quiz 1

• Radiation


  • Emission of energy as electromagnetic waves or as a moving subatomic particles, especially high-energy particles which cause ionization
  • Stream of particles or electromagnetic waves emitted by the atoms and molecules of a radioactive substance as a result of nuclear decay
• Natural sources of radiation

  • Cosmic background radiation
  • Terrestrial radiation
  • Internal radionuclide (radiation)
• Cosmic background radiation


  • Source of natural background radiation which originates in outer space and is composed of penetrating ionizing radiation (both particulate & electromagnetic)
  • Sun & stars send a constant stream of cosmic radiation to earth, much like a steady drizzle of rain
  • Small variations in temperature of the background radiation from point to point on the sky are called anisotropies
• Terrestrial radiation


  • Radioactive material is also found throughout nature such as soil, water, and vegetation
  • Low levels of uranium, thorium, and their decay products are found everywhere
  • Some of these materials are ingested with food and water, while Radon are inhaled
  • The major isotopes of concern for terrestrial radiation are uranium and decay products such as thorium, radium, and radon
• Internal radionuclides

  • Radioactive Potassium – 40 (40 K)
  • Carbon – 14 (14 C)
  • Lead– 210 (210 Pb)
• Potassium 40


  • Primary source of radiation from human body
  • The 40 K concentration in the body is fairly high
  • It is ingested in many foods that we eat and is a critically important element for proper function of the body
  • 40 K = in a 70 kg person = 5,000 Bq = 5,000 atoms undergoing radioactive decay each second
• Radioactive isotopes and their half-lives

  • Potassium 40 - 1.26 x 10^9 years
  • Carbon 14 - 5,730 years
  • Rubidium 87 - 4.9 x 10^10 years
  • Lead 210 - 22.3 years
  • Tritium (3H) - 12.43 years
  • Uranium 238 - 4.46 x 10^9 years
  • Radium 228 - 5.76 years
  • Radium 226 - 1,620 years
• Groups exposed to man-made radiation sources

  • Members of the public
  • Occupationally exposed individuals
• Member of the public


  Any individual except when that individual is receiving an occupational dose
• Occupational dose


  • Received by an individual in the course of employment in which the individuals assigned duties involve exposure to radiation or to radioactive material
  • This doesn't include the dose received from background radiation, from any medical administration the individual has received, from exposure to individuals administered radioactive materials from voluntary participation in medical research programs, or as members of public
• Sources of radiation exposure for members of the public

  • Medical procedures (most significant source)
  • Consumer products such as tobacco (Thorium), building materials, combustible fuels (gas, coals), televisions, luminous watches & dials (Tritium), airport X-ray systems, smoke detectors (Americium)
  • Nuclear fuel cycle (mining and milling of Uranium to the actual production of power at nuclear plant)
  • Shipment of radioactive materials and residual fallout from nuclear weapons testing and accidents (Chernobyl)
• Sources of radiation exposure for occupationally exposed individuals

  • Uranium, daughter products: Cobalt 60, Cesium 137, Americium 241
• Two basic types of radiation

  • Particulate radiation
  • Electromagnetic radiation
• Particulate radiation


  • Stream of atomic or subatomic particles that may be charged positively (Alpha particles) or negatively (Beta particles) or not at all (Neutrons)
  • Involves tiny fast-moving particles that have both energy and mass
  • Primarily produced by disintegration of an unstable atom
  • Also known as "Corpuscular Radiation"
• Alpha particle


  • Type of ionizing radiation ejected by the nuclei of some unstable atoms
  • Relatively heavy, high-energy subatomic particles consisting of two protons & two neutrons
  • Discovered by Ernest Rutherford (1899)
  • Has a velocity in air of approximately one-twentieth speed of light
  • Naturally occurring alpha emitters have atomic numbers of at least 82 (Lead)
• Uses of alpha emitters

  • Radium 226 – used to treat cancer by inserting tiny amounts of radium into the tumorous mass
  • Polonium 210 – serves as static eliminator in paper mills and industries
  • Americium 241 – smoke detectors
• Alpha emitters

  • Americium 241
  • Plutonium 236
  • Uranium 238
  • Thorium 232
  • Radium 226
  • Radon 222
  • Polonium 210
• Beta particle


  • High velocity electrons with an electrical charge of -1
  • "Beta" = "high speed"
  • Discovered by Henri Becquerel in 1900 (identical to electrons)
  • The speed of beta particles depends on how much energy they have
  • Their excess energy in the form of speed causes harm to living cells
  • When transferred, this energy can break chemical bonds and form ions
• Uses of beta emitters

  • Iodine 131 – Treatment of thyroid disorders such as cancer and graves disease (type of hyperthyroidism)
  • Phosphorus 32 – Molecular biology and genetics research
  • Strontium 90 – radioactive tracer in medical studies
  • Tritium – drug metabolism studies to ensure safety of potential new drugs
• Neutron radiation


  • Energy released from an atom in the form of neutral particles called "neutrons"
  • No charge and about the same mass of proton
  • Discovered by James Chadwick
  • Neutrons are high-speed nuclear particles that have an exceptional ability
• Beta particles were discovered by Henri Becquerel in 1900 (identical to electrons)
• Use of beta emitters


  • Iodine 131 - Treatment of thyroid disorders such as cancer and graves disease (type of hyperthyroidism)
  • Phosphorus 32 - Molecular biology and genetics research
  • Strontium 90 - radioactive tracer in medical studies
  • Tritium - drug metabolism studies to ensure safety of potential new drugs
• Neutron radiation


  Energy released from an atom in the form of neutral particles called "neutrons"
• Neutrons have no charge and about the same mass of proton
• Neutrons were discovered by James Chadwick
• Neutrons


  • They are high-speed nuclear particles that have an exceptional ability to penetrate other materials
  • They are the only one that can make objects radioactive, through the process "neutron activation"
  • Because of their exceptional ability to penetrate other materials, neutrons can travel great distances in air and require a very thick hydrogen-containing materials (such as concrete or water) to block them
• Neutron radiation primarily occurs inside nuclear reactors
• Positron


  The antiparticle or the antimatter counterpart of electron
• Positrons have an electric charge of +1e and have the same mass as an electron
• When a low energy positron collides with a low energy electron, annihilation occurs, resulting in the production of two or more gamma ray photons
• The existence of positrons was first concluded by Carl D. Anderson in 1932, who was awarded the 1936 Nobel Prize in Physics
• The production of positive electrons by means of radioactive sources and identification of Anderson's particle with the anti-electron was done by Paul Adrien Maurice Dirac
• Electromagnetic radiation


  Pure energy with no mass and is like vibrating or pulsating waves of electrical and magnetic energy
• Electromagnetic radiation is produced by a vibrating electric charge and as such, they consist of both an electric and a magnetic component
• Electromagnetic radiation


  Acts like a stream of small "packets" of energy called photons
• Electromagnetic radiation travels in a straight line at the speed of light

  
• Types of electromagnetic radiation

  • Radiowaves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet light
  • X-rays
  • Gamma rays

  
• Electromagnetic spectrum


  The range of wavelengths or frequencies over which electromagnetic radiation extends

  
• Electromagnetic spectrum

  • Gamma ray (Less than 0.02 nm)
  • X-ray (0.01 nm - 10 nm)
  • Ultraviolet (10 nm - 400 nm)
  • Visible light (390 nm - 750 nm)
  • Infrared (750 nm - 1 mm)
  • Microwave (1 mm - 1 meter)
  • Radiowave (1 m - 100,000 km)

  
• Radiowave


  Have the longest wavelengths in the electromagnetic spectrum and carry signals for television and cellular phones