Environmental effects of nuclear power

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Nuclear power processes involving the environment; mining, enrichment, waste heat, and geological disposal.
Nuclear power processes involving the environment; mining, enrichment, waste heat, and geological disposal.

Nuclear power, as all power sources, has an effect on the environment through a number of stages of the nuclear fuel cycle, operation, and by the lingering effects of past accidents.

Contents

[edit] Waste heat

Nuclear power plants have a thermal efficiency of about 30%. In other words, two-thirds of the energy produced by a nuclear power plant is rejected as waste heat. This thermal efficiency is comparable to coal fired power plants[1] . While the cooling towers discharge part of that heat into the atmosphere, large quantities of cooling water are needed to handle the waste heat discharge. For this reason, nuclear plants are built near large bodies of water - on the shores of lakes, rivers, and oceans.[2] Droughts can pose a severe problem by causing the source of cooling water to run out.[3] During Europe's 2006 heat wave, French, Spanish and German utilities had to secure exemptions from regulations in order to discharge overheated water into the environment. Some had to shut down some of their nuclear reactors.[4]

North Anna uses a direct exchange "hot" lake. 38°03′26″N 77°47′44″W / 38.057327, -77.79556
North Anna uses a direct exchange "hot" lake. 38°03′26″N 77°47′44″W / 38.057327, -77.79556

As a Thermal power station, nuclear plants exchange .01 to 100% of their thermal energy with a body of water or evaporate water through a cooling tower.

The cooling options are typically once-through cooling, pond cooling, or cooling towers. All three have separate concerns that come with them. Many plants will have an artificial lake like the Shearon Harris Nuclear Power Plant or the South Texas Nuclear Generating Station. Shearon Harris makes use of a cooling tower but South Texas does not and dumps directly back into the lake. The North Anna Nuclear Generating Station is another example of direct use of a cooling lake, which is typically about 30 degrees[citation needed] hotter than normal lake water, which is cited as an attraction of the area by some residents.[5] Additionally, the Turkey Point Nuclear Generating Station is credited with helping the conservation status of the American Crocodile, largely an effect of the waste heat produced. The environmental effects on the artificial lakes are often weighted in arguments against construction of new plants, and during droughts have drawn media attention.[6]

The temperature of cooling water returned to an ocean, lake, or river is regulated. Nuclear plants have sometimes shut down to avoid exceeding these temperatures. In the 2003 European heat wave, some nuclear power plants in France shut down and other were given permits to release hotter water back into rivers.[7]

Waste heat could be used in cogeneration applications such as district heating. The principles of cogeneration and district heating with nuclear power are the same as any other form of thermal power production. One use of nuclear heat generation was with the Ågesta Nuclear Power Plant in Sweden. In Switzerland, the Beznau Nuclear Power Plant provides heat to about 20,000 people.[8]

[edit] Radioactive waste

Low-level waste may have few precautions taken above typical waste.
Low-level waste may have few precautions taken above typical waste.
Main article: Radioactive waste

Moderate amounts of low-level waste are produced through the Chemical and Volume Control System of a nuclear plant. This includes gas, liquid, and solid waste which is all produced through the process of purifying the water through evaporation. The liquid waste is reprocessed continuously. The gas waste is filtered, compressed, stored, diluted, and then discharged. The rate at which this is allowed is regulated and studies must prove that such discharge does not violate dose limits to a member of the pubic, see #Radioactive effluent emissions.

Solid waste can be disposed of simply by placing it somewhere it won't be disturbed for a few years. There are three low-level waste disposal sites in the United States, in South Carolina, Utah, and Washington.[9] Solid waste from the CVCS is combined with solid radwaste that comes from handling materials before it is buried off-site.[10]

[edit] High level waste

See also: Deep geological repository

A comparatively small amount (perhaps a ton a year from a large nuclear power plant) of high-level waste is produced, and this poses a significant disposal problem.[citation needed] It can be expected to be dangerous for tens or hundreds of thousands of years (Taking 10,000 years to decay to activity levels below that of the original ore), so extremely secure disposal methods must be found.[citation needed] Currently, most such waste is stored in dry cask storage facilities which require constant monitoring. Several methods have been suggested for final disposal of the waste, including deep burial in stable geological structures, transmutation, and removal to space. Some nuclear reactors, such as the Integral Fast Reactor, have been proposed that use a different nuclear fuel cycle that avoids producing waste containing long-lived radioactive isotopes or burns those isotopes from other plants.

[edit] Environmental effects of accidents

See also: Chernobyl disaster effects#Effect on the natural world

Possible accidents at nuclear power plants pose a risk of severe environmental contamination. The Chernobyl accident at an RBMK reactor released large amounts of radioactive contamination, killing many and rendering an area of land unusable to humans for the next few centuries.

[edit] Radioactive effluent emissions

The Grafenrheinfeld Nuclear Power Plant. The tall chimney releases effluent gases.
The Grafenrheinfeld Nuclear Power Plant. The tall chimney releases effluent gases.

Commercial nuclear power plants release gaseous and liquid radiological effluents into the environment as a byproduct of electrical generation, which are monitored in the US by the EPA and the NRC. Dose to an unaffiliated member of the public as a result of these emissions is typically on the order of 0.01 mrem. The average dose per person from all sources is about 360 mrems per year.[11]

The total amount of radioactivity released through this method depends on the plant, regulatory requirements, and plant performance. Atmospheric dispersion models combined with pathway models are employed to accurately approximate the dose to a member of the public from the effluents emitted. Limits for the Canadian plants are shown below:

Regulatory limits on Radioactive Effluents from Canadian Nuclear Power Plants
Effluent Tritium Iodine-131 Noble Gases Particulates Carbon-14
Units (TBqb × 104) (TBq) (TBq-MeVc × 104) (TBq) (TBq × 103)
Point Lepreau Nuclear Generating Station 43.0 9.9 7.3 5.2 3.3
Bruce Nuclear Generating Station A 38.0 1.2 25.0 2.7 2.8
Bruce B 47.0 1.3 61.0 4.8 3.0
Darlington 21.0 0.6 21.0 4.4 1.4
Pickering Nuclear Generating Station A 34.0 2.4 8.3 5.0 8.8
Pickering B 34.0 2.4 8.3 5.0 8.8
Gentilly-2 44.0 1.3 17.0 1.9 0.91

[12]

Effluent emissions for Nuclear power in the United States is regulated by 10 CFR 50.36(a)(2). For detailed information, consult the Nuclear Regulatory Commission's database.

[edit] Comparison to coal generation

In terms of net radioactive release, the National Council on Radiation Protection and Measurements (NCRP) estimated the average radioactivity per short ton of coal is 17,100 millicuries/4,000,000 tons. With 154 coal plants in the United States, this amounts to emissions of 0.6319 TBq per year for a single plant, which still does not directly compare to the limits on nuclear plants (see above table) because coal emissions contain long lived isotopes and have different dispersion and intake pathways.

In terms of dose to a human living nearby, it is sometimes cited that coal plants release 100 times the radioactivity of nuclear plants. This comes from NCRP Reports No. 92 and No. 95 which estimated the dose to the population from 1000 MWe coal and nuclear plants at 490 person-rem/year and 4.8 person-rem/year respectively (a typical Chest x-ray gives a dose of about 6 mrem for comparsion).[13] The Environmental Protection Agency estimates an added dose of 0.09 mrem per year for living within 50 miles of a coal plant and 0.003 mren for a nuclear plant for yearly radiation dose estimation.[14]

Nuclear generation does not produce any amounts of sulfur dioxide, nitrogen oxides, mercury or other pollutants associated with the combustion of fossil fuels (pollution from fossil fuels is blamed for 24,000 early deaths each year in the U.S. alone[15]).

[edit] Carbon Dioxide

Nuclear power does not produce carbon dioxide, leading the nuclear power industry and some environmentalists, such as Greenpeace founder Patrick Moore, to advocate it to reduce greenhouse gas emissions (which contribute to global warming).[16]

According to a 2007 story broadcast on 60 Minutes,[17] nuclear power gives France the cleanest air of any industrialized country, and the cheapest electricity in all of Europe.

A fair comparison of the climate impacts from different energy sources can be made only by accounting for the emissions of all relevant greenhouse gases (GHGs) from the full energy chain (FENCH) of the energy sources.[18] Like any power source (including renewables like wind and solar energy), the facilities to produce and distribute the electricity require energy to build and subsequently decommission. Mineral ores must be collected and processed to produce nuclear fuel. These processes either are directly powered by diesel and gasoline engines, or draw electricity from the power grid, which may be generated from fossil fuels. Life cycle analyses assess the amount of energy consumed by these processes (given today's mix of energy resources) and calculate, over the lifetime of a nuclear power plant, the amount of carbon dioxide saved (related to the amount of electricity produced by the plant) vs. the amount of carbon dioxide used (related to construction and fuel acquisition).

[edit] Vattenfall comparative emissions study

A life cycle analysis centered around the Swedish Forsmark Nuclear Power Plant estimated carbon dioxide emissions at 3.10 g/kWh[19] and 5.05 g/kWh in 2002 for the Torness Nuclear Power Station.[20] This compares to 11 g/kWh for hydroelectric power, 950 g/kWh for installed coal, 900 g/kWh for oil and 600 g/kWh for natural gas generation in the United States in 1999.[21]

The Vattenfall study found Nuclear, Hydro, and Wind to have far less greenhouse emissions than other sources represented.
The Vattenfall study found Nuclear, Hydro, and Wind to have far less greenhouse emissions than other sources represented.

The Swedish utility Vattenfall did a study of full life cycle emissions of Nuclear, Hydro, Coal, Gas, Solar Cell, Peat and Wind which the utility uses to produce electricity. The net result of the study was that nuclear power produced 3.3 g/kWh of carbon dioxide. This compares to 400 for natural gas and 700 for coal (according to this study). The study also concluded that nuclear power produced the smallest amount of CO2 of any of their electricity sources.[22]

[edit] UK Parliamentary Office Study

In a study conducted in 2006 by the UK's Parliamentary Office of Science and Technology (POST), nuclear power's lifecycle was evaluated to emit the least amount of carbon dioxide (very close to wind power's lifecycle emissions) when compared to the other alternatives (fossil fuel, coal, and some renewable energy including biomass and PV solar panels).[23] In 2006, a UK government advisory panel, The Sustainable Development Commission, concluded that if the UK's existing nuclear capacity were doubled, it would provide an 8% decrease in total UK CO2 emissions by 2035. This can be compared to the country's goal to reduce greenhouse gas emissions by 60 % by 2050. As of 2006, the UK government was to publish its official findings later in the year.[24][25] On 21 September 2005 the Oxford Research Group published a report, in the form of a memorandum to a committee of the British House of Commons, which argued that, while nuclear plants do not generate carbon dioxide while they operate, the other steps necessary to produce nuclear power, including the mining of uranium and the storing of waste, result in substantial amounts of carbon dioxide pollution.[26]

[edit] Storm and Smith publication

In 2001, professors Jan Willem Storm van Leeuwen and Philip Smith released a study which argued that, though nuclear plants don't produce any CO2 directly, the energy required for the rest of the nuclear fuel cycle (uranium mining, enrichment, transportation) and power plant life cycle (construction, maintenance, decommissioning) leads to significant carbon dioxide emissions, especially as usage of lower-grade uranium becomes necessary.[27]

The report by Jan Willem Storm van Leeuwen and Philip Smith with the title Is Nuclear Power Sustainable? was prepared for circulation during the April 2001 United Nations Commission on Sustainable Development meeting, and again during the continuation in Bonn in July 2001. The report concluded that nuclear power is not sustainable because of increasing energy inputs. The report has been widely cited in arguments against nuclear power.

The report claims carbon dioxide emissions from nuclear power per kilowatt hour could range from 20% to 120% of those for natural gas-fired power stations depending on the availability of high grade ores.[28] The study was strongly criticized by the World Nuclear Association (WNA), rebutted in 2003, then dismissed by the WNA in 2006 based on its own life-cycle-energy calculation (with comparisons). The WNA also listed several other independent life cycle analyses which show similar emissions per kilowatt-hour from nuclear power and from renewables such as wind power.[29][30]

[edit] Barnaby and Kent report

A report by Frank Barnaby and James Kent lists several FENCH emissions of CO2 vary between 10 and 130 grams per kWh. Methodology from the Storm and Smith publication is cited, and similar conclusions are drawn from this literature study.[31]

[edit] Rebuttals

In 2000, however, Frans H. Koch of the International Energy Agency reported that, although it is correct that the nuclear life cycle produces greenhouse gases, these emissions are actually less than the life cycle emissions of some renewables, like solar and wind, and drastically less than fossil fuels.[32]

Nuclear power costs about the same as coal, so it's not expensive to make. It does not produce smoke or carbon dioxide, so it does not contribute to the greenhouse effect.

[edit] See also

[edit] References

  1. ^ C Johnson, Physicist (2007-09-26). Global Warming from Electric Power Plants (English).
  2. ^ Got Water? Nuclear power plant cooling water needs (English). Union of Concerned Scientists.
  3. ^ Drought could shut down nuclear power plants (English). MSNBC (2008-01-23).
  4. ^ Susan Sachs (2006-08-10). Nuclear power's green promise dulled by rising temps (English). The Christian Science Monitor.
  5. ^ Washington Post. Happy in Their Haven Beside the Nuclear Plant.
  6. ^ NBC. Dropping Lake Levels Affect Shearon Harris
  7. ^ The Observer. Heatwave shuts down nuclear power plants.
  8. ^ SUGIYAMA KEN'ICHIRO (Hokkaido Univ.) et al. Nuclear District Heating: The Swiss Experience
  9. ^ NRC. Radioactive Waste: Production, Storage, Disposal (NUREG/BR-0216, Rev. 2)
  10. ^ NRC. Radioactive Waste Management
  11. ^ [1] [American Nuclear Society]
  12. ^ RADIOACTIVE EMISSIONS DATA FROM CANADIAN NUCLEAR GENERATING STATIONS 1988 TO 1997
  13. ^ Coal Combustion - ORNL Review Vol. 26, No. 3&4, 1993
  14. ^ The EPA. Calculate Your Radiation Dose
  15. ^ Dirty Air, Dirty Power: Mortality and Health Damage Due to Air Pollution from Power Plants. Clean Air Task Force (2004). Retrieved on 2006-11-10.
  16. ^ National Public Radio (25 Apr. 2008): Environmentalists rethink stance on nuclear power
  17. ^ France: Vive Les Nukes accessed 23 July 2007
  18. ^ Joop F. van de Vate (2002). "Full-energy-chain greenhouse-gas emissions: a comparison between nuclear power, hydropower, solar power and wind power" 3: pp. 59–74. International Journal of Risk Assessment and Management. 
  19. ^ Vattenfall 2004, Forsmark EPD for 2002 and SwedPower LCA data 2005.
  20. ^ Energy Analysis of Power Systems accessed 20 October 2007
  21. ^ Electric Power Industry CO2 Emissions accessed 20 October 2007
  22. ^ nuclearinfo.net. Greenhouse Emissions of Nuclear Power
  23. ^ Parliamentary Office of Science and Technology (2006). Carbon Footprint of Electricity Generation. Retrieved on 2007-07-13.
  24. ^ 'No Quick Fix' From Nuclear Power. BBC News (2006). Retrieved on 2006-11-10.
  25. ^ Is nuclear the answer?. Sustainable Development Commission (2006). Retrieved on 2006-12-22.
  26. ^ Barnaby, Frank; Barnham, Keith; Savidge, Malcolm (2005-09-21). Memorandum by Oxford Research Group p.9. Retrieved on 2007-03-26.
  27. ^ Nuclear Power, The Energy Balance - Chapter 1 - The CO2-emission of the nuclear life-cycle
  28. ^ Jan Willem Storm van Leeuwen and Philip Smith (2003). Nuclear Power — The Energy Balance. Retrieved on 2006-11-10.
  29. ^ Energy Balances and CO2 Implications accessed 23 July 2007
  30. ^ Energy Analysis of Power Systems accessed 23 July 2007
  31. ^ Frank Barnaby and James Kent (2007-03). Secure Energy? Civil nuclear power, security and global warming. (English). Oxford Research Group.
  32. ^ "Hydropower-Internalised Costs and Externalised Benefits"; Frans H. Koch; International Energy Agency (IEA)-Implementing Agreement for Hydropower Technologies and Programmes; Ottawa, Canada, 2000

[edit] External links