Nuclear Energy is Low-Carbon

Mitigation and adaptation to climate change is the greatest challenge of the century. [8] A major driver of global warming is the emission of greenhouse gases, which can also cause respiratory diseases through air pollution. The energy sector is responsible for the vast majority of these emissions—roughly between two third and three quarters. [9] Coincidentally, the global energy mix is overwhelmingly dominated by fossil fuels. Despite all our best efforts, more than 80% of all the primary energy we consume is still coal, gas, or oil. [10]

The pessimist would say that the gap to breach is enormous. Even more so because the global energy consumption is likely to increase, especially in developing countries. The optimist would directly identify an elegant solution: massively deploy all the low-carbon energy you can get your hands on. This includes solar, wind, hydro, geothermal, and naturally also nuclear power.

Realising how little greenhouse gases nuclear energy produces is often the epiphany to bring to life new nuclear advocates. There are two reasons that explain why its footprint is so small

Figure extracted from the UNECE “Life Cycle Assessment of Electricity Generation Options” report, published in March 2021 and updated in April 2022. Even in a complete lifecycle assessment, nuclear is clearly best-in-class for low greenhouse gas emission.

First, nuclear reactions emit absolutely no greenhouse gases, such as carbon dioxide, contrary to combustion reactions that are at the basis of all fossil fuels uses. There is thus absolutely no direct emission. The white clouds coming out of cooling towers is actually water vapour which, at such a low altitude, has a near-zero or even small cooling effect. [11]

Second, the potential release of energy from a nuclear reaction is approximately a million times greater than that from a chemical reaction, such as the combustion of hydrocarbons. [12] Like any human activity, nuclear energy leads to indirect emissions: mining, transports of goods, facilities construction, etc. However, due to the sheer density of nuclear energy, these indirect emissions are completely dwarfed. As we will see later on, this point is actually valid for all externalities of nuclear power: materials requirements, land use, you name it—the environmental footprint of nuclear energy, measured per unit of energy produced, is flabbergastingly small.

As a consequence, nuclear has the smallest life-cycle greenhouse gases emissions of all energy sources. There is a small yet non-negligible margin between nuclear energy and onshore wind, which is the next best thing. However, the gap is likely to widen in the future, as nuclear energy keeps improving faster than wind.

How do we know? These numbers are typically complex to assess and will depend on a series of hypotheses such as the exact scope under consideration. It is therefore best to refer to multiple sources, hoping to find a repeating trend. Some key numbers on GHG emissions of nuclear energy are as follows.

The 2014 Intergovernmental Panel on Climate Change (IPCC) report assessed the lifecycle emissions, in terms of gCO2eq/kWh, for various energy sources. Already then, it was made clear that nuclear energy had the smallest impact, on par with wind energy.

New assessments, notably by the United Nations Economic Commission for Europe (UNECE) in 2022, narrowed the contributions of nuclear energy to lower values, with a global variation from 4.9 to 6.3 gCO2eq/kWh. [13] Comparatively, the contributions of wind energy remained at 7.8 to 23.0 gCO2eq/kWh, on par with the IPCC value.

The same UNECE report further forecasts a 25% reduction in lifecycle emissions between 2020 and 2050 for nuclear energy, due to the evolution of background electricity mixes and industrial processes. The same figure is only 10 to 13% for wind energy, and 9 to 18% for solar.

More recently, in June 2022, the French utility EDF, coincidentally also the world's largest nuclear operator, published a detailed life-cycle assessment study. It was performed following the strict international norm ISO 14040, which describes the principles and framework for life cycle assessments. It demonstrated that, for the year 2019, the French nuclear infrastructure had produced 3.7 gCO2eq/kWh. This was assessed on the basis of an operational lifetime of 40 years. Extending the facilities’ lifetime to 60 years through long-term operations reduces this figure even further down to 3.4 gCO2eq/kWh.

The average person in OECD countries consumes slightly less than 8 MWh of electricity per year. [14] Right now, the average carbon intensity of electricity production across the OECD countries is 350 gCO2eq/kWh, thus 2.8 tons of CO2eq per person. This would be reduced to approximately 30 kg of CO2eq per person if it was all produced with the French nuclear infrastructure—accounting for the full life cycle, from the uranium mine to the full dismantling of the power plant at the end of its lifetime. Approximately the same amount of carbon dioxide is produced during a 150 km drive with a medium petrol car. [15] That is insignificantly small compared to what would be obtained with fossil fuels, and still appreciably better than solar and wind.

Since the energy sector is the main driver for climate change, nuclear clearly stands out as an astonishingly good option to ensure a better future.

This argument in itself is so strong that, given the climate urgency, we could stop the book right here. However nuclear technologies have many other interesting aspects, with multiple benefits across society. Buckle up!

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