Transcript Rad
IE 419 Work Design: Productivity and Safety Dr. Andris Freivalds Class #38 IE 419 1 IE 419 Work Design: Productivity and Safety Dr. Andris Freivalds Class #38 IE 419 2 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) IE 419 3 Frequency Spectrum IE 419 Wavelength = velocity/frequency 4 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 IE 419 5 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 IE 419 6 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 IE 419 Absorption Ratio 7 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 IE 419 8 Effects of Ionizing Radiation • Blood – White cells – Red cells • • • • Bone marrow Eyes Skin Reproduction IE 419 9 Radiation Factors • Time • Intensity • Type of particles Rem 0-25 Effect None 25-100 Blood 100-200 Nausea IE 419 300 Vomiting 450 50% death 600 100% death 10 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 IE 419 95% of industrial workers < 1 rem/yr 11 Nuclear Radiation - Hiroshima • • • • Deaths = 70,000 (Nagasaki = 40,000) Heat = 6,000 °C Shock = over pressures 8-10 psi Radiation = intense Distance (km) IE 419 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 ? 12 Sources of Ionizing Radiation • • • • • • X-ray equipment Radio isotopes β sources Thorium High voltage devices Nuclear radiation – Uranium mill tailings – Nuclear waste disposal IE 419 13 Precautionary Measures • Restricted access • Shielding • Monitoring • Protective clothing • No food • Cleanup IE 419 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 14 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 IE 419 15 Effect on Human Eye IE 419 16 Types of Radiation and the Eye X-ray, γ-ray Near IR light IE 419 UV light Far IR light Visible light μ-waves 17 Precautionary Measures • Shields, screening • Warning signs • Avoid metal • Care on direction IE 419 18