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Energy Sources  >  Nuclear Power Saturday, November 22, 2014
 
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With about 19% of the energy in the USA and 12% of the energy produced in Canada, Nuclear energy is a critical supply source for North America. And while advocates tout the zero carbon dioxide emissions from Nuclear plants, opponents of Nuclear energy have been voicing concerns about the dangers for years. The Energy Information Administration of the USA projects that total energy requirements for the country are projected to increase by 10% from 2008 to 2021. Of that projected increase, less than 5% is expected to come from an increased supply in Nuclear energy. The balance is projected to come largely from coal, natural gas and petroleum sources.

A 2003 report by MIT maintains that, "The nuclear option should be retained precisely because it is an important carbon-free source of power." As noted elsewhere on this site, fossil fuel-based electricity accounts for about 40% of global greenhouse gas emissions – and 36% (ie – 83% of the 40%) comes from coal. So while coal-fired plants are economical to build, advocates say that nuclear power has to be considered a viable alternative to allow the global community to achieve gains in the control of carbon dioxide emissions. Others point out that nuclear power does have CO2 emissions associated with it because there is a lot of concrete that goes into the construction of a plant. However, wind turbines actually use more concrete than nuclear plants for the same electricity production capacity.

The United States produces the most nuclear energy, with nuclear power providing 19% of the electricity it consumes, while France produces the highest percentage of its electrical energy from nuclear reactors—78% as of 2006. For a complete list of the nuclear reactors in the USA, please see http://www.eia.doe.gov/cneaf/nuclear/page/at_a_glance/reactors/nuke1.html.

The 1979 accident at Three Mile Island and the 1986 Chernobyl disaster played a part in stopping new plant construction in many countries, although the public policy organization Brookings Institution suggests that new nuclear units have not been ordered in the U.S. because the Institution's research concludes they cost 15–30% more over their lifetime than conventional coal and natural gas fired plants.
 
  
 
 
 
 
How it works
Just as many conventional thermal power stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear power plants convert the energy released from the nucleus of an atom, typically via nuclear fission.

When a relatively large fissile atomic nucleus absorbs a neutron, a fission of the atom results. Fission splits the atom into two or more smaller nuclei with kinetic energy (known as fission products) and also releases gamma radiation and free neutrons. A portion of these neutrons may later be absorbed by other fissile atoms and create more fissions, which release more neutrons, and so on creating a chain reaction.

This nuclear chain reaction can be controlled by using neutron poisons and neutron moderators to change the portion of neutrons that will go on to cause more fissions. Nuclear reactors generally have automatic and manual systems to to shut the fission reaction down if unsafe conditions are detected.

A cooling system removes heat from the reactor core and transports it to another area of the plant, where the thermal energy can be harnessed to produce electricity or to do other useful work. Typically the hot coolant will be used as a heat source for a boiler, and the pressurized steam from that boiler will power one or more steam turbine driven electrical generators.

Uranium as a fuel source
Uranium is a fairly common element in the Earth's crust. The world's present measured resources of uranium, economically are enough to last for "at least a century" at current consumption rates.

Uranium’s contribution to the overall cost of the electricity produced is relatively small, so even a large price escalation will have relatively little effect on final price. For instance, typically a doubling of the uranium market price would increase the fuel cost for a light water reactor by 26% and the electricity cost about 7%, whereas doubling the price of natural gas would typically add 70% to the price of electricity from that source.

Nuclear Waste
The safe storage and disposal of nuclear waste is a significant challenge. The most important waste stream from nuclear power plants is spent fuel. A large nuclear reactor produces 3 cubic metres (25–30 tonnes) of spent fuel each year. Nuclear waste can be generally classified as either "low level" radioactive waste or "high level" radioactive waste. Low level nuclear waste usually includes material used to handle the highly radioactive parts of nuclear reactors. The level of radioactivity and the half life of the radioactive isotopes in low level waste is relatively small. Storing the waste for a period of 10 to 50 years will allow most of the radioactive isotopes in low level waste to decay, at which point the waste can be disposed of as normal refuse.

High level radioactive waste is generally material from the core of the nuclear reactor or nuclear weapon. Most of the radioactive isotopes in high level waste emit large amounts of radiation and have extremely long half-lives (some longer than 100,000 years) creating long time periods before the waste will settle to safe levels of radioactivity. There are a few ways to deal with this waste, but all of them have significant costs or other limitations.
 
  
 
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