1. AN INTRODUCTION TO FISSION & FUSION
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)
Energy
Mass
Light
Speed

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 large amount 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 Neutron
2 Neutrons + Kr-92 + Ba Energy
In this example, a stray neutron strikes an atom of U 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. Nuclear Fission Neutron induced in U235 Fission is Exothermic
The sum of the masses of
the resulting nuclei is less
than the original mass (about 0.1% less)
The “missing mass” is converted to energy according to E=mc2

11. Neutrons may:
1 - Cause another fission by colliding with a U235 nucleus
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Creates two smaller nuclides and free neutrons
The free neutrons potentially collide with nearby U235 nuclei
May cause the nuclide to split as well
Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y

12. 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

13. 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

14. 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

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

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

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

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

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

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

21. Quiz
Explain this equation:
E = mc2

22. Review Nuclear fission:
A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this process
Nuclear fusion:
Several small nuclei fuse together and release energy.

23. Draw a Double Bubble Map of Fusion and Fission
Differences Similarities Differences