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

2. 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

3. 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

4. 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

5. 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…

6. The Nuclear Fission Reaction
Notice that no GREENHOUSE GASES are produced

7. 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

8. 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

9. The Little Boy design

10. 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

11. The Fat Man design

12. Obtaining Weapons Grade Fuel
The fuel in a nuclear bomb must be % 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

13. 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