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

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

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

5. Mass ã Matter can be changed into Energy ã Einstein’s formula above tells us how the change occurs ã In the equation above: E = Energy m = Mass c = Speed of Light (Universal Constant) Energy Light Speed Light Speed E = mc 2

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

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

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

9. ã A classic example of a fission reaction is that of U-235: U-235 + 1 Neutron 2 Neutrons + Kr-92 + Ba-142 + Energy ã 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. Fission

10. ã 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 ã Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity

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

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

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

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

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

16. Quiz ã Mass may be converted into energy. A. True B. False

17. Quiz ã The fission process requires heavy atomic nuclei. A. True B. False

18. Quiz ã Name a nuclear reaction that occurs within the sun:

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

20. Quiz ã Explain this equation: E = mc 2