FUSION AND FISSION INTRODUCTION to FUSION AND FISSION.
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Transcript of FUSION AND FISSION INTRODUCTION to FUSION AND FISSION.
INTRODUCTION to
FUSION AND FUSION AND FISSIONFISSION
There are 1200 students in a hall. A student starts talking.
If each talking student starts 3 others to talk each second, ...
… what is the minimum time required for all students to be talking?
Warm-up
Sec. No. of talking students
0 1
1 1 + 1 3 = 4
2 4 + ____ 3 = ____
3 ____ + ____ 3 = ____
4 ____ + ____ 3 = ____
5 ____ + ____ 3 = ____
6 ____ + ____ 3 = ____
Warm-up The time required = 6 s
How to stop it How to stop it from being from being out of out of control? control? 4 16
16 16 64
64 64 256256 256 10241024 1024 4096
Ask teachers responsible for discipline to patrol around the hall.
Nuclear Nuclear ReactionsReactions
When a heavy nucleus splits upsplits up,,
When 2 light nuclei join togetherjoin together to form a heavy nucleus,
huge amount of energy is released.
E.g. atomic bomb
huge amount of energy is released.
E.g. the Sunthe Sun
Nuclear FissionNuclear Fission Fission is the process of splitting a nucleus
into two nuclei with smaller masses. Large amount of energy is releases A chain reaction is an on-going series of
fission reactions. Critical massCritical mass is the amount of fissionable
material required to continue a reaction at a constant rate
Exothermic Exothermic ReactionReaction
Nuclear fissionNuclear fission
neutron
U-235 nucleus
Ba-144 nucleus
Kr-90 nucleus
neutron
uncharged not repelled on
approaching nuclei
U23592
14456
Ba + Kr9036
+ n10
n10+ n1
0+ energy+
neutron
Nuclear fissionNuclear fission
Naturally-occurring uranium consists of 2 isotopes, U-238 (99.3%) & U-235 (0.7 %).
It is the rare isotope (U-235)(U-235) which undergoes fission.
The total mass of the fission products is found lessless than the total mass before fission takes place.
U23592
14456
Ba + Kr9036
+ n10
n10+ n1
0+ energy+
Chain reactionChain reactionWhen a uranium nucleusuranium nucleus splits, 2 or 3 neutrons are emitted.
neutronU-235
nucleus splits
If these neutrons carry on splitting other uranium nucleus...
Chain reactionChain reaction
neutron
U-235 nucleus splits
self-sustaining chain reaction
escapes
Chain reactionChain reaction
the fraction of neutrons escaping .
If a small piecesmall piece of uranium is used,
the chain will break very quickly.
If the mass of uranium is below a critical mass,
NuclearNuclear fissionfission
Neutrons may:1 - Cause another fission by colliding with a U235 nucleus
2 - Be absorbed in other material3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Each split (fission) is accompanied by a large quantity of E-N-E-R-G-Y
• Creates two smaller nuclides and free neutrons• The free neutrons potentially collide with nearby U235 nuclei• May cause the nuclide to split as well
Nuclear FUSION
DEUTERIUM
TRITIUM
HELIUM
NEUTRON
http://fusioned.gat.com
Nuclear FusionNuclear Fusion
Fusion occurs when two nuclei with low masses are combined to form one nucleus of larger mass.
Can only happen when the nuclei are moving fast enough to get “close” to each other
Temperature in stars are high enough for fusion to occur (millions of degrees Celsius)
FUSION video clip
Nuclear fusionNuclear fusion
A HUGE AMOUNTHUGE AMOUNT of energy is also released when two light nucleilight nuclei join together to form a heavy nucleus.
This process is called nuclear fusion.
Nuclear fusion
hydrogen-3 nucleus
hydrogen-2 nucleus
neutronhelium-4
He42
+H21
n10+ +energyH3
1
fusion
Nuclear fusionNuclear fusion
Since nuclei carry “+” charges, they repel each other.
For fusion to occur, the 2 hydrogen2 hydrogen nuclei must approach each other with very high very high speedspeed..
He42
+H21
n10+ +energyH3
1
hydrogen gas of high temperature (108 C)!
Nuclear fusion
Nuclear fusion occurs in the core of the SunSun, giving out heat and light. The reaction takes place continuously for billions of years.
Q1 Which of the following…
A U-235
B U-238
C Hydrogen
D Helium
Which of the following elements is used in nuclear fission?
Q2 According to Einstein’s… According to Einstein’s mass-energy equation E = mc2, what is the amount of energy produced if 1 kg of a certain element completely changes into energy?A 3 108 J
B 3 1016 J
C 6 1016 J
D 9 1016 J
Q3 In nuclear… (U)
In nuclear ___________, nuclei of uranium
are split into smaller pieces and large amount
of energy will be released. In order to
maintain the ___________ reaction, mass of
uranium used should exceed the __________
mass.
critical
fission
chain
Q4 In nuclear… (H)
In nuclear __________, nuclei of
hydrogen are joined together and
____________ nucleus is formed.helium
fusion
Every second, the sun converts Every second, the sun converts 500 million metric tons of 500 million metric tons of hydrogen to helium. Due to the hydrogen to helium. Due to the process of fusion, 5 million process of fusion, 5 million metric tons of excess material is metric tons of excess material is converted into energy in each converted into energy in each second. This means that every second. This means that every year, 157,680,000,000,000 metric year, 157,680,000,000,000 metric tons are converted into energy. tons are converted into energy.
THE SUN
Complete the Reaction
1H
4Be
1H
8O
4Be
2He
2He
1H
2He
2He
2He
6C
1H element atomic number (protons)
6C
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
U.S. Electrical Power Production by Source
Source: EIA
(2004)
Nuclear Fuel Costs
• Nuclear Fuel Costs Include– Uranium – Enrichment– Manufacturing– Waste Disposal
• Total Nuclear Fuel Cost is Only About 0.5 cents per kilowatt-hour– Uranium accounts for only about 20% of this cost or
0.1 cents per kilowatt-hour– Increasing Uranium Cost has Minimal Impact
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.