by Goutam Gadiraju
Thomas Jefferson Classical Academy, Shelby, NC
Honorable mention
“I am become death, the destroyer of worlds.”
Dr. J. Robert Oppenheimer quoted these words from the Bhagavad Gita after witnessing the sheer power and striking energy released by the first testing of the atomic bomb at the Alamogordo air base in Nevada on July 16, 1945. The world’s first nuclear fission reaction was meant to cause destruction, to end a brutal war, to give man the power of gods.
Nuclear fission, in its rawest form, is simply the action of splitting an unstable atomic nucleus, releasing massive amounts of energy expressed as heat. Though fission was first induced in malicious ways, through the atomic bomb, during the decade following the catastrophes of war scientists and governments began dreaming of a future with clean, renewable energy through peaceful forms of nuclear fission. These dreams manifested themselves in primitive nuclear reactors, which, though producing waste and radiation, seemed to provide a sustainable means of energy production. In contrast to fossil fuel burning, nuclear energy protected the atmosphere from harmful gasses, sharply reducing the projected rates of global warming and the greenhouse effect. So, beginning in the 1970s, countries around the world set out to build and design safe nuclear reactors. However, due to costs and concerns about profits, many private corporations and governments only funded low efficiency Light Water Reactors. Even today, the majority of nuclear reactors around the world are Light Water Reactors. Nuclear catastrophes such as those in Chernobyl, and recently Fukushima Daiichi have halted innovation in nuclear energy, forcing countries to continue using Light Water Reactors because of the risks of less tested, potentially dangerous theoretical models.
Energy production in Light Water Reactors begins when a neutron is fired into fuel rods containing enriched Uranium 235. This releases a tremendous amount of energy, and when one nucleus is split, its neutrons are separated and propelled into other nuclei, starting a chain reaction. Between the Uranium fuel rods is light water (water such as that which we drink), which acts as a moderator to the reactions while working as coolant. This water is converted to steam from the immense heat released in fission, powering turbines connected to generators, providing electricity through the grid to cities and houses (1).
A responsible engineer must consider the dangerous implications of new technologies. With every new technology comes potential for danger, and destruction, especially in the case of generating energy. Countless errors have occurred in fossil fuel use, such as the Deep Water Horizon oil spill of 2010. But when considering nuclear energy, the greatest concern to safety is the ever present threat of Nuclear Warfare.
The Treaty on the Non-Proliferation of Nuclear Weapons, or NPT, was officially recognized in 1970 (2). In short, the treaty aimed to provide developing countries with the resources to pursue, and achieve, nuclear fission as a means of generating energy. However, the method of Light Water nuclear fission requires the production of Uranium 235, which will gradually decay into Uranium 233 as a result of time, enrichment, or fission. From these materials and the technology provided from successful countries, a number of inexperienced countries have created nuclear weapons under the guise of peaceful motives of energy production. Such countries include France, China, India and possibly Iraq and North Korea (3).
This is where the prospect of Thorium reactors comes into place. Conventional Nuclear Reactors utilize a cycle known as the Uranium-Plutonium cycle, using enriched uranium for the reaction, producing highly radioactive, and capable of being weaponized, Plutonium. This plutonium can be used in nuclear weapons immediately after reacting enriched uranium — the same uranium provided to countries by means of the NPT. Thorium reactors utilize Thorium-Uranium cycles. Thorium-232 itself is fertile, rather than fissile, meaning it has potential to be used for fuel in its natural form, but must first be irradiated, producing Protactinium-233 while simultaneously producing and reacting Uranium-235(4). This Uranium-235 is produced in huge quantities, providing large quantities of nuclear reactant, effectively increasing energy output exponentially. Not only does the Thorium-Protactinium-Uranium cycle produce higher quantities of energy per gram of reactant, the cycle irradiates Thorium to produce Uranium-235, rather than irradiating Uranium-238. This makes it impossible for reactions to produce heavier elements such as Plutonium, Americium, Curium which can be weaponized almost instantly.The Thorium reactor cycle provides a method of nuclear energy production without producing nuclear waste that can be immediately, and secretly, weaponized.(5)
Along with the dangers of Nuclear weaponization, engineers must consider the danger of Nuclear accidents such as malfunctions and meltdowns, once again such as those of Chernobyl, and more recently, Fukushima Daiichi. Though the events occurring at these sites occurred without accidental detonation, the possibility of accidental reaction is the most dangerous disaster that results directly from human miscalculation. Enriched Uranium utilized in Light Water Reactors is extremely fissile, meaning it has been enriched to an extremely unstable state, ready to be reacted. This can result in immediate, unregulated, accidental explosion by unintended excitement such as, in the case of Fukushima Daiichi, tsunami or earthquake. In addition, the smallest of malfunctions can result in the detonation of nuclear material, due to extremely sensitive states. But since the Thorium-Uranium cycle enrichment process is simultaneous with fission, the net instability is zero, for fertile Thorium in a stable state is enriched to temporarily fertile Protactinium, which simultaneously decays into fissile Uranium-235, reacting to produce energy. This prevents accidental reactions because Thorium can’t be reacted until all parameters are met — Thorium is stable enough that it cannot begin its cycle until it is intentionally acted upon as it needs to gain mass in irradiation before fission. It doesn’t have an unstable state that would allow the fission process to occur accidentally due to some unaccounted stimulus. An engineer must evaluate his or her own error in designing a new technology. Evaluating and preventing malfunctions is the most important aspect of creating new innovations; thorium reactors provide defense from malfunctions caused by human error.
Engineers must recognize that the success of energy production rests on the ability to find renewable methods of electricity generation. However, Nuclear Fission by means of the Uranium-Plutonium cycle is a very unsustainable process. This is due to the extremely low amount of readily available Uranium deposits able to be enriched. According to geological approximations, Thorium is 3.3x more abundant than Uranium with a concentration of .00018% to .00006% (5). Popular counterarguments consider that the amount of realistically mineable deposits are equivalent, for the majority of thorium deposits may be dissolved in the ocean or unaccessible due to economic/geographic restraints. To answer this counter, one must acknowledge that the amount of Uranium-235, and energy produced, in the Thorium-Uranium cycle is exponentially higher than standard Uranium-238 enrichment and Uranium-Plutonium cycles. The reality that Thorium produces higher quantities of energy makes it a more reliable fuel for nuclear energy. But regardless of energy outputs, engineers must still consider the sustainability of the Thorium cycle; it relies upon a fuel that may become difficult to retrieve in the future.
Safety, Reliability, and Sustainability are important principles of engineering. However, none of these aspects are as important as the ultimate standards of science - health and environmental impact.The current Uranium-Plutonium cycle of fission reacts Uranium-235, which is broken into decaying Plutonium-236. This Plutonium can have a half life of up to 24,100 years (6), effectively destroying the environment by contributing to higher background radiation rates across the world. These radiation rates may contribute to higher cancer rates among humans in the next few centuries as more nuclear reactors are constructed and operated across the world. Various proposals have been made concerning stabilizing Plutonium waste, but of 30 countries harnessing nuclear energy, only Finland has made serious (yet fruitless) efforts at purifying waste. In addition, waste can easily be reprocessed into weapons. In contrast, the Thorium cycle produces Uranium-232 as waste material. This waste has a half life of 68.9 years, making it more long-term environmentally friendly. But it must be considered that it decays more dangerously during this period. Engineers must consider the balance between decay rates and time periods to judge the health and environmental implications of new methods of nuclear energy (7).
An engineer working on energy technology must consider the benefits of the Thorium cycle against the damage of the Uranium cycle. Thorium provides safer, healthier, and environmentally friendly alternatives of nuclear energy. However, the technology for Thorium is still vastly theoretical, and has many dangers we may not be aware of. A responsible engineer must consider the safety and sustainability of a new technology; Thorium seems to be the answer to safer nuclear energy, and countries such as India have set out to construct the first reactors. However, engineers must carefully observe these reactors to assure that the theory of sustainability and safety are justified by a reality of cleaner, safer, and more efficient nuclear energy.
References:
(1)Light Water Reactors. (n.d.). Retrieved January 31,2016, from http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/ligwat.html
(2)Nuclear Nonproliferation Treaty. (n.d.). Retrieved January 31, 2016, from http://www.state.gov/t/isn/npt/
(3)Nuclear Power and Nuclear Weapons. (n.d.). Retrieved January 31, 2016, from http://www.neis.org/literature/Brochures/weapcon.htm
(4)World Nuclear Association. (n.d.). Retrieved January 31, 2016, from http://www.world-nuclear.org/info/current-and-future-generation/thorium/
(5)Thorium As Nuclear Fuel. (n.d.). Retrieved January 31, 2016, from https://whatisnuclear.com/articles/thorium.html
(6)Backgrounder on Plutonium. (n.d.). Retrieved January 31, 2016, from http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/plutonium.html
(7)Uranium 232 - Nuclear Power. (n.d.). Retrieved January 31, 2016, from http://www.nuclear-power.net/nuclear-power-plant/nuclear-fuel/uranium/uranium-232/