Results 1 - 10 of 174
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[en] In some severe accident scenarios of AP1000 nuclear power plant, a breach or bypass of the containment will lead to large release to environment, which causes severe radioactive pollution of environment. Three release categories (bypass, early containment failure and containment isolation failure) have the largest contribution to large release frequency. Three typical severe accidents (steam generator tube rupture, spuriously open of automatic depressurization system valves and reactor pressure vessel rupture) were selected as typical cases corresponding to the three release categories and the fission-product source terms released to environment were calculated using MAAP code. The analysis results are provided as essential input data for quantifying the release of AP1000 nuclear power plant and the offsite dose analysis. (author)
[en] The normal residual heat removal (RHR) system is used to remove the decay heat generated in the reactor core when a nuclear power plant (NPP) is in Mid-loop condition. Once the RHR system is lost without taking any action, it could eventually lead to core damage following core boiling and uncovery. The RELAP5/Mod3.2 code was used to analyze the reflux condensation when RHR system was lost in Mid-loop condition for a 300 MW NPP. The result shows that when RCS is closed. the core may remain covered for 24 h if two SGs are filled with water, or one SG is filled with water and one auxiliary feedwater is available. Reflux condensation can be used as one of successful mitigation measures. (authors)
[en] Self-organized pattern formation on surfaces by ion beam erosion and driven by metal surfactant atoms is discussed. Si substrates were irradiated with 5 keV Xe ions at normal incidence and ion fluences up to 5.1017 Xe+/cm2 under continuous deposition of surfactant atoms. In the absence of surfactants uniform flat surfaces are obtained. With surfactants pronounced patterns like dots, combinations of dots and ripples as well as ripples with about 100 nm wavelength are generated. The surfactant coverage and deposition direction determine the pattern type and the pattern orientation, respectively. A critical steady-state coverage for onset of dot formation and onset of ripple formation is between about 1015 and 5.1015 atoms/cm2. With increasing ion fluence the pattern contrast increases but the pattern type remains unchanged. The surface region consists of a thin amorphous metal silicide layer with high metal concentration in the ripple and dot regions. Pattern formation is explained by ion induced diffusion and phase separation of the initially flat amorphous silicide layer and subsequent ion beam erosion with composition dependent sputter yield. Directed deposition of metal surfactant causes preferential deposition and shadowing and determines the final pattern orientation and morphology. First results on the dynamic behaviour of the ripples are presented.
[en] The first-principles calculations are applied to investigate the structural, elastic constants and electronic of Mg_2Y alloy with increasing pressure in a range of 0–50 GPa. These properties are based on density functional theory (DFT) method within the generalized gradient approximation (GGA) for exchange and correlation. The anisotropy, the shear modulus, and Young's modulus are also studied. It is found that pressure can significantly improve the ductility of Mg_2Y. Moreover, elastic constants, anisotropies of Mg_2Y increase monotonically with the increasing pressure. Furthermore, when external pressure reaches a high level (50 GPa), the structure phase transition of Mg_2Y may be happened. Finally, results of density of state (DOS) reveal the structural stability decreased as compressed. - Highlights: • Properties of Mg_2Y crystal are investigated by using first-principles calculation based on DFT. • Lattice parameters, elastic properties and band structure from 0 to high pressure are analyzed. • The mechanical properties for Mg_2Y compound at different pressures are estimated
[en] The normal Residual Heat Removal (RHR) system is used to remove the decay heat generated in the reactor core when a nuclear power plant (NPP) is in mid-loop condition. Once the RHR is lost, without any action, it could eventually lead to core damage following core boiling and uncovery. The RELAP5/Mod3.2 code is used to analyze the re flux condensation when loss of RHR in mid-loop condition of 300 MW NPP. It indicates that. when RCS is closed, the core may remain covered for 24 h if two SGs are filled with water, or one SG is filled with water and one auxiliary feed water is available. Reflux condensation could be used as a successful mitigation measure. (authors)
[en] Surface strengthening processes with laser and electron beams are attracting great attention. The application and development of this new technology are described, and the merits and demerits of laser versus electron beam techniques are compared. Finally, present problems and future prospects are discussed
[en] The metal-deposited magnetic catalyst microspheres (MCM-MPs) were successfully synthesized by one facile, high yield and controllable approach. Here, the bare magnetic microspheres were firstly synthesized according to the solvothermal method. Then silica shell were coated on the surface of the magnetic microspheres via sol–gel method, and subsequently with surface modifying with amino in the purpose to form SiO_2–NH_2 shell. Thus, metal particles were easily adsorbed into the SiO_2–NH_2 shell and in-situ reduced by NaBH_4 solution. All the obtained products (MCM-Cu, MCM-Ag, MCM-Pd) which were monodisperse and constitutionally stable were exhibited high magnetization and excellent catalytic activity towards dyes solution reduction. The catalytic rate ratio of MCM-Pd: MCM-Cu: MCM-Ag could be 10:3:1. Besides, some special coordination compound Cu_2(OH)_3Br had been generated in the in-situ reduced process of MCM-Cu, which produced superior cyclical stability (>20 times) than that of MCM-Ag and MCM-Pd. In all, those highly reusability and great catalytic efficiency of MCM-MPs show promising and great potential for treatment of dye-contaminated water. - Graphical abstract: Surface loaded metal particles magnetic catalyst microspheres MCM-MPs for rapid decolorizing dye-contaminated water: Synthesis, characterization and possible mechanisms. - Highlights: • A simple and high yield synthetic method for fabricate multi MCM-MPs is proposed with adequately optimize. • The highest reusability of MCM-Cu is attribute to the coordination compounds Cu_2(OH)_3Br. • MCM-MPs show excellent catalytic properties under different situations for various dyes • The catalytic mechanism of MCM-MPs is presented.
[en] A 13 MeV deuteron beam from the 1.2 M cyclotron of Sichuan Union University has been used to determine the nitrogen depth distribution in seeds of wheat and rice on the basis of 14N(d,p)15N reaction. The feasibility to use the technique for selection purposes in plant breeding is discussed. For wheat and rice, 10 and 12 seeds (without husk) have been investigated, respectively
[en] The principle and technique, which select the seeds of grain with high protein contents using 14N(d,p)15N reaction, are briefly described. Four samples are analyzed and some solution-needed questions are directed
[en] Polycrystalline CrN thin films were irradiated with Xe ions. The irradiation-induced modifications on structural and optical properties of the films were investigated. The CrN films were deposited on Si(100) wafers with the thickness of 280 nm, by using DC reactive sputtering. After deposition, the films were implanted at room temperature with 400 keV Xe ions with the fluences of 5-20×1015 ions/cm2. The films were then annealed at 700 °C in vacuum for 2 h. The combination of Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) was used for structural analyses, while changes in optical properties were monitored by spectroscopic ellipsometry. We also measured the electrical resistivity of the samples using a four point probe method. RBS analysis reveals that the concentration of Xe in the layers increases with ion fluence reaching the value of around 1.5 at.% for the highest ion dose, at a depth of 73 nm. XRD patterns show that the irradiation results in the decrease of the lattice constant in the range of 0.4160-0.4124 nm. Irradiation also results in the splitting of 200 line indicating the tetragonal distortion of CrN lattice. TEM studies demonstrate that after irradiation the columnar microstructure is partially destroyed within ∼90 nm, introducing a large amount of damage in the CrN layers. Spectroscopic ellipsometry analysis shows that the optical band gap of CrN progressively reduces from 3.47 eV to 2.51 eV with the rise in ion fluence up to 20 1015 ions/cm2. Four point probe measurements of the films indicated that as the Xe ion fluence increases, the electrical resistivity rises from 770 to 1607μ cm. After post-implantation annealing crystalline grains become larger and lattice distortion disappears, which influences optical band gap values and electrical resistivity of CrN. © 2018 University of Novi Sad Faculty of Technology. All rights reserved.