S coefficient (radiation weighted)

The equivalent dose to target region $r_T$ per nuclear transformation of a given radionuclide in source region $r_S$, Sv (Bq s)^-1.

$S_w(r_T \leftarrow r_S) = \sum_R w_R \sum_i E_{R,i} Y_{R,i} \phi (r_T \leftarrow r_s, E_{R,i})$

where $E_{R,i}$ is the energy in joules of the i^th radiation of type $R$ emitted in nuclear transformations of the radionuclide (J); $Y_{R,i}$ is the yield of the i^th radiation of type $R$ per nuclear transformation [(Bq s)^-1]; $w_R$ is the radiation weighting factor for radiation type $R$; and $\phi (r_T \leftarrow r_s, E_{R,i})$ is the specific absorbed fraction defined as the fraction of energy $E_{R,i}$ of radiation type $R$ emitted within the source region $r_S$ that is absorbed per mass in the target region $r_T$ (kg^-1).

ICRP Publication 130, 2015

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