Nuclear Reactions:

1. Nuclear Reactions: AN INTRODUCTION TO FISSION & FUSION Farley Visitors Center

2. Introduction • Nuclear reactions deal with interactions between the nuclei of atoms • The focus of this presentation are the processes of nuclear fission and nuclear fusion • Both fission and fusion processes deal with matter and energy

3. Matter and Energy • Previous studies have taught us that “matter and energy cannot be created nor destroyed” • We now need to understand that Matter and Energy are two forms of the same thing

4. E = mc2 • Matter can be changed into Energy • Einstein’s formula above tells us how the change occurs • In the equation above: E = Energy m = Mass c = Speed of Light (Universal Constant) Light Speed Energy Mass

5. E = mc2 • The equation may be read as follows: Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squared • This tells us that a small amount of mass can be converted into a very largeamount of energy because the speed of light (c) is an extremely large number

6. Fission • Fission may be defined as the process of splitting an atomic nucleus into fission fragments • The fission fragments are generally in the form of smaller atomic nuclei and neutrons • Large amounts of energy are produced by the fission process

7. Fission • Fissile nuclei are generally heavy atoms with large numbers of nucleons • The nuclei of such heavy atoms are struck by neutrons initiating the fission process • Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms

8. Fission • A classic example of a fission reaction is that of U-235: U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + Energy • In this example, a stray neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.

9. Fission • The fission process is an a natural one as a French researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to be over 2 billion years old • Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity

10. Fusion • Fusion is a nuclear reaction whereby two light atomic nuclei fuse or combine to form a single larger, heavier nucleus • The fusion process generates tremendous amounts of energy; refer back to Einstein’s equation • For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together

11. Fusion • Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars • The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions • The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy

12. Review • Mass and Energy are two forms of the same thing; neither can be created nor destroyed but mass can be converted into energy (E = mc2) • Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei • Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus

13. Quiz • Which nuclear process produces large amounts of energy? A. Fission B. Fusion C. Both fission & fusion D. Neither fission nor fusion

14. Quiz • Fission is the process that _________ atomic nuclei. A. Combines B. Burns up C. Stores D. Splits

15. Quiz • Mass may be converted into energy. A. True B. False

16. Quiz • The fission process requires heavy atomic nuclei. A. True B. False

17. Quiz • Name a nuclear reaction that occurs within the sun:

18. Quiz • Fission is a natural process that occurs on the planet Earth. A. True B. False

19. Quiz • Explain this equation: E = mc2