Transcript Nuclear Chemistry

Nuclear Chemistry
Nuclear reactions
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involve unstable nuclei becoming more
stable by emitting energy
unaffected by temperature, pressure, or
catalyst
Elements above atomic number 83 are
radioactive
Types of radiation
Alpha (α)
Beta (β)
4
2
0
1
Gamma (γ)
He low penetrating power
e
moderate penetrating power
high penetrating power
Transmutation- change in no. of
protons, creating a new element
Particle emitted Mass number
Atomic number
alpha (α) 4 He -4
-2
beta (β)
2
0
1
e
same
+1
positron
0
1
e
same
-1
neutron
1
0
n
-1
same
proton
1
1
p
-1
-1
same
-1
K-capture
(add e-)
Electric charge and mass numbers
are conserved
14
7
N  He  F
4
2
18
9
An alpha particle is captured
U
239
92
Np 
239
93
A beta particle is emitted
0
1
e
214
83
Bi  He  ?
4
2
210
81
Tl
An alpha particle is emitted
66
29
Cu 
Zn  ?
66
30
0
1
Beta emission- a neutron turns into a proton
e
Nuclear stability
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More stable nuclei have
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Low atomic number
Ratio of neutrons to protons is 1:1
Nuclear stability
Nuclei in
region C will
emit positrons
or capture
electrons
Nuclei in region A
will emit
neutrons or beta
particles
Nuclei in region B will emit beta particles
Half life
The time it takes for half of the nuclei to
decay.
 Carbon-14 emits beta radiation and
decays with a half-life of 5730 years. If
you start with 2.00 x 10-12 grams of
carbon-14, how many grams remain after
3 half lives?
2.00 x 10-12 g x ½ x ½ x ½ = .250 x 10-12g
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A 0.456 mg sample of hydrogen-3 was
collected. After 24.52 years, 0.114 mg of
the sample remains. What is the half-life
of hydrogen-3?
0.114 = 1 = 1 2
0.456 4 2
Two half lives!
Nuclear binding energy
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The energy needed to break apart the
nucleus.
E = mc2
Mass of one proton = 1.0078252 amu
Mass of one neutron = 1.008665 amu
Mass defect = expected mass – actual
mass
Binding energy for
16O
8(1.0078252) + 8(1.008665) = 16.1319232
Actual mass
= 15.9949150
mass defect
= 0.1370082
0.1370082amu x 1.66 x 10-27kg = 2.27 x 10-28 kg
1 amu
(2.27 x 10-28 kg) (3.0 x 10 m/s)2 = 2.04 x 10-11 J
Binding energy per nucleon
2.04 x 10-11 J
16 nucleons = 1.28 x 10-12 J/nucleon
The greater the binding energy per nucleon,
the greater the stability of the nucleus.
Fission- breaking apart of a nucleus
Can cause a chain reaction
Nuclear energy
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Control rods slow or stop the chain
reaction by absorbing neutrons (made of
boron or cadmium)
neutron moderator reduces the speed
of neutrons (made of graphite or water)
235
239
Use 92 U or 94 Pu as fuel
Coolant (water) absorbs and transfers the
heat energy.
Containment vessels keep radioactive
material from escaping.
Nuclear reactor
Cooling
water
Image Source Page: http://www.islandbreath.org/2008Year/07-energy/0807-20NStilloNukes.html
High-level radioactive waste
management
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After 5% of a nuclear fuel rod has reacted
that rod is no longer able to be used as fuel.
Scientists are experimenting on how to
recycle these rods to use as fuel.
A typical nuclear reactor produces about 20
metric tons of spent nuclear fuel per year.
Over the past four decades, the entire
industry has produced about 65,200 metric
tons of used nuclear fuel.
Spent fuel rods stored on site
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We have 104 reactors in 31 states providing
one-fifth of the nation's electricity generation
overall.
The nation has already accumulated 60,000
metric tons of spent nuclear waste, and the
material is going to have to be isolated from the
environment for hundreds and thousands of
years .
Yucca Mountain was supposed to be where the
highly toxic material was sent. But Obama's
energy budget leaves it out.
By Gail Russell Chaddock Staff writer of The Christian Science Monitor
Nuclear power plants in the U.S.
March 12, 2011
Fukushima, Japan
Fusion
Fusion Power
Benefits
 abundant fuel (deuterium)
 No greenhouse gases emitted
Drawbacks
 Extremely high temperatures required
150 000 000° Celsius!!!
Challenging to contain high-energy plasma
ITER - International Thermonuclear
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Experimental Reactor
3.9 mile long particle
accelerator at Fermilab
Outside Chicago
National Institute of Nuclear Physics and
Particle Physics in France
Nuclear medicine
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Imaging
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Positron Emission Tomography (PET scans)
Magnetic Resonance Imaging (MRI)
Treatment
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injecting radioisotopes (tracers)
radiation kills rapidly growing cells