Exhaustion of World Uranium Reserves

Introduction

Fig. 1: Nuclear Power Plant in Belleville-sur-Loire, France. France generates a larger proportion of its energy with nuclear power than any other country. [5] (Source: Wikimedia Commons)

As global temperatures continue to rise, the need for low-carbon energy sources rises as well. In the last year, human sources around the world emitted 31.5 billion metric tons of CO₂ into the atmosphere. To avoid catastrophic levels of global warming, scientists predict that CO₂ emissions must be reduced by 45% in the next decade. [1]

Although renewable solar, wind, and hydroelectric power has become more popular in recent years, both in share of energy generation and in public opinion, nuclear energy has remained somewhat overlooked. Nuclear energys share of electric power generation has remained mostly constant over the past decade, despite comparable CO2 emissions per joule generated versus traditional renewable sources, such as wind and solar. [2,3] The lack of growth in the nuclear energy sector can be largely attributed to public opinion. According to a 2022 poll, only 45% of Americans support the use of nuclear power plants. [4] However, the recent growth of nuclear energy in Europe and East Asia, as well as future projections, suggest nuclear energy may contribute to a larger percentage of the global energy matrix in the next decade.

While nuclear power is considered to be clean energy, it is not renewable in the same sense as wind and solar. Uranium must be consumed to fuel nuclear reactors, and the Earths uranium resources, while large, are finite.

Analysis

For simplicity, we shall assume that all generation comes from Pressurized Water Reactors (PWRs), the most common form of nuclear reactor currently active. [5] Fig. 1 shows a pair of PWRs in Belleville-sur-Loire, France. PWRs consume low-enrichment uranium; in the case of the PWR, the uranium must be enriched to 3.2% U-235. U-235 is a naturally uncommon isotope of uranium, comprising only 0.71% of uranium mined or otherwise extracted. Fission of a U-235 atom releases 230 MeV of energy as heat. From this number, the energy in one kilogram of natural uranium is:

However, the typical thermal efficiency of a PWR must be taken into account. At a thermal efficiency of 32%, one kilogram of uranium actually releases 2.09 × 10¹¹ J kg^-1. [6] A typical PWR is rated at 1000 MWe; such a reactor can generate 31.536 petajoules (1 petajoule = 1015 joules) of energy per year. The amount of natural uranium required to provide this energy is therefore:

In 2021, world energy consumption from all sources was estimated to be 595 exajoules (1 exajoule = 10¹⁸ joules). [2] To meet this energy demand using solely PWRs, 18,867 such reactors would need to be in operation, consuming 2.85 × 10⁶ tons of natural uranium per year. With world uranium reserves estimated to be 8.07 × 10⁶ tons in 2020, the world could be completely powered by PWRs for 2.83 years. [5]

Conclusion

Although the concluded number of 2.83 years may seem disheartening, the scenario analyzed above is, in many ways, a worst-case scenario. Renewable energy sources such as wind, solar, and biofuels already generate nearly 30% of the worlds power. Furthermore, the calculations above ignore fuel recycling techniques and higher efficiency in emerging reactor technologies. Fuel-recycling breeder reactors could theoretically match the output of PWRs with only 1% of the needed natural uranium; however, such reactors are held back by technological constraints and the associated threat of nuclear weapons proliferation. [7] However, if such technology were to become widespread, nuclear power could sustain the world for the coming centuries.

© Nicholas Murphy. 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.

References

[1] "Global Energy Review," International Energy Agency, 2020, 2021.

[2] "BP Statistical Review of World Energy 2022," June 2022.

[3] Climate Change 2014: Mitigation of Climate Change (Cambridge University Press, 2015).

[4] T. Gardner, "Americans Split on Nuclear Energy as Safety Worries Linger - Reuters/Ipsos Poll," Reuters, 6 Jun 22.

[5] "Uranium 2020: Resources, Production and Demand," Nuclear Energy Agency, NEA 7551, 2020.

[6] O. Breeze, Nuclear Power (Academic Press, 2016), Ch. 4.

[7] S. Fetter, "How Long Will the World's Uranium Supplies Last?" Scientific American, 26 Jan 09.