[en] The geoscientific study on geological disposal for radioactive wastes has established the stepwise site characterization program, methods and investigation technology. However the intrinsic properties of geological material such as heterogeneity and scale dependent properties make difficulty on satisfactory understanding of geological conditions. To avoid unnecessary time delay and unexpected extra-cost for site investigation, the accurate and complete site investigation program should be established in a stepwise manner and the QC programs for investigation methods and procedures. Moreover, the technical requirements and preferences for a repository should be distinguished and be assessed at the end of each investigation step

[en] Iron doped TiO_2 nanoparticles were prepared under the high temperature and pressure conditions by mixture of metal nitrates solution and TiO_2 sol. Fe doped TiO_2 particles were reaction at the temperature range of 170°C–200°C for 6 h. The microstructure and phase of synthesized particles were studied by SEM(FE-SEM), TEM and XRD. Thermal properties of the synthesized particles were investigated by TG-DTA analysis. Also, Specific Surface Area of synthesized particles were studied by BET analysis. X-ray diffraction pattern shows that the synthesized particles shows the coexistence of anatase and rutile reaction at the temperature range of 170°C to 200°C for 6 h. The amount of rutile phase on the synthesized particles increased with decreasing Ag concentration in solution because the less a content of the transposition metal, the easier to phase transition in the same temperature condition. The average size and distribution of the synthesized particles was about 10nm and narrow, respectively. The average size of the synthesized particles increased as reaction temperature increased. Also, BET surface areas of synthesized particles by a hydrothermal process were found to be larger than that of pure TiO_2 which is synthesized by a sol-gel process

[en] Nanosized SrFe₂O₄ powders were prepared by precipitation followed by reaction at the moderate temperature and pressure. Nanosized SrFe₂O₄ powders were obtained by reaction at 200 deg C for 6 h. The average size of synthesized particles was in the range of 5 to 20 nim and the phase of synthesized particles was crystalline. The magnetic character of the synthesized SrFe₂O₄ particles was superparamagnetic. The effects of pH of starting solution is discussed. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd

[en] The preparation of CoFe_2O_4 nanoparticles in Igepal CO-520-cyclohexane-water reverse micelle solutions has been studied. Transmission electron microscopy and X-ray diffraction pattern analyses revealed the resultant particles to be CoFe_2O_4. The average size and distribution of synthesized particles calcined at 600"0C for 2 hrs were in the range of 30 to 70 nm and broaden, respectively. The phase of synthesized particles was crystalline. The magnetic behavior of the synthesized particles was ferromagnetism. The effects of synthesis parameters, such as the molar ratio of water to surfactant and calcination temperature, are discussed

[en] The block scale hydrogeological model around KURT area was suggested. In order to construct the hydrogeological model including the major water conducting features around KURT area, the uncertainties on hydrogeological understandings, which were included in previous model, was identified. To access the hydrogeological change after KURT extension, the hydrogeological model including MWCF around KURT were constructed. Water head pressure, geochemical data and ground water samples through the depth were analyzed from the multi-packered monitoring boreholes in KURT. Geochemical characteristics were evaluated in respect of redox condition and reactions between water and fracture-filling minerals in MWCF. With the calculated cluster density, the correlation length for background fractures was estimated and suggested as an appropriate domain size for stochastic DFN modeling. To characterize the solute transport properties of MWCF, requisites for minimizing the experimental errors in a tracer test were introduced. Considering the introduced requisites, the tracer injection and sampling systems for a tracer test at MWCF were designed and manufactured. Considering the conclusions of the previous studies, tracer tests were conducted, and the transport characteristics of MWCF were evaluated. To validate groundwater flow modeling around KURT area, the results from modeling were compared with the results of in-situ hydraulic tests (long term interference test). The results from hydrological model using particle backward tracking also showed the groundwater flow rate was negligible below 450m in KURT site. Thus, both of approaches can be applied together to determine the depth or location for radioactive waste disposal based on geochemical and hydrological characteristics of KURT site.

[en] Trivalent europium-ion-doped Y₂SiO₅ phosphors are synthesized by using the reverse micelle and the sol-gel processes. The crystallinity, morphology, and chemical states of the ions are characterized, and the photophysical properties are studied by taking absorption, excitation, and emission spectra for various concentrations of europium. Y₂SiO₅:Eu³⁺ is a red-emitting phosphor, has a higher efficiency for operation under near UV excitation, and may be a promising candidate for photonic applications.

[en] The mechanical properties of SiC based composites reinforced with different types of fabrics have been investigated, in conjunction with the detailed analyses of their microstructures. The thermal shock properties of SiC_f/SiC composites were also examined. All composites showed a dense morphology in the matrix region. Carbon coated PW-SiC_f/SiC composites had a good fracture energy, even if their strength was lower than that of PW-C_f/SiC composites. SiC_f/SiC composites represented a great reduction of flexural strength at the thermal shock temperature difference of 300 deg. C.