2.9.1 Units related to Activity
Activity represents the rate of disintegrations resulting from a given radioactive decay, and is expressed in SI units in Becquerel (s-1). Historically, activity has been expressed in Curies (Ci). The conversion is 1 Ci = 3.7 x 1010 Bq. Activity is sometimes expressed per unit of mass, volume or surface area. The table below summarizes the SI units for activity.
| Quantity | Symbol | Unit | Dimension | Use/Conversion of older units |
|---|---|---|---|---|
| Activity | A | Becquerel (Bq) | s-1 | radioactivity of objects |
| Specific activity | a | becquerel per kilogram (Bq/kg) | kg-1s-1 | radioactivity of unit mass |
| Activity concentration | cA | becquerel per cubic metre (Bq/m3) | m-3s-1 | radioactivity of gases and liquids |
| Surface activity | as | becquerel per squared metre (Bq/m2) | m-2s-1 | radioactivity of unit area |