Nuclear Energy E = mc 2 E: energy m: mass c: speed of light c = 3 x 10 8 m/s.

Nuclear EnergyNuclear Energy

E = mcE = mc22E: energym: massc: speed of lightc = 3 x 108 m/s

E = mcE = mc22

Mass can be converted to energyEnergy can be converted to massMass and energy are the same thing

The total amount of mass plus energy in the universe is constant

Mass Defect of Alpha ParticleMass Defect of Alpha Particle

Mass difference = 0.0304 u

Binding energy = 28.3 MeVFusion product has less mass than the sum of the parts.

Nuclear Mass vs Atomic Nuclear Mass vs Atomic Number is NOT LinearNumber is NOT Linear

Mass/Nucleon vs Atomic Mass/Nucleon vs Atomic NumberNumber

Fusion

Fission

Binding Energy/Nucleon vs Binding Energy/Nucleon vs Number of NucleonsNumber of Nucleons

Mass Defect in FissionMass Defect in Fission

When a heavy element (one beyond Fe) fissions, the resulting products have a combined mass which is less than that of the original nucleus.

U-235 – Neutron U-235 – Neutron BombardmentBombardment

U-235 -- FissileU-235 -- Fissile

Possible U-235 FissionPossible U-235 Fission

How Stuff Works SiteHow Stuff Works Site

Visit the How Stuff Works Site to learn more details about nuclear energy

Chain ReactionChain Reaction

Abundance of U-235Abundance of U-235

Plutonium ProductionPlutonium Production

U-238 – Not FissileU-238 – Not Fissile

Breeder ReactionBreeder Reaction

Breeder ReactorBreeder Reactor

Small amounts of Pu-239 combined with U-238

Fission of Pu frees neutronsThese neutrons bombard U-

238 and produce more Pu-239 in addition to energy

PlutoniumPlutonium

Plutonium is fissileHalf-life of Plutonium is 24,000

yearsPlutonium can be chemically

separated from uranium – easier than separating U-235 from U-238

Plutonium is chemically poisonous (just like lead and arsenic)

PlutoniumPlutoniumPlutonium attacks the nervous system and

can cause paralysis (or death in sufficient doses)

Plutonium combines rapidly with oxygen to form compounds which are chemically biologically harmless

Plutonium is always radioactively toxic – worse than uranium but not as bad as radium

Plutonium emits high energy alphas which kill cells

Greatest danger – nuclear fission bombs

Einstein PredictionEinstein Prediction

"I do not know with what weapons World War 3 will be fought, but World War 4 will be fought with sticks and

stones."A. Einstein

World Energy Consumption and World Energy Consumption and Fossil Fuel Supply vs TimeFossil Fuel Supply vs Time

Basic Nuclear Power PlantBasic Nuclear Power Plant

Fission Power AdvantagesFission Power Advantages

Supplies plentiful electricityConserves coal, oil, and natural

gasReduces pollution from burning

fossil fuel – sulfur oxides and carbon oxides

Fission Power DisadvantagesFission Power Disadvantages

Storage of radioactive wastesProduction of plutoniumDanger of nuclear weapon

proliferationLow-level release of radioactive

materials into air and groundwaterRisk of accidental release of large

amounts of radioactivity

Controlling Nuclear FusionControlling Nuclear Fusion

Fusion occurs at very high temperatures (on the order of 108 degrees) & densities

Problem?– All materials melt and vaporize at the

temperature required for fusionSolution – magnetic bottle or laser

confinementStill not cost or energy efficientDifficult to sustain the reaction

Fusion BenefitsFusion BenefitsNo danger of runaway reactionsNo air pollution – only helium is

producedBy-products of fusion are not radioactiveFuel is hydrogen (deuterium and tritium)

– 30 kilograms of seawater contain 1 gram of deuterium

– Fusion of 1 gram of deuterium releases as much energy as 10,000 liters (~2500 galllons) of gasoline or 80 toms of TNT

Nuclear LinksNuclear Links

http://www.ccnr.org/nuclear_primer.html

http://www.energy.ca.gov/education/story/story-html/chapter07.html

http://www.howstuffworks.com/nuclear-power1.htm

http://www-formal.stanford.edu/jmc/progress/nuclear-faq.html

http://sol.sci.uop.edu/~jfalward/nuclearreactions/nuclearreactions.html

Chain Reaction – Critical MassChain Reaction – Critical Mass

http://www.npp.hu/mukodes/anim/sta1-e.htm http://www.npp.hu/mukodes/anim/div2a-e.htm

Critical MassCritical Mass

critical mass a self sustaining reaction starts

for pure metal U235 (without moderator) the critical mass is somewhat less than 50 kg

Because of the very high density (19.2 g/cm3) this amount of uranium makes a sphere whose diameter is about 17 cm.

ModeratorModeratorshould have as low atomic mass

number as possibleits neutron absorbing ability

should be as low as possiblewater (H2O), heavy-water (D2O),

graphite (C) and beryllium (Be)

Cherenkov RadiationCherenkov Radiation

Bluish glow when charged particles travel faster than the speed of light in the medium

Mass SpectrometerMass Spectrometer