The chemistry behind analytical actinide separations

Both environmental and nuclear waste materials contain important actinides (Th, U, Np, Pu, Am, Cm) the concentration and isotopic composition of which are typically measured either by alpha spectrometry or by mass spectrometry. In most cases the actinides need to be chemically separated from interfering radionuclides and stable elements to enable their measurement. In solid geological samples (rock, soil, sediments) both thorium and uranium are abundant while in ground waters only uranium is relevant. For the measurement of thorium and uranium by alpha spectrometry they need to be removed from other emitting radionuclides, ²²⁶Ra and ²¹⁰Po. Measurement of uranium concentration directly from natural waters by ICP-MS is practical but if accurate isotopic composition is needed mass spectrometric measurements also require radiochemical separations of Th and U