Arun Kumar Shrestha asked "how to calculate" in this and a previous question. Most multichannel spectrometer systems have algorithms to calculate activity. The operator must supply geometry information to obtain concentration. It is not possible to supply detailed calculations without detailed information about your system. In situ calculations are very different from calculations for a sample of known shape and homogeneous distribution of radionuclides.

Tes. Ra-226 and U-238 may be reliably calculated from progeny, if they are in equilibrium with the progeny.