1. Atomic Energy 3U Physics

2. Mass-Energy Equivalence All matter is a form of stored energy.

3. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to:

4. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to: E = mc 2

5. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to: E = mc 2 c = 3.0 x 10 8 m/s

6. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

7. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

8. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

9. The Mass Defect More practically, we look at the energy equivalent of the mass defect.

10. The Mass Defect More practically, we look at the energy equivalent of the mass defect.

11. The Mass Defect Consider a Carbon 12 nucleus:

12. The Mass Defect Consider a Carbon 12 nucleus: 6 protons, 1.007276 amu each + 6 neutrons, 1.008665 amu each = 12.095646 amu

13. The Mass Defect Consider a Carbon 12 nucleus: 6 protons, 1.007276 amu each + 6 neutrons, 1.008665 amu each = 12.095646 amu Actual mass of Carbon 12 nucleus: = 11.996709 amu

14. The Mass Defect The 0.098937 amu mass defect is the binding energy of the nucleus. E = mc 2 E ≈ (0.098937)(1.66 x 10 -27 kg)(3.0 x 10 8 m/s) 2 E ≈ 1.5 x 10 -11 J

15. The Mass Defect Energy stored in the nucleus can be released in nuclear reactions such as radioactive decay:

16. The Mass Defect Energy stored in the nucleus can be released in nuclear reactions such as radioactive decay: The energy is released in the form of kinetic energy (of the resulting particles).

17. Nuclear Fission However, in a nuclear reactor, we don’t sit around waiting for a radioactive decay.

18. Nuclear Fission However, in a nuclear reactor, we don’t sit around waiting for a radioactive decay. We trigger them by bombarding nuclei with neutrons:

19. Nuclear Fission Notice that the reaction produces more neutrons, which can then bombard more nuclei in a chain reaction:

20. Nuclear Fusion Energy can also be obtained by fusing together light elements, e.g. hydrogen into helium:

21. Nuclear Fusion However, fusing nuclei requires overcoming the electrostatic repulsion between the nuclei.

22. Nuclear Fusion However, fusing nuclei requires overcoming the electrostatic repulsion between the nuclei. This requires enormous temperatures and pressures such as those produced in the core of the Sun.

23. Nuclear Power The ejected neutron has too much energy to start another nuclear reaction on its own…

24. CANDU Reactor Fuel rods are surrounded by “heavy water” Deuterium: istotope of hydrogen with one neutron Makes water 11% more dense Heavy water heats up; free neutrons slow down Chain reaction continues E K of neutron becomes E th of water Steam turns turbine, generates power

25. CANDU Reactor http://www.youtube.com/watch? v=jNOzh4Kwgpwhttp://www.youtube.com/watch? v=jNOzh4Kwgpw Is it environmentally friendly?

26. Radioactive Waste Unstable atoms are called “radioactive” They have the ability to decay into another substance and emit radiation The rate of decay is predictable

27. Half-Life The average length of time it takes a radioactive material to decay to half its original mass Ex. If a 10 kg sample of radioactive material has a half- life of 5 years, how much will be left after 5 years? 10 years?

28. Types of Decay Type of Decay Radiation Emitted Particle Penetrating Power alphaalpha particle helium nucleus skin or paper (slow moving) beta negative beta particleelectrona few sheets of aluminum foil gammagamma raysphotona few centimetres of lead