450 likes | 1.06k Views
“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.
E N D
“DOSIMETRY” Measuring Radiation National 5
What can be measured? • We are concerned with 3 quantities of measurement in radioactivity • Activity • Absorbed Dose • Equivalent Dose
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.
Example A radioactive source gives off 300 radioactive emissions in 2 minutes. What is the activity of the source in Becquerels? Activity = Number of emissionstime(s) A = 300 / 120 Activity = 2.5 Bq
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.
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)
Example “Exposure to a radiation dose of four Gray will typically kill about half of all healthy adults.”
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)
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).
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