Potentiometric multisensor system for tetra- and hexavalent actinide quantification in complex rare earth metal mixtures related to spent nuclear fuel reprocessing

Abstract

A potentiometric multisensor system, composed of 12 cross-sensitive sensors, is proposed for uranium and thorium quantification in multi-component mixtures simulating PUREX process tailing solutions. Various ligands with high extraction capacity to lanthanides and actinides were used as active compounds in plasticized polymeric sensor membranes. The sensitivity of the individual sensors to tetra- and hexavalent actinides (UO22+ and Th4+) in aqueous nitric acid solutions with pH = 2 has been studied for the first time. The sensors with pronounced sensitivity to actinides were comprised into the multisensor system that was applied for UO2+2 and Th4+ quantitative determination in presence of each other and lanthanides cations (La3+, Pr3+, Sm3+, Gd3+, Yb3+). The nitric acid quantification in the set of mixtures with UO2+2 and La3+ was also performed using the same system. Projection on latent structures (PLS) algorithm was used for multivariate regression models calculation. The results of PLS models validation with independent test set show the possibility of UO2+2 and Th4+ quantification with mean relative error (MRE) equal to 17% and 14% correspondingly, and HNO3 quantification with MRE = 7%. This accuracy is appropriate for real-time technological control of PUREX process.