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Radiation Concepts

Radiation Concepts. Definitions. Ionizing Radiation energy in the form of particles or waves, given off by unstable (radioactive) atoms or by accelerated charged particles Radioactive Material any material which emits ionizing radiation Radioactive Contamination

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Radiation Concepts

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  1. Radiation Concepts

  2. Definitions Ionizing Radiation energy in the form of particles or waves, given off by unstable (radioactive) atoms or by accelerated charged particles Radioactive Material any material which emits ionizing radiation Radioactive Contamination radioactive material in an unwanted place 101-04

  3. Radiation Ionizing Radiation Radioactive Atom Alpha Particle Neutron Particle Beta Particle Gamma Ray (X Ray)

  4. Radioactive Material Gamma Ray Gamma Ray Radioactive Material- any material containing atoms that emit radiation.

  5. Contamination External Radiation Contamination

  6. Radioactive Contamination Radioactive Contamination- is radioactive material in an unwanted place.

  7. Neutrons and Protons Ejected Electron Ionization Radiation Ionizing Radiation Ionizing Radiation- radiation with enough energy to remove an electron from its atom.

  8. Alpha Particle a Characteristics • +2 charge • 2 protons • 2 neutrons • Large mass Range • Very short range • 1" -2" in air Shielding • Paper • Outer layer of skin Hazards • Internal Sources • Plutonium • Uranium • Radium • Thorium • Americium a a a a a

  9. Beta Particle b Shielding • Plastic safety glasses • Thin metal Characteristics • -1 charge • Small mass Range • Short range • About 10' in air Hazards • Skin and eyes • Can be internal Sources • Radioisotopes • Activation Products • Sealed sources

  10. Gamma Ray g Characteristics • No charge • No mass • Similar to x-rays Range • Long range • About 1100' in air Shielding • Lead • Steel • Concrete Hazards • External (whole body) • Can be internal Sources • X-ray machines • Electron microscopes • Sealed sources • Accelerators • Nuclear reactors • Radioisotopes Paper Plastic Lead

  11. Neutron Particle h Characteristics • No charge • Found in nucleus Range • Extended range Shielding • Water • Plastic Hazards • External (whole body) Sources • Fission • Reactor operation • Sealed sources • Accelerators Paper Lead Water

  12. Radiation Units roentgen (R) • measures exposure (ionization) of air by X-rays & gamma-rays rad (radiation absorbed dose) • measures energy deposited in any material by any type of ionizing radiation rem (Roentgen Equivalent to Man) • estimates biological damage or health risk due to absorption of ionizing radiation • unit of dose equivalent

  13. Radioactivity Units Measure the number of nuclear transformations (disintegrations) which occur in a certain time period Curie (abbreviated, Ci) = 37,000,000,000 disintegrations per second (dps) = 2,200,000,000,000 disintegrations per minute (dpm) Radioactive contamination measures an amount of activity over a unit of surface area. e.g. 5000 dpm/100 cm2 2

  14. Prefixes Used with Radiation Units Prefix Symbol Translation Numerical Value Scientific Notation Tera T 1 trillion 1,000,000,000,000 1012 Giga G 1 billion 1,000,000,000 109 Mega M 1 million 1,000,000 106 Kilo k 1 thousand 1,000 103 Milli m 1 thousandth 1/1,000 10-3 Micro m 1 millionth 1/1,000,000 10-6 Nano n 1 billionth 1/1,000,000,000 10-9 Pico p 1 trillionth 1/1,000,000,000,000 10-12

  15. Prefixes – Examples Nuclear plant - 1000 megawatts (MW) electric power 1 kilogram (kg) weighs 2.2 pounds Chest X-Ray dose = 5 millirem (mrem) Biochemist might use a 10 microCurie (mCi) source 10 nCi/100 cm2 = low level radioactive contamination Natural radium content of soil = 1 picoCi/gram (pCi/g)

  16. millirem Abbreviation: mrem 1000 mrem = 1 rem millirem- is the basic unit of radiation dose equivalent. It measures biological risk in humans.

  17. The time required for the amount of radioactive material to decrease by one-half 1200 1000 800 Activity 600 400 200 0 New 1 Half- 2 Half- 3 Half- 4 Half- Life Lives Lives Lives Half-Life

  18. Acute Radiation Dose Acute radiation dose refers to persons who receive large amounts of radiation over a short period of time.

  19. Chronic Radiation Dose Chronic radiation dose refers to persons who receive small amounts of radiation over a long period of time.

  20. Chronic Radiation Dose Chronic radiation dose refers to persons who receive small amounts of radiation over a long period of time. There is a slight risk that cancer may be caused by chronic radiation doses. This risk level is very small compared to the natural occurrence rate of cancer.

  21. LNT Assumption The previous statements assume a Linear, No-Threshold (LNT) response to radiation. There is a growing body of scientific evidence that this assumption is incorrect, and that low levels of radiation exposure are not harmful. There is also evidence that low levels of radiation exposure can have a beneficial (i.e., hormesis) effect.

  22. Four Ways Radioactive Material Can Enter the Body Inhalation • Breathing • Smoking Wound or Cut Ingestion • Eating • Drinking • Chewing Absorption

  23. Cells are undamaged. Cells are damaged, repair damage and operate normally. Cells are damaged, repair damage and operate abnormally. Cells die as a result of damage. Biological Effects of Radiation

  24. Health Effects • Radiation effects on cell chromosomes: Somatic Effects observed in the exposed individual Heritable (Genetic) Effects observed in future generations of exposed individual

  25. RW I Factors Affecting Biological Damage • Total radiation dose • Dose rate • Type of radiation • Area of body exposed • Cell sensitivity • Individual sensitivity 102-13

  26. The fetus is MORE sensitive than an adult. RW I

  27. No Heritable Effects from Ionizing Radiation Have Been Observed in Humans Heritable effects have been observed in laboratory animals.

  28. Terrestrial Sources Cosmic Radiation Radon Radon Internal Sources Other The average annual dose to the general population from natural background and man-made sources is 360 mrem.

  29. Cosmic 28 mrem Terrestrial 28 mrem Radon 200 mrem Internal 40 mrem Medical X-Rays 40 mrem Nuclear Medicine 14 mrem Consumer Products 10 mrem Natural Sources Man-Made Sources Other 3 mrem Average Annual Dose

  30. Comparison of Radiation Dose

  31. Relative risk of dying: 1 in a million odds. RW I • Smoking 1.4 cigarettes (lung cancer) • Eating 40 tablespoons of peanut butter • Eating 100 charcoal broiled steaks • 2 days in New York City (air pollution) • Driving 40 miles in a car (accident) • Flying 2500 miles in a jet (accident) • Canoeing for 6 miles • Receiving 10 mrem radiation dose (cancer)

  32. Risk – Loss of Life Expectancy Days of Average Life Expectancy Lost Due to Various Causes 3500 2250 1600 1100 777 365 227 207 60 10 6 Being an unmarried male Smoking (1 pack/day) Being an unmarried female Being a coal miner 25% overweight Alcohol abuse (U.S. average) Being a construction worker Driving a motor vehicle All industries Radiation: 100 mrem/yr x 70 years Coffee

  33. Basic Protective Measures Time Distance Shielding

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