Disequilibrium in the uranium and actinium series in oil scale samples

We have investigated the disequilibrium of the uranium and actinium series and have found both 226Ra (90,200 ± 4300 Bq/kg) and 228Ra have activity concentrations orders of magnitude higher that 238U (1.83 ± 0.36 Bq/kg) and 232Th (7.0 ± 0.4) which are at the head of the decay series. As well the activity concentration of 210Pb (24,400 ± 1200 Bg/kg) was about 3.6 times less than 226Ra. Once an efficiency curve was constructed summing corrections for specific isotopes in the decay change also needed to be taken in consideration. Furthermore, self-attenuation of the photons especially the 46.5 keV belonging to 210Pb was calculated to be 78% since the scale had elevated elemental concentrations of high-Z elements such as barium and strontium. •NORM in oil scale samples.•Disequilibrium in scale 238U and 232Th daughter products.•Gamma-ray self attenuation.