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Nuclear Reactions:

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Nuclear Reactions:

AN INTRODUCTION TO FISSION & FUSION

Farley Visitors Center

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

- 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

- 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

- 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

- 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

- 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

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.

- 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

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

- 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

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

- Which nuclear process produces large amounts of energy?
A. Fission

B. Fusion

C. Both fission & fusion

D. Neither fission nor fusion

- Fission is the process that _________ atomic nuclei.
A. Combines

B. Burns up

C. Stores

D. Splits

- Mass may be converted into energy.
A. True

B. False

- The fission process requires heavy atomic nuclei.
A. True

B. False

- Name a nuclear reaction that occurs within the sun:

- Fission is a natural process that occurs on the planet Earth.
A. True

B. False

- Explain this equation:
E = mc2