1. Nuclear
Reactions

2. n Energy Nuclear Fission a small amount of mass changes to energy
Nuclear Fission is when a large nucleus splits into two smaller nuclei, releasing neutrons and energy
Heavier nuclei tend to be more unstable n 1
Energy
a small amount of mass changes to energy
What does Fission mean?

3. Nuclear Fission E = mc2 a small amount of mass changes to energy
Matter and energy are interchanged in a nuclear reaction (the mass of the products is slightly less than the mass of the reactant)
Who is this man?
What does the equation mean?
All nuclear power generation is accomplished through nuclear fission.

4. Nuclear reactions vs Chemical reactions
mass is conserved, and energy changes are relatively small.
There are no changes to the nuclei in chemical reactions.
Nuclear reactions:
the actual nucleus of atoms changes.
Protons, neutrons, electrons, and/or gamma rays can be lost or gained.
Small changes in mass = huge changes in energy
The nuclear fission of 1 g of uranium-235 produces the same amount of energy as burning 2 tonnes of coal!

5. Nuclear Fission of U-235
It is much easier to crash a neutral neutron than a positive proton into a nucleus to release energy.
Most nuclear fission reactors and weapons use this principle.
A neutron crashes into an atom of stable U-235 to create unstable U-236, which then undergoes radioactive decay.
After several steps, atoms of krypton and barium are formed, along with the release of three neutrons and huge quantities of energy.
Why is it easier to use neutrons?

6. The EXACT same Process

7. The EXACT same Process

8. Try these…

9. Chain Reactions
Once the nuclear fission reaction has started, it can keep going.
The neutrons released trigger more reactions on other U-235 atoms.
This chain reaction can quickly get out of control.
materials that absorb neutrons help to control the chain reaction.
eg: Cadmium Rods
Nuclear bombs are uncontrolled reactions

10. CANDU Reactors Hazardous wastes CANadian Deuterium Uranium reactor
safe and easy to shut down in an emergency.
produces a lot of heat to generate steam to drive a turbine that produces electricity.
Hazardous wastes
Some waste products, like fuel rods, can be re-used.
Some products are very radioactive, however, and must be stored away from living things.
Most of this waste is buried underground or stored in concrete.
It will take 20 half-lives (thousands of years) before the material is safe.

11. Nuclear Fusion
Nuclear Fusion is when two small nuclei join together into one larger nucleus, releasing large amounts of energy
Energy

12. Nuclear Fusion
Nuclear Fusion produces much more energy for a given mass of fuel than Nuclear Fission.
The Sun and other stars
Hydrogen Bomb
the basic source of energy in the universe (how all elements are formed)
e.g.:

13. Nuclear Fusion continued
As an energy source it is clean and plentiful, however it is very hard to control as it needs very high temperatures (100,000,000°C)
Scientists cannot yet find a safe, manageable method to harness the energy of nuclear fusion.

14. Cold Fusion
So-called “cold fusion” would occur at temperatures and pressures that could be controlled.

15. Questions??
Before I assign today’s work do you have any questions from or 11.3?

16. Classwork Homework Read 11.2 + CYU 11.2 Q’s 4,6-12,14

17. Upcoming dates
Next Class: Review Chapter 11 Next Next Class: Chapter 11 Checkpoint/Review Note: This Checkpoint will be worth HALF as much Next Next Next Class: Chapter 8,10,11 Unit Test