Radium isotopic measurements in the search for uranium in palaeodrainage channels

Analyses have been made of many groundwater samples, some of which were collected from the vicinity of uranium deposits and others from unmineralized areas, for dissolved uranium and for the four naturally occurring isotopes of radium: ²²⁶Ra (²³⁸U decay series, t _{1 2} = 1600 y), ²²⁸Ra and ²²⁴Ra (²³²Th decay series, t _{1 2} = 5.75 y and 3.8 d) and ²²³Ra (²³⁵U decay series, t _{1 2} = 11 d). The radium isotopes ²²⁶Ra, ²²⁴Ra and ²²³Ra, are measured by alpha-spectrometry after extraction from a water sample soon after collection and ²²⁸Ra at a later time by determining the amount of ingrown ²¹²Po.