Nuclear Decarbonization

Elaine Lui
February 19, 2021

Submitted as coursework for PH241, Stanford University, Winter 2021

The Need for Decarbonization

Fig. 1: A pressurized water nuclear reactor. Steam from water boiled from splitting uranium atoms is converted to electricity. Cooled water condenses the steam back to water, which can be reused. (Source: Wikimedia Commons).

The rising significance of climate change and the depletion of fossil fuels and other nonrenewable resources has given rise to a growing need for alternative, carbon-free sources of power. While renewable resources such as wind and solar energy have penetrated some markets, such as backup power for traditional natural gas power plants, the weather-dependent intermittency of renewable energy has its limitations as a reliable primary energy source. [1] Nuclear energy, which harnesses energy from the combination (fusion) or splitting (fission) of atoms, is one available alternative source of power with no carbon emissions, as seen in Fig. 1, which shows how steam in a nuclear reactor is converted to electricity. Despite its potential to radically change the energy landscape, nuclear energy today only constitutes 5% of primary energy production in the world. [1] There are several factors limiting the growth of the nuclear energy sector, including the high time and capital costs needed to build new nuclear power plants, the safety concerns associated with nuclear reactors and waste, and the politicization of nuclear power. [2]

Feasibility of Decarbonization via Nuclear Energy

In the United States, almost 40% of primary energy consumption is used to produce electricity, and the net electricity generation worldwide is projected to grow at a rate of 1% per year in developed nations and almost 2% in developing countries. [3] Deep decarbonization of the electrical energy sector, which involves a reduction of greenhouse gas (GHG) emissions by at least one order of magnitude, is required to mitigate the effects of global warming. [1] This has been quantified and widely accepted as limiting the global average warming to 2°C by 2050. While there are several methods to reduce carbon emissions, to reach this target, the U.S. would need to reduce its carbon emissions from electricity generation by more than 97%, from 500 g CO2/kWh to 15 g CO2/kWh. [3]

To give some perspective on the feasibility of a 97% reduction in electricity carbon emissions, let us take the electrical energy generation in the U.S. in 2019, which was approximately 4 trillion kWh. Of this electricity generation, 63%, or 2.52 trillion kWh, was from fossil fuels and other gases. [3] This means that 2.44 trillion kWh (97% of the carbon-emitting sources) of electricity would need to be generated from an alternative, carbon-free source. Assuming this energy comes entirely from nuclear power generation, and assuming each nuclear reactor is 1 GW in size, this amounts to

2.44 × 1012 kWh yr-1 × 3.6 × 106 J kWh-1
1 × 109 W × 3600 s h-1 × 24 h day-1 × 365 days yr-1
= 278 reactors
Fig. 2: Nuclear power plant in Cattenom, France. (Source: Wikimedia Commons)

Given that there were 94 operable nuclear power plants in the U.S. in 2020, we currently need about 3 times more reactors than we have. [3] Note that in the calculation of this metric, we have zeroed in on the electrical energy needs for the U.S. alone. When we broaden our scope to global energy demands, in order for nuclear energy to contribute significantly to the energy landscape, nuclear fission plants need to produce 10 TW of power over a sustained period. [4] Given our assumption of 1 GW per reactor, this is equivalent to 10,000 reactors, which is two orders of magnitude higher than the 443 nuclear power reactors currently in operation across the world. [5] Furthermore, since radioactive metals used in nuclear fission reactions, such as uranium, are not infinite resources, at this usage rate, the level of uranium in the earth would be depleted within 10 years. [4] It is thus clear that nuclear energy alone cannot substitute fossil fuel and carbon emitting energy resources, although it may certainly play an important role within the deep decarbonization portfolio.

Future Outlook

While nuclear energy may not be the sole solution to deep decarbonization and overhead costs for building new nuclear infrastructures may be prohibitively high, utilizing existing nuclear power plants (such as shown in Fig. 2) as a complementary energy source to renewable energy sources, such as wind and solar, can mitigate the global warming crisis and reduce the overall costs of deep decarbonization. [6] Furthermore, advances in nuclear technologies have enabled inherent, passive safety features and enhanced thermal efficiency, which reduce the risks and costs associated with building new nuclear plants. [1] That being said, there are still significant risks involved in the transportation and storage of radioactive waste from nuclear energy production, both in terms of safety in handling and in preventing theft for nefarious purposes.

© Elaine Lui. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. Buongiorno et al., "The Future of Nuclear Energy in a Carbon-Constrained World," Massachusetts Institute of Technology, 2018.

[2] E. Papadis and G. Tsatsaronis. "Challenges in the Decarbonization of the Energy Sector," Energy 205, 118025 (2020).

[3] "Monthly Energy Review, January 2021," U.S. Energy Information Administration, DOE/EIA-0035(2021/1), January 2021.

[4] N. Armaroli and V. Balzani, "The Future of Energy Supply: Challenges and Opportunities," Angew. Chem. Int. Ed. 46, 52, (2006).

[5] "Nuclear Power Reactors in the World," International Atomic Energy Agency, Reference Data Series No. 2, 2020.

[6] J. Parsons et al., "A Fresh Look at Nuclear Energy," Science 363, 105 (2019).