Chapter 12Chapter 12Nuclear EnergyNuclear Energy

Introduction to Nuclear Introduction to Nuclear EnergyEnergy Nuclear Energy - Nuclear Energy -

the energy released the energy released by nuclear fission or by nuclear fission or fusionfusion

Atoms and RadioactivityAtoms and Radioactivity

Nucleus Nucleus Comprised of Comprised of

protons (+) and protons (+) and neutrons (neutral)neutrons (neutral)

Electrons (–) orbit Electrons (–) orbit around nucleusaround nucleus

Introduction to Nuclear Introduction to Nuclear EnergyEnergy Nuclear energyNuclear energy

Energy released by nuclear fission or fusionEnergy released by nuclear fission or fusion Nuclear fissionNuclear fission

Splitting of an atomic nucleus into two Splitting of an atomic nucleus into two smaller fragments, accompanied by the smaller fragments, accompanied by the release of a large amount of energyrelease of a large amount of energy

Nuclear fusionNuclear fusion Joining of two lightweight atomic nuclei into Joining of two lightweight atomic nuclei into

a single, heavier nucleus, accompanied by a single, heavier nucleus, accompanied by the release of a large amount of energy the release of a large amount of energy

Atoms and RadioactivityAtoms and Radioactivity

Atomic massAtomic mass Sum of the protons and neutrons in an Sum of the protons and neutrons in an

atomatom Atomic numberAtomic number

Number of protons per atomNumber of protons per atom Each element has its own atomic numberEach element has its own atomic number

IsotopeIsotope Atom where the number of neutrons is Atom where the number of neutrons is

greater than the number of protonsgreater than the number of protons

Radioactive IsotopeRadioactive Isotope

Unstable isotopeUnstable isotope Radioactive DecayRadioactive Decay

Emission of energetic particles or rays Emission of energetic particles or rays from unstable atomic nucleifrom unstable atomic nuclei

ExampleExample Uranium (U-235) decays over time to Uranium (U-235) decays over time to

lead (Pb-207)lead (Pb-207) Each isotope decays based on its Each isotope decays based on its

own half-lifeown half-life

Radioactive Isotope Half-Radioactive Isotope Half-liveslives

Nuclear FissionNuclear Fission

How Electricity is ProducedHow Electricity is Produced

Breeder Nuclear FissionBreeder Nuclear Fission

A type of nuclear fission in which A type of nuclear fission in which non-fissionable U-238 is converted non-fissionable U-238 is converted into fissionable Pu-239 into fissionable Pu-239

Pros and Cons of Nuclear Pros and Cons of Nuclear EnergyEnergy ProsPros

Less of an immediate environmental Less of an immediate environmental impact compared to fossil fuelsimpact compared to fossil fuels

Carbon-free source of electricityCarbon-free source of electricity May be able to generate H-fuelMay be able to generate H-fuel

ConsCons Generates radioactive wasteGenerates radioactive waste Many steps require fossil fuels (mining Many steps require fossil fuels (mining

and disposal)and disposal) ExpensiveExpensive

Pros and Cons of Nuclear Pros and Cons of Nuclear EnergyEnergy

Cost of Electricity from Cost of Electricity from Nuclear EnergyNuclear Energy

Cost is very highCost is very high 20% of US electricity is from Nuclear 20% of US electricity is from Nuclear

EnergyEnergy Affordable due to government subsidiesAffordable due to government subsidies

Expensive to build nuclear power Expensive to build nuclear power plantsplants

Fixing technical and safety issues in Fixing technical and safety issues in existing plants is expensiveexisting plants is expensive

Safety Issues in Nuclear Safety Issues in Nuclear Power PlantsPower Plants

MeltdownMeltdown At high temperatures the metal encasing At high temperatures the metal encasing

the uranium fuel can melt, releasing the uranium fuel can melt, releasing radiation radiation

Probability of meltdown is lowProbability of meltdown is low Public perception is that nuclear power Public perception is that nuclear power

is not safeis not safe Sites of major accidents:Sites of major accidents:

Three Mile IslandThree Mile Island Chornobyl (Ukraine)Chornobyl (Ukraine)

Three-Mile IslandThree-Mile Island

1979 - most serious reactor accident in 1979 - most serious reactor accident in USUS

50% meltdown of reactor core50% meltdown of reactor core Containment building kept radiation from Containment building kept radiation from

escapingescaping No substantial environmental damageNo substantial environmental damage No human casualtiesNo human casualties

Elevated public apprehension of Elevated public apprehension of nuclear energynuclear energy Led to cancellation of many new plants in Led to cancellation of many new plants in

USUS

ChornobylChornobyl

1986 - worst 1986 - worst accident in accident in historyhistory Large amounts of Large amounts of

radiation escaped radiation escaped into atmosphereinto atmosphere

ChornobylChornobyl

Radiation spread was unpredictable Radiation spread was unpredictable and unevenand uneven

Radioactive WastesRadioactive Wastes

Long term solution to Long term solution to wastewaste Deep geologic burial – Deep geologic burial –

Yucca MountainYucca Mountain As of 2004, site must As of 2004, site must

meet EPA million year meet EPA million year standard standard

Possibilities:Possibilities: Above ground mausoleumsAbove ground mausoleums Arctic ice sheetsArctic ice sheets Beneath ocean floorBeneath ocean floor

Radioactive WasteRadioactive Waste

Temporary storage solutionsTemporary storage solutions In nuclear plant facility (require high In nuclear plant facility (require high

security)security) Under water storageUnder water storage Above ground concrete and steel casksAbove ground concrete and steel casks

Need approved permanent options Need approved permanent options soon.soon.

Decommissioning Nuclear Decommissioning Nuclear Power PlantsPower Plants Licensed to operate for 40 yearsLicensed to operate for 40 years

Several have received 20-year extensionsSeveral have received 20-year extensions Power plants cannot be abandoned Power plants cannot be abandoned

when they are shut downwhen they are shut down Three solutionsThree solutions

StorageStorage EntombmentEntombment Decommissioning (dismantling)Decommissioning (dismantling)