Effect of alkali and alkaline-earth chloride addition on electrolytic reduction of UO2 in LiCl salt bath

The electrolytic reduction process of actinide oxides in a LiCl salt bath at 923 K has been developed for nuclear fuel reprocessing. Since some salt-soluble fission products, such as Cs, Sr and Ba, accumulate in the LiCl salt bath, their effect on UO₂ reduction was investigated. In the experiments, UO₂ specimens were reduced by potential- or current-controlled electrolysis in various LiCl salt baths containing up to 30 mol% of KCl, CsCl, SrCl₂ or BaCl₂. The rate of UO₂ reduction in a LiCl salt bath was considerably decreased by the addition of alkali metal chlorides (KCl and CsCl) and slightly decreased by BaCl₂ addition. SrCl₂ addition had no appreciable effect. It was suggested that the diffusion of O²⁻ ions from the inside of UO₂ specimens to the bulk salt determined the reduction rate during the electrolysis and that the effect of salt composition was related to the solubility of O²⁻ ions in the salt bath.     

Experimental investigation on self-leveling behavior in debris beds

During a hypothetical core-disruptive accident in a sodium-cooled fast breeder reactor, degraded core materials can form debris beds on the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of core material pool. Coolant boiling may lead ultimately to leveling of the debris bed that is crucial to the relocation of molten core and heat-removal capability of the debris bed. In the present study, we elected to use depressurization boiling to simulate an axially increasing void distribution in the debris bed. Bottom-heating boiling was also chosen to confirm that characteristics of the self-leveling process do not depend on the boiling mode. Particle size (between 0.5 and 6 mm), shape (spherical and non-spherical), bed volume (between 5 and 8 l) and density (namely of alumina, zirconia, lead and stainless steel) along with boiling intensity and total volume were taken as experimental parameters to obtain the general characteristics of the self-leveling process. A series of experiments with simulant materials were conducted and analyzed in detail. The good concordance of the transient processes obtained from the different boiling methods sufficiently demonstrates that the present results obtained using the depressurization boiling method exhibit these general self-leveling characteristics. Detailed comparisons of deduced time variations of the inclination angle provides qualitative tendencies based on the experimental parameters considered influential to self-leveling behavior. The rationale behind the definition introduced for equivalent power density is also presented.     

Detection of cytochrome P450 substrates by using a small-molecule droplet array on an NADH-immobilized solid surface

Seeing below the surface: A small-molecule droplet array platform on an NADH-immobilized solid surface and a biotinylated acetophenone derivative were developed to identify the substrate candidates for soluble P450 enzymes of interest. This methodology is thought to be easily applicable to other class I P450 systems, including those that use NADPH as cofactor.     

Generation control circuit for photovoltaic modules

Photovoltaic modules must generally be connected in series in order to produce the voltage required to efficiently drive an inverter. However, if even a very small part of photovoltaic module (PV module) is prevented from receiving light, the generation power of the PV module is decreased disproportionately. This greater than expected decrease occurs because PV modules which do not receive adequate light cannot operate on the normal operating point, but rather operate as loads. As a result, the total power from the PV modules is decreased if even only a small part of the PV modules are shaded. In the present paper, a novel circuit, referred to as the generation control circuit (GCC), which enables maximum power to be obtained from all of the PV modules even if some of the modules are prevented from receiving light. The proposed circuit enables the individual PV modules to operate effectively at the maximum power point tracking, irrespective of the series connected PV module system. In addition, the total generated power is shown experimentally to increase for the experimental set-up used in the present study     

Stress intensity factors of a surface crack near an interface end

Due to the singular behavior of the stress field near the interface edge of bonded dissimilar materials, fracture generally initiates near the interface edge, or just from the interface edge point. In this paper, an edge crack near the interface, which can be considered as being induced by the edge singularity and satisfying two conditions, is analyzed theoretically, based on the singular stress field near the interface edge and the superposition principle. It is found that the stress intensity factor can be expressed by the stress intensity coefficient of the edge singular stress field, the crack length, the distance between the interface and the crack, as well as the material combination. Boundary element method analysis is also carried out. It is found that the theoretical result coincides well with the numerical result when the crack length is small. Therefore, the theoretical representation obtained by this study can be used to simply evaluate the stress intensity factor of an edge singularity induced crack for this case. However, when the crack length becomes larger than a certain value, a significant difference appears, especially for the case with large edge singularity.     

Effect of Moisture on the High-Temperature Stability of Unidirectionally Solidified Al2O3/YAG Eutectic Composites

The corrosion resistance of a unidirectionally solidified alumina/yttrium aluminum garnet (Al₂O₃/YAG) eutectic mixture was investigated at high temperature. Samples were exposed to high temperature (1200°–1800°C) in different atmospheres, which included argon, argon/water vapor, air, and air/water vapor. The most important microstructural changes occurred at the interface between the YAG and the Al₂O₃. Those changes consisted of localized thermal grooving, especially when the corrosive atmosphere contained water vapor. The samples exhibited significant weight loss at high temperature (1800°C) after 20 h of exposure. The calculated volume gain that was induced by the increased surface relief was low and limited, except when the corrosive atmosphere contained air, which indicated that the presence of air (particularly oxygen) induced a more-active corrosion process. On the other hand, no change in the flexural strength was observed, even after 100 h at 1800°C in a humid atmosphere, because of the cross-linked structure of the composite, which limited propagation of the groove.     

Wavelength optimization for machining metals with the harmonic generations of a short pulsed Nd:YAG laser

The wavelength conversion for a short pulsed Nd:YAG laser has been implemented from infrared to visible and to ultraviolet spectra by using nonlinear optical crystals. The analytical method of wavelength optimization for machining metals with various harmonic generations of a Nd:YAG laser is presented in this paper. Combining the absorptivity of metal and the conversion efficiency of laser apparatus, the absorption efficiency is proposed to select an optimum machining wavelength. Various metals have different optimum machining wavelengths. The optimum machining wavelengths for gold, silver, and copper are in the third-, fourth- and second-harmonic generations of a Nd:YAG laser, respectively. For other metals, such as nickel, their optimum machining wavelengths are all in the fundamental wavelength of a Nd:YAG laser.     

Effects of Mg doping on structural, optical, and electrical properties of CuScO2(0001) epitaxial films

CuScO₂ thin films with different Mg concentrations were grown on a-plane sapphire substrates by combining the two-step deposition and post-annealing techniques using Cu₂(Sc_1−xMg_x)₂O_y [X = 0.01, 0.05, 0.10] targets. The effects of the Mg doping in the Sc-site on the structural, optical, and electrical properties of the films were investigated. A Mg-doped CuScO₂[3R](0001) epitaxial film was obtained at a Mg concentration of 1 at%. The slight increase in the a-axis lattice constant and the slight decrease in the c-axis lattice constant of the film were confirmed using two-dimensional X-ray reciprocal space mapping. No significant increase in optical absorption was observed in the film, and the energy gap for direct allowed transition was estimated at 3.7 eV. The film showed an increase in the electrical conductivity and carrier concentration and a decrease in the Hall mobility compared with those of the non-doped epitaxial film. The decrease in the overlap of Cu 3d orbitals due to the increase in the a-axis lattice constant is one cause of the decrease in the Hall mobility of the film. The temperature dependence of the electrical transport properties of the film exhibited semiconducting characteristics, and the activation energy estimated from the temperature dependence of the carrier concentration was 0.55 eV.     

Synthesis of an Enantiocomplementary Catalyst of β‐Isocupreidine (β‐ICD) from Quinine

Compound 20 , a pseudoenantiomer of β‐isocupreidine (β‐ICD), was synthesized from quinine employing a Barton reaction of nitrosyl ester 13 and acid‐catalyzed cyclization of carbinol 18 as key steps. The Baylis–Hillman reaction of benzaldehyde, p‐nitrobenzaldehyde, and hydrocinnamaldehyde with 1,1,1,3,3,3‐hexafluoroisopropyl acrylate (HFIPA) using 20 as a chiral amine catalyst was found to give the corresponding S‐enriched adducts in high optical purity (>91% ee) in contrast to the β‐ICD‐catalyzed reaction which affords R‐enriched adducts. This result suggests that compound 20 can serve as an enantiocomplementary catalyst of β‐ICD in the asymmetric Baylis–Hillman reaction of aldehydes with HFIPA.