1. Nuclear Fission and Fusion An energetic discussion

2. A little bit on the atom…  - - - - - - - -        Negative electrons Positive protons Neutral neutrons Nucleus

3. Conservation of Energy/Mass Energy cannot be created or destroyed – it can only change form. KE can become PE or vice versa. E = mc 2 Mass is really a form of energy

4. Another look at E = mc 2 E = energy (J) m = mass (kg) c = speed of light (3 x 10 8 m/s) Mass is really just another form of energy!

5. How much energy in a buck? A dollar bill has a mass of 1 gram. G: m = 0.001 kg; c = 3 x 10 8 m/s; E = ? ER: E = mc 2 C: E = (0.001 kg)(3 x 10 8 m/s) 2 E = 9 x 10 13 J = 90,000,000,000,000 J E = 12 kilotons of TNT-equivalent

6. Fiss vs. Fuse Fiss = break down Start with a larger atom and finish with two or more smaller atoms Fuse = build up Start with two smaller atoms and finish with one larger atom

7. Nuclear Fission Break down of the nucleus or splitting an atom Uranium 235 is hit with a neutron to become Uranium 236 Uranium 236 splits apart to become two smaller atoms and 2 or 3 neutrons The mass of the products is less than the mass of the Uranium 236. The mass that was “lost” became energy.

8. Uranium 235 Fission

9. Using one fiss to cause another… A neutron from one fission event hits another Uranium 235 atom Releases more neutrons Enough Uranium 235 atoms = sustained chain reaction Critical mass = 52 kg for U 235

10. A Chain Reaction

11. How fission can be used? GOOD –A controlled chain reaction in a reactor used in nuclear power plants to produce electricity. EVIL –An uncontrolled chain reaction is used to create incredibly powerful weapons – the atomic bombs dropped on Japan.

12. Nuclear Fusion Build up of nucleus or fusing of two nuclei to form one large nucleus Occurs at exceptionally high temperatures – over 100 million degrees Laboratory Experiments –Deuterium and tritium accelerated –Collide to form one new atom with a larger helium nucleus and a neutron is released –Mass of helium and neutron less than mass of deuterium and tritium –Mass that was “lost” became energy

13. The Sun Proton-proton chain reaction Two hydrogen atoms (protons) fuse together to create deuteron A third hydrogen atom collides with deuteron to create a helium isotope Helium isotopes fuse to make beryllium which breaks down Two protons are released and it starts again.

14. How fusion can be used? GOOD –A controlled reaction in a reactor used to produce cleaner, inexpensive electricity??? EVIL –A fission bomb starts a fusion chain reaction to create an incredibly powerful weapon – thermonuclear weapons (H-bombs), MUCH more destructive than atomic bombs.

15. A-bomb vs. H-bomb Atomic bomb (Hiroshima) –Killed over 66,000 people instantly –13 kilotons of TNT-equivalent –2 exploded in warfare Hydrogen bomb –10 megatons (million-tons) of TNT-equivalent –NEVER exploded in warfare –Is it the bomb too big to ever be used???

16. Sources Fission and Fusion Animations: http://reactor.engr.wisc.edu/fission.htm http://reactor.engr.wisc.edu/fission.htm Fission graphic: http://hyperphysics.phy- astr.gsu.edu/hbase/nucene/u235chn.htmlhttp://hyperphysics.phy- astr.gsu.edu/hbase/nucene/u235chn.html