Nuclear Energy

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

E = mc 2 Mass can be converted to energy Energy can be converted to mass Mass and energy are the same thing The total amount of mass plus energy in the universe is constant

Mass Defect of Alpha Particle Mass difference = u Binding energy = 28.3 MeV Fusion product has less mass than the sum of the parts.

Nuclear Mass vs Atomic Number is NOT Linear

Mass/Nucleon vs Atomic Number Fusion Fission

Binding Energy/Nucleon vs Number of Nucleons

Mass 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 Bombardment

U Fissile

Possible U-235 Fission

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

Chain Reaction

Abundance of U-235

Plutonium Production

U-238 – Not Fissile

Breeder Reaction

Breeder Reactor Small amounts of Pu-239 combined with U-238 Fission of Pu frees neutrons These neutrons bombard U-238 and produce more Pu-239 in addition to energy

Plutonium Plutonium is fissile Half-life of Plutonium is 24,000 years Plutonium can be chemically separated from uranium – easier than separating U-235 from U-238 Plutonium is chemically poisonous (just like lead and arsenic)

Plutonium Plutonium 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 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 Fossil Fuel Supply vs Time

Basic Nuclear Power Plant

Fission Power Advantages Supplies plentiful electricity Conserves coal, oil, and natural gas Reduces pollution from burning fossil fuel – sulfur oxides and carbon oxides

Fission Power Disadvantages Storage of radioactive wastes Production of plutonium Danger of nuclear weapon proliferation Low-level release of radioactive materials into air and groundwater Risk of accidental release of large amounts of radioactivity

Controlling Nuclear Fusion Fusion occurs at very high temperatures (on the order of 10 8 degrees) & densities Problem? – All materials melt and vaporize at the temperature required for fusion Solution – magnetic bottle or laser confinement Still not cost or energy efficient Difficult to sustain the reaction

Fusion Benefits No danger of runaway reactions No air pollution – only helium is produced By-products of fusion are not radioactive Fuel 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 Links l l ry/story-html/chapter07.html ry/story-html/chapter07.html power1.htm power1.htm formal.stanford.edu/jmc/progress/nucle ar-faq.html formal.stanford.edu/jmc/progress/nucle ar-faq.html reactions/nuclearreactions.html reactions/nuclearreactions.html

Chain Reaction – Critical Mass

Critical 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.

Moderator should have as low atomic mass number as possible its neutron absorbing ability should be as low as possible water (H2O), heavy-water (D2O), graphite (C) and beryllium (Be)

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

Mass Spectrometer