Design Study of Top Lid with Clamp Structure in JT-60SA Cryostat

JT-60SA is a fully superconducting coil tokamak upgraded from the JT-60U. This paper focused on the integrity of the top lid of cryostat in JT-60SA. The design requirement for the cryostat in normal operations is to achieve vacuum insulation of 10 3 Pa, and the top flange of the top lid is lightly welded onto its body flange. The weld is tensile-loaded by bending deformation of the top lid due to vacuum pressure of external 0.1 MPa. This weld integrity is evaluated with tensile-load reduction, which results in clamp reinforcement. The structural integrity of the top lid is validated.     

Pore Structure of Calcium Silicate Hydrate in Hydrated Tricalcium Silicate

Adsorption of N₂ and water vapor was studied in completely hydrated tricalcium silicate and in fully hydrated tricalcium silicate from which Ca(OH)₂ had been extracted. Compared with results obtained using N₂, water vapor adsorption led to increased values for small-pore volume, peak shifts to smaller sizes, and decreased values for large-pore volume. Marked hysteresis was observed in the case of water vapor adsorption; the resorption branch apparently represents the true pore structure. Extraction of Ca(OH)₂ from the paste increased the calculated volume of small pores strikingly, suggesting that adsorption is hindered by Ca(OH)₂; this tendency is more obvious in water vapor adsorption. The adsorption measurements indicate the existence of two kinds of pores, i.e. a wider intergel-particle pore and a smaller pore existing within the gel particle. The latter pore was further classified into intercrystallite and intracrystallite pores.     

Development of High‐Power Density Interleaved dc/dc Converter with SiC Devices

We developed an interleaved dc/dc converter with SiC devices. We applied full‐SiC modules including MOSFETs and SBDs to the interleaved dc/dc converter to achieve a high‐power density. An SiC has a high temperature resistance, which facilitates an improvement in high‐frequency drives. We achieved a high‐power density by utilizing this high temperature resistance. We also fabricated a prototype and tested it with loads up to 65 kW.     

Limonoid Glucosides in Fruit, Juice and Processing by-products of Satsuma Mandarin (Chus unshiu Marcov.)

In a study on improving utilization of waste from processing of Satsuma mandarin (Citrus unshiu Marcov.) the limonoid glucosides of fruit, juice, and by-products were measured using HPLC and TLC. All materials had the 17-β-D-glucopyranoside derivatives of limonoids reported in other commercial citrus fruit. Citrus molasses was a good source for industrial scale extraction of limonoid glucosides. An extraction system using polystyrene divinylbenzene resins, was developed which could be expanded to industrial scale.     

Study on Mechanism of Hydrogen Generation from Lubricants

To establish fundamental countermeasures for hydrogen embrittlement that occurs to several kinds of bearings, the mechanism of hydrogen generation from lubricants was studied. Sliding tests were conducted, and the amount of hydrogen generated from several kinds of lubricants during sliding was measured. It is concluded that the lubricant is decomposed and hydrogen is generated through a catalytic reaction with the fresh steel surface. The amount of hydrogen generated from each lubricant depends on its lubricity, not on its chemical structure. It is also confirmed that the lubricant with the larger wear brings more generated hydrogen into steel. Based on the above mechanism of hydrogen generation, methods of inhibiting hydrogen brittle flaking with additives were investigated. It is clarified that the addition of corrosion inhibitors that form a passive state film on the steel surface effectively inhibits generation of hydrogen from lubricants and penetration of hydrogen into steel.

     

Solid Solutions in the System Taeniolite-Sodium Taeniolite and Their Properties

Solid solutions in the system taeniolite (KMg₂LiSi₄O₁₀F₂)-sodium taeniolite (NaMg₂LiSi₄O₁₀F₂) were synthesized to study the solid solubility and swelling characteristics. Based on their melting behavior, crystals were grown for X-ray structural analysis. A complete solid solution series does not form in this system; there are two types of micas, K-rich taeniolite (0≤ x <0.5, x = Na/Na + K) and Na-rich taeniolite (0.8< x ≤l). The Na-rich taeniolite exhibits swelling properties, which become less pronounced with increasing potassium content. Melting and crystallization behavior were investigated by DTA. Solid solutions with higher sodium content melted at lower temperatures and crystallization occurred over a wide range of temperatures. To obtain larger crystals, the samples containing small crystallites were remelted at slightly above their melting points, then cooled slowly.     

Composition and Morphology of Hydrated Tricalcium Silicate

Hardened C₃S paste cured for 1 year at 20°C was examined to confirm the composition and the morphology of hydrated tricalcium silicate. A new technique was used in which the samples for scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were etched in 1% HNO₃-alcohol or in glycerol-alcohol (4:6 by volume). After the surface was etched in 1% HNO₃-alcohol, SEM clearly showed the difference in texture in the outer and inner C-S-H products. The existence of a zonal texture within the inner C-S-H products was shown, in addition to the unreacted core; particles 0.1 to 0.2 μm in diameter were observed. After free CH extraction with glycerol-alcohol, two new types of C-S-H grains could be identified. One type has a smooth surface, which seems to be produced from C₃S grains trapped within the growing CH crystals in the early stage of hydration, the C/S mol ratio for these being >3. The other type is covered with many acicular outer C-S-H gel hydration products and has a C/S mol ratio >3.     

Mechanical properties of toughened ZrO2-Y2O3 Ceramics

Tetragonal zirconia polycrystals were produced from high-purity powders containing 1.5 to 5.0 mol% Y₂O₃ by cold isostatic pressing and sintering, hot-pressing, and hot isostatic pressing. The mechanical properties and microstructures of these resulting materials were examined, with emphasis on the relation between strength and fracture toughness.     

Limonoid glucosides in Orange Molasses

The concentrations of limonoid glucosides in orange molasses, a byproduct of citrus juice processing, were measured. The 17-β-D-gluco-pyranoside derivatives (glucosides) of limonin, nomilin, nomilinic acid and obacunone were present and quantified. Orange molasses contained an average of 568 ppm of total limonoid glucosides at 11.8°Brix. Orange molasses (3.8L) contained up to 12.5g of total limonoid glucosides. The molasses could be used as a source for commercial isolation of citrus limonoid glucosides.     

Mechanical Properties of Y2O3-Stabilized Tetragonal ZrO2 Polycrystals After Ageing at High Temperature

Yttria-partially-stabilized zirconia (Y-PSZ) materials containing 2.5, 3.0, and 5.0 mol% of Y₂O₃ prepared by hot pressing were subjected to ageing in air for >10 h at temperatures in the range of 800°C and 1200°C. The sintered materials were measured to determine the mechanical properties and microstructures and analyzed for trace elements. A sharp reduction in bending strength was observed after the ageing, the cause for which was suggested to be the formation of cavities produced by the oxidation of carbon.