Numerical modelling for the interpretation of a laboratory mock-up experiment of bentonite/granite interface

AbstractPerformance assessment of a deep geological repository requires understanding diffusion and determining diffusion parameters under real conditions because diffusion is a key transport mechanism in hosting geological formation. FEBEX (Full-scale Engineered Barrier Experiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of the high-level radioactive waste repository. To support field investigations of FEBEX in situ test, a large–scale laboratory mock-up experiment (MUE) is being performed at CIEMAT facilities to study tracer migration at the bentonite/granite interface. Numerical models of MUE are presented here for HTO, 36Cl- and 137Cs+. Experiments are modeled with 2-D axi-symmetric finite element grids and are solved with CORE2D V4. Model results indicate that numerical solutions with reference parameters reproduce measured data for HTO and 36Cl- but show large discrepancies for 137Cs+. Relevant diffusion and retention parameters are identified by sensitivity analysis for tracer concentrations in borehole, bentonite and granite, respectively. Interpretation of 137Cs+ data measured in the tracer chamber is perfomed by taking into account the uncertainties in initial activity C0 and initial time t0. Optimum values of C0 and t0 are obtained. The best fit is obtained with De-filter equal to 2.03.10-10 m2/s and Kd-bentonite equal to 5m3.Kg-1

Effect of TiB2/TiC ratio on the microstructure and mechanical properties of high volume fractions of TiB2/TiC reinforced Fe matrix composite

Dense high volume fractions of different molar TiB2/TiC ratios reinforced Fe matrix composite were successfully fabricated through the SHS reaction assisted with pressure. The reaction mechanisms for three systems were dissolution–precipitation. The TiB2 morphology changed from plate-like to clubbed and further to cubic with decreasing TiB2/TiC ratios from 2:1 to 1:2. The composites with 2:1 and 1:1 ratios of TiB2/TiC have a similar highest Vickers hardness and flexural strength while the composite with 1:1 ratio of TiB2/TiC has the best fracture toughness. The improvement of the fracture toughness was attributed to the reduction of thermal stress and the modification of TiB2 morphology. The optimal ratio of TiB2/TiC was recommended to be 1:1

Research on the Removal of Impurities from Crude Nickel by Vacuum Distillation

AbstractThe removal of impurity elements from crude nickel by vacuum distillation was carried out at the temperature 1773K∼1973K and the pressure less than 10Pa using crude nickel(≥99.9%)as raw materials. A series of results of the impurity elements were obtained under the experimental conditions aforementioned.The experimental values βi andγio of the product were also calculted in this paper. The seperation of certain impurities from main element nickel was disscussed from the viewpoint of thermodynamics and alloy composition. Nickel (≥99.99%) was obtained and the purification and impurity removal from crude nickel by vacuum distillation method was feasible and determined. A China Patent on this new technology was also authorized. We consider that the vacuum distillation process of nickel can serve as a pretreatment step for the prepartion of highpurity nickel, and can relieve the following purification of the electrolyte, so that the whole process of preparation of the high-purity nickel is simplified, energy consumption and environmental pollution are reduced. Therefore, the vacuum distillation process is a green metallurgical method

An investigation of decoupling performance for a novel lateral axis gyroscope with varying environmental parameters

This paper makes an investigation on the decoupling performance for a novel lateral axis gyroscope with varying environmental parameters. The testing results show that the decoupling performance of the gyroscope depends on the environment pressure and temperature. The coupling varies from 0.05% to 0.25% with the pressure range of 150Pa to 100kPa. The characteristic of coupling with temperature is measured from 20??C to 100??C, which varies from 0.35% to 0.41%. With the high quality factor and small coupling, the device can worked well even at atmospheric pressure. The sensitivity and nonlinearity are 6.7mV/??/s and 0.51% with full scale of 800??/s, respectively. ?2009 IEEE.EI

Drivers of Change for Grassland and Forage Systems: A Case Study of China

Grassland and forage systems have changed dramatically across the world. This paper describes some of the key drivers of change of grassland and forage systems using examples from China as a case study. The key drivers of change for grassland and forage systems include political, economic, social, technical and environmental factors and their impact on changes in grasslands ecosystems in China is discussed. There are interactions among the drivers and their impact is similar in many developing countries