Nuclear Energy: When Will the Lights Go Out?
By Barbara Sitzman and Regis Goode
ChemMatters, April 2011
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Regis: Most of the energy that we use every day to light our homes, power our cars, or simply recharge our cell phones, comes from fossil fuels—nonrenewable resources, such as oil, gas, and coal. Since we all depend on fossil fuels to meet our energy needs, once they are depleted, will we plunge into a world of darkness?
Barbara: Probably not! We can produce energy from other sources, such as the sun, wind, water (hydroelectric energy) and heat from deep within the Earth (geothermal energy). Unfortunately all of these energy sources present problems. For instance, we are out of luck if the sun doesn’t shine and the wind doesn’t blow (although we could solve this problem if we were able to store solar and wind energy). Also, to retrieve geothermal energy, we need expensive drilling equipment, and hydroelectric generators require a constant source of flowing water.
Regis: Currently, about 45% of our electricity is produced by burning coal. But we could switch to nuclear energy, which is the source of 75% of the electricity in France. So, why not use nuclear energy? Let’s see how the process—called nuclear fission— works. It starts when a neutron strikes the nucleus of a heavy atom, such as uranium-235. This collision splits the nucleus into two nuclei of smaller mass, releases some neutrons, and produces a tremendous amount of energy. The neutrons released are then available to split additional.uranium-235 nuclei to sustain the fission process. This process forms a chain reaction similar to a line of dominoes falling after the first one has been pushed (Fig. 1).
Barbara: This process occurs in a nuclear reactor. The energy released by the nuclear fission reactions is in the form of heat, which produces steam to turn mechanical turbine engines that power electrical generators. With all the energy involved, are nuclear reactors safe?
Regis: Accidents have happened in the past. You may have heard of the Chernobyl reactor’s explosion in Ukraine or the Three-Mile Island accident in Pennsylvania. These were serious accidents but nuclear power is one of the most heavily regulated industries in the world. Newer reactors are designed to be safer.
Barbara: These safety features add significant expense to the construction costs. Yet, the cost of producing electricity from nuclear energy is comparable to that of fossil fuels because very small amounts of uranium create huge amounts of energy. An average power plant would require 9,000 tons of coal per day, but a nuclear reactor would use only 3 kilograms of uranium-235 per day. Burning coal produces large amounts of solid waste, including toxic heavy metals.
Regis: Best of all, nuclear energy doesn’t pollute the air! There would be no concern about the emission of greenhouse gases, such as carbon dioxide, which is produced when coal is burned. According to the Nuclear Energy Institute, our current nuclear power plants save about 2 billion metric tons of carbon dioxide per year, compared to coal.
Barbara: But is nuclear energy really clean? Mining and refining uranium ore creates radioactive wastes and uses fossil fuels that generate carbon dioxide. Once the nuclear fuel is used it is highly radioactive and must be isolated for thousands of years.
Regis: Radioactive waste is the real problem. Currently, the U.S. government has not decided where to store it permanently. The same goes with spent nuclear fuel rods, which are placed in large pools of water containing boric acid that absorbs some of the radioactivity. The fuel rods are waiting for a permanent storage site.
Barbara: Scientists believe that storing the radioactive wastes deep underground is the most favorable option. The area should have little groundwater and little or no geological activity, such as earthquakes. Groundwater could erode containers that store the waste, allowing the waste to enter the environment. We don’t want to put the waste in an area prone to earthquakes either.
Regis: Why don’t we reprocess the fuel by separating the uranium-235 that didn’t react from the radioactive waste, so we can reuse it? This option could reduce the waste, and provide more usable uranium for use in power plants.
Barbara: Actually, fuel reprocessing is being carried out in many countries but not in the United States. But maybe it will become a reality in the United States in the future. What do you think? Will nuclear energy keep us out of the dark until we develop new technology to provide enough energy to meet our needs? Send your opinions to email@example.com.
Barbara Sitzman and Regis Goode are high school chemistry teachers at Granada Hills Charter High School, Granada Hills, Calif., and Ridge View High School, Columbia, S.C., respectively.