Air-kerma rate constant

A characteristic constant for a radionuclide, which is defined in terms of an ideal point source, as $\Gamma _\delta =$ $\frac{\iota^2\ \dot{K}_\delta}{A}$ , where $\dot{K}_\delta$ is the air-kerma rate due to photons (gamma and x rays) of energy greater than δ at a distance $\iota$ in a vacuum from a point source of the radionuclide of activity A. (Adapted from ICRP Publication 107)

ICRP Glossary entry - 22 February 2019