Transcript FUSION AND FISSION

Wilhelm Rontgen •
1895 German Scientist
Playing with a Crookes
tube
• Sitting in a dark lab,
tube covered with black
paper, held up a book
to the tube . . .
• Image of key appeared
on paper painted with
Barium across the
room
• The key had been a
bookmark
Rontgen’s
Lab
•
•
•
•
Rontgen thought he was hallucinating
Told no one
Shut himself in the dark lab for seven weeks
Held up a metal plug and saw … his BONES
“Black Magic”
• Took a picture of wife’s
hand (afraid, she never
went back to the lab)
• Showed that these
images were real
• Rontgen began to
document and
rationalize his work w/
physics knowledge of
the time
The Nobel Prize in Physics
1901
Wilhelm Conrad Röntgen
Namesake Element:
Rontegenium
• Atomic #
111
• Atomic Weight 272
Discovered in 1994,
Germany
Highly Radioactive, but
this element does not
emit x-rays
FUSION AND FISSION
First, a little bit about energy
Forms of Energy
• The five main forms of
energy are:
– Heat
– Chemical
– Electromagnetic
– Nuclear
– Mechanical
Heat Energy
• The internal motion of the atoms is
called heat energy, because moving
particles produce heat.
• Heat energy can be produced by
friction.
• Heat energy causes changes in
temperature and phase of any form of
matter.
Chemical Energy
• Making and Breaking bonds
• Chemical Energy is required to
bond atoms together.
• And when bonds are broken,
energy is released.
Chemical Energy
• Fuel and food
are forms of
stored
chemical
energy.
Electromagnetic Energy
• Power lines carry electromagnetic energy
into your home in the form of electricity.
Electromagnetic Energy
• Light is a form of
electromagnetic energy.
• Each color of light (Roy G
Bv) represents a different
amount of electromagnetic
energy.
• Electromagnetic Energy is
also carried by X-rays, radio
waves, and laser light.
Mechanical
• Kinetic /Potential
Nuclear Energy
• The nucleus of an
atom is the
source of nuclear
energy.
• Energy holding
nucleus
together
Nuclear Energy
• Nuclear Energy is the most
concentrated form of energy!
• 2 major reactions :Fission & Fusion
Fusion
• Nuclear fusion is the process by which
multiple nuclei join together to form a
heavier nucleus.
• The fusion of two nuclei lighter than iron or
nickel generally releases energy.
• The fusion of nuclei heavier than them
absorbs energy.
Result: gain or loss of energy
Nuclear Fusion
Nuclear Fusion Example
The sun’s energy
is produced from
a nuclear fusion
reaction in which
hydrogen nuclei
fuse to form
helium nuclei.
NUCLEAR FISSION
• 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
More about fission
• 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
Nuclear Fission
Neutron induced in U235
Neutrons may:
1 - Cause another fission by colliding with a U235 nucleus
• Creates two smaller nuclides and free neutrons
• The free neutrons potentially collide with nearby U235 nuclei
• May cause the nuclide to split as well
Each split (fission) is
accompanied by a large
quantity of E-N-E-R-G-Y
2 - Be absorbed in other material
3 - Lost in the system
If sufficient neutrons are present, we may achieve a chain reaction
Fission Example
Where does the energy come
from?
We often say that matter cannot be
created nor destroyed. However . . .
Einstein taught us that Energy and matter
are different forms of the same thing!
E=
2
mc
Mass Defect
• The nucleus
– is composed of protons and neutrons
– the actual mass is less than the mass of
the separate particles.
• The "missing" mass is in the form of
energy holding the nucleus together.
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Uranium-238
The nuclear mass
of uranium-238 is
238.0003 amu
nucleons
(protons & neutrons)
238U
92
atomic number
(protons)
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A proton is 1.00728 amu
A neutron is 1.00867 amu
What mass is expected
for the nucleus of 238U?
Uranium-238
92 protons
(92)(1.00728) = 92.6698
146 neutrons (146)(1.00867) = 147.2658
predicted mass
= 239.9356
actual mass
= 238.0003
mass defect
= 1.9353 amu
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Masses of Atoms
The nuclear mass of 238U is 238.0003
Why does the Handbook of Chemistry and Physics
list the mass of uranium238 as 238.0508?
(92)(0.0005488) + 238.0003 = 238.0508
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Binding Energy
• The mass defect indicates the total
energy involved in holding the nucleus
together.
• To determine the stability of the
nucleus, the binding energy per
nuclear particle is a better measure.
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Binding Energy of 238U
actual mass
238.0003
predicted mass
239.9356
1.9353 amu
DE = Dmc2 = 931.5 MeV/amu
What is the binding energy per nucleon of 238U?
Binding Energy of 238U
Binding energy
per nucleon
(1.9353 amu)(931.5 MeV/amu)
=
238 nucleons
=
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7.57 MeV
Binding Energy
62Ni
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The nuclei with the greatest
binding energy per nucleon
are the most stable.
E=
2
mc
• Matter can be changed into energy
• In the equation above:
– E = energy
– m = mass
– c = speed of light
• Small amount of mass becomes a
HUGE amount of energy
Chemical
Reactions
• Involve changes in
electrons
– Acids & Bases,
combustion, displacement
• The same atoms appear
on both sides of the
reaction.
• Follows Dalton’s Law of
Conservation of Mass
• Small amount of energy
generated
– Burning fossil fuels
Nuclear
Reactions
• Involve changes in the
nucleus
– Nuclear fusion, nuclear
fission
• New atoms appear as
products of the reaction.
• Breaks Dalton’s Law of
Conservation of Mass
• Large amount of energy
generated
– 1 million times more than
chemical reactions
– Nuclear fusion on the sun
– Nuclear fission for reactors
Decay vs. Nuclear Reactions
• Alpha, beta, and gamma • Nuclear reactions involve
decay occur as ONE
more than just getting rid of
atom tries to increase
a few protons or neutrons.
it’s stability by getting rid
The new atoms produced
of a few neutrons, or
are VERY different
protons & neutrons.
elements than the reactant.
• The product is an alpha, • Nuclear reactions must be
beta, or gamma particle
started, so there are 2
and ONE new atom.
things on the left hand side.
There is only ONE thing
– Nuclear fission: makes 2
on the left hand side.
or more much smaller
atoms
– Nuclear fusion: makes 1
much larger atom
Nuclear Fission
Alpha Decay
What are the differences between the 2 above
nuclear equations??
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
Quiz
• Which nuclear process produces large
amounts of energy?
A. Fission
B. Fusion
C. Both fission & fusion
D. Neither fission nor fusion
Quiz
• Fission is the process that _________
atomic nuclei.
A. Combines
B. Burns up
C. Stores
D. Splits
Quiz
• Mass may be converted into energy.
A. True
B. False
Quiz
• The fission process requires heavy
atomic nuclei.
A. True
B. False
Quiz
• Name a nuclear reaction that occurs
within the sun:
Bonus
• Explain this equation:
E = mc2