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الرحيم ّ الرمحن ّ بسم هللا Course : Health Safety & Radiation Protection (RAD453) Chapter 3: Sources of Radiation Omrane KADRI, Ph.D. [email protected] Office 2021 1 Outline 1) Introduction 2) Natural Background Radiation 3) Man-Made radiation sources 4) Source of exposure 5) How radiation is used 6) Summary 2 2) Introduction Scientists have studied radiation for over 100 years and • we know a great deal about it. Radiation is part of nature. All living creatures, from the • beginning of time, have been, and are still being, exposed to radiation. Sources of radiation can be divided into two categories: • Natural Background Radiation • Man-Made Radiation • 3 3) Natural Background Radiation Cosmic Radiation • Terrestrial Radiation • Internal Radiation • Radon • 4 3) Cosmic Radiation The earth, and all living things on it, are constantly bombarded by radiation from outer space, similar to a steady drizzle of rain. • Charged particles from the sun and stars interact with the earth’s atmosphere and magnetic field to produce a shower of radiation. • The amount of cosmic radiation varies in different parts of the world due to differences in elevation and to the effects of the earth’s magnetic field. • 5 3) Terrestrial Radiation Radioactive material is also found throughout nature in soil, water, and vegetation. • Important radioactive elements include uranium and thorium and their radioactive decay products which have been present since the earth was formed billions of years ago. • Some radioactive material is ingested with food and water. Radon gas, a radioactive decay product of uranium is inhaled. • The amount of terrestrial radiation varies in different parts of the world due to different concentrations of uranium and thorium in soil. • 6 3) Internal Radiation People are exposed to radiation from radioactive material inside their bodies. Besides radon, the most important internal radioactive element is naturally occurring potassium-40 but uranium and thorium are also present. • The amount of radiation from potassium-40 does not vary much from one person to another. However, exposure from radon varies significantly from place to place depending on the amount of uranium in the soil. • On average, in the United States radon contributes 55% of all radiation exposure from natural and manmade sources. Another 11% comes from the other radioactive materials inside the body. • 7 3) Radon Naturally occurring radioactive gas Second leading cause of lung cancer Estimated 14,000 deaths per year Easy to test for short and long term tests available EPA guideline is 4 pCi/L Fixable Radon in water from drilled wells can also be an entry method 8 4) Man-Made Radiation Sources Annual Dose from Background Radiation Total exposure Man-made sources Medical X-Rays 11 Radon 55.0% Other 1% Internal 11% Cosmic 8% Man-Made 18% Terrestrial 6% Nuclear Medicine 4% Consumer Products 3% Total US average dose equivalent = 360 mrem/year 9 4) Man-Made Radiation Sources The Nuclear Regulatory Commission and other federal and • state agencies regulate exposure from man-made radiation sources. Different regulations apply to two distinct groups: Members of the public– Occupational workers– 10 5) Source of Exposure Examples of man-made sources • of radiation to members of the public: 11 Student activity: Guess which sources contribute the most to man-made radiation exposure: Natural gas – (1) – Lantern mantles – (2) – Medical diagnosis – (3) – Building materials – (4) – Nuclear power plants – (5) – Coal power plants – (6) – Tobacco – (7) – Phosphate fertilizers – (8) – • 12 0 0.4 0.2 Nuclear Plant Lantern Mantles 2 Coal Plant 4 Natural Gas 10 Phosphate Fertilizer 30 Building Material 70 Medical Smoking (perWeek) 5) Source of Exposure Annual Average Dose (mrem/year) man-made source 60 60 50 40 25 20 7 0.15 6) How Radiation is Used Science • carbon dating to determine age – instruments to measure density – power satellites – Medicine • x-rays and nuclear medicine – diagnose and treat illness – Industry • smoke detectors – kill bacteria and preserve food – 13 6) How Radiation is Used Radiation in Medicine Radiation used in • medicine is the largest source of man-made radiation. Most of our exposure is • from diagnostic x-rays. 14 Summary • Sources of Radiation Exposures – Occupational (work-related) • Radiography in aircraft activity – Non-occupational • Naturally occurring sources – Radon – Sources in the human body – Sources in earth’s crust (terrestrial) – Cosmic radiation • Manmade sources – Tobacco products Medical radiation – Building materials Consumer products – Industrial sources Atmospheric testing of nuclear weapons. 15 16 Quiz N°2 Take a white paper • Write (on top of the page): • Quiz N°2 (RAD 453) – Full Name: – Student Number: – Answer: • 17