies have already been taken, and further away, more difficult land or sea locations are now the only option for development.6

Whether an (almost) all-renewables portfolio could provide the required clean energy, and whether it is realisable quickly enough remains a matter of debate. But in a way that is not the point either; because if you aren’t 100% sure you can realise this renewables-only portfolio, then as time is so short, failing to look into energy portfolios that include nuclear would be both unwise and irresponsible. We won’t have time for a second chance at getting this right.

The Intergovernmental Panel on Climate Change (IPCC) states that a considerable proportion of our energy production should come from nuclear; and that the nuclear energy capability needs to be increased significantly (up to sixfold) if we are to curb global warming sufficiently to avoid the worst scenarios.7

Given the scale and urgency of the decarbonisation challenge, we need to look carefully at the evidence about the impact and likelihood of the undesirable elements of nuclear power, and the evidence around the effects of continuing to rely on fossil fuels (more specifically the future of coal). We should not simply pit nuclear against renewables; nuclear and renewable energy technologies will have to work alongside each other. If we do not consider the benefits of nuclear power, then any demand that cannot be provided by renewables will have to be met by the continued use of fossil fuels.

Replacing coal: a safe, reliable, sustainable path to clean energy

As decarbonising is the principal challenge we face, we need  sources of clean energy. Nuclear is a clean source of energy. Nuclear energy doesn’t create air pollution or release greenhouse gases. The steam created in the energy production process is recycled into the atmosphere and the relatively small amount of fuel that is needed to provide the required energy can be stored safely. We do need to ensure our long-term solutions for storing spent fuel are fit for purpose, but we will only have the time to worry about that if we tackle the immediate climate crisis.

As such, although nuclear energy itself isn’t technically renewable, we can be confident of the fact that it is a flexible, clean energy source already known to complement renewables well, and which can be used to create a reliable power grid.8 Flexible, advanced reactors sit alongside wind and solar in markets with high penetrations of renewables, and can enable similarly high penetrations of variable renewables in future energy systems. Together, renewables plus advanced nuclear (with thermal energy storage) can reduce emissions and improve performance in future electricity grids, lowering overall system cost.9

Current and emerging advanced heat sources (new generation nuclear reactors) can do more than just provide reliable, clean electricity. They can offer added flexibility for power grids, decarbonise heating and industrial processes, and produce low-cost hydrogen and synthetic fuels.

According to the Expert Group on Resource Management of the United Nations Economic Commission for Europe, nuclear energy is an ‘indispensable tool’ for achieving the UN’s sustainable development goals (SDGs). It will have a crucial role in providing affordable energy and climate change mitigation, as well as eliminating poverty, achieving zero hunger, providing clean water, economic growth and industry innovation.10

In terms of what is safe and clean, fossil fuels are far more dangerous than renewables and nuclear energy.11

Arguing against the benefits of nuclear power, opponents will list additional reasons why we should not use nuclear: cost, feasibility and the energy required to mine uranium and create nuclear power stations. But the same aspects are a matter of debate for renewables. These objections are perfectly relevant in determining the right mix for our energy production portfolio. But because we are trying to determine whether nuclear energy is clean and safe, we focus on the likelihood and scale of the negative aspects of nuclear.

The main objections to nuclear are:

We should not use nuclear because of radioactive waste storage issues
We should not use nuclear because of radiation risks
We should not use nuclear because of accident risks

Storing spent fuel is an important aspect to consider as some spent fuel emits radiation for a long time. Opponents of nuclear argue that no long-term strategy for storing waste has been developed. The nuclear industry responds that a lot of industrial processes also produce toxic materials that need to be handled responsibly over a long period of time. The nuclear industry currently has ways of storing different waste products appropriately.12 The materials that remain radioactive for the longest periods of time can be stored in deep geological formations.13

With regards to potential radiological impacts on the environment and human health, analyses demonstrate that appropriate measures to prevent occurrence of potentially harmful impacts, or mitigate their consequences, can be implemented using existing technology at reasonable cost.14 Provided that all industrial activities in the nuclear fuel cycle comply with regulatory frameworks and related Technical Screening Criteria, measures to control and prevent potentially harmful impacts on human health and the environment are in place to ensure very low impact.15 The average annual exposure of a member of the public, due to effects attributable to nuclear-energy-based electricity production (including mining) is about 0.2 mSv, 10,000 times less than the average annual exposure due to natural background radiation.16 

Opponents generally agree on this, but argue that sometimes facilities are not managed appropriately and therefore risk can increase. The likelihood and impact of accidents with nuclear reactors is – contrary to what is generally believed – considerably less than in traditional energy industries. Nuclear is much closer to renewable energy in terms of safety and greenhouse gas emissions. Traditional fossil fuels are much more dangerous in extraction and operation.

The main cause of death related to energy production is air pollution from fossil fuels.17

Solution: replacing coal with new nuclear power

More than 2,000 Gigawatts (GW) of coal-fired capacity is operating in the world today, adding roughly 15 billion tons of CO₂ emissions per year. This amounts to almost half of all carbon emissions.

Mainstream climate thinking that assumes countries will shut down their coal plants is not realistic. Most coal plants are young: more than half are less than 14 years old. Existing coal-fired power plants have enormous value in terms of established markets for their power, grid connections, access to cooling water and experienced personnel necessary for the generation and distribution of power.

But even though coal plants themselves are the largest single source of carbon, they can also act as flexible generators, complementing renewables in support of delivering reliable, affordable, and resilient electricity grids. Installing advanced heat sources, such as small modular reactors (SMRs), to replace the coal-fired boilers at existing coal plants will enable the continued use of existing infrastructure for emissions-free electricity generation, providing substantial help with our decarbonisation efforts.

Repowering coal offers a fast, low-risk, large-scale contribution to decarbonising the world’s power generation.

So, together with Terra Praxis, other specialists and key stakeholders, we are developing a solution that will contribute to creating a huge market for rapid, low-cost repowering of coal and gas plants with carbon-free advanced heat sources, while delivering a substantial portion of the clean electricity required to help achieve Net Zero by 2050.18

The answer is nuclear and renewables

We are facing a climate crisis, and a rapidly closing window of opportunity in which to address it. The terms of the debate, where ‘nuclear’ is used to cover old technology and its associated problems, must be updated. Rather than frame the debate as either / or, we should be looking objectively at all the potential decarbonisation solutions we have. No technology is entirely problem-free – including renewables – and we must review the benefits of nuclear power carefully, and on the evidence.

One thing we know for sure is that we need to decarbonise, and quickly.

To learn more about our Design to Value approach to design and construction, sign up for our monthly newsletter here:



  1. US Energy Information Administration - EIA
  3. International Energy Agency (IEA) (2019). Global Energy & CO2 Status Report 2019: The latest trends in energy and emissions in 2018
  6. Lucid Catalyst (2020)
  8. Clean Energy Ministerial (2020), Flexible Nuclear Energy for Clean Energy Systems, Technical Report, September 2020
  9. LucidCatalyst (2020). Cost and Performance Requirements for Flexible Advanced Nuclear Plants in Future U.S. Power Markets. Report for ARPA-E MEITNER Program.
  10. Expert Group on Resource Management of the United Nations Economic Commission for Europe (2021)
  13. European Commission (2021) JRC Science for Policy Report: Technical assessment of nuclear energy with respect to the ‘do no significant harm’ criteria of Regulation (EU) 2020/852
  14. Ibid.
  15. Ibid.
  16. Ibid.
  18. For more information about the proposed strategy, see: 
    Repurposing Coal: how a P-DfMA approach will help coal-fired power stations fight climate change.
    Bryden Wood unveils digital platform for decarbonising electricity production by 2050