IE 419
Work Design:
Productivity and Safety
Dr. Andris Freivalds
Class #38
IE 419
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IE 419
Work Design:
Productivity and Safety
Dr. Andris Freivalds
Class #38
IE 419
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Radiation (Ch. 27)
• Electromagnetic radiation – energy emitted
in:
– Small pulses or quanta or
– Wave-like patterns
• Wide range of problems
– Nuclear power (Three-mile Island, Chernobyl)
– Medical X-rays
– Environmental (radon)
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Frequency Spectrum
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Wavelength = velocity/frequency
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Radiation Terminology
• Ionizing – radiation causing ions (bad!)
• Nonionizing – not enough energy for ions
• Radioactivity – substance decomposing into
smaller particles
– Alpha particles (α) = He++, large, ↓ penetration
– Neutron = ½ α mass, but no charge
– Beta particles (β) = electrons, ↑ penetration
– X-rays, γ-rays = massless energy, ↑↑penetration
• Half life – length of time for decomposition
process to consume ½ the original mass
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Radiation Units
• Curie = amount of radioactive substance
producing 3.7x1010 disintegrations/sec
• Roentgen (R) = energy absorption in dry air
• Rad (Roentgen absorbed dose) = energy
absorption per unit mass of tissue
• Rem (Roentgen equivalent man) = Dose of
ionizing radiation & biological effect of 1Rad
• RBE (Relative Biological Effectiveness)
• Rem = Rad x RBE
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Comparison of Radiation
Radiation
Roentgen
Rad
X-ray
Energy
Level
(MeV)
8 keV-2
1
1
γ-ray
0-3
1
1
Beta
0-3.5
-
1
Alpha
4-8
-
20
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Absorption Ratio
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Comparison of Radiation
• 1 Rem = 1 R = 1 Rad of X-rays
• 1 Rem = 0.1 Rad of Neutrons → RBE=10
• 1 Rem = 0.05 Rad of α → RBE = 20
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Effects of Ionizing Radiation
• Blood
– White cells
– Red cells
•
•
•
•
Bone marrow
Eyes
Skin
Reproduction
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Radiation Factors
• Time
• Intensity
• Type of particles
Rem
0-25
Effect
None
25-100 Blood
100-200 Nausea
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300
Vomiting
450
50% death
600
100% death
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OSHA Limits (1910.1096)
Body Part
Rems per calendar quarter
Whole body
1.25
Hands, feet
18.75
Skin
7.5
Occupational exposure < 5(N-18) N=age
Under 18, only 10% of above limits
Natural exposure = 0.1 rem/yr
Medical exposure = 0.1 rem/yr
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95% of industrial workers < 1 rem/yr
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Nuclear Radiation - Hiroshima
•
•
•
•
Deaths = 70,000 (Nagasaki = 40,000)
Heat = 6,000 °C
Shock = over pressures 8-10 psi
Radiation = intense
Distance (km)
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Effects
% Deaths
0-0.5
Fever, severe bleeding
98
0.5-1
Fever, bleeding, vomiting
90
1-2
Vomiting, hair loss, colds
35
2-4
Hair loss, ↓white cells
?
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Sources of Ionizing Radiation
•
•
•
•
•
•
X-ray equipment
Radio isotopes
β sources
Thorium
High voltage devices
Nuclear radiation
– Uranium mill tailings
– Nuclear waste disposal
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Precautionary Measures
• Restricted
access
• Shielding
• Monitoring
• Protective
clothing
• No food
• Cleanup
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Shielding (mm)
Particle
Air
H2O Alum Lead
α
2.8
0.4
0.4
0.4
β
13m
15
5
1.4
γ
-
210
69
7
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Nonionizing Radiation
• Ultraviolet
– Natural
– Industrial
• Visible
– High intensity lamps
– Sun
– Welding
• Microwaves
– Absorption, ↑heat
– Oven, dryers
– Radar
– OSHA standards
• Power < 10mW/cm2
• Energy < 1mWhr/cm2
• Infrared
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Effect on Human Eye
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Types of Radiation and the Eye
X-ray, γ-ray
Near IR light
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UV light
Far IR light
Visible light
μ-waves
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Precautionary
Measures
• Shields, screening
• Warning signs
• Avoid metal
• Care on direction
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