Transcript Fusion & Fission PPT

Nuclear Fission & Fusion
History:
Hahn & Strassman (1939)
•Bombarded Uranium-235 samples with neutrons
expecting the Uranium-235 to capture neutrons
•Instead, the products showed different chemical
properties that they could not explain
Meitner & Frisch
•Explained Hahn & Strassman results.
•Instead of heavier Uranium, it had split
into smaller elements = Nuclear Fission
Mass Defect
• Difference between the mass of an atom
and the mass of its individual particles.
4.00260 amu
E =
2
mc
4.03298 amu
E: energy (J)
m: mass defect (kg)
c: speed of light
(3.00×108 m/s)
Nuclear Fission – splitting of
heavier nuclei into lighter
nuclei.
235
92
U
1
+
0
n
137
56
Ba
84
+
36
Xe
1 + energy
+15 0
n
Nuclear Chain Reactions:
•Nuclear fission releases more neutrons which trigger
more fission reactions
•The number of ________
neutrons released determines the
success of a chain reaction
Nuclear Power
Nuclear Fusion
- Energy released when
two light nuclei combine or fuse
1
1
H
1
+
1
H
2
1
H
+
0
1
e
+ energy
•However, a large amount of energy is required
to start a fusion reaction:
repulsion forces
o Need this energy to overcome ________
of protons.
o Extremely high temperatures can provide start-up
energy.
**More energy in fusing hydrogen that fission of uranium
Nuclear Fusion
Stars energy is produced
through fusion reactions
Fusion occurs until Fe is
produced because less
energy is released than
required to fuse Fe nuclei =
Star ____
burns ____
out
_____
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