Team Gamma Ray Can Nuclear Energy Be Revived?

Overview of Nuclear Energy

1. Introduction

   Can nuclear energy be revived in the United States? The answer to that is heavily influenced by opinion, politics, and public perception as much as fact. Despite common misconception, nuclear energy is safe and it is not only used to provide electricity and power to homes and businesses. Nuclear material is also used in medical and dental applications, in smoke detectors, in science and technology industries, and in experimental research. While not nuclear energy per say, nuclear material is none-the-less pervasive in all aspects of life. This analysis shall attempt to provide an objective view with respect given to both sides of the argument based solely upon the facts. In order to answer that question we must first have a good understand what nuclear energy is and how it is used to generate electricity. Then we can examine whether or not it can be revived.
   
   
   

2. What Is Nuclear Energy?

   Nuclear energy in its most basic form is the energy stored within the nucleus of an atom. Atoms are the building blocks of matter and life. They are composed of three basic parts: protons and neutrons contained within a nucleus, and electrons orbiting the nucleus. Energy is released through processes called fission and fusion. Fission is the process by which an atom is split into fragments to release the energy stored within the sub-atomic bonds contained within the nucleus. Fusion on the other hand, is a naturally occurring process that exists abundantly within nature. Atoms are fused together at high temperatures and speeds to produce and release energy. Fusion is the process that powers the stars and our own sun helping to sustain life on Earth. Unlike fission, fusion requires incredibly high temperature (45-400 million degrees Celsius!) and pressure to initiate and maintain a nuclear reaction. However, because of current technical limitations in reactor materials and design, the temperatures and pressures, as well as the power required to produce fusion-generated power are difficult and expensive to achieve and the reaction is hard to control and sustain. Now that we have a basic understanding of what nuclear energy is and its two different forms, we can explain how nuclear energy is used to generate electricity.
   
   
   

3. How Do We Generate Electricity From Nuclear Power?

   As stated before, nuclear energy is the energy contained within the nucleus of an atom. We can harness this energy, or atomic power, to produce electricity which can be used to run businesses, households, and electronic devices. Because of technical limitations, all power-producing, non-research nuclear reactors in the world use the process of nuclear fission. There are however, several particle accelerators (CERN) which are capable of conducting experiments in nuclear fusion although they are unable to maintain a stable reaction for more than a split second.
   
   
   
   

   1. Introduction to the Process

      In order to create the necessary nuclear conditions to produce electricity we must have several things, which without any single one, the process as a whole would not work. Nuclear power generation requires:
      
      
      
      1. A Nuclear Fuel Source Obtained through mining and extraction
      2. Preparation of Fuel into a Needed and Usable Form
      3. An Understanding of How a Nuclear Reaction occurs
      4. A Safe Nuclear Reactor Design
      5. Methods to Control and Moderate a nuclear reaction
      
      
      
      

   2. Mining and Extraction of Nuclear Fuel

      First and foremost, nuclear energy requires a suitable fuel source. An important distinction should be noted however. Nuclear fuel should not be confused with the same type of fuel used in automobiles or home heating. It is not a ‘soup’ or liquid like oil or gasoline. Nuclear reactions involve changes in atomic nuclei, not in the chemical bonds holding atoms together as is the case in traditional fuels. Nuclear fuel is mineral ore, usually Uranium. According to the World Nuclear Organization, "in many respects uranium mining is much the same as any other mining. Projects must have environmental approvals prior to commencing, and must comply with all environmental, safety and occupational health conditions applicable. Increasingly, these are governed by international standards, with external audits". Additionally, all potentially dangerous gasses, elements, and by-products produced as a result of and associated with Uranium mining must be contained on-site. Potential health hazards to workers must be minimized or eliminated all-together through safety-conscious mining practices and mine design. Despite safety precautions and site-clean up regulations, uranium mining sites are still none-the-less dangerous and pose a health risk to workers and environmental damage if contaminated material is not properly contained and disposed of.
      
      In nature there exist only three forms of naturally occurring Uranium. Remember that an atom is composed of a nucleus which contains protons and neutrons, and electrons orbiting the nucleus. An isotope is an element like Uranium which contains the same number of protons as the regular element according to the periodic table but a differing number of neutrons. The balance between neutrons and protons in the nucleus determines whether the atom is considered to be characteristically ‘stable’ or ‘unstable’. Unstable atoms are considered to be radioactive. Radioactivity, or radioactive decay, is the process by which an unstable atom throws out protons or neutrons or other particles and forms of energy in order to regain stability (a balanced number of protons and neutrons within the nucleus). Radioactivity is often confused with radiation. Radiation is the energy that is released as a result of radioactive decay. Radiation is what is harnessed to produce electricity the method of which will be discussed later. It should be mentioned that radiation is not simply limited to nuclear fuels. We are exposed to natural background radiation from the Earth, from cosmic rays, and from medical procedures everyday.
      
      In nuclear fuel, the difference in the number of neutrons determines whether or not an element is considered stable and what the potential as a fissionable fuel is. A fissionable fuel is simply an unstable element which can attain and maintain nuclear fission through radioactive decay. The three naturally occurring Uranium isotopes are:
      
      
      
      1. Uranium-234 (U-234)
      2. Uranium-235 (U-235)
      3. Uranium-238 (U-238)
      
      
      Of these three, two are highly radioactive (U-234 and U-238) and only one is naturally fissionable (U-235) as a fuel that can be used directly in nuclear reactors without significant refining. According to Professor Sarma V. Pisupati, Associate Professor of Energy and Geo-Environmental Engineering at Penn State University, “Out of the three naturally occurring isotopes, U-238 is the most abundant in nature. Approximately 99% of all uranium found in nature is Uranium-238. Uranium-238 is safe enough to pet or put in your pocket. The other two isotopes, U-234 and U-235 are rare in nature. Approximately .006% and .714% of all uranium is U-234 and U-235 respectively”. Of these three, Uranium-234 has a radioactive half-life of approximately 244 thousand years, U-235 a half-life of 704 million years, and U-238 a half-life of 4.5 billion years according to Steve Maddox of North Dakota University. A radioactive half-life is the time it takes for half of the atoms in an element to decay (emitted as radiation). The shorter the half-life of a substance the more radioactive it is. That is, more particles are being emitted faster in relation to a substance with a longer half-life. That is why U-238 is safer than Uranium-234. Post-extraction, fuel must be prepared and enriched into a desired and usable form.
      
      
      

   3. Preparing and Enriching Nuclear Fuel

      As stated before, the majority of Uranium is U-238 and is naturally non-fissionable. While we are able to directly mine U-235 for use in nuclear reactors, the bulk of mined Uranium must under-go refining and enrichment in order to extract U-235 from other materials, including other unusable types of uranium. According to internet library and encyclopedia Thinkquest.org, “when U-238 is struck by a loose neutron, it absorbs the neutron into its nucleus and does not fission. Without fission a chain reaction doesn't occur, the nuclear reactions can't sustain themselves, the reactor shuts down, and millions of people are without electrical power. In order for a chain reaction to occur, the pure uranium ore must be refined to raise the concentration of U-235. This is called enrichment and is primarily accomplished through a technique called gaseous diffusion” . Essentially this process combines fluorine and uranium to create a new compound. The compound is then heated and passed through a series of filters. Because the molecular size of U-235 atoms is smaller than U-238, it is possible to separate fissionable U-235 from mined U-238 ore. The result is enriched uranium ore. This enriched fuel is used in nuclear reactors throughout the United States. Fuel rods used in nuclear reactors are filled with this enriched uranium at a concentration of about 3-4% uranium. This concentration is required to produce a chain-reaction and subsequent nuclear fission. However, it is possible to also make man-made nuclear fuel as well. Basically, by adding 1 extra neutron to the nucleus of Uranium-238 atoms and Thorium-232 atoms we can ‘breed’ fissile nuclear fuel. Uranium-238 and Thorium-232 bombarded by an extra neutron turns into Plutonium-239 and Uranium-233 respectively, both which can be used as nuclear fuel. Breeding is a process by which U-238 is turned into WEAPONS GRADE Plutonium-239. Pu-239 is the material that is used in our nuclear weapons. Because of security issues involving proliferation if nuclear material, the US does not currently employ breeder reactors and uses Uranium-235 as the primary fuel in its reactors due to fears of proliferation of weapons grade material that can be used against the country. Now we can need to understand the components of a nuclear reactor/reaction and we can answer how nuclear power is used to generate electricity.
      
      
      

   4. Components of a Nuclear Reactor/Reaction

      As we have seen, a nuclear reaction needs both a suitable fuel and a nuclear reactor designed to start and control the reaction. So what is a nuclear reaction and how does it produce the electricity we use?
      
      Now that we have an understanding of what radiation is and what radioactive decay is, radiation is what we harness to produce electricity, and this is how we do it.
      
      A nuclear reactor consists of five major components. First and foremost is the nuclear fuel. Within the United States fuel is usually U-235 at a 3-4% concentration (enriched uranium) although weapons-grade Plutonium-239 can be used as a nuclear fuel as well. Second is a system to control the reaction. After a nuclear reaction is started there are three phases it can achieve. The first is phase is called critical. Critical does not mean that the nuclear reaction is going to explode. In fact, a nuclear reactor can never explode like a nuclear bomb. The physics and design of both are radically different. The second phase is called sub-critical. If a nuclear reaction is sub-critical it means that the reaction cannot be sustained and the rate of it is decreasing. The third and final phase is known as supercritical. This is a reaction that is out of control which is increasing in speed. It is the job of the control system to prevent the reaction from going supercritical, to maintain the reaction at a critical level thereby allowing enough reaction level to occur to be utilized for generating electricity and if need be, and to slow the reaction to sub-critical to shut down the reactor. The control system is usually made up of what is known as control rods which are suspended above the core and can be lowered into place to control and slow the reaction. These rods are made of a material that can absorb neutrons. Think back to what was said about radioactive decay and radiation. When atoms emit particles, they are considered to be unstable and thus radioactive. These particles are typically, but not always neutrons. When a fissionable atom like U-235 is hit by a neutron it absorbs that neutron. The resulting imbalance between the number of protons and neutrons in the nucleus causes the U-235 atom to emit more particles in order to gain stability. Basically, if you hit a single atom of uranium with a neutron it will release 3 additional neutrons . Those neutrons will hit more atoms of uranium which will release 3 more neutrons each and the reaction will spiral out of control quickly reaching supercritical. The control rods are composed of materials, usually Boron or Cadmium, which absorb neutrons and do not throw particles off like Uranium does. Instead of 1 neutron creating 3 additional neutrons, when a neutron hits a U-235 atom and produces 3 new neutrons, the control rods will absorb around 1 or 2 of those neutrons, thereby controlling the reaction and allowing it to remain at a stable, critical level. Thirdly, a moderator is needed to control the speed of neutrons. A moderator is a liquid like water which sits between the fuel rods of a reactor. When unstable atoms emit particles like neutrons, they come out traveling at a very high velocity. If the neutrons were allowed to flow unimpeded, there is no guarantee they would hit another uranium atom thereby continuing the reaction. The function of the moderator is to slow the movement of the neutrons so that we increase the chance they will hit another uranium atom and continue the nuclear reaction. Almost all nuclear power plants in the United States use water as a moderator. Unlike graphite, another moderator which can burn at high temperature, if a nuclear reaction goes supercritical, the resulting increase in heat vaporizes the water into steam. Because water slows the speed of neutrons so that they can maintain a reaction, consequently, without water the speed of neutrons increases and the reaction slows. It is a built-in security feature which is one of a number of reasons that makes US nuclear reactors the safest in the world. Fourth, a cooling system is needed. In the United States the cooling method is typically water passing through pipes close to the reactor. Finally, a radiative shield is required. A radiative shield is simply a material which entombs the reactor and its components and traps radiation from escaping into the surrounding environment. Typical radiative shields are large concrete structures encasing the reactor that are very thick. So what does all of this mean and how does it produce electricity?
      
      
      

   5. How Electricity is Produced from Nuclear Power

      The rough part is finally over. Now that we understand what nuclear energy is and the components of a nuclear reaction are, we can explain how electricity is generated. Remember that unstable atoms emit particles, often neutrons. These particles physically move, much like an automobile. As your automobile moves along the road it is said to possess kinetic energy. The mass, or weight, of your car traveling at a certain speed contains a certain amount of energy. That is why high speed collisions cause more damage to your vehicle and body. The particles emitted from radioactive decay possess kinetic energy. That kinetic energy is called radiation. As the particles hit the walls of the reactor, they hit with enough force to generate heat. One particle will not produce a lot of heat, but combined, all of the particles being emitted create tremendous temperatures. Inside the nuclear reactor is a system of pipes which carry a coolant. This coolant, usually pressurized water, collects the heat from the reactor and carries it out to a heat exchanger, a device which passes the heat from one set of pipes to another without any physical exchange of coolant. The reason we use pressurized water inside the reactor is because of the extremely high temperatures. Water boils at 212 degrees Fahrenheit/100 degrees Celsius. By increasing the pressure of water, we increase the temperature at which water boils, otherwise the water would vaporize into steam and the reaction would slow (remember water moderates the reaction allowing it to occur). The use of two separate sets of closed pipes eliminates radioactive contamination of water outside of the reactor. Extreme heat from the reactor coolant converts water inside the second set of closed-off pipes to high-pressure and temperature steam. This steam then turns a turbine which is connected to a generator to produce electricity. Minus the nuclear reactor, the method to generate electricity is the same as in traditional coal and natural gas fired power plants. Because US reactors use pressurized water in the reactor to extract heat, and two sets of independent pipes and coolants, we refer to them as binary loop pressurized water reactors. We also use another type called a boiling water reactor. The difference between the two types is that unlike in a pressurized system, boiling water reactors do not use two isolated coolants. There is one set of pipes that runs from the reactor out to the turbines. This carries radioactive steam to the turbine. So that is how nuclear energy produces electricity. But how important is nuclear power in the United States and what are some issues and concerns involving its use?
      
      
      
      

      Pressurized Water Reactor	Boiling Water Reactor

   
   
   
   

4. History of Nuclear Power in the United States

   Nuclear power has its origins in the late 18th and 19th centuries with the discovery of uranium and its radioactive properties. It wasn’t until the advent of World War II that major scientific research on a grand-scale was undertaken to harness the immense power of the atom under the guises of the Manhattan Project which aimed at developing an atomic bomb. In July 1945, the first nuclear explosion took place in Alamogordo, New Mexico and on August 6th and 9th, 1945, the devastating power of the atom was unleashed on the Japanese cities of Hiroshima and Nagasaki, bringing World War II to a close with the unconditional surrender of the Japanese Empire. After World War II many countries began a crash program to develop atomic weapons of their own, the most infamous being the Soviet Union. This eventually led to the cold war which threatened global nuclear annihilation at every turn. However, it was the advances in nuclear and atomic knowledge made by scientists working on the Manhattan Project that provided the basis for the development of commercial nuclear power technology. Today many countries use nuclear power to complement or supplement traditional fossil fuels generated electricity. Among them are nations like France, Lithuania, and countries of the Former Soviet Union, which also rely very heavily upon nuclear power to provide electricity. Unlike the United States, opposition to nuclear power within these countries is limited. France for example relies upon nuclear power to provide close to 80% of its total annual electricity generation. According to the Nuclear Regulatory Commission, “there are currently 104 licensed to operate nuclear power plants in the United States (69 Pressurized Water Reactors and 35 Boiling Water Reactors), which generate about 20% of our nation's electrical use. The first fully functional commercial nuclear power plant began operating in Shippingsport, Pennsylvania in 1957. Prior to that, the first nuclear powered naval vessel, the submarine USS Nautilus was launched in 1954” . There are no new nuclear power plants slated for construction in the United States. Many of our existing power plants were built between 20 and 40 years ago and are still in operation today. However, advances in reactor and material design have improved generating efficiency and safety greatly. Despite this, public opposition to nuclear power plants mounted after two reactor accidents. Safety and environmental concerns became the primary culprits behind stymieing construction of new nuclear power plants and in promoting the controlled phase-out of nuclear power.