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Radiation Protection Course

Radiation Protection Course. Radiation Protection Service. Radiation Protection Course. Background Physics Michael Watt. Contents. Atomic Structure Types of Radiation Attenuation & Shielding Activity & Half Life. Atomic Structure 1. Nucleus. Electrons -ve charge. Atomic Structure 2.

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Radiation Protection Course

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  1. Radiation Protection Course Radiation Protection Service

  2. Radiation Protection Course Background Physics Michael Watt

  3. Contents • Atomic Structure • Types of Radiation • Attenuation & Shielding • Activity & Half Life

  4. Atomic Structure 1 Nucleus Electrons -ve charge

  5. Atomic Structure 2 Proton +ve

  6. Atomic Structure 3 Neutrons

  7. Carbon 12 Atomic Mass - no. protons and neutrons C 12 6 Atomic Number - No. protons

  8. Carbon 12

  9. Definition of Isotope Atom protons fixed – number of neutrons can vary to form different isotopes. Example carbon has 2 stable isotopes 126C, 136C To be stable number of N and P must be about equal

  10. Stability Curve p=n No..of Protons No. of Neutrons

  11. Definition of Radioactive Isotope This occurs when the ratio of Neutrons to protons is too great or too small, and the atom spontaneously attempts to become stable Example carbon has five radioactive isotopes C-10, C-11, C-14, C-15, C-16

  12. Carbon 14 Atomic Mass - no. protons and neutrons C 14 6 Atomic Number - No. protons

  13. Ion • An atom or molecule which has lost or gained one or more electrons • An ion will have a positive or negative electrical charge

  14. Ionisation

  15. Types of ionising radiation -VE or +VE

  16. Sources of Ionising Radiation

  17. X-Rays Produced by accelerating electrons from a cathode onto an anode inside an evacuated glass tube. Less than 1 % of energy converted to x- rays, rest to heat. X-rays have the same physical properties as gamma photons.

  18. Energy of Ionising radiation The energy of Alpha, Beta and Gamma radiations is measured in ELECTRON VOLTS eV, normally keV and MeV 1eV = 1.6 x 10-19 J Higher energy = more penetrating (for a given type of radiation)

  19. Shielding Materials • Alpha particles – Paper, dead layer of skin • Beta particles – 1 cm perspex or tissue • Gamma Photons – dense material such as lead or DU

  20. New Unit Becquerel 1 disintegration per second. Old Unit Curie Based on number of disintegrations from 1 g of radium-226. 3.7 x 1010 dps. Activity

  21. Specific Activity Measure of the activity per unit mass or volume Bq/g or Bq/ml

  22. Half Life ( T1/2 ) Time 1 half life 1 half life 1 half life

  23. Half Life • Fluorine-18 110 min • Phosphorus-32 14.3 d • Phosphorus-33 25.6 d • Iodine-125 59.9 d • Sulphur-35 87.5 d • Cobalt-60 5.3 y • Tritium (Hydrogen-3) 12.3 y • Carbon-14 5730 y

  24. Radiation Dose Gray (Gy) – absorbed dose. Defined as 1 Joule of energy absorbed per kilogramme of material. Sievert (Sv)– Unit of equivalent dose and effective dose 100 rad = 1 Gray ( 100 rem = 1 Sv) 1mrad = 10 µGray ( 1 mrem = 10 µSv)

  25. Next… • Short video: • Working Safely with Radioactivity

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