Nuclear power
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Climate change, brought about by humankind's reliance on fossil fuels and energy hungry lifestyle means that that an alternative power source needs to be found. Fast. Nuclear power has been experimented with since the 1950s with limited success. About 17% of the world's electricity is produced by nuclear power plants. The US is the single largest user of nuclear power, producing about 20% of its electricity. France uses nuclear power for 80% of its electricity generation.
The cost, perceived dangers, and impact of accidents such as Chernobyl have prevented it from reaching early expectations.
Understanding the nuclear power
History
Is nuclear power powerful enough?
How does nuclear power work?
All nuclear power generation facilities rely on nuclear fission. There are two types of nuclear reaction, fission and fusion,
which can be used to generate energy. Currently, fusion reactors are not commercially viable because non have been made that
produce more energy than they consume. The technology for fusion reactors has proven much more difficult to develop than for
fission reactors, but if successful the benefits could be enormous. Unlike fission reactors, fusion reactors do not produce
significant quantities of radioactive waste, and the fuel supplies are large. If they ever become commercial, they are likely to
run on a variety of hydrogen called deuterium, plus the metal lithium. Deuterium is present in sea water since about 0.015% of
water is actually deuterium oxide instead of hydrogen oxide. Lithium is much scarcer, and is also in demand for rechargeable
batteries. Fusion reactors might be developed though that use just deuterium.
Fission reactors (and nuclear weapons that rely on fission) make use of the radioactive properties of uranium. Natural uranium is composed of two isotopes, U238 and U235. These are chemically the same, but with a slightly different atomic weight. U235 comprises 92 protons and 143 neutrons (in the nucleus of the atom), which is surrounded by many orbiting electrons. U238 has 146 neutrons.
U238 is radioactive, but at quite a low level. It has a long half life of about 4.5 billion years, which means that every 4.5
billion years half the U238 decays radioactively into other elements. The decay of natural uranium provides much of the heat that
makes the centre of our planet hot, and allows the continental plates to move on molten magma.
U235 is more readily split than U238, and is the key component of a fission reactor. When an atom of U235 is struck by a stray neutron it can split, throw off 2 or 3 extra neutrons and release a lot of heat. These extra neutrons can then go on to cause other atoms of U235 to split, thus casuing a self sustaining chain reaction which produces a large amount of heat energy.
In a nuclear bomb this chain reaction is encouraged to continue in an uncontrolled fashion, and this is what generates their enormous destructive power.
In a nuclear fission power station the chain reaction is controlled and a manageable amount of heat is released. This heat is then used to drive the turbines that generate electricity in the same way as in all other types of power station.
Types of Reactors
There are currently two broad categories of reactor types:
- Thermal reactors
- Fast neutron reactors
Pressurised Water Reactor
Fast Breeder Reactor
Boiling Water Rector
Integral Fast Reactor
An experimental reactor type of which only prototypes have been built.
Unlike the older fast breeders reactors, plutonium is not separated from other fuel elements in the fuel cycle. This greatly reduces the possibility that plutonium can be diverted for weapons production.
Fuel is reprocessed on site, and there are no long lived radioactive waste products (compared to other reactor types). The waste produced has a short half life and the levels of radioactivity fall to the levels of the original ore within 300 years
Integral Fast Reactor Wikipedia
Is nuclear power safe
There are three key safety issues with nuclear power:
- Waste disposal
- Power generation related accidents
- Diversion of nuclear fuel for use as weapons
The accidents at Chernobyl and Three Mile island have had a huge impact on the perceptions of the safety of nuclear power.
Other power generation technologies also have safety problems. The main danger of coal power generation is that the release of carbon dioxide will cause catastrophic climate change. On a smaller scale coal power generation produces toxic gases other than CO2, and substantial solid wastes (about 200,000 tonnes ash per 1000 MW per year). The number of deaths associated with older and dirtier coal power generation plants is significant - 51 of the worst such plants in the US have been estimated to shorten the lives of 9000 people each year (see this Sierra Club report for more detail)
The accident at Chernobyl initially killed several dozen people, and it has been estimated that possibly more than 200,000 people will be affected by cancer caused by the radioactive fallout. Very large areas of land have been rendered unihabitable around the site of the power station.
The accident at the Three Mile Island Three mile Island power plant in the US was much smaller than Chernobyl. There were no identifiable injuries or deaths associated with the partial meltdown, the average radiation exposure to residents within a 10 mile (16km) radius was equivalent to one chest X-ray, with the maximum exposure to any single individual estimated to be about 10 times that. The projected number of cancer deaths associated with the radiactivity released was estimated in a government report to be one.
Cost-benefit analysis of nuclear power
Greenhouse emissions reduction potential
Bi-products of nuclear power industry
Depleted uranium shells.
Weapons grade plutonium - this can be produced by fast breeder type power stations. For this reason most nuclear power stations are not of the fast breeder type, and use thermal type reactors.
What are the alternatives
Organisations that work on nuclear power
Companies that are involved in nuclear power plants and related technologies:
Toshiba, Hitachi, Westinghouse, General Electric, Mitsubishi, British Nuclear Fuels Ltd, COGEMA, Nuclear Regulatory Commission (USA)
See also
Books
Movies
The Simpsons - they're not a movie but if you think the antics of Homer aren't based on reality do some research into Sellafield nuclear reactor in the UK.
