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“DOSIMETRY”

“DOSIMETRY”. Measuring Radiation National 5. Why should we measure radiation?. What can be measured?. We are concerned with 3 quantities of measurement in radioactivity Activity Absorbed Dose Equivalent Dose. Activity of a source. Activity of a source.

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“DOSIMETRY”

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  1. “DOSIMETRY” Measuring Radiation National 5

  2. Why should we measure radiation?

  3. What can be measured? • We are concerned with 3 quantities of measurement in radioactivity • Activity • Absorbed Dose • Equivalent Dose

  4. Activityof a source

  5. Activity of a source • The activity (A) of a radioactive source is the number of decays per second and is measured in becquerels • One becquerel (1Bq) is one decay per second.

  6. Example A radioactive source gives off 300 radioactive emissions in 2 minutes. What is the activity of the source in Becquerels? Activity = Number of emissionstime(s) A = 300 / 120 Activity = 2.5 Bq

  7. Absorbed Dose

  8. Absorbed Dose • Not all of the emissions from a radioactive source will be absorbed by a body. • Much of the ‘activity’ from a radioactive source will miss the body. • Some will pass straight through without being absorbed.

  9. Absorbed Dose • The absorbed dose (D) is the energy absorbed by each kg of the body. • The gray (Gy) is the unit of absorbed dose. • One gray is one joule per kilogram. (1 Gy = 1J/kg)

  10. Example “Exposure to a radiation dose of four Gray will typically kill about half of all healthy adults.”

  11. Equivalent Dose

  12. Biological effects of radiation • The actual effect of the radiation on a body will depend on several factors; • How much energy is absorbed (the absorbed dose: D) • What kind of tissue receives the radiation (bone, muscle, brain, etc.) • What type of radiation the tissue is exposed to (a, b, g, neutron, proton)

  13. Equivalent dose • The equivalent dose (H) takes into account the type of radiation and the total energy absorbed. • Equivalent dose is measured in sieverts (Sv).

  14. Typical levels of Equivalent Dose

  15. Typical levels of Equivalent Dose

  16. Typical levels of Equivalent Dose

  17. Summary

  18. Comparison with rain!

  19. Safety with Radioactivity

  20. Safety with Radioactivity • What are the safety procedures necessary when handling radioactive substances. • What are the 3 methods of reducing the equivalent dose • Include the radioactive hazard sign and state where it should be displayed

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