[en] Optogalvanic spectra have been recorded by axially irradiating hollow uranium cathode glow discharge with a single-mode diode laser. Fifty uranium transitions have been tabulated with optogalvanic signal magnitudes in the 662-680, 774-792, 834-862 nm region for wavelength calibration. Atomic excitation temperature has been determined by the measured signal magnitudes

[en] A commercial power reactor generates transuranic elements (Np, Pu, Am, and Cm) in its fuel (UO_2). Understanding the dynamic interaction between these actinides and the environmental components is important for the safety assessment of a nuclear waste disposal in geologic repositories. In order to understand the actinide's behaviors in the environment, the detailed information about their physical and chemical reactions such as the redox, complexation, solubility, sorption, and transport, in natural waters should be investigated. In general, solubilities of actinide compounds are very low, therefore, the application of conventional absorption spectroscopy is limited for the study of physical and chemical reactions of actinides. A number of laser spectroscopic methods, TRLFS (Time Resolved Laser Fluorescence Spectroscopy) and LPAS (Laser induced Photo Acoustic Spectroscopy), have been developed with high sensitivity. These methods facilitate the direct chemical speciation of actinides with trace level concentration (below 10"-6"mole/L). On the other hand, LIBD (Laser Induced Breakdown Detection) method has been developed to measure colloidal nanoparticles in an aqueous solution. These nanoparticles in groundwater serve as a crucial carrier for the migration of water soluble radionuclides. Therefore, an accurate determination of the sizes of these nanoscale particles will improve our understanding of their behavior for the safety assessment of a nuclear waste disposal. In this work, a brief overview on TRLFS, LPAS, and LIBD is presented for the fields of application. Among these methods, the main topic is focused on the physical speciation of colloidal nanoparticles by LIBD

[en] The LIBS (laser induced breakdown spectroscopy) is one of the best methods to analyze the elemental composition of metal oxide samples without the pre-treatment process such as the dissolution of samples. In general, as the intensities of emission spectra caused by laser beams depends mainly on the structure and composition of target materials so called the matrix effect, the emission spectrum database on various metallic oxides should be prepared in order to apply the LIBS technique for the analysis of CRUD. In the present study, we prepared various metal mixed oxides to obtain LIBS spectrum database for the analysis of CRUD. The metal oxides were synthesized by a hydrolysis of nickel nitrate and iron nitrate mixed solutions and heat treated under a high temperature steam condition. Their composition, crystal structure and chemical bonding were identified by using ICP-AES (Inductive Coupled Plasma - Atomic Emission Spectroscopy) spectra, XRD (X-Ray Diffraction) patterns and FT-IR (Fourier Transform-Infrared Spectroscopy) spectra, respectively. After this, the emission spectrum database of the metals including Ni, Fe, Cr, B in the oxides were established in order to analyze the CRUD. In addition, we established a laser beam transport technique by using an optical fiber to improve the mobility of the analysis system

[en] we have fabricated solid-state dyes with PMMA and sol-gel materials. We developed various kinds of solid-state dye lasers, such as single mode laser, a self-seeded laser, a dualwave laser oscillator and DFDL with solid-state dyes and investigated their operation characteristics. And we have constructed the 3-color solid-state dye laser oscillator and amplifier system and observed 3-color operation. We studied the photostability of the solid-state dyes by adding various kinds of additives and achieved 3 times and 5 times enhancement in photostability in PMMA and sol-gel samples, respectively

[en] we have fabricated solid-state dyes with PMMA and sol-gel materials. We developed single longitudianl mode solid-state dye laser with the linewidth of less than 500MHz. We have constructed a self-seeded laser and observed the increase of the output power because of self-seeding effect. We investigated the operating characteristics of the dualwave laser oscillator and DFDL with solid-state dyes. And we have constructed the 3-color solid-state dye laser oscillator and amplifier system and observed 3-color operation. We also improved the laser oscliiator with disk-type solid-state dye cell which can be translated and rotated with the help of the two stepping motors. With the help of computer control, we could constantly changed the illuminated area of the dye cell and, therefore, were able to achieve long time operation and to use almost the entire region of the solid-state dye cell

[en] Actinide ions form stable aqueous complexes with anions such as hydroxide, carbonate and humic substance, which are ubiquitous in natural water. Since a dissolution and sorption of actinide ions largely depend on their species distribution in a groundwater condition, a microscopic understanding of their chemical behavior is required for a precise analysis of their safety in a radioactive waste disposal. Lanthanide ions, especially the Eu(III) ion, are used as chemical analogues of Am(III) or Cm(III) ions for a study of the chemical behaviors in a groundwater. Although the speciation of actinide ions has been studied by various means, still the exact feature in a natural aqueous solution is not clearly understood. Capillary electrophoresis (CE) has been developed to be applied not only to a separation and analysis but also to the determination of the physical parameters of chemical compounds, such as the mobility of colloidal particles and the stability constants of complexes. CE has advantages of a high separation efficiency, a high analysis speed, and a small sample requirement. CE separates chemical species in an electric field based on their charge and size properties which is observed as a migration time. The measurement of the stability constants of quick reversible equilibrium and kinetically inert systems can be approached by a direct formation, a ligand exchange, a metal exchange and a double exchange technique. In this report, the experience of setting-up a primeval CE system, and the measurement of ligand [acetate, picolinate, pyridine-2,6-dicarboxylate (PDA) and ethylenediaminetetra-acetate (EDTA)] effect on the electrophoretic migration of Eu(III) ions in a capillary column are described

[en] Speciation of actinide in natural aquatic system is of great interest for the safety assessment of a nuclear waste disposal in deep geological system. Actinide ions form complicate complexes with various ligands such as OH^-, CO₃^2-, and humic substances in groundwater. These complexes can enhance or reduce the migration of actinide elements. The direct speciation of these complexes in groundwater requires a highly sensitive and selective method which is capable to determine trace amount of actinides (down to 10^-9 M) and to identify the different complexes without separation. Time-resolved laser-induced fluorescence (TRLIF) spectroscopy is a very suitable method for trace analysis of some actinides such as uranium, curium and americium due to their fluorescence feature. In our recent work, a TRLIF system using a photomultiplier tube (PMT) coupled to a spectrometer was applied to investigate various U(VI) complexes. In this work, a modified TRLIF system using an intensified charge-coupled device (ICCD) camera is introduced and its performance is compared with the previous system for the speciation of uranium complexes. We have investigated the effect of background materials, such as HClO₄ and NaClO₄, on the lifetime of the UO₂²⁺ ions in liquid solutions. In addition, the speciation of U(VI)-OH complexes has been carried out in considering the lifetime of the free uranyl ions at a certain background material

[en] From the nuclear chemical point of view, ternary complex formation of actinide ions with ligands has attracted attention for understanding radionuclides' migration in the environment. There are various ligands in natural aquatic systems which can form stable ternary actinide complexes. Humic substance in a near-neutral groundwater is one of them and carboxylic groups in a humic substance are considered as the most likely functional group which interacts with actinides. In this work, the formation of the ternary complex of U(VI) with salicylic acid (SAH2) was investigated by two different laser-based spectroscopic methods, i.e., laser-induced breakdown detection (LIBD) and time-resolved laser fluorescence spectroscopy (TRLFS). The notable features are as follows: (i) the breakdown probability increases slightly, (ii) the absorbance of U(VI) increases, whereas the fluorescence intensity decreases with increasing salicylic acid concentration. The increase of the breakdown probability indicates that insoluble species are formed due to the complexation of U(VI) with SAH2. The decrease of the fluorescence intensity is due to the quenching effect of the SAH2 in the complexes. With regards to the instrumentation, the characteristics of a newly developed LIBD system adopting a probe beam deflection method are presented. We report also on the improved speciation sensitivity (∼10^-9M for UO₂²⁺) of the TRLFS system

[en] Actinide ions of a hard acid form stable aqueous complexes with anions of a hard base such as a hydroxide, carbonate and carboxylate which are ubiquitous in natural water. Since a dissolution and sorption of actinide ions depend on their chemical species distribution in groundwater conditions which largely influences their migration through a hydrogeological system, a microscopic understanding of their interaction with a ligand functional group is required for a precise analysis of their safety in a radioactive waste disposal site

[en] The chemical reaction of radionuclides at the interface between groundwater and geological mineral is an important process determining their retardation of transport through groundwater flow in a nuclear waste disposal. Clay minerals are major components of soil and argillaceous rock, and some of them are considered to be important base materials in the design of high-level nuclear waste repository due to their large swelling, low-permeability, large surface area, and strong and large sorption of radionuclides. Clay materials are phyllosilicates containing accessory minerals such as metal oxides, hydroxides, oxyhydroxides. Their structures are condensed 1:1 or 2:1 layers of tetrahedral SiO_3/2OH and octahedral Al(OH)_6/2 sheets. An accurate knowledge about the properties of clay surface is required as a parameter for a long-term estimation of radionuclide retardation effects. Electric surface charge is a primary property determining ion exchange and surface complexation of radionuclides on its surface. The sources of electric surface charge are a permanent structural negative charge on a basal plane and a dissociable charge at an edge surface. Investigation of proton sorption is a prerequisite to the understanding of radionuclide sorption. The reactions on a permanently charged site and on an edge site are measured by an electrokinetic measurement and by potentiometric titration, respectively. However, side reactions such as complexation, proton/cation exchange, dissolution, hydrolysis, precipitation and re adsorption, and the reaction of secondary minerals hinder an experimental measurement of accurate acid-base properties. This presentation describes the pH change on dispersing various clays in water and adding acid, base or Eu(III) ion to these solutions, and the effect of Eu(III) ion on acid-base titration of clay solutions