4.6 No CO2 Emissions! The Pros and Cons of Nuclear Energy: Geology and Alternate Energy Sources

4.6 No CO2 Emissions! The Pros and Cons of Nuclear Energy: Geology and Alternate Energy Sources

Roughly 8% of the energy demand of the United States is being met by nuclear power plants. The fuel for these facilities comes from radioactive materials that release energy by the process of nuclear fission. Fission is accomplished by bombarding the nuclei of heavy atoms, commonly uranium-235, with neutrons.

This causes the uranium nuclei to split into smaller nuclei and to emit neutrons and heat energy. The ejected neutrons, in turn, bombard the nuclei of adjacent uranium atoms, producing a chain reaction. If the supply of fissionable material is sufficient and if the reaction is allowed to proceed in an uncontrolled manner, an enormous amount of energy would be released in the form of an atomic explosion.

In a nuclear power plant, the fission reaction is controlled by moving neutron-absorbing rods into or out of the nuclear reactor. The result is a controlled nuclear chain reaction that releases great amounts of heat. The energy produced is transported from the reactor and used to drive steam turbines that turn electrical generators, which is similar to what occurs in most conventional power plants.


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Uranium-235 is the only naturally occurring isotope that is readily fissionable and is therefore the primary fuel used in nuclear power plants. Thorium, although not capable by itself of sustaining a chain reaction, can be used with uranium-235 as a nuclear fuel. Although large quantities of uranium ore have been discovered, most contain less than 0.05% uranium. Of this small amount, 99.3% is the non-fissionable isotope uranium-238 and just 0.7% consists of the fissionable isotope uranium-235. Because most nuclear reactors operate with fuels that are at least 3% uranium-235, the two isotopes must be separated in order to concentrate the fissionable uranium 235. The process of separating the uranium Isotopes is difficult and substantially increases the cost of nuclear power.

Although uranium is a rare element in Earth’s crust, it does occur in enriched deposits. Some of the most important occurrences are associated with what are believed to be ancient placer deposits in stream beds. For example, in Witwatersrand, South Africa, grains of uranium ore, as well as rich gold deposits, were concentrated by virtue of their high density in rocks made largely of quartz pebbles. In the United States, the richest uranium deposits are found in Jurassic and Triassic sandstones in the Colorado Plateau and in younger rocks in Wyoming. Most of these deposits have formed through the precipitation of uranium compounds from groundwater. Precipitation of uranium occurs as a result of a chemical reaction with organic matter, as evidenced by the concentration of uranium in fossil logs and organic rich black shales.

At one time, nuclear power was heralded as the clean, cheap source of energy to replace fossil fuels. However, several obstacles have emerged to hinder the development of nuclear power as a major energy source. Not the least of these is the skyrocketing cost of building nuclear facilities that contain numerous safety features. More important, perhaps, is the concern over the possibility of a serious accident at one of the nearly 200 nuclear plants in existence worldwide.

The 1979 accident at Three Mile Island near Harrisburg, Pennsylvania, helped bring this point home. Here, a malfunction led the plant operators to believe that there was too much water in the primary system instead of too little. This confusion allowed the reactor core to lie uncovered for several hours. Although there was little danger to the public, substantial damage to the reactor resulted.

Unfortunately, the 1986 accident at Chernobyl in the former Soviet Union was far more serious. In this incident, the reactor ran out of control and two small explosions lifted the roof off the structure, allowing pieces of uranium to be thrown over the immediate area. During the ten days that it took to quench the fire that ensued, high levels of radioactive material were carried by the atmosphere and detected as far away as Norway. In addition to the 18 people who died within six weeks of the accident, many thousands more faced an increased risk of death from cancers associated with the fallout.

It should be emphasized that the concentrations of fissionable uranium-235 and the design of reactors are such that nuclear power plants cannot explode like an atomic bomb. The dangers arise from a possible escape of radioactive debris during a meltdown of the core or other malfunction. In addition, hazards such as the disposal of nuclear waste and the relationship that exists between nuclear energy programs and the proliferation of nuclear weapons must be considered as we evaluate the pros and cons of employing nuclear power.’

Among the pros for nuclear energy is the fact that nuclear power plants do not emit carbon dioxide. By contrast, the generation of electricity from fossil fuels produces large quantities of carbon dioxide. Thus, substituting nuclear power for power generated by fossil fuels represents one option for reducing carbon emissions.

 

 

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