Nuclear

Nuclear Power Plants

May 7, 2012, 6:44 pm
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Nuclear electric power plant. A reactor core filled with uranium fuel rods heats up an exchange fluid in a containment building. Control rods inserted between the fuel rods limit the rate of the fission reaction. Exchange fluid produces steam in a steam g

Nuclear power has major advantages. It is “clean” in the sense that it neither releases significant amounts of greenhouse gases nor particulate air pollutants. Known reserves of fissionable materials can supply nuclear power plants at the current rate for roughly 50 years. [1] If the price of uranium were to rise above $200 per kilogram, exploration for new sources, new nuclear reactor technologies, and fuel rod reprocessing have the potential to supply nuclear fuel for several centuries. [2]

 

Location of nuclear power plants. World map indicating operating nuclear power plants. [After International Nuclear Safety Center 2009.]

 

 

Nuclear power plants harness the energy released during nuclear fission. In this process, unstable (radioactive) isotopes of uranium (235U) or plutonium (239Pu) in fuel rods expel neutrons and disintegrate into 231Th or 235U, respectively. The process releases vast amounts of energy (77 × 1012 J per kg of 235U) because of the high conversion value. Neutrons expelled from the fuel rods may strike other uranium or plutonium atoms and induce them to expel neutrons, building a self-sustaining fission reaction.

The critical mass of fissionable material in the fuel rods is always below that necessary to start a nuclear explosion. To control the rate of the fission reaction and the temperature of the core, nuclear power plants insert control rods of neutron-absorbing silver, indium, cadmium, or boron alloys between the fuel rods. Elaborate heat exchange systems transfer energy from the reactor core to a generator that converts water to high-pressure, high-temperature steam. The components outside of the containment building are common to most types of electric power plants: Steam, generated by the reactor core, drives turbines that spin electrical generators.

The downside of nuclear power is the radioactive waste produced during extraction of fissionable materials from mines, processing of these materials into fuel rods, and disposal of spent fuel rods. A typical nuclear plant generates 3 cubic meters of highly radioactive waste each year. After about 40 years, 99% of the radioactivity has decayed, but the remainder will stay dangerous for another 10,000 years.

Radioactive materials emit energetic ionizing radiation when they decay. When this radiation strikes DNA (deoxyribonucleic acid), it may cause changes in the coding sequence (resulting in genetic mutations) and interfere with DNA replication. This often proves lethal to rapidly dividing cells such as cancer cells, bone marrow cells, and cells that form the walls of the intestines, and provides the basis of medical radiation treatments as well as radiation poisoning.

Storing highly radioactive materials for millennia is a formidable task. In the United States, a facility for long-term storage of radioactive materials is under construction at Yucca Mountain, Nevada. Opposition to the facility has delayed completion, and the earliest feasible opening date is now in 2021. Debate continues about the stability of geological formations below Yucca Mountain and the risks of transporting radioactive materials. The lack of such a facility, however, forces US nuclear power plants to store their radioactive waste on site.

During the past 2 decades, designs and operating procedures for nuclear power plants drastically decreased the probability of accidents (such as those at Three Mile Island and Chernobyl Nuclear Power Plant). At present, 439 nuclear power plants operate in 30 different countries without major incident and generate about 15% of the world’s electricity.

Nuclear electric power is sometimes heralded as one of the best options for mitigating greenhouse gas emissions. However, the history of past accidents, along with the relatively low cost of coal power, the difficulties in disposing of nuclear waste, and the volatility in uranium prices, have deterred new facility construction. Worldwide, only 33 new nuclear power plants are under construction and will begin operation during the next decade.

[1] (NEA and IAEA 2006)

[2] (World Nuclear Association 2007).

This is an excerpt from the book Global Climate Change: Convergence of Disciplines by Dr. Arnold J. Bloom and taken from UCVerse of the University of California.

©2010 Sinauer Associates and UC Regents

Glossary

Citation

Bloom, A. (2012). Nuclear Power Plants. Retrieved from http://www.eoearth.org/view/article/51cbf0397896bb431f6a0c5a

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