1 / 38

D OSE CONCEPTS, QUANT I T I ES AND UN I TS , BAS I C PR I NC I PLES AND PRIMARY METHODS OF RAD I AT I ON PROTECT I ON

D OSE CONCEPTS, QUANT I T I ES AND UN I TS , BAS I C PR I NC I PLES AND PRIMARY METHODS OF RAD I AT I ON PROTECT I ON. Module IV. Radiation exposure. Traditional unit: Roentgen (R) = 2.58x10 -4 coulomb/kg = 1esu/cm 3. Absorbed dose (D). Energy imparted to matter

nova
Télécharger la présentation

D OSE CONCEPTS, QUANT I T I ES AND UN I TS , BAS I C PR I NC I PLES AND PRIMARY METHODS OF RAD I AT I ON PROTECT I ON

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. DOSE CONCEPTS, QUANTITIES AND UNITS,BASIC PRINCIPLES AND PRIMARY METHODS OF RADIATION PROTECTION Module IV

  2. Radiation exposure Traditional unit: Roentgen (R) = 2.58x10-4 coulomb/kg = 1esu/cm3 Module IV

  3. Absorbed dose (D) Energy imparted to matter from any type of radiation D = E/m D:absorbed dose E: energy absorbed by material of mass ‘m’ Module IV

  4. Units of absorbed dose The SI unit: gray (Gy) 1 Gy = 1 joule/kilogram Old unit : rad 1 Gy=100 rad Module IV

  5. Equivalent dose (HT) Accounts for biological effect per unit dose radiation weighting absorbed factor ( WR) X dose (D) HT= WRxD X Module IV

  6. Radiation weighting factors (WR)ICRP 60 (1991) Module IV

  7. Unit of equivalent dose SI unit: sievert (Sv) HT (Sv) = WR x D (Gy) Old unit: rem (roentgen equivalent man) HT (rem) =( WR) x D (rad) 1 Sv = 100 rems Module IV

  8. Effective dose (E) Risk related parameter, takingrelative radiosensitivity ofeach organ and tissue into account E(Sv)= ΣT WT x HT WT: tissue weighting factor for organ T HT: equivalent dose received by organ or tissue T Module IV

  9. Tissue and organ weighting factors Module IV

  10. Conversion between units used in radiation protection Module IV

  11. Committed equivalentdose HT(t)and committed effective dose E(t) Module IV

  12. Projected and avertable dose Projected dose Averted dose Averted dose Module IV

  13. Collective effective dose (S) Total radiation dose incurred by population Ei:average effective dose in the population subgroup i Ni: number of individuals in subgroup i Unit:man-sievert (man.Sv) Module IV

  14. Sources and levels of radiation exposure to population Module IV

  15. Sources of radiation dose to general population Module IV

  16. Background radiation • Terrestrial radioactivity • Cosmic radiation • Internal radioactivity Natural background radiation doses in Europe Module IV

  17. Terrestrial radiation:external and internal exposure • U-238 Ra-222 • Th-232 Ra-220 Module IV

  18. Cosmic radiation Module IV

  19. Internal radioactivity • Radioactivity in diet • lead-210 • polonium-210 • potassium-40 Module IV

  20. Average ocupational radiation doses received during various types of work ‘Non-coal’ mining 16.3 milisieverts Dose in milisieverts Module IV

  21. Occupational exposure Public exposure 50 mSv maximum in any 1 year 100 mSv in 5 years 5 mSv in any 5 consecutive years (Working figure 20 mSv per year) (Working figure 1 mSv per year Dose limits recomended by ICRP (1991)-whole body Module IV

  22. Annual doses to tissues Occupational Public Lens of the eye 150 mSv 15 mSv Skin (1cm2) 500 mSv 50 mSv Hands and feet or individual organ 500 mSv Dose limits recomended by ICRP (1991)- tissues Module IV

  23. Radiation protection Basic principles and primary methods Module IV

  24. Basicprinciples of radiationprotection • Justification of practice • Optimization of protection • Individual dose limits Module IV

  25. ALARA Aslow as reasonably achievable Module IV

  26. Basic methods of protection against exposureto ionizing radiation • Three basic factors • Time • Distance • Shielding Module IV

  27. Time Exposure rate =10mGy/h Time = Total dose X 1 hour = 10 mGy 2 hours = 20 mGy Module IV

  28. Distance Module IV

  29. Inverse square law d=50cm 150 mSv/h 0.06 mSv/h Module IV

  30. Shielding Module IV

  31. Shielding photons Module IV

  32. Halfvaluelayer (HVL) Module IV

  33. Internal exposure Module IV

  34. Inhalation Module IV

  35. Ingestion/Absorption Module IV

  36. Protective clothing and hand washing Module IV

  37. Medical exposureRelative effective dose and equivalent period of exposure to natural background radiation Module IV

  38. Review points • Becquerel, coulomb per kilogram, gray, and sievert are part of International System of Units (SI). • Absorbed dose of radiation in SI units is expressed in gray. Ability of some types of radiation to cause more significant levels of biological damage taken into account with radiation weighting factor used to determine equivalent dose, expressed in sieverts • Goal of radiation safety: keep radiation exposure as low as reasonably achievable (ALARA) Module IV

More Related