1. Boiling Water Reactor Collin Azinger and Kaleigh Smith Pressurized Water ReactorRankine Cycle History and Applications Nuclear Fission Electricity Generation The energy released from the fission reaction can be harnessed using a Boiling Water Reactor or a Pressurized Water Reactor, which both produce steam. This steam is constantly condensed and expanded through a Rankine Cycle, in which the expanded steam rotates a turbine, generating power. During a nuclear fission reaction, the nucleus of a radioactive isotope is struck by fission neutrons and splits into two smaller nuclei. Neutrons are emitted during this process that strike other atoms, creating a self-sustaining chain reaction. A typical fission event yields about 200 million eV of energy. There are a series of emergency cooling pumps that prevent overheating by flushing cold water into the reactor core to keep the temperature down during a shutdown or accident. The generated steam is then transported to the steam turbine through the main steam system to power the turbine and generate electricity through the Rankine Cycle. The water within the reactor core of a boiling water reactor serves to cool the reaction core and thus the lower temperature water is boiled and produces steam directly in the core. A pressurized water reactor generates steam from the fission-produced energy through a system of two isolated water loops, and two to four separate cooling systems. The water in these reactors is kept at pressures reaching upwards of 2,250 psi, and temperatures of 530-590º F while remaining in a liquid state. Steam is produced through a combination of the hot water and the cooling systems. The steam goes through the Rankine Cycle to generate electricity. Radiation is the most prominent concern dealing with nuclear reactors. Nuclear radiation arises when unstable atoms spontaneously decay to become different atoms, emitting alpha particles, beta particles, gamma rays, or neutrons. This ionizing radiation can damage living tissue when presented in significant amounts. The lowest yearly dose linked to cancer risk is 100,000 μSv, compared to the average radiation given off during a dental x-ray: 100 μSv. People living within fifty miles of a nuclear reactor receive 0.1 μSv per year. Human radiation values are so small due to the extent of containment and safety checks that a nuclear power plant provides. Since air pollution from the burning of coal is estimated to be causing 10,000 deaths per year, there would have to be twenty five nuclear meltdowns per year for nuclear power to be equally as dangerous as the burning of coal. Nuclear power in weaponry also sparks controversy due to the disastrous effects it may have. The Untied States bombing of Hiroshima and Nagasaki had a death toll of over 420,000. After WWII the United Nations began working towards controlling atomic energy to ensure that it would be used only for peaceful applications. Many multi-national treaties have since been implemented to further attempt to restrict nuclear weaponry such as the Treaty of the Non-Proliferation of Nuclear Weapons. Enrico Fermi led the first self-sustaining nuclear chain reaction in December 1942 : The Chicago Pile 1. Fermi went on to play a lead role, along with Albert Einstein, in the Manhattan Project, and the development of the atomic bomb used in World War II. The first atomic bomb was successfully detonated at Trinity Site near Alomogordo, New Mexico on July 16, 1945. The first nuclear reactor was built to power the USS Nautilus. The project was authorized in 1951 and was planned and supervised by Admiral Hyman G. Rickover, the “Father of the Nuclear Navy.” Rickover also oversaw the first commericial nuclear power plant in Shippingport, PA. These events led to the advancement of nuclear power generation on a large scale today. BoilerTurbine CondenserPump Water is evaporated in the boiler until it is completely converted to steam. The vapor expands in the turbine, causing the blades to rotate and produce work. This work may be converted to electricity. The vapor leaving the turbine is condensed back to a liquid state. The water is passed through the feed pump where the pressure is raised, then the cycle repeats. All types of power plants use the fundamental system of the Rankine Cycle. During this cycle, an operation fluid (water, in the case of nuclear reactors) is continuously evaporated and condensed to ultimately generate electricity through four main mechanisms: a boiler, turbine, condenser, and pump. The cycle differs slightly from an ideal Rankine Cycle however, because less energy is produced due to fluid friction and heat loss to the surroundings, so heat addition is required to maintain the same work output at the end of each cycle. Concerns regarding sustainability in the modern world include resource availability, pollution, cost, and more. Although it is not renewable, nuclear fission-generated power ranks among the cleanest and most efficient power sources available. Fission reactions release neutrons which allow for more fission to occur, creating a self-sustaining chain-reaction. Essentially, the products of the reaction serve as the reactants of the following reaction. Therefore, a relatively small amount of material is needed for a large energy output. The radioactive waste produced, however, must be contained and managed. Some high-level waste materials may not decay for billions of years. The nuclear industry is the only power industry that takes full responsibility of its wastes, so the cost to contain the waste is already factored into the product. Furthermore, all byproducts are safely contained, compared to the carbon dioxide released into the atmosphere by the burning of fossil fuels. The abundance of material is another key component of sustainability of nuclear fission. Not only is Uranium an already abundant element, but recycled Uranium from reprocessed used fuel can also be used for fission. Some used Uranium can even be re-enriched to serve as fuel. Moreover, the yearly use of Uranium continues to slowly decline due to advancements in efficiency. Ethics Sustainability