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Nuclear Reactors and Nuclear Energy
• Conversion of mass-energy to electrical energy
• mass-energy thermal kinetic electric
• Produces large amounts of electrical energy for large-scale use (city, province, country)
• small-scale: submarines, large ships
• Energy released by Fission of Uranium-235
• Reactions occur in Nuclear Reactor
• Electricity produced by spinning electric generator
Nuclear Reactor
www.ems.psu.edu/~pisupati/
cbc.ca
Pickering Nuclear Power plant
Fuel
• Natural uranium: 99% uranium-238 , 1% uranium-235
• Energy produced by chain reaction (nuclear decay produces neutrons that can initiate other reactions)
• U-238 cannot produce chain reaction, U-235 can
• Nuclear fuel = 3 – 5 % U-235 (enriched uranium)
• Uranium formed into fuel pellets
• Fuel pellets inserted in fuel rods, fuel bundles
www.nti.org
www.virginmedia.com/digital/science/pictures/
Moderator• neutrons produced by fission may be too fast to initiate decay
• slowed down by a moderator
• ordinary water can slow down neutrons (but can absorb many)
• heavy water (D2O) slows down neutrons without absorbing
Control Rods• rate of reactions controlled by material that absorbs neutrons (cadmium, boron)
• rods inserted into fuel bundle to slow or allow reactions (prevents overheating)
reference.findtarget.com/
commons.wikimedia.org
The Core
• core = fuel bundles, control rods, immersed in coolant
• coolant (water) pumped into core, absorbs heat from reactions
• coolant pumped to steam generator
• heat from coolant boils water
Steam• steam used to turn turbine
• steam condensed back to water using cool water (lake or river)
• 3 separate water circuits core turbine cooling
www.hk-phy.org/energy/power/
Energy Output
• Large scale: CANDU reactor – 800 MW per reactor Power plant = several reactors
• Bruce Power (Lake Huron): 8 reactors (enough for 20% of Ontario’s hospitals, homes, schools)
• More than 50% of Ontario’s electricity produced by nuclear
• Submarines, ships about 100 MW
CANDU• Canada Deuterium Uranium
• Designed in 1950’s
• Uses natural uranium
• U-238 can produce plutonium-239, which also produces chain reactions
• Uses heavy water as moderator www.nucleartourist.com/type/candu2.htm
Safety
• Reactors buildings heavily shielded by concrete and steel
• Interior at low air pressure so material won’t leak
• Uncontrolled reactions could lead to meltdown (Three Mile Island 1979)
explosion (Chernobyl 1986)
– releases radioactive material to atmosphere
• Reactions can be stopped quickly by dumping moderator dropping control rods into core
www.wired.com/wiredscience/2009/05/threemile/
toxipedia.org/display/toxipedia/Chernobyl+Accident
Environmental Concerns
• rods removed when useful reactions too low (“spent” fuel)• still radioactive, with some long half-life isotopes
stored in large pools of water later removed to dry storage
sometimes stored in glass (vitrification) could eventually be stored deep underground possibly contaminate environment if leaked
• heat from cooling process could alter marine ecosystems
www.world-nuclear.org/info/inf04.htmlwww.biopxenor.com/tag/nuclear-waste-storage
Country Megawatt capacityNuclear share of
electricity production
France 63,236 75.2%
Slovakia 1,760 53.5%
Belgium 5,943 51.7%
Ukraine 13,168 48.6%
Slovenia and Croatia 696 37.9% + 8.0%
Armenia 376 45.0%
Hungary 1,880 43.0%
Switzerland 3,252 39.5%
Bulgaria 1,906 35.9%
Korea, South (ROK) 17,716 34.8%
Sweden 9,399 34.7%
Czech Republic 3,686 33.8%
Finland 2,721 32.9%
Japan 47,348 28.9%
Germany 20,339 26.1%
Taiwan (ROC) 4,927 20.7%
Romania 1,310 20.6%
United States 101,229 20.2%
United Kingdom 10,962 17.9%
Russia 23,084 17.8%
Spain 7448 17.5%
Canada 12,679 14.8%
Argentina 935 7.0%
Mexico 1,310 4.8%
South Africa 1,800 4.8%
Netherlands 485 3.7%
Brazil 1,901 3.0%
Pakistan 400 2.7%
India 4,780 2.2%
China (PRC) 10,234 1.9%
World 376,313 14%
http://en.wikipedia.org/wiki/Nuclear_power_by_country