# Presentation: 018423

## Nuclear Fission and Fusion

- An energetic discussion

## A little bit on the atom...

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- Negative **electrons**

- Positive **protons**

- Neutral **neutrons**

**Nucleus**

## Conservation of Energy/Mass

**Energy cannot be created or destroyed – it can only change form.**
- KE can become PE or vice versa.
- E = mc2
- Mass is really a form of energy

## Another look at E = mc2

- E = energy (J)
- m = mass (kg)
- c = speed of light (3 x 108 m/s)
- Mass is really just another form of energy!

## How much energy in a buck?

- A dollar bill has a mass of 1 gram.
- 	G: m = 0.001 kg; c = 3 x 108 m/s; E = ?
- 	ER: E = mc2
- 	C: E = (0.001 kg)(3 x 108 m/s)2
- 	    E = 9 x 1013 J = 90,000,000,000,000 J
- 	    E = 12 kilotons of TNT-equivalent

## 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

## 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.

## Uranium 235 Fission

## 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 U235

## A Chain Reaction

## 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.

## 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

## 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.

## 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.

## 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???

## 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.html](http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/u235chn.html)_