Nuclear energy is used for things such as atomic bombs, hydrogen bombs, and other nuclear weapons. Nuclear energy can also be used for powering electricity-generating plants all over the world. There are many arguments for and against nuclear power.
Nuclear power is an inexpensive, clean source of power. However, some people feel that because of the hazardous radiation emitted during the production of the power and the radioactivity of the material used, nuclear power is not as good as the alternatives, which are fossil fuels and solar power. (Hansen, 1993) If matter changes state or composition, it is accompanied by the production of energy. Processes such as combustion produce energy by rearranging the atoms or molecules of that substance.
(Brain, 1998) An example of this is the combustion of methane (natural gas): CH(4) + 2O(2) = CO(2) + 2H(2)O + energy. In this example, the amount of energy released is eight electron volts or 8 eV. The electron-volt unit is the unit used by nuclear physicists. The electron volt represents the gain in kinetic energy when an electron is accelerated through a potential drop of one volt. (Brain, 1998)
The most common nuclear reaction is nuclear fission. Nuclear fission is the process in which a heavy nucleus combines with a neutron and separates the heavy nucleus into two lighter nuclei. (Roy, 1993) The most typical fission reaction is that of uranium-235, which is as follows: 92 U235 + 1 neutron = 38 Sr96 + 54 XE138 + 2 neutrons + energy.
Another type of nuclear reaction is nuclear fusion. Nuclear fusion occurs when two light elements combine to form a heavier atom. (Grisham, 1993) An example of this is: 1 H(2) + 1 H(3) = 2 He(4) + 1 neutron + energy.
Nuclear Fission: Nuclear fission is a complex process, but many products are formed during this process. Not only the two nuclei, but also neutrons, beta particles, neutrinos, and gamma rays are created during the fission process. (Roy, 1993) There are more than fifty different ways a nucleus may undergo fission. Some of the ways are much more common than others. During the fission process, the nucleus breaks into two unequal parts, one lighter fragment and a heavier fragment. These nuclei are formed with excess energy that they do not usually have in their ground state; they must lose the extra energy. They release this extra energy in the form of gamma radiation or sometimes neutron emission.
The primary fragments are rich in neutrons and are radioactive. Uranium-235, which contains 92 protons and 143 neutrons, is more likely to undergo fission when bombarded by low-energy neutrons. (Hansen, 1993)
Nuclear Fission Used in Bombs
The fission process was discovered in the late 1930s. In late 1939, two scientists, Otto Frisch and Lise Meitner, discovered the fissioning of uranium into lighter particles while they were doing an experiment involving neutron irradiation of uranium. The possibility of a self-sustaining chain reaction was apparent, and this caused an accelerated rate of research. (Hansen, 1993) The United States Government researched the possible applications of nuclear fission at the beginning of World War II.
In order for the weapon to be able to work properly, it would require a self-sustaining fission reaction to be created and also an adequate amount of fissionable material to be produced for use in a weapon. (Brain, 1998) On December 2, 1942, at the University of Chicago, Enrico Fermi and his team developed the world’s first self-sustaining reactor. The reactor was fueled with natural uranium embedded in graphite blocks. (Hansen, 1993) The fission occurred in the isotope of uranium, U-235. An important factor in developing the nuclear bomb was to separate U-235 from U-238. Natural uranium only contains 0.7% of U-235, and the remaining 99.3% of natural uranium is U-238. The problem with this is that U-238 does not fission except with very high-energy neutrons, which are not available from the fission process. To separate the two materials, gaseous diffusion is used. Another way of making nuclear weapons is to use a different fissionable nucleus. Another material that is used is a synthetic isotope of plutonium, P-239.
Nuclear Fusion
In most fusion reactions, after the two atomic nuclei merge together to form a heavier nucleus, a free nucleon is also formed. In just about all fusion reactions between light nuclei, a portion of their rest mass is converted into kinetic energy of the reaction products, or into gamma rays. (Grisham, 1993) The kinetic energy and gamma rays that are released in the process of fusion heat the inside, keeping the temperature very high so the fusion can continue occurring. At thermonuclear temperatures, matter can only exist in the plasma state. Matter at thermonuclear temperature consists of electrons, positive ions, and very few neutral atoms.
If fusion reactions occur within plasma, the reactions heat the substance even more, because a portion of the reaction energy is transferred to the bulk of the plasma through collisions. (Grisham, 1993) Stars produce their energy through many types of fusion reactions. Scientists know that fusion reactions have clear potential as a power source on earth due to the fact that fusion reactions have been driving the stars for billions of years. (Hansen, 1993) For many decades now, scientists have tried to develop thermonuclear fusion reactions that will produce useful power.
Nuclear Waste
Nuclear waste is one of the biggest downfalls to nuclear power. Nuclear waste is any radioactive material that is created by nuclear technology.
www.hydro.on.ca, 1999. The most common form of nuclear waste is that which is produced by the civilian nuclear industry and the nuclear weapons program. There are many other sources of nuclear waste, including radioactive material produced by medical research, research on nuclear power, industrial applications, and contaminated sections of dismantled nuclear facilities. Radioactive material decays through different forms of radiation.
Two different forms of radiation are gamma rays and alpha particles. The decay of nuclear waste is characterized by the type of emission, the energy of the emitted radiation, and the rate at which decay occurs. The decay rate of radioactive material is usually measured in terms of half-life, which is the time required for half of the radioactive material to decay. (Brain, 1998) The half-life of each radioactive material is different and can range from less than a millionth of a second to billions of years. The danger of radioactive material is that emitted radiation may come into contact with the human body and cause damage to cells.
The effects of exposure to radioactive material can vary from mild, temporary illness to death. The effects of exposure can occur immediately or be delayed, depending on the amount of radiation received. (Hansen, 1993) There are many different types of nuclear waste. Nuclear waste is normally characterized by its physical and chemical properties and its source of origin. For example, in the United States, all waste from the nuclear defense program is classified as military waste and is usually treated separately.
Chernobyl is a Soviet Union nuclear power plant located about 130 km north of Kiev in Ukraine. On April 26, 1986, the world’s worst nuclear-reactor disaster occurred at the Chernobyl nuclear power plant. On that day, the power plant’s number 4 reactor exploded during an experiment with the graphite-moderated reactor running but its emergency water-cooling system turned off. The nuclear reactor suddenly went out of control because of some miscalculations that allowed a neutron build-up in the core. The power surge shattered the fuel, and a steam-induced explosion blew the lid off of the reactor because the reactor was not designed for such pressure. Another chemical explosion followed and scattered fragments around the plant, causing local fires. (Grolier, 1993)
This nuclear accident killed 31 persons either immediately or shortly thereafter, and the nuclear blast also caused the hospitalization of 500 others. People living within 30 km of the power plant were evacuated within a few days of the blast. Much of the radioactivity was carried away from the site at high altitudes due to the explosions and the fire.
(Brain, 1998) The radioactivity was spread across the Northern Hemisphere. The heaviest of the radioactivity descended upon western Soviet Union and some of Europe. These areas took preventive steps to protect their food supplies. The data on the effects of the radioactivity on the world remain inconclusive.
The area within 30 km of the power plants removed the heavily contaminated soil and trees to try to get rid of any nuclear waste left there. In 1990, the authorities acknowledged that several million people were still living on contaminated ground. Illnesses such as thyroid cancer, leukemia, and other radiation illnesses are much higher than normal among these people living on contaminated ground. At the plant, reactor number 4 was entombed in concrete.
Two of the three reactors at Chernobyl are still in operation. There have been other accidents since reactor number 4 blew up because of this. Ukraine’s Parliament in 1991 pressed for a complete shutdown of the plant. This idea is highly unlikely because it is the only power source for the region. (Hansen, 1993)
Nuclear Energy Today
Nuclear power has become a major source of the world’s electric energy since the discovery of fission 50 years ago. At the end of 1989, there were 416 nuclear power plants operating worldwide producing 17% of the world’s electricity. There were 130 plants that were under design at the end of 1989.
Nuclear power is used in 27 different nations, and another three nations have plants under construction. The United States has the world’s largest nuclear energy program at the end of 1989 with 108 operating plants having the operating capacity of 100,000 MW, providing 20% of the U.S. with their power. In 1989, nuclear power was the second-largest source of electricity in the U.S., exceeded only by coal, which contributes 55% of the U.S.’s electricity. Other sources of power are natural gas 9%, oil 6%, and hydro power 9%.
(Hansen, 1993) In Ontario, 40% of the electricity that is used is produced by nuclear power. Ontario nuclear power plants produce 8728 MW of electricity. (www.hydro.on.ca, 1999) Nuclear power plants are more complex and cost more to build than plants that use fossil fuels. The cost of fuel for nuclear power is much lower than the cost of fossil fuel. In the long run, nuclear electricity is much cheaper for most nations because of the differences in fuel prices. For industrialized countries of Europe and Asia, the difference in cost may be as large as a factor of half the cost. In some countries, the nuclear power program has come to a standstill. In the United States, there hasn’t been an order to build a nuclear power plant since the mid-1970s.
The main reason for the standstill is the move towards increased efficiency in the consumption of oil and also a drop in the demand for energy. The public is also concerned about the safety of nuclear power plants and the increasing awareness of the problems with nuclear waste. The reason for the increase in safety awareness is the accidents that have occurred. Before 1979, the public was all for nuclear energy, but since then, a reactor in Three Mile Island leaked radioactive material into the environment. The largest reason why the public changed their view was the explosion of reactor four at the Chernobyl power plant.
Nuclear power is an important factor in all of our lives. If it is used safely, it provides us with inexpensive electricity, but if used carelessly, it can make us ill, destroy the land, and even kill us. It is believed that in the future, nuclear power will be safer for all. The pros and cons of nuclear power are balanced because it is much more inexpensive and it will not run out like fossil fuels eventually will. Nuclear reactors do not explode all that often.
