Health, Safety and Environment . Radiation Basics 101 Atomic Structure.
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Transcript of Health, Safety and Environment . Radiation Basics 101 Atomic Structure.
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Health, Safety and Environmentwww.hse.ubc.ca
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Radiation Basics 101
Atomic Structure
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Nuclear Formula
A 29-38 X SulphurZ 16
A = Mass Number (P+N)
Z = Atomic Number (P)
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Hydrogen - +
Deuterium - +
Tritium - +
XA
ZH
11
H1
2
H1
3
_
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Nuclear Stability• Stability related to the ratio of protons to
neutrons:Name: Protons / Neutrons Stability
Hydrogen 1/0
Deuterium 1/1
Tritium 1/2
Carbon-12 6/6
Carbon-13 6/7
Caron-14 6/8
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Radioactivity
Spontaneous nuclear transformationsthat result in the formation of atoms
of a different element.During the decay process
energy and/or particles are emittedthat are capable of ionizing matter
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Radioactive Decay• Unstable isotopes undergo a spontaneous
decay of the nucleus which improves proton to neutron ratio = more stable
• Particle decay:
• Alpha (α++)
• Beta (β-)
• Positron (β+)
• Electron Capture
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Alpha Decay
• Nuclear Fragment ~ Helium nucleus
• 2 Protons and 2 Neutrons
A A-4
X Y + ++
Z Z-2
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Alpha Decay
• External Exposure:Not significant hazard
• Internal Exposure:Very hazardous- highly ionizing
e.g. Polonium 210
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AlexanderLitvinenko
Polonium 210poisoning
Ingested 2GBq(50 mCi ~10ug)
~200x med. lethal dose
(Click on photo for story)
(November 2006)
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238 Pu Uranium 94 234 U + ++
92
Alpha Decay
Plutonium
e.g. Plutonium 238
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Click on photo for a video on alpha decay
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Beta Decay
• Negative Electron• Very Small Mass
A A
X Y + ß-
Z Z+1
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32 P -15 32 S 16 14 C - 6 14 N 7
1.71 MeV
0.156 MeV
Max. Energy
eg. Cl-36
Beta Decay
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Beta Decay• A.K.A:
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Click on photo for a video on beta decay
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Beta Decay Internal Exposure:
Can result in high internal exposure depending on isotope and activity
External Exposure: Can give high dose to skin : erythemaCan damage eyesSecondary radiations can be penetrating
Bremsstrahlung
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Bremsstrahlung
Produces X-rays
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Dental X-ray Unit
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Inside a Dental X-Ray Tube
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Positron Decay
Positive ElectronSame mass as negative electronAnnihilation radiation 511 keV
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Positron DecayA A
X Y + ß+
Z Z-1
22
Na ß+ 22
11 Ne 10
ßß--511 keV511 keV
*
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Positron Decay
• Positrons are not hazardous
– Immediately disappear upon emission. The secondary x-ray ‘annihilation radiations’ are hazardous.
•Internal Exposure:–Can result in high internal dose.
•External Exposure: –Can give equally high dose to skin and deep body core.
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PET Scan
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Electron Capture
Electron falls into nucleus + proton=Neutron
Releases daughter related gamma radiation
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Photons – Ionizing Radiation
• No Mass• No Charge
• Gamma- originate from within nucleus
• X-ray- originate from outside nucleus
(Bremsstrahlung)
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Photons•Internal and External Exposure:Internal and External Exposure:
•Can give equally high dose to skin and Can give equally high dose to skin and
deep body core.deep body core.
•Highly PenetratingHighly Penetrating•function of photon energyfunction of photon energy•Shielding efficacy is mass dependentShielding efficacy is mass dependent
eg. Cs-137
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• Temperature drop60o C - 37o C280 joules
absorbed energy
X-rays• LD/50/60
– 280 joules absorbed energy
COFFEE
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Click on photo for a video on gamma rays
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Linear Energy Transfer
Air Tissue
β
* * * * * * * * *
* * * * * * * * ** * * * * * *
********
* * * * * * *
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Ionizing Radiation:
Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions.
Examples include alpha particles, beta particles, gamma rays or x rays, and cosmic rays.
The minimum energy of ionizing radiation is a few electron volts (eV).
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1010 1024 10-16
108 1022 10-14
106 1020 10-12
104 1018 10-10
102 1016 10-8
10 1014 10-6
10-2 1012 10-4
10-4 1010 10-2
10-6 108 1010-8 106 102
10-10 104 104
10-12 102 106
Energy (eV) Frequency (Hz)Wavelength (m)
12.4 eV
IR
UVVIS
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Penetration
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-Radioisotope produced by absorption of a neutron
-The resulting radioisotope is unstable and may emit a proton, alpha particle,beta particle, gamma ray or a combination
Mo-99* Tc-99m*
T1/2 = 66h T1/2 = 6h
MDS-Nordion
Neutron Activation
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1 n0
+ U-235 U-236*
fission
heat
Fissionfragments
neutrons
Radiopharmaceuticals
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Questions?• An unstable isotope has a shortage of
neutrons (too many protons), what type of particles might be emitted?– Alpha, positron
• For the same isotope, what kind of shielding would be most useful?– Alpha – anything thin– Positron – lead due to production of gamma
radiation
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Questions?• An unstable isotope has a shortage of
protons (too many neutrons), what type of particles might be emitted?– Beta particle
• For the same isotope, what kind of shielding would be most useful?– Beta particle = plexiglass
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So…Something to think about…• Current debates:
– Use of UV light to sterilize water?– Use of ionizing radiation to kill pathogens on
food?
• What do you think?