Unit 1.3 Nuclear Chemistry

1. Unit 1.3Nuclear Chemistry 1.3-2 Nuclear Reactions and Energy

2. Important Terms • Nuclear Fission • Chain Reaction • Nuclear Reactor • Nuclear Fusion

3. The Power of the Nucleus • Nuclear reactions involve enormous changes in energy. E=mc2 • E – energy • m – mass • c – speed of light (3.00 x 108 m/s) • During a nuclear reaction a small amount of mass can be converted into a large amount of energy.

4. Nuclear Fission • Nuclear fission is the process of splitting a nucleus into two or more smaller fragments. • This is accompanied by a large release of energy.

5. Nuclear Fission Using Uranium-235 • Note that the sums of the mass numbers on the left and right are equal.

6. Nuclear Fission • As WWII started scientists were trying to find a way to sustain nuclear fission in a chain reaction. • A chain reaction is a continuing series of reactions in which each produces a product that can react again.

7. Nuclear Fission • In the fission of uranium, each neutron produced has the potential to cause the fission of another atom of uranium-235. • In order for a chain reaction to occur there must be enough of a sample of the material for the neutrons to collide with other atoms.

8. Nuclear Fission • Critical Mass: the point where the chain reaction can become self-sustaining is referred to as critical mass • Supercritical mass • If the amount of fissionable material is much greater than the critical mass the chain reaction escalates out of control and an explosion results.

9. Nuclear Fission – Supercritical • All of the energy is released at once. • This is what happens when an atomic bomb explodes.

10. Nuclear Fission and Nuclear Energy • In order for nuclear energy to be useful the reaction must be controlled so that the energy can be released slowly.

11. Nuclear Fission • Nuclear power plants generate electrical energy through the controlled fission of uranium. • This is done in a nuclear reactor • A nuclear reactor is a device that is used to extract energy from radioactive fuel.

12. Nuclear Fission - Reactors

13. Nuclear Reactors and Pollution • Nuclear reactors do not produce CO2 and other pollutants. • They do produce radioactive waste that is difficult to safely dispose of. • New technologies allow much of the waste to be decayed, reducing the amount of hazardous waste produced. • There is some risk of the release of this nuclear waste into the environment.

14. Nuclear Fission: Problems with Nuclear Reactors • Nuclear energy costs more to produce than energy produced through the burning of fossil fuels. • It is more expensive than using fossil fuels

15. Nuclear Fusion • Nuclear fusion is the process of combining two or more nuclei to form a larger nucleus. • Nuclear fusion is the process that occurs in the sun and other stars to produce energy. • Nuclear Fusion…Hydrogen to Helium

16. Nuclear Fusion on the Sun

17. Nuclear Fusion • The fusion of hydrogen to produce helium produces 20x more energy than the fissionof the same amount of uranium. • It does not produce any radioactive waste. • Fusion reactions are easier to control than fission reaction.

18. Problems with Nuclear Fusion • Difficulty initiating and containing a fusion reaction has prevented its use as a practical energy source. • Nuclear fusion reactions require a large amount ofenergy to start the fusion reaction. • In order to initiate a fusion reaction on earth a temperature greater than 100million Kelvins would be required. • No material exists on earth that could contain the reaction. • A great goal for the future!!!

19. Fission vs Fusion