Assignment 3

Budny 10:00 L15

Disclaimer: This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering. This paper is a student paper, not a professional paper. This paper is based on publicly available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other than this author’s partial fulfillment of a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering, users are doing so at their own risk.

ASSIGNMENT 3

Ian Barker ([email protected])

INTRODUCTION lighter elements and three new neutrons which then bombard other uranium or plutonium nuclei and split those. Two of the biggest problems facing the world today are This is used to generate heat which is captured by water the changing climate and the dwindling supply of fossil fuels surrounding these fuels. The water boils and turns which currently provide the majority of society’s power generators, creating power. This process produces a production. These two issues go hand in hand. The use of sizeable quantity of energy but also creates radioactive fossil fuels produces greenhouse gasses like carbon dioxide waste. Nuclear fusion compares favorably to fission in all that trap heat from the sun in our atmosphere and cause the aforementioned aspects which is why physicists and planet to gradually heat up. This process has intensified in engineers are so interested. recent years and has been linked to rising sea levels, melting The definition of nuclear fusion according to ice caps, and even an increase in strength and number of Merriam-Webster is this “a process in which the nuclei hurricanes [1]. Scientists have been providing possible of atoms are joined” [3]. However, the atoms are not solutions to the problem of increased greenhouse gas necessarily joined, but simply close enough together to emissions for years such as. One advancement could solve form two new atomic nuclei and accompanying subatomic both these problems. Nuclear fusion for civil purposes was particles. This produces a tremendous amount of energy proposed nearly 70 years ago, when focus shifted after initial since the difference in mass of the products and reactants is experiments in the military sector proved the possibility to converted to energy [4]. The fusion that scientists hope to recreate the process on Earth. Nuclear fusion recently began recreate, helium-hydrogen fusion, is also carried out in the to seem viable again with advances in technology. Nuclear Sun. The process takes deuterium, an isotope of hydrogen fusion is the process that powers the stars in the solar system and fuses the deuterium with tritium, another hydrogen and would provide earth with a large amount of clean isotope, to produce helium-4 which is the most common sustainable energy. The process would produce no isotope of helium [5]. The process does not require radioactive waste and could replace fossil fuel power plants radioactive elements, nor does it produce any. The almost entirely. The current goal for the most advanced efficiency of the reaction is also much higher than fission. fusion reactor is to produce 500 megawatts of power on a A problem is that fusion only takes place at certain limited 20-minute run. One average coal-fired power plant conditions. Namely, the conditions at the core of a star. For produces 500 megawatts [2]. One of the main technologies fission to occur, a temperature of millions of degrees that is creating renewed interest in nuclear fusion as a viable Celsius and a high pressure are required to compact the replacement is the tokamak. Although the design has been superheated plasma enough for consistent collisions around for over 60 years, the device was abandoned due to a between molecules. Since these conditions are so extreme, lack of efficiency in original large-scale models. recreating the necessary conditions on Earth has been hard Technological and material advancements, most notably for scientists. There have been many technologies produced advances in the materials available for magnets, have since that attempt to mimic the conditions. These include the brought the tokamak back to the forefront as one of the most magnetic confinement, inertial confinement, and electric promising sources of a nuclear fusion reaction. at the pinches. By far, the most promising design have been those forefront is the ITER project located in. This tokamak is that use magnetic confinement devices, more specifically going to be the largest ever constructed the tokamak. NUCLEAR FUSION TOKAMAK Currently all of the world's nuclear power is produced The tokamak was designed in the 1950s by Igor by nuclear fission which is when the nuclei of an atom are Tamm and Andrei Sakharov. The name tokamak comes split by neutron bombardment, and these atoms split other from the Russian translation of “toroidal chamber with atoms causing a chain reaction. A chain reaction can be magnetic coils”. The tokamak is a toroidal shaped vacuum produced if an element such as uranium or plutonium is chamber made of beryllium. The toroidal shape was chosen bombarded with a neutron and splits. This creates two so that the particles in the plasma would be confined to the

University of Pittsburgh, Swanson School of Engineering 1 10.31.2017 Ian Barker central region. Since these particles in the plasma follow a by 4 K supercritical helium will be used to achieve the high helical path, the twists of the toroidal shape help alternate pumping rates and vacuum levels in the cryostat and torus” the particles that are on the outside of the plasma stream [8]. The magnet system will also be unlike any other between hot and cold. This prevents the plasma from tokamak. “The ITER magnet system comprises 18 getting too cold. This creates a flux surface that also helps superconducting toroidal field and 6 poloidal field coils, a confine the plasma. There is an array of incredibly central solenoid, and a set of correction coils that powerful magnets surrounding this vacuum chamber. The magnetically confine, shape and control the plasma inside magnets create a magnetic field that keeps the superhot the vacuum vessel. Additional coils will be implemented to plasma confined to the center of the vacuum chamber. The mitigate Edge Localized Modes (ELMs), which are highly magnets are cooled with liquid helium to avoid damaging energetic outbursts near the plasma edge that, if left them. The tokamak superheats a mixture of tritium and uncontrolled, cause the plasma to lose part of its energy” deuterium fuel to hundreds of millions of degrees Celsius to [9]. These magnets will crate a field of 13.5 teslas. The forma plasma. Inside this plasma, the two different ultimate goals of this project are not to create a power plant, molecules collide and form helium and release energy in they are simply to test the construction materials by the form of heat. exposing them to the environment of a fusion reaction to However, before this can happen, certain criterion for see how they perform. This technology will change the plasma density, confinement time and plasma temperature lives of millions of people by providing cheap energy. [6]. These criteria dictate whether the reaction is profitable energy-wise or not. If these criteria are met, the reaction has CONCLUSION reached ignition which means that the heat of the products Although the project is still a few years from completion, of the reaction are enough to maintain the temperature of there is much to be excited about. If this project succeeds, the plasma. The fusion reaction will start in the tokamak the road to completely eliminating the dependence on fossil and the fuel will be injected to sustain this reaction. The fuels will be smoothed considerably. Eliminating the reaction will produce many high energy neutrons which dependence on fossil fuels will help decrease the rate of will pass through both the vacuum chamber and magnets. climate change and prevent the sea level from rising even When the tokamak is designed to produce electricity, there further. This is important to me because I would appreciate will be a shield of liquid metal to absorb the kinetic energy it if Florida was still a state that I could visit without of the neutrons to heat water and power generators. There SCUBA gear in the future. At the current rate, this will be are 30 experimental tokamaks in operation all over the unlikely. The tokamak may not be fully refined, but the world. They vary in size and capacity, but all of them pale technology is being improved everyday. One day I hope to in comparison to the planned ITER Tokamak which is an be able to contribute to this research. international effort from 7 countries to produce sustained and energy profitable nuclear fusion. This will allow countries to provide energy to people at a fraction of the SOURCES cost. The fact that fusion produces no greenhouse gases helps reduce climate change. [1] “The ITER Story” ITER Project ITER TOKAMAK https://web.archive.org/web/20120930124110/http://www.it The ITER Tokamak is currently in the construction phase, er.org/proj/iterhistory Accessed 10.30.17 but once done it will be the largest tokamak on the planet. [2] The tokamak is designed as a large-scale proof of concept [3] Nuclear Fusion definition https://www.merriam- to create sustainable energy. The size of the tokamak is webster.com/dictionary/nuclear%20fusion unlike any other. The tokamak was proposed as a joint [4] “What is Fusion?” ITER Project venture between the US and the Soviet Union since the https://web.archive.org/web/20120922161103/http://www.it researchers believed that the budget in not affordable by er.org/sci/whatisfusion Accessed 10.29.17 one country. Today, seven countries are providing some [5] “Fusion on Earth” ITER Project assistance to the project. The tokamak will make use of https://web.archive.org/web/20120922161103/http://www.it several new technologies in its design. It will include a er.org/sci/whatisfusion Accessed 10.30.17 lithium breeder blanket to produce new tritium fuel from [6] “What Is The Lawson Criteria, Or How to Make the products of the reaction, thereby sustaining itself [7]. Fusion Power Viable” Science World Report The cooling system will be highly complex. “The http://www.scienceworldreport.com/articles/5763/2013032 ITER magnets will be cooled with supercritical helium at 4 3/lawson-criteria-make-fusion-power-viable-iter.htm K (-269°C) in order to operate at the high magnetic fields Accessed 10.29.17 necessary for the confinement and stabilization of the [7] “Tritium Breeding” ITER Project plasma. They will be surrounded by a large cryostat and an https://web.archive.org/web/20121020143410/http://www.it actively-cooled thermal shield with a forced flow of helium er.org/mach/tritiumbreeding Accessed 10.29.17 at 80 K. Additionally, large cryo-absorption panels cooled

Ian Barker

[8] “Cryogenics” ITER Project https://web.archive.org/web/20121020143609/http://www.it er.org/mach/cryo Accessed 10.29.17 [9] “Magnets” ITER Project https://web.archive.org/web/20121020140329/http://www.it er.org/mach/magnets Accessed 10.29.17

ADDITIONAL SOURCES “Some Criteria for a Useful Thermonuclear Reactor” J. Lawson https://www.euro-fusion.org/wpcms/wp- content/uploads/2012/10/dec05-aere-gpr1807.pdf Accessed 10.30.17 “Nuclear Fusion” https://en.wikipedia.org/wiki/Nuclear_fusion Accessed 10.29.17 “Tokamak” https://en.wikipedia.org/wiki/Tokamak

ACKNOWLEDGEMENTS

I would like to thank my dorm neighbor, Sam Barker, who helped me with organization and proofreading of this paper. I would also like to thank Beth Newborg for answering all questions about this assignment with prompt email responses. I would like to thank the School of Engineering for creating this assignment and causing me to discover a new topic that interests me.