Re-evaluation of Radiation-Energy Transfer to an Extraction Solvent in a Minor-Actinide-Separation Process Based on Consideration of Radiation Permeability

ABSTRACT

Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process.     

Combustion synthesis of AlN doped with carbon and oxygen

Carbon-and-oxygen-doped AlN specimens were prepared by combustion synthesis using Al, graphite, and AlN. Graphite addition changed the product color from white to blue. By XRD, the lattice constant increased slightly with increasing carbon content. Blue AlN powder was synthesized with a molar ratio of the diluent AlN of 0.2-0.5 with a fixed graphite content of 0.05. At an AlN molar ratio exceeding 0.6, carbon was not successfully incorporated due to the lower reaction temperature. Calcination at 800°C in air removed residual graphite without changing the crystal structure or product color. Oxygen, nitrogen, and carbon analyses revealed that blue AlN powders contained 0.45-0.54 mass% carbon and 1.4-1.6 mass% oxygen, while the undoped AlN contained 0.021 mass% carbon and 0.94 mass% oxygen. The origin of the white-to-blue color change was investigated via reflection measurements. Blue AlN exhibits an absorption peak at 634 nm (1.96 eV). From first-principles electronic structure calculations, the C-doped AlN and carbon-and-oxygen-doped AlN with a 1:1 ratio could be classified as p-type, whereas the O-doped AlN and 1:3 carbon-and-oxygen-doped AlN were n-type. One reason for the absorption peak at 634 nm may be a transition from the conduction band to an upper unoccupied state. These results suggest the possible control of optical and electronic properties of AlN via carbon-and-oxygen doping.     

Effect of Milling on Slip Casting of Partially Stabilized Zirconia

Specimens of partially stabilized zirconia were slip cast from aqueous suspensions and sintered at 1500°C for 3 h. The relative density of the cast specimens and the firing shrinkage of the sintered specimens depend on the milling time for the suspension. Vickers hardness and K_IC values of 11.46±s0.07 GN/m² and 6.10 ±0.04 MN.m^3/2, respectively, were obtained for all sintered specimens. The dispersion of the suspension is important in increasing the relative density of the cast specimens.     

Photocatalytic Property and Electronic Structure of Lanthanide-based Oxysulfides

Lanthanide-based oxysulfides and sulfide, LnTaO_3.5S_0.5, Ln₁₀OS₁₄ (Ln = La, Pr, Nd, Sm) and La₄In₅S₁₃, were successively synthesized by sulfurization in a flowing H₂S. The sulfurization decreased the band-gap energies from >4 eV to <3eV, because of the formation of occupied S3p orbitals on the top of valence band. In accordance with the small band gap, the H₂ evolution from a 0.01 M Na₂S and 0.01 M Na₂SO₃ solution system was observed under irradiation of light up to >500 nm. The rate of H₂ evolution under light irradiation of >500 nm increased in the order of Ni/LaTaO_3.5S_0.5 < Ru/La₁₀OS₁₄ < Pt/La₄In₅S₁₃.     

A transceiver PIC for bidirectional optical communication fabricated by bandgap energy controlled selective MOVPE

A transceiver PIC consisting of a DFB-LD, a receiver PD and a Y-shaped branch waveguides is realized by in-plane bandgap energy controlled selective MOVPE. Both active and passive core layers are formed in one step selective growth, and complicated fabrication procedure is no longer required. More than 1 mW fiber coupled power and 7 GHz receiver bandwidth are obtained. The modulation and detection operations at 500 Mb/s are successfully demonstrated.     

Efficacy of interferons in treating children with chronic hepatitis C

Twenty-two children with chronic hepatitis serologically positive for hepatitis C virus (HCV) were treated with interferon-alpha (IFN-alpha). Liver biopsy showed chronic active hepatitis in 13 and chronic persistent hepatitis in 9 patients. A sustained clearance of HCV was observed in 8/22 children 12 months after the administration of IFN-alpha for 26 weeks, associated with normalization of HCV core antibody. Of these eight patients six had HCV genotype III and two HCV genotype II or IV. Hepatitis relapsed in seven other patients after completion of IFN-alpha with an increase in HCV core antibody titre, five with HCV genotype II, and two with HCV genotype III or IV. A second course of IFN-alpha suppressed the reactivation of HCV in all seven patients. Three of seven responders who relapsed after the first course remained negative for HCV RNA 12 months after their second course of IFN-alpha. However, the remaining four patients with HCV genotype II again relapsed after completing their second course of IFN-alpha. Seven children with the HCV genotype II resistant to IFN, including 8 weeks of IFN-beta administration, and showed no significant reduction in HCV core antibody titre. CONCLUSION: The genotype of HCV (III) and a reduction in the core antibody titre appear to be useful parameters for predicting the response to IFN-alpha therapy.     

Stabilization of bioethanol recovery with silicone rubber‐coated ethanol‐permselective silicalite membranes by controlling the pH of acidic feed solution

In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry