nuclear reactions: an introduction to fission & fusion farley visitors center
TRANSCRIPT
Nuclear Reactions:
AN INTRODUCTION TO
FISSION & FUSION
AN INTRODUCTION TO
FISSION & FUSION
Farley Visitors Center
Nuclear reactions deal with interactions Nuclear reactions deal with interactions between the nuclei of atomsbetween the nuclei of atoms
The focus of this presentation are the The focus of this presentation are the processes of nuclear fission and nuclear fusionprocesses of nuclear fission and nuclear fusion
Both fission and fusion processes deal with Both fission and fusion processes deal with matter and energymatter and energy
Introduction
Matter and Energy
Previous studies have taught us that “matter Previous studies have taught us that “matter and energy cannot be created nor destroyed”and energy cannot be created nor destroyed”
We now need to understand that Matter and We now need to understand that Matter and Energy are two forms of the same thingEnergy are two forms of the same thing
MassMass
Matter can be changed into EnergyMatter can be changed into Energy
Einstein’s formula above tells us how the change Einstein’s formula above tells us how the change occursoccurs
In the equation above:In the equation above:E = EnergyE = Energym = Massm = Massc = Speed of Light (Universal Constant)c = Speed of Light (Universal Constant)
EnergyEnergy LightSpeedLightSpeed
E = mc2
E = mc2
The equation may be read as follows:The equation may be read as follows:
Energy (E) is equal to Mass (m) multiplied Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squaredby the Speed of Light (c) squared
This tells us that a This tells us that a small amount of mass can small amount of mass can be converted into a very largebe converted into a very large amount of amount of energyenergy because the speed of light (c) is an because the speed of light (c) is an extremely large numberextremely large number
c = 3.0 x 10c = 3.0 x 1088 m/s m/s 300,000,000 m/s300,000,000 m/s
Fission
Fission may be defined as the process of Fission may be defined as the process of splitting an atomic nucleus into fission splitting an atomic nucleus into fission fragmentsfragments
The fission fragments are generally in the form The fission fragments are generally in the form of smaller atomic nuclei and neutronsof smaller atomic nuclei and neutrons
Sufficient neutrons will create a chain reactionSufficient neutrons will create a chain reaction
Large amounts of energy are produced by the Large amounts of energy are produced by the fission processfission process
Fission
Fissile nuclei are generally Fissile nuclei are generally heavy atoms with heavy atoms with large numbers of nucleonslarge numbers of nucleons
The nuclei of such heavy atoms are struck by The nuclei of such heavy atoms are struck by neutrons initiating the fission processneutrons initiating the fission process
Fission occurs due to electrostatic repulsion Fission occurs due to electrostatic repulsion created by large numbers of protons within the created by large numbers of protons within the nuclei of heavy atomsnuclei of heavy atoms
A classic example of a fission reaction is that of A classic example of a fission reaction is that of U-235:U-235:
U-235 + 1 Neutron U-235 + 1 Neutron
2 Neutrons + Kr-92 + Ba-142 + Energy2 Neutrons + Kr-92 + Ba-142 + Energy In this example, a stray neutron strikes an atom of U-235. In this example, a stray neutron strikes an atom of U-235.
It absorbs the neutron and becomes an unstable atom of It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.can strike other U-235 atoms to initiate their fission.
Fission
Fission Reaction
Fission
The fission process is an a natural one as a The fission process is an a natural one as a French researcher found a natural uranium French researcher found a natural uranium reactor in Gabon, West Africa; it has been reactor in Gabon, West Africa; it has been estimated to be over 2 billion years oldestimated to be over 2 billion years old
Fission produces large amounts of heat energy Fission produces large amounts of heat energy and it is this heat that is captured by nuclear and it is this heat that is captured by nuclear power plants to produce electricitypower plants to produce electricity
U.S. Electrical Power Sources
Fusion is a nuclear reaction whereby Fusion is a nuclear reaction whereby two light two light atomic nuclei fuse or combine to form a single atomic nuclei fuse or combine to form a single larger, heavier nucleuslarger, heavier nucleus
The fusion process generates tremendous The fusion process generates tremendous amounts of energy; refer back to Einstein’s amounts of energy; refer back to Einstein’s equationequation
For fusion to occur, a large amount of energy For fusion to occur, a large amount of energy is needed to overcome the electrical charges is needed to overcome the electrical charges of the nuclei and fuse them togetherof the nuclei and fuse them together
Fusion
Fusion and Energy
Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable.
The fusion of two nuclei lighter than iron or nickel generally releases energy.
The fusion of nuclei heavier than them absorbs energy.
FUSIONDEUTERIUM
TRITIUM
HELIUM
NEUTRON
http://fusioned.gat.com
Fusion
Fusion reactions do not occur naturally on our Fusion reactions do not occur naturally on our planet but are the principal type of reaction planet but are the principal type of reaction found in starsfound in stars
The large masses, densities, and high The large masses, densities, and high temperatures of stars provide the initial temperatures of stars provide the initial energies needed to fuel fusion reactionsenergies needed to fuel fusion reactions
The sun fuses hydrogen atoms to produce The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts helium, subatomic particles, and vast amounts of energyof energy
Every second, the sun converts 500 million metric tons of hydrogen to helium. Due to the process of fusion, 5 million metric tons of excess material is converted into energy in each second. This means that every year, 157,680,000,000,000 metric tons are converted into energy.
THE SUN
Cold Fusion
Efforts are being made to start and sustain a fusion reaction at lower temperatures, in other words with a lower amount of input energy
Mass and Energy are two forms of the same Mass and Energy are two forms of the same thing; neither can be created nor destroyed but thing; neither can be created nor destroyed but mass can be converted into energy (E = mcmass can be converted into energy (E = mc22))
Fission is a nuclear reaction in which a heavy Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nucleiatomic nucleus is split into lighter atomic nuclei
Fusion is a nuclear reaction in which 2 light Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, atomic nuclei are combined into a single, heavier atomic nucleusheavier atomic nucleus
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.
Review
Quiz
Which nuclear process produces large Which nuclear process produces large amounts of energy?amounts of energy?
A. FissionA. Fission
B. FusionB. Fusion
C. Both fission & fusionC. Both fission & fusion
D. Neither fission nor fusionD. Neither fission nor fusion
Quiz
Fission is the process that _________ atomic Fission is the process that _________ atomic nuclei.nuclei.
A. CombinesA. Combines
B. Burns upB. Burns up
C. StoresC. Stores
D. SplitsD. Splits
Quiz
Mass may be converted into energy.Mass may be converted into energy.
A. TrueA. True
B. FalseB. False
Quiz
The fission process requires heavy The fission process requires heavy atomic nuclei.atomic nuclei.
A. TrueA. True
B. FalseB. False
Quiz
Name a nuclear reaction that occurs Name a nuclear reaction that occurs within the sun:within the sun:
Quiz
Fission is a natural process that occurs Fission is a natural process that occurs on the on the planet Earth.planet Earth.
A. TrueA. True
B. FalseB. False
Quiz
Explain this equation:Explain this equation:
E = mcE = mc22