The sievert is the special name for the SI unit of equivalent dose, effective dose, and operational dose quantities.

The unit is joule per kilogram

It is used both to represent the risk of the effect of external radiation and internal irradiation

Conventionally the sievert is not used for high levels of radiation which produce deterministic effects. These effects are compared to the physical quantity absorbed dose measured by the unit gray (Gy).

The sievert is of fundamental importance in dosimetry and radiation protection, and is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dosage measurement and research into the biological effects of radiation.

NB:Equivalent dose

  • Is derived from absorbed dose multiplied by a radiation weighting factor
  • Is measured in Sieverts (Sv)
  • Is not averaged over all tissues of the body
  • Is not the same as absorbed dose for neutrons; As the radiation weight factor for neutrons range from 5 to 20