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