Radiation Objectives –Understand the concepts of ½ life and ½ thickness in radiation...
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Transcript of Radiation Objectives –Understand the concepts of ½ life and ½ thickness in radiation...
![Page 1: Radiation Objectives –Understand the concepts of ½ life and ½ thickness in radiation –Differentiate between fusion and fission –Describe the processes.](https://reader036.fdocuments.net/reader036/viewer/2022072011/56649e155503460f94b00262/html5/thumbnails/1.jpg)
Radiation
• Objectives
– Understand the concepts of ½ life and ½ thickness in radiation
– Differentiate between fusion and fission
– Describe the processes involved in radioactive decays (alpha, beta, and gamma)
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Elementary Particle Properties
Particle Symbol Charge Weight Weight Ratio (e-)
proton p+ +1 1.007 amu 1838 heavy
electron e- -1 0.0005 amu 1 light
neutron n0 0 1.008 amu 1840 heavy
1 Atomic Mass Unit (amu) = 1.66 x 10-24 grams
Atoms are electrically neutral with no net charge.
Ions are atoms that have been stripped of one
or more of their electrons and have a net charge.
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Isotopes• Identical Chemical Properties, Different Atomic Weight• Difference = presence of number of neutrons in the nucleus
Hydrogen = 1.0079 amu
ISOTOPE Constituents Atomic Mass Occurrence
H 1 proton 1 electron 1.0070 amu 99.985 %
Deuterium 1 proton 1 electron 2.0141 amu 0.014 %
1 neutron
Tritium 1 proton 1 electron 3.0220 amu 0.001 %
2 neutrons
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Hydrogen 11H 1 proton, 0 neutrons
Helium-4 42He 2 protons, 2 neutrons
Uranium-235 23592U 92 protons, 143 neutrons
neutron 10n
proton 11p
electron 0-1e
Isotope Designations
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Radiation
• Three types of Nuclear Radiation.
• Revealed by their deflection in a magnetic field as neutral, charged negative or charged positive.
NS
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Radioactive Particles• Alpha
Ejection of 2 protons and 2 neutrons from an
unstable nucleus. 42He =
• Beta Ejection of an electron from an unstable
nucleus
as part of the decay of a neutron. 0-1e =
• Gamma Atomic nucleus transition, yielding high
energy
photons.
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Nuclear Reactions 226
88Ra 22286Rn + 4
2He
Note that the numbers all add-up (conservation of particles).
AZX
A nucleons Total particles in nucleus 226 = 222 + 4
Z protons Number of protons 88 = 86 + 2
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Alpha Decay• Alpha = 4
2He
Parent 22688Ra Radium
Daughter 22286Rn Radon
Radiation 42He
22688Ra 222
56Rn + 42He
Most of the energy is with the lighter particle, in this case
the alpha particle.
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Beta Decay• Beta = 0
-1e
10n 1
1p + 0-1e
The decay of a neutron into a proton and electron.
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Beta Decay• Beta = 0
-1e
10n 1
1p + 0-1e
The decay of a neutron into a proton and electron.
146C 14
7N + 0-1e (Radioactive Carbon)
9038Sr 90
39Y +
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Gamma Radiation• Gamma E = h fVery high energy photons are emitted from the nucleus.
Excess radiation emitted from an excited nucleus….
8738Sr* 87
38Sr +
Excess radiation emitted as part of another process….60
27Co 6028Ni + +
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Radioactive Decay
If you start out
with a sample of
parent atoms (No),
after some time
there will be fewer
because of
radioactive decay
into the daughter
atoms.
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ShieldingWe can detect the radiation from a
radioactive source.
Say we get X counts/minute (cpm).
Geiger Counter
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ShieldingWe can shield the source with various
materials to test their usefulness in
protecting against the radiation.
Geiger Counter
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Half Thickness
Half Thickness: The thickness of a material needed to
cut the count rate by 1/2.
If a 4 inch thickness of lead, drops a count rate
from 1000 cpm to 500 cpm, the half thickness must
be 4 inches.
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Half Thickness
Half Thickness: The thickness of a material needed to
cut the count rate by 1/2.
If 12 inches of wood, drops a count rate
from 2000 cpm to 125 cpm, the half thickness must
be 3 inches.
2000 1000 500 250 125
0 3 6 9 12
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Shielding Efficiency
Cotton Fabric Wood Lead
’s are the most penetrating type of radiation.
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Nuclear Energy Generation B
indi
ng E
nerg
y/nu
cleo
n
Atomic Mass Number
Uranium
Iron
Hydrogen
Fission
Fusion