| Popis: |
Uranium series radionuclides were determined in a sample collected from a rainwater puddle at the Ranger Uranium Mine (Northern Territory, Australia). The 1 l sample contained 0.25 g of uranium with a 234U/238U activity ratio of 1.07. The activities of the 238U daughter products mobilised by the rainwater were 3.8 Bq for 230Th and 66 Bq for 226Ra. These values are 0.1% and 2.2%, respectively, of the activities required for secular equilibrium with 0.25 g uranium. The activities of two daughters of 235U were 12.5 Bq for 227Ac and between 18.7 and 32.8 Bq for 227Th, values that represent 9.0% and between 13 and 24%, respectively, of the activity required for secular equilibrium with 0.25 g uranium. The results indicate that 234U, 227Th and 227Ac were the most readily mobilised daughter radionuclides of the uranium and actinium series. If 227Th and 227Ac are generally mobile, this could account for the frequent observations of 223Ra in Australian ground waters in concentrations higher than would be expected for an isotope with a half-life of 11.3 days. |
