In Vitro Solubility Testing of Airborne Uranium Tetrafluoride

Full text: Uranium tetrafluoride (UF4) is an important intermediate compound in the uranium industry. Inhalation of UF4 aerosols can occur and may therefore constitute a healthy hazard. In order to assess the radiation dose from the intake of this compound it is necessary to know its transportability class, based on its dissolution rate in extracellular aqueous environment of lung fluid. The International Commission on Radiological Protection (ICRP) has assigned UF4 to Inhalation Class W (lung retention half-time of 10 to 100 days). Solubility profiles of UF4 aerosols were determined by performing in vitro solubility tests on air samples containing UF4 aerosols. The dissolution rate was determined over 100 days in a simulant solution of the extracellular airway lining fluid (SUF Serum Ultra Filtrate). The studies were conducted by using the static method in which the filter sample was confined between two membrane filters which was held together using an open face cassette. These filters were immersed in a teflon vial holding 60 ml of SUF fluid, which was maintained at 37oC inside a thermostatic bath and at a physiological pH of 7.2-7.6 by keeping a layer of CO2 enriched environment over the solution. The vials containing the solution were shaken to simulate the conditions inside the extracellular aqueous environment of lung as much as possible. A comparison was also made with tests conducted with the batch/filter method and SLF (simulated lung fluid) simulant solution. (author)