[en] Highlights: • Eu"3"+ ions occupy C_1 point group of the Zr"4"+ site in ZrW_2O_8 crystals. • The optimum doping concentration of Eu"3"+ was determined for the red emission. • ZrW_2O_8:Eu possess high quantum efficiency and suitable chromaticity coordinates. - Abstract: ZrW_2O_8:Eu"3"+ nanophosphors (ca. 60 nm) with different Eu"3"+ doping concentrations were obtained using hydrothermal syntheses. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), photoluminescence excitation and emission spectra as well as decay curve measurements were used for the characterization. Under 466 nm excitation, strong red emission at 616 nm corresponding to "5D_0–"7F_2 transition of Eu"3"+ was observed for ZrW_2O_8:Eu"3"+ (9 mol%) phosphors. The values of intensity parameter Ω_2 and Ω_4 are 17.82 × 10"−"2"0 cm"2 and 1.092 × 10"−"2"0 cm"2, respectively. The high quantum efficiency of 83.5% of the ZrW_2O_8:Eu"3"+ (9 mol%) suggests this material could be promising red phosphor for generating white light in phosphor-converted white light-emitting diodes (LED)

[en] Eu³⁺-Yb³⁺-Y³⁺ tri-doped cubic ZrO₂ (abbreviated as YSZ:Eu,Yb) phosphors with different doping concentrations of Yb³⁺ can be synthesized via the Pechini sol-gel method. Efficient near-infrared (NIR) emission in YSZ:Eu,Yb phosphors was demonstrated. The dependence of the intensities of visible and NIR emissions, decay lifetimes and energy-transfer efficiencies on the Yb³⁺ doping concentration was investigated in detail. It is found that Eu³⁺, acting as a sensitizer, can efficiently transfer its energy to Yb³⁺ activator ions in YSZ:Eu,Yb phosphors

[en] The core makeup tank (CMT) is a principal component of the passive high pressure safety injection systems for AC600 and has a function to inject cold borated water into reactor vessel during abnormal events. The purpose of this experiment is to verify the gravity drain behavior of the CMT and to provide experimental data to verify the computer codes used in the safety analyses. Five experiments with simulative small and medium break conditions are conducted at AC600 core makeup tank performance test facility of Nuclear Power Institute of China (NPIC). The author provides the results of one test. The simulated accident is a small break loss-of-coolant accident

[en] The entry tube locates at the coolant inlet of the fast reactor fuel assembly, which directly determines the flow rate of the sodium coolant entering the interior of the fuel assembly to cool the fuel-rod bundles. It has important influence on the pressure drop and flow-velocity distribution of the fuel assembly. At present, the research on fast reactor fuel assembly is mostly focused on the thermal-hydraulic characteristics of the fuel-rod bundles, while there is lack of the research about the entry tube, especially there is no uniform design standard. Therefore, it is necessary to further study the flow characteristics about the entry tube of fast reactor fuel assembly to provide a reference for structure design. In this study, the distribution of resistance coefficient and the relationship between flow rate and pressure drop of entry tube with different diameter are studied by hydraulic experiment. The results show that the diameter of the entry-tube hole has the significant impact on the flow characteristics of sodium coolant, so the inlet flow rate of the fuel assembly in different core-region can be adjusted by changing the diameter of the entry-tube hole to achieve the balance of pressure drop of fuel assembly. In addition, a dimensionless contraction coefficient of the entry tube is introduced and the empirical correlations of the resistance coefficient are formulated which are used to estimate the pressure drop of the in fast reactor fuel assembly. Finally, based on the design requirements of pressure drop and flow-velocity limitation, a recommended program is presented of diameter selection about the entry-tube hole, which can be used as a reference for relevant experiments or engineering. (authors)

[en] The control assembly is an important safety component of sodium-cooled fast reactor. The entry-tube geometrical structure has a significant effect on flow characteristics. The flow characteristics of plate-throttle entry-tube were investigated by hydraulic experiment, and the fluid-structure coupling numerical simulation was verified by experiment data. The results show that reducing the thickness of throttle plate and increasing the diameter of connecting rod can effectively improve the entry-tube throttling capacity. Considering the limitation of flow velocity, the dimensionless thickness-diameter ratio of 0.5 and connecting rod diameter of 20 mm are regarded as the optimum structure parameters of entry-tube. Due to the shortage of plate-throttle entry-tube in experiment, an alternative project of square-groove entry-tube was proposed. It is verified that this project is feasible with the similar flow velocity and pressure distribution in two types of entry-tubes. (authors)

[en] Highlights: • For the entry tube of fast reactor fuel assembly, there is lack of available resistance-coefficient experiment data, empirical correlation and criterion equation. This study tries to fill this gap. • A new plate-throttle entry tube for fast reactor fuel assembly is designed. • The flow characteristics of fuel assembly are experimentally investigated. • The resistance coefficient empirical correlations are obtained. • The empirical criterion equation are obtained by regression analysis. - Abstract: The entry tube of fast reactor fuel assembly plays an important role in controlling flow rate, adjusting pressure drop and limiting flow velocity, which has a significant effect on safety and economy of fast reactor. Due to some shortcomings of traditional straight-through entry tube, an optimized plate-throttle entry tube is designed and manufactured in the current investigation. Reynolds number from 8.99 × 10⁴ to 1.65 × 10⁶ is considered and experiment data are generated from hydraulic experiment conducted at constant water temperature (84 °C). The experiment results indicate that the flow characteristics of plate-throttle entry tube is excellent, i.e. it can significantly increase pressure drop with the large-diameter entry-tube holes to avoid excessive vibration. It is verified that the pressure drop of plate-throttle entry tube is more sensitive to the width of plate throttle rather than the diameter of entry-tube holes. In the experiments or practical engineering applications, the pressure drop should be adjusted by changing the width of plate throttle as much as possible to reduce cost. A dimensionless number called the throttling-area ratio is introduced to represent the geometrical parameters effect on flow characteristics of plate-throttle entry tube. The resistance-coefficient empirical correlations and an empirical criterion equation are obtained by regression analysis of experiment data, which can be used for structure design of sodium-cooled fast reactor and preliminary estimation of entry-tube flow characteristics.

[en] The fabrication of optically active inorganic nanomaterials with chiral superstructures attracts attention because of their potential applications in chemical sensing and non-linear optics. Here, we present a facile way to prepare TiO_2 nanofibres, in which the nanocrystals are helically arranged into a chiral superstructure. Notably, the chiral superstructure shows strong optical activity due to the difference of absorbing left- and right-handed circularly polarized light. This special optical activity resulted from electron transition from the valence band to the conduction band of TiO_2 through a vicinal effect of helically arranged TiO_2 nanocrystals. (focus issue paper)

[en] The multi-hole entry tube widely used in engineering has some shortcomings in adjustment of flow characteristics and processing accuracy. In this paper, an alternative method of few-hole entry tube was proposed. By hydraulic experiment, the flow characteristics of multi-hole and few-hole entry tubes, such as the distribution of resistance coefficient, the corresponding relationship between flow rate and pressure drop, were compared and studied. The results show that the flow characteristic of the few-hole entry tube with 12.0 mm in diameter is almost the same as that of the multi-hole entry tube with 6.2 mm in diameter, which all can meet the design requirements. It is verified that the alternative method of few-hole entry tube proposed in this paper is feasible. In addition, the flow characteristics can be more effectively adjusted by the few-hole entry tube. Moreover, the empirical correlation between the resistance coefficient of the entry tube and its structure parameters is formulated, which can be used in relevant experiment or engineering. (authors)

[en] Precipitation phase has a profound influence on the hydrological processes in the Naqu River basin, eastern Tibetan plateau. However, there are only six meteorological stations with precipitation phase (rainfall/snowfall/sleet) before 1979 within and around the basin. In order to separate snowfall from precipitation, a new separation scheme with S-shaped curve of snowfall proportion as an exponential function of daily mean temperature was developed. The determinations of critical temperatures in the single/two temperature threshold (STT/TTT2) methods were explored accordingly, and the temperature corresponding to the 50 % snowfall proportion (SP50 temperature) is an efficiently critical temperature for the STT, and two critical temperatures in TTT2 can be determined based on the exponential function and SP50 temperature. Then, different separation schemes were evaluated in separating snowfall from precipitation in the Naqu River basin. The results show that the S-shaped curve methods outperform other separation schemes. Although the STT and TTT2 slightly underestimate and overestimate the snowfall when the temperature is higher and colder than SP50 temperature respectively, the monthly and annual separation snowfalls are generally consistent with the observed snowfalls. On the whole, S-shaped curve methods, STT, and TTT2 perform well in separating snowfall from precipitation with the Pearson correlation coefficient of annual separation snowfall above 0.8 and provide possible approaches to separate the snowfall from precipitation for hydrological modelling.

[en] Using first-principles calculations in combination with Wagner–Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in $\mathrm{L}{1}_2{\mathrm{\gamma <!--\; ??\; -->}}^{\mathrm{\prime <!--\; ???\; -->}}$-Ni₃Al were investigated. The formation energies of the point defects and the migration energies for solutes were calculated. Adding alloying elements can decrease the defect-formation energies of Ni_Al, increase the defect-formation energies of Al_Ni, and have little effect on the formation energy of V_Ni. The migration energies of solutes are related with the site preference and the diffusion mechanism. The diffusion coefficients of Ni, Al, and solutes were calculated, and the concentration of antisite defects plays a crucial role in the elemental diffusion. (paper)