Clearing Nuclear Fears

Grace Huang Edited by Teknos Staff 2019-2020

From the moment you wake up and turn on the lights, you may not be aware of it, but you are already using nuclear energy. In the U.S, there is a 20% chance that the energy you use comes from a nuclear power plant, and this number is only increasing. Nuclear energy is becoming a significant part of our everyday lives, affecting everything from the fruits we eat to the clothes we wear [4]. However, while we enjoy these conveniences, harmful effects produced by incidents like the Three Mile Island accident are posing a debatable question: how do we find the balance between energy efficiency and environmental safety?

To analyze the properties of nuclear power plants, we must understand how it operates first. Nuclear fission is the process nuclear reactors utilize to generate energy [3]. Uranium-235, a radioactive isotope of uranium, undergoes nuclear fission, or the splitting of the nucleus, to gain stability. This reaction first starts with an artificial neutron bombardment, which causes uranium atoms to split into smaller, more stable atoms. The uranium atoms then release neutrons that bombard other uranium atoms, creating a chain reaction. The fuel used in the reactors contain approximately 3% uranium-235, a sufficient amount to start a powerful yet controllable chain reaction of nuclear fission, which provides the core energy in a nuclear reactor [3].

Currently, two types of nuclear reactors operate in the U.S. One third of them are boiling water reactors, and the rest are pressurized water reactors [6]. In a boiling water reactor, heat generated from the chain reaction boils water to produce steam, which drives a steam turbine to generate electricity. A pressurized water reactor, on the other hand, also heats up the water but keeps it under pressure, preventing it from boiling. A secondary water loop boils using the heat received by the primary water loop, producing steam that drives the turbine and generates electricity. Since the secondary water loop is physically separate from the nuclear reactions, it does not become radioactive. After the heat-releasing reactions, the steam condenses back to water in the hourglass-shaped cooling tower that you may have recognized as a nuclear power plant before [6].

These nuclear power plants can achieve unimaginable energy efficiency. For instance, one pound of uranium generates as much energy as three million pounds of fossil fuels [6]. However, such benefits come with concerns. Nuclear power is the only main power source that has the waste disposal cost factored into the price of the product [8]. It is no secret that nuclear reactors generate radioactive waste, but were you aware that waste production starts when uranium is mined [6]? Uranium mining creates radioactive waste that has the potential to affect the health of miners and pollute nearby bodies of water. In fact, in Wyoming and the Four Corners region, where most of our uranium comes from, half of the mine workers are employed to clean up the waste instead of actually mining [6]. The process of uranium mining is hazardous already. What happens when you add the dangers of the radioactive waste produced by the nuclear reactors themselves?

That waste, also known as “spent fuel”, consists of uranium that has been used in a reactor and is no longer capable of producing energy efficiently [5]. The U.S. Nuclear Regulatory Commission considers the radioactive waste produced after nuclear fission reactions high-level waste [5]. High level nuclear waste makes up 3% in weight of total nuclear waste yet carries 95% of total radioactivity [7]. As mentioned before, the uranium atom splits into lighter atoms, which includes cesium-137 and strontium-90 [5]. These “fission products” are responsible for most of the radioactive waste people fear. Their half-life, however, is only about 30 years. This number is trivial in comparison to the half-life of another type of waste product, plutonium. Plutonium-239 has a half-life of 24,000 years. This transuranic (heavier than uranium) element is created when neutrons intended to bombard and split an uranium atom combine with it instead. This particular type of waste releases considerably less radiation when decaying compared to the fission products, but concerns nuclear scientists due to their long-lasting property [5].

High-level radioactive waste can have both a direct and indirect impact on the human race and the environment [5]. The radiation released by fission products can remain fatal for a long time. The surface of the spent fuel can release radiation for up to 10 years after decaying begins at a rate of 10,000 REM per hour, which is 20 times the fatal dose for a human being. Even worse, if nearby bodies of water become contaminated, and radiation subsequently enters aquatic food webs, it will eventually become part of our diet. The effect may seem insignificant in terms of dose, yet it is catastrophic in terms of the number of people affected [5].

Nuclear engineers have noticed these problems and have been improving the method of nuclear waste storage and disposal since the rise of nuclear energy in the 1950s. Right after spent fuel forms in nuclear power plants, it is transported to a spent fuel pool [5]. The pools’ reinforced concrete walls protect workers from radiation for five to ten years until these pools reach their capacity. Then, the high-level waste travels to stainless steel canisters called “dry cast” where it can stay for up to 40 years. Currently, there are no permanent disposal sites for the next step. There are two proposed sites in Texas and New Mexico for storage until scientists achieve permanent disposal. A site in Yucca Mountain, Nevada was suggested and is highly likely to become a permanent storage site, but the U.S. Department of Energy canceled this project midway for political and environmental reasons [5, 6]. With U.S. nuclear power plants generating around 2,000 tons of radioactive waste every year, nuclear waste disposal remains a concern to the global scientific community [6].

Since conventional nuclear reactors pose various issues and the global demand for electricity increases exponentially every year, nuclear scientists have begun exploring advancements in nuclear reactor designs. For example, a novel “small modular reactor” has grabbed the attention of the Department of Energy [1]. These small modular reactors offer many advantages, the most important one already included in its name — small. Their relatively small size leaves room for more flexibility, reduces capital investment, and minimizes restriction in terms of location [1]. Moreover, they can possibly be constructed underground or underwater, which may be less harmful to the environment [9]. Currently, there are many creative designs for this type of reactor [1]. These small reactors can also employ light water (ordinary water) as a coolant, as well as other innovative alternatives like gas and liquid metal. In fact, light water-cooled small nuclear reactors are under licensing review by the Nuclear Regulatory Commission and may be put into use in 10 to 15 years [1]. According to Edward McGinnis, former member of the Department of Energy Office of Nuclear Energy, small modular reactors are “key to the future of nuclear energy” [2].

Ever since the opening of the first nuclear power plant in the U.S. on May 26, 1958, debates over the pros and cons of nuclear energy have not stopped. While people enjoy the energy efficiency and reduced greenhouse gas emissions of nuclear power plants, they can’t help but worry about safety issues due to unfortunate incidents like the Three Mile Island tragedy. We love and fear nuclear energy, almost like a double-edged sword. However, if we continue to improve our understanding and balance the properties of nuclear energy, we will eventually handle this sword and become the most fearless defender of our environment and ourselves.

References

[1] Department of Energy. (n.d.). Advander small modular reactors (SMRs). Retrieved from https://www.energy.gov/ne/nuclear-reactor-technologies/small-modular-nuclear-reactors

[2] Department of energy. (2018, April 10). New wave of innovation coming to nuclear energy. Retrieved from https://www.energy.gov/ne/articles/new-wave-innovation-coming-nuclear-energy

[3] Dingrando, L., Tallman, K., Hainen, N., & Wistrom, C. (2005). Chemistry: Matter and change.

[4] Mueller, M., & Harman, S. (2018, February 6). Infographic: How much power does a nuclear reactor produce? Retrieved from https://www.energy.gov/ne/articles/infographic-how-much-power-does-nuclear-reactor-produce

[5] Nuclear Regulatory Commission. (2019, July 23). Backgrounder on radioactive waste. Retrieved from https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/radwaste.html

[6] Union of Concerned Scientists. (2010, July 27). How nuclear power works. Retrieved from https://www.ucsusa.org/resources/how-nuclear-power-works

[7] World Nuclear Association. (2020, February). Radioactive waste management. Retrieved from https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-wastes/radioactive-waste-management.aspx

[8] World Nuclear Association. (2020, March). Economics of nuclear power. Retrieved from https://www.world-nuclear.org/information-library/economic-aspects/economics-of-nuclear-powr.aspx

[9] World Nuclear Association. (2020, May). Small nuclear power reactors. Retrieved from https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/all-nuclear-power-reactors.aspx