Jae Hyung Yoo

Precipitation characteristics of palladium from a simulated radioactive liquid waste by Ascorbic Acid

The precipitation characteristics of palladium (Pd) from a simulated radwaste solution by ascorbic acid was investigated. Pd was selectively precipitated by the reduction reaction of Pd with ascorbic acid. When the nitric acid concentration in the 8 component system was below 2.0 M, Pd over 99.5 % was selectively precipitated at an ascorbic acid concentration above 0.06 M, while other elements mainly remained in solution. The precipitation yield of Pd by ascorbic acid decreased with the increase of the nitric acid concentration.

Laser-induced Fluorescence Studies on Sm(III) and Cm(III) Complexes in the HNO3/DHDECMP Extraction System

Laser-induced fluorescence(LIF) studies of Sm(III) and Cm(III) complexes in the HNO3/DHDECMP solvent extraction system have been carried out. Luminescence lifetime together with LIF spectra were measured to determine the number of water molecules coordinated to Sm(III) and Cm(III) in a nitric acid solution and in the DHDECMP phase. The hydration number of Sm(III) and Cm(III) in the nitric acid solution decreased linearly with an increasing nitric acid concentration. The hydration numbers of Sm(III) and Cm(III) in the DHDECMP phase decreased with an increase of nitric acid concentration and the water molecules in the inner coordination sphere were not completely removed at the low nitric acid concentration.

Metal hydride characteristics by Zr and Ti

Hydrogen absorption experiments were carried out using zirconium (Zr) and titanium (Ti) in the form of a metal sponge, strip and rod to investigate the metal hydride characteristics. The Zr and Ti sponges showed a high hydrogen absorption capacity despite a low reaction temperature. The H/M, which indicates the capacity of hydrogen absorption, was measured at 2.0 for the Zr/Ti sponge at 25 ‡C. In the case of the Zr/Ti strip and rod, however, the hydrogen absorption capacity was very low at 25 ‡C. The capacity of hydrogen absorption increased with an increase in the reaction temperature. When the Ti strip was not activated, the H/M ratio was measured at 0.58. When the Ti strip was once and twice activated at 800 ‡C for 1 hour, the H/M ratio increased to 1.6 and 1.83, respectively. The hydrogen absorption capacity decreased with the increment of concentration of helium in hydrogen due to a blanketing effect of metal surface by the helium. A pulverizing phenomenon during the metal hydriding was observed in both the Zr/Ti strip and the Zr/Ti rod. However, this pulverizing phenomenon was not observed in the Zr/Ti sponges because of their high surface area.

Modeling of Mass Transport with Simultaneous Diffusion and Chemical Reaction in Liquid Membrane Systems

ABSTRACT A Model of general use for the interpretation of mass transport within emulsion drops in liquid surfactant membrane processes is presented. This model is focused on the mass transfer rate at the internal surfaces around encapsulated droplets inside the drops, which can be enhanced by a fast chemical reaction. Since the mass transfer rate at the internal boundaries is a major rate controlling step in the emulsion-type membranes, both the diffusivity of permeating species and the internal mass transfer rate are simultaneously considered as rate determining parameters in the model. The model predictions are compared with the experimental results for an aniline separation process.