Influence of tungsten–carbon mixed layer and irradiation defects on deuterium retention behavior in tungsten

The D₂⁺ fluence dependence on deuterium (D) retention was studied to clarify the D retention mechanism in tungsten. The additional D desorption stage was observed around 660 K in the TDS spectrum for a sample implanted with D₂⁺ up to the fluence of 10²³ D⁺ m^?2, which desorption stage was not observed the D₂⁺ implanted sample with the fluence less than 10²² D⁺ m^?2. The TEM observation showed that the highly dense voids were formed in tungsten by D₂⁺ implantation with the fluence of 10²³ D⁺ m^?2, considering that the D would be trapped by voids. To understand the D trapping by voids in C⁺ implanted tungsten, C⁺–D₂⁺ sequential implantation experiments at various C⁺ implantation temperatures were performed. It was found that the amount of D desorbed around 560 K was increased by increasing the C⁺ implantation temperature. The formation of the voids was observed with increasing the C⁺ implantation temperature by TEM, indicating that the increase of D desorption around 560 K was caused by the formation of voids. However, the desorption temperature of D trapped by voids in C⁺ implanted sample was lower than that in D₂⁺ implanted one. TEM observation and XPS measurement indicated that this difference was caused by the increase of void size and/or the presence of implanted carbon.     

Study on chemical structures of poly (tetrafluoroethylene-co-perfluoroalkylvinylether) by soft-EB irradiation in solid and molten state

Poly (tetrafluoroethylene-co-perfluoroalkylvinylether) (PFA) was irradiated by soft electron beam (soft-EB) under nitrogen gas atmosphere in solid-state and its molten state, respectively. The changes of thermal property and chemical structures of irradiated PFA in solid-state and molten state were studied by differential scanning calorimetric analysis (DSC) and solid-state ¹⁹F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. By DSC analysis, the melting temperature shifted to lower temperatures, and crystallinity decreased with increasing soft-EB dose. By solid-state ¹⁹F MAS NMR spectroscopy, the new signals was observed and the detected new signals in irradiated PFA at 315 °C and at 30 °C were due to the tertiary carbon group with branching site (Y-type crosslinking site), perfluoro-propylene site and chain end methylene groups, respectively.Moreover, the molar ratio of perfluoroalkylvinylether (FAVE) structure to -CF₂- units decreased with increasing dose.     

Present status of beryllides for fusion and industrial applications in Japan

Beryllides have remarkable characteristics besides their low density, such as high radiation resistance, high chemical stability, low hydrogen isotope retention and good high temperature mechanical strength especially for fusion applications. In order to have a practical usage for industrial applications, it is important to compile a set of quantitative data on such properties. It is also important to develop fabrication and processing paths to assure the processing of inherently brittle beryllides.The characterization and manufacturing technologies development have been carried out mainly on the Be₁₂Ti interemetallic compounds at the Be-rich side of the Be-Ti binary system. In the present paper, up-dated results on several properties are described for the compound fabricated by hot isostatic pressing (HIP) and ingot metallurgy. Mechanical properties of the compounds having a duplex microstructure with neighboring phases are evaluated by compressive tests from room temperature to 1273 K. Radiation damage of the compound is preliminary studied by charged particle irradiation. Oxidation in air and the interaction with water vapor are evaluated. Thermal desorption of the deuterium is examined by using transmission electron microscopy (TEM) and thermal desorption spectrometry (TDS). Through these evaluations it seems that Be₁₂Ti is superior as neutron multiplier with respect to pure Be metal.     

Hot carrier magnetophonon spectroscopy of semiconductors in high magnetic fields up to 40 T

Hot carrier magnetophonon resonances of n-type Si, short channel InP and p-type InSb were investigated in pulsed high magnetic fields up to 40 T. Using a recently developed high resolution technique in pulsed high fields, many new features of the hot carrier-phonon interactions in high magnetic fields were found.     

Preloading clayey deposit by vacuum pressure with cap-drain: Analyses versus performance

A method of improving soft clayey deposit by combining cap-drain (CPVD) with vacuum pressure is described. The method uses a surface or subsurface soil layer as a sealing layer with no need to place an air-tightening sheet on the ground surface. It is explained that the method has advantages for the following situations: (a) a higher air/water permeability layer at ground surface and (b) combining vacuum pressure with embankment load. A case history of consolidating a reclaimed clayey deposit by combining CPVD with vacuum pressure is analyzed and discussed. The site was in an under-consolidated state before starting the project. It is shown that the method is effective, and the method proposed by Chai et al. [Ground deformation induced by vacuum consolidation. Journal of Geotechnical and Geoenvironmental Engineering, ASCE 131(12), 1552–1561] for calculating the vacuum-pressure-induced ground deformation is useful for the design of the vacuum consolidation project. The back-calculation shows that for this under-consolidated deposit, vacuum pressure caused plane strain type isotropic deformation near the ground surface.     

Polonium evaporation and adhesion experiments for the development of polonium filter in lead–bismuth cooled reactors

Fundamental experiments were performed to determine the adhesion characteristics of polonium to different metals and to develop a filter for polonium evaporated from neutron-irradiated LBE. The results of the first experiments suggested that adhesion characteristics are almost the same for stainless steel and nickel metal. The results of the preliminary experiments for a polonium filter suggested that stainless steel mesh with thin wires could effectively collect polonium evaporated from neutron-irradiated LBE. In the experiments, stainless steel wire mesh was used, but from the results of adhesion experiment, it is expected that the same effect can be obtained with wire mesh made of other kinds of metal.     

The effect of probability of coalescence on the evolution of bubble sizes in a turbulent pipeline flow: A numerical study

A population balance method in which continuum and discrete phases are integrated is developed to simulate the evolution of polydisperse population of bubbles in a turbulent pipeline flow. The investigation is focused on the effect of the coalescence efficiency on this evolution. A dilute system of bubbles under microgravity conditions is considered. It is found that if the initial coalescence efficiency is low, a slight increase produces a significant effect on the bubble coalescence rate, and thus on the evolution of the population. If, however, the initial coalescence efficiency is high, its increase results in a marginal effect on the way the population evolves. The results of simulations are validated against experimental data on the population mean.     

Characteristics of a Nonstoichiometric Gd3+δ(Al,Ga)5−δO12:Ce Garnet Scintillator

We have developed a new nonstoichiometric Gd_3+δ(Al,Ga)_5−δO₁₂:Ce garnet scintillator for an X-ray CT scanner. For commercially used scintillators, reproducible luminescence properties are of great importance. We have found that the afterglow properties of the garnet change drastically in the vicinity of the stoichiometric compositions. The most suitable properties are obtained at slightly excess (Gd,Ce) compositions from the stoichiometry. In order to investigate the afterglow properties, crystallography arrangements, phase equilibrium relationship between crystal phases, and luminescence characteristics of host material doped with different valence ions have been examined. The luminescence properties are explained by isoelectronic traps based on the difference in the electronegativity of the dopant and host ions, which would act as electron trap centers and hole trap centers within the band gap.     

Voluntary exercise influences behavioral development in rats exposed to alcohol during the neonatal brain growth spurt.

Children exposed to alcohol prenatally may suffer from severe brain damage, expressed as a variety of behavioral problems, including hyperactivity and learning deficits. There is a critical need to identify effective treatments for fetal alcohol effects. Physical exercise enhances cognitive ability and increases neurogenesis in the hippocampus, a brain area important for learning and memory. Thus, the present study examined whether physical exercise might reduce the severity of alcohol-induced behavioral alterations. Sprague-Dawley rats were intubated with 5.25 g/kg/day ethanol during the third trimester equivalent (postnatal days [PDs] 4-9). Intubated sham control and nontreated controls were included. From PD 21 to PD 51, half of the subjects were given access to running wheels. On PD 52, subjects were tested on the Morris water maze, and on PD 60, open field activity levels were measured. Morris maze performance was significantly impaired among ethanol-exposed subjects; exercise significantly improved performance of all groups. Similarly, ethanol-exposed subjects were overactive in the open field, an effect attenuated with exercise. In sum, these data suggest that exercise may increase neuronal plasticity not only in controls, but also in subjects exposed to alcohol during development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Liquidus and solidus temperatures of Ni-solid solution in Ni-Al-X (X: Ti, Zr, and Hf) ternary systems

A systematic investigation has been carried out to determine both the γ liquidus and solidus surfaces above the Ni solid solution in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis. Each of the group IV elements in the periodic table, Ti, Zr, and Hf, was chosen as the ternary additive X in the present study. As a basis, γ liquidus and solidus temperatures in the Ni-Al binary system were reinvestigated and evaluated. The γ solvus was also taken into account to determine a temperature range for a solid-solution treatment above the γ solvus, generally called “the window,” as well as the maximum solubility limit of γNi solid solution.