Influence of radionuclide adsorption on detection efficiency and energy resolution for flow-cell radiation detectors

Flow-cell and batch test experiments were performed to determine the uranyl ion adsorption onto and/or complexation with CaF₂:Eu scintillator as a function of pH. The flow-cell experiments were modeled with an energy dispersive Monte Carlo algorithm. At pH 2, the flow-cell and batch tests gave consistent results, detection efficiency ~60% and distribution coefficient (K_d ) ~0.3-0.7 mL/g, with the model. At pH 8, the comparison was not as good and assumed to be due to variation in scintillator particle size realized in the experiment. From the flow-cell experiments performed at pH 8, the detection efficiency was determined to be 68% which correlated reasonably well with the model (60%). Where the experiments and model differed greatly was with K_d which was determined to be 102 and 60 for the flow-cell and batch experiments, respectively, and 0.43 from the model