Transcript Nuclear Fission and Fusion

Nuclear Fission and Fusion
Nuclear Reactions
• Nuclear reactions deal with interactions
between the nuclei of atoms
• Both fission and fusion processes deal with
matter and energy
• Matter and energy cannot be created nor
destroyed (Law of Conservation of Energy)
• Matter and energy are two forms of the same
thing
E = mc2
• Matter can be changed into Energy
• Einstein’s formula above tells us how change
occurs
• In the equation:
E = Energy
m = Mass
c = Speed of Light (Universal Constant)
E = mc2
• The equation may be read:
•
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
Parent and daughter elements
• Parent – radioactive
element before nuclear
decay
• Daughter element – new
element created as a
result of nuclear decay
• Half-life – time needed for
½ of parent element to
change into daughter
product
Nuclear Fission
• Fission is Exothermic
(gives off heat)
• 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
Fission
• Nuclei of heavy atoms are struck by neutrons,
initiating the fission process
Nuclear fission:
A large nucleus splits into several
small nuclei when impacted by a
neutron; energy is released in this
process
Nuclear Fusion and the Sun
• Proton-proton chain reaction
• Hydrogen nuclei (protons) fuse together to
create a helium isotope
• Helium isotopes fuse to make beryllium which
breaks down
• Two protons are released and it starts again.
Nuclear fusion:
Several small nuclei
fuse together and
release energy.
Nuclear Fusion
In nuclear fusion, two nuclei with low mass numbers
combine to produce a single nucleus with a higher mass
number.
2
3
H
H
+
1
1
4
1
Energy
He
n
+
+
2
0
Nuclear Fusion
DEUTERIUM
NEUTRON
HELIUM
TRITIUM
Nuclear Fusion
.993 kg Helium
1kg Hydrogen
Nuclear Energy for good or ill
Uses for radioactive isotopes
• Radiocarbon dating
Uses for radioactive isotopes
• Establishing age of earth and solar system
Uses for radioactive isotopes
• Plate tectonics
Uses for radioactive isotopes
• Medical diagnostics and treatment
Uses for radioactive isotopes
• Energy
References
• www.southerncompany.com/learningpower/pdf/Introduction%20to%20Fis
sion%20and%20Fusion.ppt
• www.worldofteaching.com/powerpoints/physics/Fission%20and%20Fusio
n.ppt
• education.jlab.org/jsat/powerpoint/fusion_and_fission.ppt
• nuclear.inl.gov/teachers-workshop/2007/d/danel_fission_and_fusion.ppt
• courses.washington.edu/twsteach/ESS/302/302433%20PP/ESS302NumDat
ingpt1.ppt
• www.genestn.org/ppts/GENES-1.PPT
• www.lsa.umich.edu/UMICH/physics/Home/Seminars%20and%20Colloquia
/Saturday%20Morning%20Physics/.../311.ppt
• www.worldofteaching.com/powerpoints/physics/Radioactive%20Decay.p
pt
• en.wikipedia.org/wiki/nuclear
A review of atomic structure
Neutral neutrons
-
Nucleus
-
-
  

 

-
-
Positive protons
Negative electrons
• Alpha decay: the nucleus of the radioactive isotope
emits and alpha () particle, comprising of 2 Alpha
Decay: neutrons and 2 protons. The atomic number of
the isotope decreases by 2, while the mass number
decreases by 4. 234U decays to 230Th by alpha decay.
• Beta Emission (Decay): a neutron emits a beta
() particle (similar to an electron) and is
transformed into a proton. The atomic
number of the atom has increased by one
while the mass number remains unchanged.
The decay of 14C to 14N occurs via  emission.
The Fusion Process
2
1H
3
1H
The Fusion Process
2
1H
3
1H
The Fusion Process
2
1H
3
1H
The Fusion Process
The Fusion Process
The Fusion Process
The Fusion Process
1
0
4
2 He
n
The Fusion Process
1
0
4
2 He
n
A Chain Reaction caused by Fission
The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus.
1
0
n
235
92 U
The Fission Process
A neutron travels at high speed towards a uranium-235
nucleus.
1
0
n
235
92 U
The Fission Process
The neutron strikes the nucleus which then captures
the neutron.
1
0
n
235
92 U
The Fission Process
The nucleus changes from being uranium-235 to
uranium-236 as it has captured a neutron.
236
92 U
The Fission Process
The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.
The Fission Process
The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.
The Fission Process
The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.
The Fission Process
It then splits into 2 fission fragments and releases
neutrons.
1
0
n
1
0
n
1
0
n
141
56 Ba
92
36 Kr
• Electron ()- Capture: a proton captures an
electron and is transformed into a neuton;
emits a gamma () particle. The atomic
number of the atom has decreased by one
while the mass number remains unchanged.
The decay of 40K to 40Ar occurs via capture.