The document discusses nuclear energy and weapons, beginning with an explanation of Einstein's mass-energy equivalence formula E=mc2. It then covers nuclear fission and fusion processes, how they are used for energy production and weapons. Key challenges of controlled nuclear fission in reactors are maintaining critical mass and dealing with radioactive waste. Nuclear fusion is potentially an even greater energy source but has proven much more difficult to achieve control of on Earth.

1. Today: E=mc 2 , Fission, Fusion, Nuclear Energy / Weapons

2. Highly Recommended Reading Richard Rhodes’ “The Making of the Atomic Bomb” You will understand the physics very well after these past couple weeks of class

3. What does E = mc 2 mean? The album name means "(E) Emancipation (=) equals (MC) Mariah Carey (²) to the second power" Hmmm In this case Einstein is more comprehensible and has higher credibility

6. “ Binding energy” of isotopes High mass atoms can yield energy via nuclear fission Low mass atoms can yield energy via nuclear fusion Energy available from U-235

7. Fission and Fusion Energy 1 kilogram of FUSION fuel Enough for 676 people per year 1 kilogram of FISSION fuel Enough for 176 people per year Hyperphysics @ Georgia State U.

12. Critical mass required for neutron efficiency In a small mass, nuetrons are more likely to escape from the surface of the material A larger mass will have more interior volume, and more chances to absorb neutrons Eventually, the size of the sphere is large enough to sustain a chain reaction More surface area! A sphere has the highest volume to surface area ratio… most efficient…used for critical mass definition

21. About 6 kg of plutonium needed for implosion weapon About softball-sized Plutonium weapons much more difficult than with highly enriched Uranium But much less material is needed!

22. Uranium-235 and Plutonium only practical NW fuels Highly difficult to purify Very easy to construct a nuclear weapon Emits little radiation while idle Easier to make / purify (from spent “peaceful” fuel) Somewhat difficult to construct a nuclear weapon Weapons-grade emits little radiation Uranium-235 Plutonium (mostly Pu-239)

28. Core of nuclear power reactors similar in principle “ CANDU” heavy water nuclear reactor Graphite replaced with “heavy water” as a neutron moderator Can operate with lower-grade uranium than light water reactor http://www.youtube.com/watch?v=fjgdgAhOzXQ&feature=related

30. Some pros and cons of nuclear fission energy Pros: Only gaseous emission is water (steam) Large amount of energy from small amount of fuel Cons: Fuel is transformed into radioactive “waste” Careless operation can result in “nuclear accidents” Reactors can produce weapons-grade nuclear fuel

32. Immediately, Nuclear Fusion was recognized as an even greater source of energy And of course, hydrogen is a very abundant element!