美国水利工程规划与评价

美国水资源规划与评价通常强调拟建工程的未来成本与效益。《水资源与土地资源实施研究的经济和环境原则与指南》是指导美国水利工程规划工作的一部详细的规划导则。但是,没有合适的文件来指导水利工程与项目实施后的回顾评价。在工程实施后,社会目标可能已发生了重大变化。不对工程实施后的情况进行评价可能会阻碍可行工程的实施和政策调整。拓展水资源管理的范围,使其包括更多的事后评价将有助于解决美国在水资源问题上存在的一些争论。配合管理机构官员工作的独立科学家的介入,将有助于保证事后评价的客观性与可靠性。适应性管理有助于解决美国水利政策所面临的挑战,其成功实施必须依赖有效的事后评价。     

钢水喷镁精炼及其对钢性能的影响

由于镁对钢的脱氧、脱硫、净化钢水及转变夹杂物形态的良好作用,近年来许多冶金工作者致力于加镁精炼钢水的研究工作,但因在冶金温度下镁的蒸汽压很高,而其在钢水的溶解度又极小,加入困难,这方面的研究多归于失败。本文利用阿亨大学热力学数据库计算了以氩作为载气喷镁的脱氧、脱硫作用,以及压力和氩量对其影响,通过实验制定了行之有效的喷吹工艺,选择了合适的控制参数。
在1-3大压下,氩量为0.1-0.3N.L/m:n,可以向钢水成功地喷入镁。经过镁精炼的钢水,氧含量可降至4ppm,硫含量降至10ppm,氧化物及硫化物的评级均为0级,其尺寸均在5μm之下。随着喷镁量的增加(钢水重量的0.062至%0.56%),夹杂物中镁的氧化物及硫化物量增加,夹杂物总量减少且呈球形,此种夹杂物在热形变中不变形。因此在通常材料中所存在的各向异性完全消失,特别是缺口冲击韧性横向性能值提高了2~3倍。文章对材料在不同温度下的冲击韧性、过渡温度及断口夹杂物的形态进行了研究和论述。     

Stability analysis of single-phase thermosyphon loops by finite-difference numerical methods

In this paper, examples of the application of finite-difference numerical methods in the analysis of stability of single-phase natural circulation loops are reported. The problem is addressed here for its relevance to thermal-hydraulic system code applications, with the aim to point out the effects of truncation error on stability prediction. The methodology adopted for analyzing in a systematic way the effect of various finite-difference discretization can be considered the numerical analogue of the usual techniques adopted for PDE stability analysis. Three different single-phase loop configurations are considered involving various kinds of boundary conditions. In one of these cases, an original dimensionless form of the governing equations is proposed, adopting the Reynolds number as a flow variable. This allows for an appropriate consideration of transition between laminar and turbulent regimes, which is not possible with other dimensionless forms, thus enlarging the range of validity of model assumptions.     

Accuracy aspects in multiphase flow metering using X-raytransmission

The composition of a mixture of several components flowing through a pipe can be determined by means of an X-ray transmission technique/analysis. We present some aspects of the theory relating to an application in which the component volume fractions of an oil, water, and gas mixture are determined. It will be shown that on fundamental grounds, this technique has its limits regarding the number of components that can be distinguished in relation to the achieved accuracy of the measured attenuation     

Corium spreading and coolability: CSC Project

In the context of severe accidents, large R&D efforts throughout the world are currently directed towards ex-vessel corium behaviour. Among the mitigation means which can be envisaged, the European industries and utilities are considering the implementation of a core-catcher outside the reactor pressure vessel in order to prevent basemat erosion and to stabilize and control the corium within the containment. The CSC project focused on two key phenomena for external core-catcher efficiency, reliability and safety: spreading and coolability. An experimental programme, covering different scenarios and including both simulant and real materials provided a lot of results which now constitute a large database and which enabled the qualification of computer codes.