1 / 49

Nuclear Science Merit Badge:

Nuclear Science Merit Badge:. Radiation Health & Safety. Radiation. Learning Objectives. Types of Radiation Consequences of exposure to radiation Uses in the medical field Radiation containment. What is Radiation ?.

lot
Télécharger la présentation

Nuclear Science Merit Badge:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Nuclear Science Merit Badge: Radiation Health & Safety

  2. Radiation

  3. Learning Objectives • Types of Radiation • Consequences of exposure to radiation • Uses in the medical field • Radiation containment

  4. What is Radiation? • Radiation is the process in which energetic particles or waves travel through a medium or space. • Generally refers to electromagnetic (EM) radiation (charged particles) • Examples: Sunlight, Microwaves, Sound waves (non-EM)

  5. Types of EM Radiation • Non-Ionizing • Radio waves • Visible light • Microwaves • Ionizing • X-rays • Gamma rays

  6. Ionizing Radiation • Ionization is caused when an electron is added to or removed from an atom. • Ionizing radiation is radiation that has sufficient energy to strip electrons from atoms, thus making them ions. • The remaining positively charged atom and the free electron are called “ion pairs.”

  7. Ionizing Radiation • An X-ray is a type of ionizing radiation that has a wavelength in the range of 0.01 to 10 nanometers. • A Gamma rayis a type of ionizing radiation that has higher energy than X-rays and has a wavelength less than .01 nanometers. • Concrete or lead are needed to shield against these radiations

  8. Electroscope

  9. History Behind Radiation • X-rays were first discovered by Wilhelm Roentgen in 1895. • He noticed how the rays could pass through some materials and not others. • The rays could be detected using a photographic plate

  10. History Behind Radiation • Henri Becquerel discovered that uranium caused a photographic plate to be fogged, just like X-rays. • In 1898, Marie Curiegave this property the name radioactivity. • Radioactivityis the tendency of an element to give off charged particles or rays (i.e., to emit energy).

  11. Charged Particles • Two charged particles that are emitted by a radioactive element are • Alpha (α) particles • Beta (β) particles

  12. Charged Particles • An alpha particle has two protons and two neutrons • Same as He2+ • Mass: 4 AMU • No electrons!

  13. Charged Particles • A beta particle is an electron or a positron. • Electron charge: -1 e • Positron charge: +1 e

  14. Cloud Chamber • A cloud chamber can be used to track the path of electrically charged particles. • When a magnetic field is applied it is able to identify the charge and velocity of the particle. • Cloud Chamber Video

  15. Radioisotopes • Isotopes of an atom that are radioactive are called radioisotopes. • These atoms are radioactive because they have too much energy to be stable; they will release energy until they become stable. • This is called radioactive decay. The modern words are “spontaneous nuclear transformation.”

  16. Radioactive Decay • In the process of radioactive decay, an atom actually changes from one element to another by changing its number of protons. • The half-life of a radioactive substance is the amount of time required for it to lose one half of its radioactivity and transform into another element.

  17. Activity Time!! Let’s demonstrate half-life using a piece of paper!

  18. Radioactive Decay • Radioactivity (or “activity”) is measured in units of: • “curie” • Ci • Defined as 3.7 x 1010 decays per second • The traditional unit • “becquerel”. • Bq • Defined as 1 decay per second • The SI unit

  19. Types of Radioactive Decay • Alpha decay • Nucleus emits an α particle • Loses 2 protons, 2 neutrons • Beta decay • Nucleus emits a βparticle • Converts a neutron into a proton and an electron (i.e., the beta particle)

  20. Examples Half life = 5.2 years • colbolt-60 that is used in cancer therapy, decays to • nickel-60 with loss of a β particle. Half life = 4,468,000,000 years • radioactive decay of Uranium-238 by alpha emission.

  21. Radiation Hazards and Safeguards

  22. The International Radiation Symbol • The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory. • At the time, it was rendered as magenta with a blue background. • The modern version is black against a yellow background

  23. Why should ionizing radiation be controlled? • Ionizing radiation can damage living tissue in the human body. • It can create reactive molecules that are poisons in the body.

  24. Acute (Deterministic) Radiation Effects • Acute radiation symptoms are caused by high levels of radiation usually over a short period of time • They cannot be predicted with certainty. • Examples: erythema (redness of the skin) and epilation (hair loss)

  25. Chronic (Stochastic) Radiation Effects • Chronic radiation symptoms are caused by low-level radiation over a long period of time. • Effects are based on probabilities. • Exposure to low levels of radiation increase a person’s chances to get cancer.

  26. Radiation Exposure Levels & Effects 0.62 rem/y – average annual radiation exposure in the U.S. 2 rem/y – international radiation exposure limit 5 rem/y – current US NRC radiation exposure limit 25 rem – measureable blood changes 100 rem – onset of radiation sickness

  27. Radiation Exposure Levels & Effects 200 rem – radiation sickness with worse symptoms in less time 400 rem – approximately the lethal dose for 50% of the population in 30 days 1,000 rem – death probable within about 2 weeks, effects on the gastrointestinal tract 5,000 rem – death probable within 1-2 days, effects on the central nervous system

  28. Nuclear Technologies

  29. Radiation in Medicine • Radiology: X-ray imaging. • Nuclear Medicine: Following radioactive tracers in the body. • Radiation Therapy: for the treatment of cancer http://www.missouristate.edu/assets/HPER/rib_x-ray.jpg

  30. Radiation Therapy • External beam treatments • Radionuclide treatments (brachytherapy)

  31. Radiation in Agriculture • Radiation used to kill pests, preserve harvested crops. • Helps detect level of pollution and fertilizer in crops. • Delay sprouting and spoilage

  32. Radiation in Industry • Process control using radiation gauges • Check for leaks in underground pipes. • Control thickness of manufactured materials http://www.gcsescience.com/Thickness-Control-Radioactivity.gif

  33. Radiation in Security • X-ray checks of baggage • Whole-body scanners of passengers • Smoke detectors in homes and offices

  34. Radiation in Space • Mars rovers • Satellites • International Space Station • Deep-space Probes • Radioisotope Thermoelectric Generators (RTG)

  35. Radiation in Science • Radiocarbon Dating – Carbon-14 • Neutron activation - “Finding a needle in a haystack” • Engine testing

  36. Differences in dose types

  37. Thought experiment • Alpha particles do MUCH more biological damage with a given amount of dosage than gamma rays. • Why?

  38. Answer • Gamma rays penetrate straight through virtually any material, including tissue, while alpha particles are easily stopped by thin barriers, including human skin. • Alpha particles will thus deposit their energy into a human much more readily than gamma rays, resulting in more tissue damage.

  39. Typical Radiation Detectors • Film packet • Thermoluminescent Dosimeter (TLD) • Ionization chamber • Geiger-Müller (GM) Detector • Scintillation Detector

  40. Radiation Kit

  41. Thought experiment 2 • How does distance effect the measurement of radiation? • How does shielding effect the measurement of radiation? • How does time effect the measurement of radiation?

  42. Answer • With increasing distance the radiation dose rate drops since the concentration of particles decreases

  43. Answer #2 • Shielding reduces the amount of radiation that reaches you, reducing the dose rate

  44. Answer #3 • A shorter time period doesn’t reduce the dose rate, however since you’re exposed to the source for less time you receive less dose.

  45. Background Radiation • Background Radiation is radiation that is a natural part of our environment. • Rocks and soil • Cosmic radiation • Solar radiation • Radon gas • Food and water • From human made sources • X-ray machines • Other medical uses • Tritium dial wristwatches • Gas lantern mantles • Smoke detectors

  46. Radiation Regulations • ALARA- As Low As Reasonably Achievable • Time, Distance, and Shielding • National and International limit – 5 rem/y (5000 mrem/y) • Public limit – 100 mrem/y • Radiation Hazard symbol • Displayed at places where radioactive materials are used and stored.

  47. ALARA SCENARIOS

  48. What we learned • Types and effects of Radiation • Uses of radiation • Consequences of exposure • Containment techniques

More Related