Automated interfacial tension device for the determination of Purex solvent quality

The Purex and HM Processes at the Savannah River Plant (SRP) employ tributyl phosphate in n-paraffin as an extraction solvent. The presence of undesirable radiolytic- and hydrolytic-degradation products alters the miscibility of the solvent with aqueous solutions. Consequently, the solvent quality may be judged by its miscibility with an appropriate aqueous reagent. In the past, solvent integrity has been judged at SRP by the disengaging ratio technique, where the solvent is mixed with an aqueous reagent and the separation of the two phases is timed. In principle, this method is a simple and accurate measure of the solvent/aqueous miscibility. However, in practice the endpoint of the phase separation was often judged differently by different operators. Thus, the method suffered from poor reproducibility. To provide a reliable measure of the solvent/aqueous miscibility, an automated device was developed to quantify the interfacial tension between the two phases. The interfacial tension device is constructed from common laboratory equipment and is simple to operate. It is specifically designed for remote operation within a radioactive containment environment. A description of the device and a comparison of solvent quality data obtained by interfacial tension and disengaging ratio measurements are presented.