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Abstract: Out-of-pile tritium release experiments under different water uptake contents and purge gas chemistry were performed on Li4SiO4. Water measurement was performed on samples under different experimental procedures. It was found that water was adsorbed on the sample during its transferring and storage process. A strong dependence of tritium release behavior on water uptake was determined. By doping H2 in the sweep gas, the formation of water in orthosilicate was observed in addition to the isotope exchange reaction with H2 gas. Thermal desorption peaks of the water formation reaction and H2 isotope exchange reaction appeared at 668°C and 463°C, respectively, at ramping rate of 5°C/min. [Copyright &y& Elsevier]

Abstract: As a ceramic material proposed for tritium breeding in a fusion reactor blanket, lithium orthosilicate (Li4SiO4) is being examined in view of the influence of water uptake on tritium release behavior. In this work, out-of-pile tritium release experiments were performed on Li4SiO4 samples that were transferred and stored under different moisture environments. The water content was measured on the samples that were treated in similar conditions. Effects of water adsorption on the chemical form and temperature of released tritium were investigated. It is found that with the water content increases, the gaseous tritium fraction decreases and the proportion of low-temperature desorption of HTO increases. The results of this study can be used later for engineering and design activities for fusion reactor blankets. [Copyright &y& Elsevier]

Abstract: Out-of-pile tritium release examinations of irradiated Li4SiO4 pebbles were performed in TRINPC-I experiments for evaluating material performance and verifying the system design. To generate tritium the specimens were irradiated with neutrons. Li4SiO4 pebbles were made by a freeze-drying method. In the experiments, concentrations of tritium in the form of tritium gas (HT+T2) and tritiated water (HTO+T2O) in the outlet streams of a reactor tube were measured separately with an ionization chamber and a liquid scintillation radiometer. The results show that the percentage of tritium gas (HT+T2) and tritiated water trapped by the breeder pebbles were about 72% and 19% of totally released tritium, respectively. Thus, more tritium was released in the form of tritium gas in this work. In addition to tritium trapped by the breeder pebbles, the amount of free tritium was also measured by breaking on-line a quartz capsule containing Li4SiO4 pebbles, the percentage of which was 9% of totally released tritium. The temperature peaks of tritium gas mainly appeared at about 477°C and 654°C, while the temperature peak of tritiated water appeared at about 402°C, under which most of tritiated water released. [Copyright &y& Elsevier]

Abstract: Ethyl-bridged periodic mesoporous organosilicas (PMOs) functionalized with diphenylphosphino (PPh2) ligands were synthesized by one-step evaporation-induced self-assembly (EISA), which were used as a support to immobilize Pd(II) organometallic catalyst by coordination reaction. The as-prepared Pd(II)–PPh2–PMO(Et) exhibited high activity in water-medium C–C coupling reactions and could be used repetitively. The high activity could be attributed to the high dispersion of Pd(II) active sites and ordered mesopore channels which effectively diminished the steric hindrance and thus, diffusion limit. Meanwhile, the ethyl-fragments and the PPh2-ligands in the support wall could synergic enhance surface hydrophobicity, which promoted the adsorption for organic reactant molecules. [Copyright &y& Elsevier]

The correlation between water desorption and tritium release from Li 4 SiO 4 pebbles was studied by temperature programmed desorption. The released water and tritium from irradiated samples were monitored simultaneously. The main peak for tritium release from the irradiated samples that were exposed to air for more than a month, was shifted from 500 to about 250 °C, as compared to that from the unexposed samples. The peak temperatures for water desorption and tritium release overlapped very well, suggesting a strong correlation between the two processes. Accordingly, a two-step mechanism, involving isotope exchange between the tritium trapped on the grain surface and the surface hydroxyls (–OH), and subsequent desorption of tritiated water through recombination of the –OH/–OT groups, was proposed to explain the tritium release behavior for the air-exposed samples. It is believed that the formation and desorption of surface hydroxyl groups at 200–300 °C can affect the behavior of tritium release from Li 4 SiO 4 significantly. [ABSTRACT FROM AUTHOR]

Abstract: Tritium release kinetics in lithium orthosilicate (Li4SiO4) ceramic pebbles irradiated with low thermal-neutron fluence was studied by out-of-pile annealing experiments. It was found that the tritium produced in Li4SiO4 pebbles was mainly released as tritiated water vapor (HTO). The apparent desorption activation energy of tritium on the pebble surface was consistent with the diffusion activation energy of tritium in the crystal grains, indicating that tritium release was mainly controlled by diffusion process. The diffusion coefficients of tritium in the crystal grains at temperatures ranging from 450K to 600K were obtained by isothermal annealing tests, and the Arrhenius relation was determined to be D =1×10−7.0 exp(−40.3×103/RT) cm2 s−1. [Copyright &y& Elsevier]

Abstract: A new meteor radar system was installed at the Amundsen–Scott station South Pole in 2001 to further the understanding of the dynamics of the Antarctic region. The antenna array consists of four yagis pointed along the 0°, 90°, 180°, and 270° meridians and five folded crossed dipoles arranged in a cross configuration and operating as an interferometer to provide position measurements for the detected radio meteors. The four yagis are time division multiplexed and used for both transmitting and receiving while the five folded crossed dipoles are only used for reception. The current arrangement of data acquisition (DAQ) systems at the South Pole allows the collection of meteors in a configuration similar to the previous meteor radar system that operated at the South Pole in the mid 1990s while also using an interferometer to accurately determine the meteor positions in the sky, which enables the determination of the vertical structure of the observed waves. This has been accomplished through the use of two DAQ and post-processing systems: COBRA (Colorado Obninsk radar) connected to the yagis and MEDAC (meteor echo detection and collection) connected to the folded crossed dipoles. With two separate DAQ systems operating in parallel we have the ability to directly compare the results and understand the inherent variability in the derived scientific results based on different system architectures and processing assumptions. The impact of operating a system without an interferometer on the amplitudes and phases of the observed wave components is considered. We find that the lack of altitude resolution of the COBRA DAQ system leads to an underestimation of the amplitude of the s =1 component of the semidiurnal tide of ∼20% during the summer months. [Copyright &y& Elsevier]