Radiation Source Activity Minimal Significant

The minimum significant activity of a radiation source is the maximum activity of an open source of radioactive radiation, at which sanitary inspection authorities do not require special permission to obtain and use the source.

The activity of a source is the number of nuclei of radioactive elements formed in a source per unit of time. The unit of activity of radiation sources is the curie (Ci) or the number of decays per unit of time (decays per second).

The maximum activity of a radiation source in the air at which its use is allowed without permission from sanitary authorities is called the minimum significant activity.

The minimum significant activity varies for different radiation sources. For example, for a uranium source it is 4.7 curies, for a plutonium source it is 2.5 curies.