In vitro dissolution characteristics of aged and recrystallised high-fired 232ThO2

The dissolution characteristics of 232Th from ThO2 in the lung have been determined in an in vitro study. Two types of ThO2 were examined to determine if the age of the material had any effect; an aged high-fired ThO2 that had its progeny in secular equilibrium, and a recently recrystallised and high-fired ThO2 in disequilibrium. The results show the amount of 232Th that dissolved from the aged ThO2 was approximately 10 times greater than the amount that dissolved from the recrystallised and fired ThO2 which was the result of recoil damage to the crystal structure of the aged material. A model based on nuclear track theory was developed to relate the size of the observed rapidly soluble fraction of 232Th to the age of the material and its experimentally determined surface area.