The basis for old bombs and new energy Nuclear Fission The basis for old bombs and new energy

History of Nuclear Fission In 1939, German scientists Lise Meitner and Otto Hahn discovered that the uranium nucleus could be split (review atomic structure on board) Fission is the fancy word for splitting The fission reaction produced a lot of energy MUCH more energy than burning fossil fuels Fission could result in a chain reaction that could grow faster and more energetic quickly The energy comes from E = mc2

History of Nuclear Fission Meitner sent the information to her nephew, Otto Frisch, in the U.S. Germans had the info the info could be used to make a bomb Meitner’s colleague, Leo Szilard, wrote the famous letter to FDR the letter argued for an intense effort to create a nuclear weapon before the Germans the letter was signed by Einstein FDR initiated the Manhattan Project as a result

History of Nuclear Fission Hahn received a Nobel prize, Meitner didn’t. Meitner emigrated to the US but she refused to work on the Manhattan Project

The Fission Reaction U-235 + neutron  U-236* U-236* is very unstable and undergoes spontaneous fission U-236*  2 fission products + 3 neutrons + ENERGY The 3 neutrons can go on to cause 3 more fissions, creating 9 neutrons The 9 neutrons can go on to cause 27 more fissions etc…

The Nuclear Fission Reaction Notice that no GREENHOUSE GASES are produced

Fission Weapons Making the Atom Bomb is easy in theory the fission reaction does NOT need to be controlled The key is to rapidly create a supercritical mass of fissionable material A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. must bring together two subcritical masses

The Hiroshima Bomb Gun barrel design called Little Boy Uses enriched Uranium fuel Uranium is naturally occurring Uranium is a less efficient fuel Bomb was approx. 33 lbs fuel = 16 kilotons TNT = 32,000,000 lbs TNT = 800 semi-trucks fully loaded One subcritical mass is fired down a tube at the other subcritical mass Bomb resulted in approx 140,000 deaths

The Little Boy design

The Trinity and Nagasaki Bombs Spherical implosion design called Fat Man (or “The Gadget”) Very complicated, which is why they tested it Uses Plutonium fuel Plutonium is not naturally occurring Must be bred from fertile fuel, usually U-238 Plutonium is a more efficient fuel Bomb was approx. 11 lbs fuel = 20 kilotons TNT = 40,000,000 lbs TNT = 1000 semi trucks fully loaded Two hemispheres of fuel are imploded inward toward each other The Nagasaki bomb resulted in approx. 80,000 deaths

The Fat Man design

Obtaining Weapons Grade Fuel The fuel in a nuclear bomb must be 80-100% pure Natural uranium is only 0.7% U-235 (99.3% U-238) Power plant fuel only about 3% Uranium is naturally occurring but it must be concentrated, or enriched Enrichment is VERY difficult, requires huge centrifuges Plutonium does not occur naturally but it can be made from waste nuclear fuel process is EASY, but requires a breeder reactor

Good news, Bad news The bad news is that nuclear weapons are easy to make if you have weapons grade fuel The good news is that weapons grade fuel is VERY difficult to come by We are reluctant to let rogue nations build any kind of nuclear facility we’re afraid the plant might be a centrifuge for enriching Uranium or a reactor for breeding Plutonium