CFD studies on the phenomena around counter-current flow limitations of gas/liquid two-phase flow in a model of a PWR hot leg

In order to improve the understanding of counter-current two-phase flow and to validate new physical models, CFD simulations of a 1/3rd scale model of the hot leg of a German Konvoi pressurized water reactor (PWR) with rectangular cross section were performed. Selected counter-current flow limitation (CCFL) experiments conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) were calculated with ANSYS CFX using the multi-fluid Euler–Euler modelling approach. The transient calculations were carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a shear stress transport (SST) turbulence model.In the simulation, the drag law was approached by a newly developed correlation of the drag coefficient (Höhne and Vallée, 2010) in the Algebraic Interfacial Area Density (AIAD) model. The model can distinguish the bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows a good qualitative agreement. The results indicate also a quantitative agreement between calculations and experimental data for the CCFL characteristics and the water level inside the hot leg channel.     

Radiation protection issues for laser-based accelerators

Radiation particles, besides their application to fundamental research, are widely applied in all fields of science (medicine, material science, chemistry, etc.). Up to today the radiations were produced by radiation sources such as accelerators, X-ray tubes, radioactive sources with the well-known problems of costs, parameters and safety. For the last few years, following the development of lasers able to focus ultra-short high-intensity pulses onto targets, the generation of ionising radiation by intense lasers has become possible. The paper will focus on some radiological protection aspects around the Frascati Laser for Acceleration and Multidisciplinary Experiments, 300 TW laser being commissioned at National Laboratories of Frascati.     

Effects of loading-unloading and wetting-drying cycles on geomechanical behaviors of mudrocks in the Colombian Andes

The mudrocks in the Colombian Andes, particularly those exhibiting low cementation （bonding）, are susceptible to degradation when the environmental conditions change, which are challenging issues for engineering works. In this paper, the changes in physico-mechanical properties of mudrocks were moni- tored in laboratory, and some influential factors on the mechanical competence of geomaterials were studied. The geotechnical characteristics and experimental designs were developed from physical, chem- ical, mechanical and compositional points of view. In the tests, the techniques such as vapor equilibrium technique （VET） were employed to apply wetting-drying cycles and to control relative humidity （suction- controlled） and loading-unloading cycles through ultrasonic wave velocities technique. The results show that the main failure mechanisms for the laminated mudrocks start on the microscopic scale by fissures coalescence, exhibiting physico-chemical degradation as well; the global geomechanical behavior presents a state between a ductile, like rock, and a fragile, like soil. The obtained results can provide engineering values according to monitoring laboratory set, when compared with in situ conditions.     

Solid state sintering of very low and negative thermal expansion ceramics by Spark Plasma Sintering

Lithium aluminosilicate powder precursors of compositions Li₂O:Al₂O₃:SiO₂ as 1:1:2; and 1:1:3.11 were synthesized and sintered by the Spark Plasma Sintering technique. The sintering conditions were adjusted to obtain dense ceramic materials in an attempt to avoid the presence of a glassy phase. XRD and SEM images were employed for composition and microstructure characterization. The coefficient of thermal expansion of the sintered samples was studied down to cryogenic conditions. Rietveld quantification was performed with the use of an external standard. Pure β-eucryptite of different compositions in dense ceramic bodies was obtained with a negative expansion coefficient.     

A Case Study of GAMM (Graphical Analysis for Maintenance Management) Applied to Water Pumps in a Sewage Treatment Plant,Chile

This article presents a case for practical application of the GAMM method, which has been developed and published by the authors. The GAMM method supports decision making in the overall maintenance management, through the visualization and graphical analysis of data. In addition, it allows for the identification of anomalous behavior in the equipment analyzed, whether derived from its own operations, maintenance activities, improper use of equipment or even as a result of design errors in the equipment itself. As a basis for analysis, the GAMM method uses a nonparametric estimator of the reliability function using all historical data or, alternatively, part of the history, allowing it to perform an analysis even with limited available data. In the case study presented, the GAMM method has been used to analyze two existing equipment parts in a sewage treatment plant located in Chile. The equipment analyzed were two progressive cavity pumps (BCP) which are part of the industrial process in the treatment plant. Both pumps are the same make and model and subjected to the same maintenance program, but one had a higher failure rate compared to its counterpart. The application of the GAMM method has identified deficiencies in each of the pumps being studied, thus improving decision‐making and problem‐solving process related to the maintenance of the pumps. RCM methodology was used to draft a new maintenance plan. Copyright © 2013 John Wiley & Sons, Ltd.     

维修工程系统——维修功能的演化机遇（续）

下图(图4)是维修工程过程的示意图。整个过程基本上可以分为以下几个步骤:第1步:系统逻辑配置。对生产设备的功能、辑和影响进行分析。第2步:数据。有两种获取数据的方法。第一是通过对设备功能的历史数据分析,第二是通过标准或者制造商的说明来获得数据。第3步:寿命周期费用决