The nuclear industry provides the modern world with rather substantial amounts of energy. However, all processes that are involved in the production of this energy result in equal amounts of waste and are highly radioactive in general. Learning from mistakes of the past, modern science operates with an extensive number of nuclear waste disposal methods and continues to design new ways and technologies to secure nuclear energy production. Nuclear catastrophes in Chernobyl and Fukushima gave an impetus to numerous studies of nuclear fusion that present a profitable alternative to nuclear fission. The international science community’s search for safe nuclear fuel processing methods will eventually lead to success in this sphere because even at the present moment there are numerous ways of advantageous nuclear waste treatment as well as successful studies of nuclear fusion.
Sources of Nuclear Power
Nuclear plants use uranium fuel in order to produce energy through a process of nuclear fission. As a rule, the fission of the uranium nucleus provides 200 MeV of energy, which is a rather significant amount (Sharrad et al. 40). With the high energy density of nuclear fuel and small volumes of this fuel that are required to produce the energy, the nuclear industry proves to be very profitable. Nuclear fission largely depends on the thermal neutron fission of the natural isotopes 235U and 238U that have approximately 0.025 eV of energy (Sharrad et al. 41). By neutron irradiation, these isotopes are processed into artificial isotopes such as 239Pu, which are used in the production of energy. Thus, nuclear fuel has to undergo four stages of processing before being used in a reactor: mining, enrichment, conversion, and fabrication.
Uranium ore that may be extracted in open and closed mines serves as the main source of uranium fuel. In the process of leaching with sodium carbonate solution or sulfuric acid, uranium is extracted from the crushed ore. After that, with the help of ion exchange or solvent extraction, it is concentrated from the obtained leachate (Sharrad et al. 41). When uranium is extracted and concentrated, it undergoes the process of enrichment in which the initial proportion of natural isotopes is increased and converted into UF6 fuel. Enrichment results in two products: enriched and depleted uranium. The amounts of the latter are rather significant, but, in present days, science only studies the ways of its practical implementation. After the enrichment, UF6 is shipped to the nuclear facilities where it is reconverted into UO2 and formed into solid pellets. Only after the pellets are loaded into stainless steel tubes they can be used in reactors for the production of energy (Sharrad et al. 42).
Given that uranium ore contains not only natural isotopes 234U, 235U, and 238U, but also other radioisotopes, uranium mining and extraction result in significant radionuclide wastes, especially when low-grade ore is used for the extraction. Besides that, the process of enrichment is also radioactive and implies plenty of wastes. With this consideration in mind, the processes of nuclear waste utilization and its possible minimization should be considered.
The Problem of Nuclear Waste
Although the nuclear power industry allows obtaining high amounts of energy from a small amount of fuel with an equally small amount of wastes, the latter is radioactive and must be treated as hazardous. The nuclear industry has to deal with different types of radiation, namely, alpha, beta, and gamma radiation (“Waste Management” 10). The most dangerous type is gamma radiation that penetrates into the body causing severe damage to the central nervous system and inner parts. To protect people from this radiation, several inches of concrete and lead as well as three feet of water should be used.
Basing on the amount and types of radioactivity, science distinguishes low-level, medium-level and high-level wastes. The time during which wastes remain hazardous also plays an important role in their treatment. It depends on half-life characteristics of the type of radioactive isotopes that are contained in wastes. Some isotopes have half-lives of a second, some – of centuries. However, the level of radioactivity tends to decline with time and wastes become stable and non-radioactive.
There are three approaches to nuclear waste treatment: concentrate-and-contain, dilute-and-disperse, and delay-and-decay (“Waste Management” 7). The first two approaches are employed in the handling of both radioactive and non-radioactive wastes. In these approaches, wastes are processed and secluded, or attenuated to appropriate levels of radioactivity and then let out to the environment. Delay-and-decay approach implies the storage of wastes until their radioactivity is naturally decreased through the radioisotope decay.
The problem of nuclear waste has another method of solution. Scientists stress the necessity of nuclear waste minimization that implies both the reduction of generated waste and volumes of waste that exist already. There are three approaches to waste minimization: reduction of the source, recycle and reuse, and optimization of waste processing (International Atomic Energy Agency 4). The reduction of the source means the elimination of waste in the process of nuclear fuel extraction and use. Recycle and reuse imply the utilization of valuable materials from generated waste in the original nuclear production process. Optimization of waste processing requires special technology that improves the quality of generated waste and minimizes its volume for storage and discharge into the environment.
Cases of Chernobyl and Fukushima
Accidents in Chernobyl, Ukraine, and Fukushima, Japan in 1986 and 2011 have one common reason – problem with reactors. One of the Chernobyl Nuclear Power Plant reactors was destroyed by the steam explosion. In the case of Fukushima, the Tohoku earthquake destroyed the cooling system of three reactors at the Fukushima Nuclear Power Plant which resulted in the nuclear meltdown and the discharge of radioactive products in the environment. Further, there is a detailed study of the exact reasons for these nuclear tragedies.
On 26 April 1986, the reactor staff of the Chernobyl Nuclear Power Plant conducted a series of planned technical tests in Unit 4, during which the power level was accidentally decreased. The concentration of xenon-135 that absorbs neutrons in order to balance the reaction rate in the nuclear reactor thus increased, which led to the xenon poisoning of the reactor (Steinhauser et al. 801). Initially, all attempts of the reactor stuff to increase the power level failed. However, as a result of the subsequent sharp increase of the power level, xenon was burned out, and the voids of cooling water were disabled (Steinhauser et al. 801). Because of the latter, the reaction rate sharply increased. Thus, the reactor was destroyed by sudden power excursion caused by the steam explosion and inflammation of graphite moderators.
On 11 March 2011, the Tohoku Earthquake occurred in the Pacific Ocean, 163 km northeast of the Fukushima I Nuclear Power Plant, causing a tsunami that created immense destructions along the coastline. The three of six boiling water reactors were automatically shut down, the diesel generators of the three others were severely damaged, leaving the main cooling systems disabled. As a result, the partial meltdown of the fuel elements occurred (Steinhauser et al. 801). In addition, the high temperatures lead to the oxidation-reduction reaction between water and zirconium, which caused the generation of extreme amounts of hydrogen gas. In order to release the overpressure, the staff initiated urgent ventilation. As a result, hydrogen gas and radioactive products were discharged into the lower level of the reactor facilities. This caused three oxy-hydrogen gas explosions that destroyed four nuclear power plant buildings (Steinhauser et al. 801). Thus, the reactors were destroyed due to the loss of cooling caused by the earthquake.
Problems of Safety
The previous section makes it possible to conclude that the problem of nuclear power reactors security is essential for the safe operation of nuclear facilities. After the tragedies in Chernobyl and Fukushima, specialists became concerned with the question of the possibility to make nuclear power reactors safe or at least safer than they were. Apparently, in the nuclear industry, as in other industries of energy production, the matter of safety addresses the questions of intelligent planning, high-quality equipment, proper design of the supporting systems, as well as the well-developed safety culture of operational performance.
In response to these requirements, Western science developed the “defense-in-depth” approach which principles are expressed in the triple slogan “Prevention, Monitoring, and Action” (“Safety of Nuclear Power Reactors” 28). This approach considers such aspects as the design and construction of nuclear power facilities that allow for the prevention of mechanic disturbances as well as human mismanagement; complex monitoring programs that are based on a regular equipment testing; diverse systems of damage control and radioactive release prevention; and systems that provide certain limits to significant fuel damage (“Safety of Nuclear Power Reactors” 30).
Three main functions should be performed in the facility in order to provide safety of a nuclear reactor: control of reactivity, fuel cooling, and the containment of radioactive substances.
The most important factors for the safety of reactors are the negative temperature and void coefficients. The majority of existing reactor safety systems require active participation, that is, the mechanical operation via command. However, some of reactor safety systems operate passively. There is a common misconception that inherent reactor safety designs depend on the operation of engineered components. In fact, they depend on various physical phenomena such as gravity, convection, and high-temperature resistance. Although the majority of existing reactors operate with the help of inherent safety elements, the design of active cooling systems may help to eliminate the risk of accidents similar to the Fukushima tragedy, in which the electrical power loss resulted in the loss of cooling.
The idea of nuclear fusion was introduced back in 1920 when science had a rather small understanding of the atomic nucleus nature. Arthur Eddington, the British theoretical physicist, expressed the belief that someday people will learn how to release and use the sub-atomic energy. Nuclear fusion is almost a limitless source of safe, pure, and self-sustaining energy. However, in almost a century, science made only one little step towards nuclear fusion. The problem with fusion power is that fusion reactions occur at immensely high temperatures because atomic nuclei must have a large amount of energy to collide, overcome the Coulomb repulsion, and near to the powerful nuclear force that merges them. There are many possible fusion reactions; however, practically all present-day fusion studies are aimed at obtaining power from the deuterium-tritium reaction because it is the easiest reaction to initiate (Cowley 385).
Currently, nuclear science faces two problems: initiation and maintenance of the reaction. As of today, it has managed to heat nuclear fusion plasma to 900 million degrees Fahrenheit and maintain it for almost four minutes, although with the help of different reactors (Cowley 387). The studies are performed in the United States, the United Kingdom, Japan, India, France, etc. The main problem that is common for all countries is funding because nuclear fusion is the sphere of scientific research that has a prolonged timescale. Although the benefits of nuclear fusion research are rather obvious since they address the issue of energy scarcity that is important for the modern world, the international community will not perceive them in a prolonged time.
The nuclear industry is superior to other energy production industries since it allows us to produce large amounts of energy using small amounts of fuel. The problem of the radioactivity of nuclear waste has a set of methods helping to solve it. Nuclear accidents in Chernobyl and Fukushima initiated the number of researches aiming at the design of secure nuclear facilities. As a result, Western science has developed a defense-in-depth approach to the maintenance of nuclear power plants. Currently, nuclear power production is based on nuclear fission. However, scientists continue their research in a nuclear fusion that provides pure and self-sustaining energy. There is much that has to be done, but with essential funding and governmental support, nuclear science will eventually progress.
Cowley, Steven C. “The quest for fusion power.” Nature Physics, vol. 12, no. 5, 2016, pp. 384-386.
International Atomic Energy Agency. “Minimization of Waste from Uranium Purification, Enrichment and Fuel Fabrication.” IAEA Scientific and Technical Publications. 1999, Web.
“Safety of Nuclear Power Reactors.” World Nuclear Association, 2016, Web.
Sharrad, Clint A., et al. “Nuclear Fuel Cycles: Interfaces with the Environment.” Nuclear Power and the Environment, edited by Roy M. Harrison and Ronald E. Hester, Royal Society of Chemistry, 2011, pp. 40-56.
Steinhauser, Georg, et al. “Comparison of the Chernobyl and Fukushima Nuclear Accidents: A Review of the Environmental Impacts.” Science of the Total Environment, vol. 470, no. 1, 2014, pp. 800-817.
“Waste Management: Overview.” World Nuclear Association. 2012, Web.