Nuclear Accedents Essay Example | Topics and Well Written Essays - 2000 words

Nuclear Accedents - Essay Example Nuclear Fission. Nuclear fission is described as the process of splitting a heavy atom into two or more lighter atoms by bombarding the heavy atom with a slow moving neutron. As the heavy atom splits, a large amount of energy is released. In addition, a number of neutrons are released which in turn splits other heavy atoms. This creates a chain reaction that releases the energy required to generate electricity in nuclear power plants (Washington State Department of Health 2003). As shown in Figure 1, a slow moving neutron hits a heavy atom, in this case Uranium-235 and splits it into two lighter atoms, Krypton-92 and Barium-141, and 3 neutrons. Figure 1. Nuclear fission (FastFission 2010b). In Figure 2, the three neutrons either: (1) gets absorbed by Uranium-238 and does not split the atom; (2) does not hit any other atom, which stops the reaction; or (3) hits another Uranium-235 atom and causes it to split, replicating the previous process. This continuous process of splitting atoms is called a nuclear fission chain reaction. Breeze (2005) described the energy produced as enormous. Theoretically, one kilogram of naturally-occurring Uranium can produce about 140 GWh of energy, which is equivalent to the power output of a 1000 MWh coal-fired power plant operating at full power for approximately 6 days. Figure 2. Fission chain reaction (FastFission 2010). Nuclear Power Plants. To generate electrical power, nuclear fission is harnessed in a way that a controlled nuclear reaction can take place and continue indefinitely. In a nuclear reactor, fission is controlled by the use of boron rods which absorb the neutrons generated, stopping the chain reaction from proceeding. Another crucial component in nuclear reactors is the presence of a moderator, usually in the form of water or graphite. Water slows the neutrons down, making fission possible. Otherwise, fast moving neutrons cannot initiate a fission reaction (Breeze 2005). Figure 3. A typical pressurized water react or setup (United States Nuclear Regulatory Commission 2007) Figure 3 illustrates how a nuclear power plant works. As Uranium undergoes fission, an enormous amount of energy is generated. This energy is released in the form of heat which raises the temperature of the water inside the reactor. As the water heats up, it is pumped through pipes and flows into a steam generator. As the pipes get in contact with the colder water stored in the steam generator, steam is produced. The steam then drives the turbines connected to the generators, producing electricity. The hot water from the reactor does not come in contact with the water in the steam generator since the hot water is separated by the pipes. This eliminates the risk of radioactive materials going outside the reactor (Breeze 2005). NRX accident in Canada. The NRX reactor was created to demonstrate the use of heavy water or D2O as a moderator for nuclear reactors and served as the forerunner of the Canada Deuterium Uranium or CAND U reactor. It was constructed in Canada during in 1947. The NRX reactors utilized uranium fuel rods contained in a pressure tube cooled by light water flowing between the rods and the pressure tube wall. Meanwhile, heavy water is utilized as the moderator flowing between pressure tubes (Martin 2006). Figure