Non-Fossil Electric Energy

W. Addy Majewski

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• Nuclear Power
• Hydroelectric Power
• Wind & Solar Power

Nuclear Power

Commercial nuclear power technology utilizes the heat of nuclear fission reactions to generate steam, which drives steam turbines to produce electricity. Most nuclear power is produced by nuclear fission of uranium-235 (²³⁵U) and plutonium-239 (²³⁹Pu). Uranium is found naturally on Earth, but is composed in over 99% of the non-fissile ²³⁸U isotope. To become fissile, uranium must be enriched to contain a higher percentage of ²³⁵U. Most nuclear reactors use fuels containing 3-5% of ²³⁵U, while naval propulsion reactors and nuclear weapons use uranium containing more than 20% of ²³⁵U. Plutonium is present on Earth only in trace quantities, and fissile plutonium is produced from uranium in nuclear reactors—either as a by-product or made specially for military purposes. Dismantled nuclear weapons are an important source of plutonium for nuclear power plants.

At some time, nuclear power had raised significant hopes for the future of energy. Somewhat ironically, the confidence in nuclear power was shared by the authors of the Limits to Growth report, who presumed that “the technology of controlled nuclear fission has already lifted the impending limit of fossil fuel resources” [3762]. Nuclear energy, with its apparently limitless potential, was believed by many to become “too cheap to meter”, releasing us from the dependency on oil, gas and coal—a similar complacency is now being repeated by some advocates of renewable energy.

The advantages of nuclear power include very low carbon emissions, a decent EROI of about 10 [4410], and high power density (on the order of 100 W/m²). Nuclear power is one of the very few options to decarbonize electricity generation that has been demonstrated to be viable technically and commercially, and to be scalable—France derives about 75% of its electricity from nuclear energy. Nonetheless, these advantages come with a number of issues, including:

• potential for accidents at nuclear powerplants;
• radioactive waste disposal;
• rising costs of nuclear power; and, ultimately,
• depletion of world’s uranium resources.

Over its entire history, the nuclear power industry experienced only three serious accidents: the Three Mile Island accident in 1979, the Chernobyl disaster in 1986, and the Fukushima Daiichi accident in 2011. As the number of casualties was limited, the safety record of the nuclear power industry looks quite good when compared to the death toll in the global coal mining industry, which is considered an unfortunate yet generally accepted cost to maintain the supply of coal power. However, nuclear incidents carry a much higher fear factor for the public, and there is always a potential for an even greater disaster in the future. In monetary terms, nuclear powerplant accidents may involve astronomical costs for remediation work.

Spent fuel from a nuclear reactor includes a number of isotopes that are considered radioactive waste. This radioactive waste can be disposed of in a solid state, shielded and packaged, in deep geological formations where it would remain contained for long periods of time. As the amount of waste is relatively small, this task appears technically achievable. Notwithstanding potential issues, such underground storage would provide the best possible protection against the release of radioactive material into the environment. However, due to public and political opposition to radioactive waste sites, the problem of radioactive waste disposal has never been solved. In the United States, for example, the Yucca Mountain nuclear waste repository project was canceled in 2009 [4442]. As a result, quantities of spent fuel are stored under water in spent fuel pools at nuclear power plants—at hundreds of locations worldwide. The temperature in these pools must be controlled by circulating cooling water. The water pumps require continuous supply of electricity, which makes this method of storage vulnerable to a number of natural and human-made disasters—flooding, earthquakes, terrorist attacks, war, or a prolonged electrical grid outage. Economically, the need to store radioactive waste on premises is an added financial burden for powerplant operators.

After a few decades of growth, the nuclear power industry entered a period of stagnation and decline. One contributing factor was the 2011 Fukushima accident, and another was the increasing cost of nuclear power. Nuclear technologies have become expensive due to the huge regulatory and institutional burdens that stand in the way of building and operating these plants, long time horizons that increase risks, as well as the increasing costs of nuclear power plant decommissioning. While the financial profitability of nuclear power has always been a contentious issue—nuclear power often received government subsidies and could be motivated by military purposes—at the current cost levels, nuclear powerplants are no longer competitive with other sources of generation, such as natural gas.

Due to the lack of investment and closures of the existing plants that reach their end-of-life dates, the future of nuclear power is uncertain. The IEA has estimated that advanced economies could lose 25% of their nuclear capacity over 2019-2025, and as much as two-thirds of it by 2040 [4443]. The lost nuclear capacity would be replaced, at least to some degree, by natural gas generation, contributing to increased GHG emissions. The primary growth markets for nuclear energy are limited to Russia and China.

The final limit for nuclear power is the depletion of uranium resources. For a number of years, mining of uranium has been insufficient to fuel the world’s nuclear reactors. As of 2014, mineral uranium accounted for about 80% of the demand [4444]. The gap was filled by uranium recovered from the stockpiles of the military industry and from the dismantling of old nuclear warheads. Various models predict peak uranium to occur some time in the 2020s, depending on the rate of growth or decline of the nuclear power industry.

Escaping the limitations of mineral uranium supply would require breeder reactors, where a fissile isotope is created from a more abundant, naturally occurring non-fissile isotope. One idea involves transforming thorium-232 into the fissile 233 isotope of uranium (²³³U). Another approach is to breed fissile plutonium from the non-fissile ²³⁸U. Breeder reactors were found to be expensive, difficult to manage, and prone to failure—in the United States, the idea has been abandoned [4444]. The development continued in Russia, where the world’s first breeder reactor, the BN-800, reached its full power production of 880 MW in 2016. The reactor is burning a mixed oxide (MOX) uranium-plutonium fuel, arranged to produce new fuel material as it burns.

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