Solubility of various forms of strontium titanate in lungs: in vitro and in vivo studies.

Abstract

At the In-Tank Precipitation Facility of the Savannah River Site, strontium and other radionuclides are removed from high-level radioactive waste and sent to the Defense Waste Processing Facility. Strontium removal is accomplished by adsorption using a slurry that includes monosodium titanate, which forms strontium titanate with unknown lung solubility characteristics. The purpose of this study was to determine the solubility of strontium titanate in the form created at the In-Tank Precipitation facility. An in vitro dissolution study was done with a slurry simulant and with several types of strontium titanate, and the results were compared. An in vivo study was also performed with high-fired SrTiO3 in rats. Strontium and titanium were measured by inductively-coupled plasma/atomic emission spectrometry. The data from both studies were used independently to assign the compounds to an absorption type based on criteria specified in ICRP 71. Results of the in vitro studies showed that the Defense Waste Processing Facility simulant should be assigned to Type M and the strontium titanate should be assigned to Type S. Results of the in vivo study verified that SrTiO3 should be assigned to Type S. Lung clearance data of SrTiO3 from rats showed that 85% cleared within the first 24 h and the remaining 15% cleared with a half-time of 130 d. The initial rapid clearance is attributed to deposition in airways as compared to the alveolar region.