Influence of 231Th in the activity determination of 234Th by Cerenkov counting

A precise and simple method for the determination of 234Th activity by Cerenkov counting is described. A calibrated natural uranium solution (having 234mPa and 238U in secular equilibrium) in 0.1 M HNO3 is used to construct the calibration curve. Because 231Th (a β-emitting nuclide present in the decay chain of 235U) contribution to Cerenkov counting is experimentally proved to be negligible only in the case of low enriched uranium samples, simple calculations are needed to accomplish the activity determination.