Standardization of 234Th by Cerenkov counting

We take advantage of the secular equilibrium between the first two descendants of 238U to calibrate 234Th in a conventional liquid scintillation spectrometer by Cerenkov counting. The dependence of the Cerenkov counting efficiency on the conditions of the medium other than the refractive index is studied. In particular, we show that the decrease of the counting efficiency observed for samples in HNO3 is generated by light absorption. We compare the Cerenkov counting standardization method with other alternative calibration methods (i.e. liquid scintillation or gamma spectrometry) obtaining discrepancies less than 2%.