Radioactive Units of Measure

Activity is a measure of the quantity of radioactivity emitted by a radioisotope and is used to determine the amount of radioactive material that may be transported in various types of packaging. Activity is determined by the half-life of the radioactive material, which is the time it takes for the radionuclide to lose half of its value by decay. The unit of activity is the Becquerel (Bq).

The SI unit for radiation exposure is the coulomb per kilogram (C/kg). The SI unit for the dose-equivalent, which measures the biological effect in humans, is the sievert (Sv). This measurement is used to establish the permissible working limits provided to reduce radiation exposure.

Transport Index (TI) is the single number assigned to a package, overpack, or freight container to provide control over radiation exposure. The TI is shown on Category II-Yellow and Category III-Yellow labels, and it is used to establish spacing requirements and the number of packages allowed during transport.

Criticality Safety Index (CSI) is the number assigned to a package, overpack, or freight container used to provide control over the accumulation of fissile material.

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