Light water reactor fuel performance modeling and multi-dimensional simulation

Light water reactor fuel is a multicomponent system required to produce thermal energy through the fission process, efficiently transfer the thermal energy to the coolant system, and provide a barrier to fission product release by maintaining structural integrity. The operating conditions within a reactor induce complex multi-physics phenomena that occur over time scales ranging from less than a microsecond to years and act over distances ranging from inter-atomic spacing to meters. These conditions impose challenging and unique modeling, simulation, and verification data requirements in order to accurately determine the state of the fuel during its lifetime in the reactor. The capabilities and limitations of the current engineering-scale one-dimensional and two-dimensional fuel performance codes is discussed and the challenges of employing higher level fidelity atomistic modeling techniques such as molecular dynamics and phase-field simulations is presented.     

Pressurized water reactor fuel crud and corrosion modeling

Pressurized water reactors circulate high-temperature water that slowly corrodes Inconel and stainless steel system surfaces, and the nickel/iron based corrosion products deposit in regions of the fuel where sub-cooled nucleate boiling occurs. The deposited corrosion products, called ‘crud’, can have an adverse impact on fuel performance. Boron can concentrate within the crud in the boiling regions of the fuel leading to a phenomenon known as axial offset anomaly (AOA). In rare cases, fuel clad integrity can be compromised because of crud-induced localized corrosion (CILC) of the zirconium-based alloy. Westinghouse and the Electric Power Research Institute have committed to understanding the crud transport process and develop a risk assessment software tool called boron-induced offset anomaly (BOA) to avoid AOA and CILC. This paper reviews the history of the BOA model development and new efforts to develop a micro-scale model called MAMBA for use in the Consortium for Advanced Light Water Reactor Simulation (CASL) program.     

Discontinuously reinforced aluminum: Current status and future direction

Conclusions There are now a number of important production applications for DRA, which span the transportation, aerospace, recreation, and electronics industries and that demonstrate the material’s attractive combination of structural, thermal management, an d wear properties. While large materials suppliers have mostly exited the area, many smaller suppliers are forging ahead to make DRA a success. Expanding this success depends upon the ability of researchers and engineers to continue increasing our fundamental understanding of the materials, to work together in close cooperation to transition the material, and to make the material more user friendly by publishing user handbooks, standardized property databases, and application case studies. he is the advisor to JOM from the TMS Composite Materials Committee. Warren H. Hunt, Jr., is with Aluminum Consultants Group, Inc. For more information, contact B. Maruyama, U.S. Air Force, Air Force Research Laboratory, 2230 10th Street, Suite 1, AFRL/MLLM, Wright-Patterson Air Force Base, Ohio 45433; (937) 255-1310; fax (937) 255-3007; e-mail benji.maruyama@ml.wpafb.af.mil.     

PEM fuel cells: status and challenges for commercial stationary power applications

The past decade has seen tremendous advances in proton exchange membrane fuel cell (PEMFC) technology: However, there remain many challenges to bring commercially viable stationary PEMFC products to the market. This review, from a manufacturer's perspective, focuses on system reliability and materials compatibility and their strong impact on stack life and overall system durability. Statistical analysis is based on field data from more than 600 stationary PEMFC systems for both continuous and back-up power applications. Sealing materials and coolants are used to illustrate the approaches taken to evaluate materials compatibility studies.     

Space fission reactor structural materials: Choices past,present, and future

Nuclear powered spacecraft will enable missions well beyond the capabilities of current chemical, radioisotope thermoelectric generator and solar technologies. The use of fission reactors for space applications has been studied for over 50 years. Structural material performance has often limited the potential performance of space reactors. Space fission reactors are an extremely harsh environment for structural materials with high temperatures, high neutron fields, potential contact with liquid metals, and the need for up to 15–20 year reliability with no inspection or preventative maintenance. Many different structural materials have been proposed. While all of those proposed meet many of the requirements for space reactor service, none satisfy all of them. However, continued development and testing may resolve these issues and provide qualified materials for fission reactors for space power.     

Current and future corrosion challenges for a reliable and sustainable development of the chemical,refinery, and petrochemical industries

The chemical, refinery, and petrochemical industries are facing new challenges in order to develop more environment friendly processes and to manufacture “green” products. Corrosion management is an essential element for the development of a sustainable industrial society, including issues such as the selection and development of corrosion resistant materials, coatings, and environment friendly inhibitors. In this paper, some specific challenges will be discussed. In the chemical industry, the replacement of volatile and toxic solvents by green ones such as supercritical water processes, ionic liquid, or the use of carbon dioxide as an alternative solvent, requires specific corrosion management policies. Another issue for the refinery industry concerns new feedstocks such as opportunity crudes containing corrosive naphthenic acids or the transformation of biomass feed into bio‐oils and biomaterials. Synthetic gas is also becoming a crucial intermediate in natural gas, coal or biomass to hydrocarbon liquids (XTL) processes. Other environmental aspects are the limitation of green house gas (GHG) release from the plants by implementation of CO₂ capture processes and the environment friendly management of water including more restrictive steps concerning its disposal. The implementation of advanced inspection and corrosion control management is also a major element of progress for a sustainable development of the chemical, refinery, and petrochemical industries.     

有色金属冶金基础研究的现状及对今后的建议

介绍了我国有色金属冶金基础研究现状及所取得的重要成果,提出了拟定我国有色金属冶金发展战略的原则,并从以下几方面对如何进一步开展我国有色金属冶金基础研究提出了建议:复杂界面交互作用、矿物的生物加工理论与技术、丰产元素资源的深加工、再生金属资源化和"三废"资源化、无污染冶金、冶金过程热力学和动力学、机械活化冶金、膜科学与技术在冶金中的应用基础、冶金电化学新前沿、熔盐电解、冶金过程和设备的数字仿真与优化、传感器与自动控制等.     

多级热处理对柔性立管用高强钢组织性能影响

为了探究高强度海洋柔性管铠装层用钢焊接接头失稳问题,以600 MPa级耐蚀钢为闪光对焊焊接母材,研究不同闪光留量与顶锻留量对接头显微组织及力学性能的影响规律. 结果表明,随顶锻留量增加,焊缝及热影响区粗晶区多边形铁素体含量增加,组织逐渐粗化,接头强度先增加后降低,顶锻留量大于5 mm,接头强度急剧恶化;随闪光留量的增加,焊缝及粗晶热影响区板条贝氏体组织逐渐粗化,接头强度逐渐增加后急剧下降,当闪光留量8 mm时,接头强度严重恶化. 二者都使断后伸长率逐渐提高,但顶锻留量对断后伸长率的影响较大. 闪光留量和顶锻留量为7 mm和4 mm时,焊接样品力学性能最优,热影响区针状铁素体板条宽度大约为0.59 μm,抗拉强度达到688 MPa,屈服强度达到586 MPa,断后伸长率为15%,拉伸断口形式为韧性断裂. 闪光留量与顶锻留量参数的适当匹配形成细小且弥散分布粒状贝氏体可以有效强化钢基体.     

Prediction of residual stress and distortion of ferrous and non-ferrous metals: Current status and future developments

The quantitative prediction of the consequences of a heat treatment, in terms of microstructure and hardness, residual stresses and distortions, implies a thorough knowledge of the coupled thermal, metallurgical, and mechanical phenomena that occur during the treatment and their modeling. Recent progress made in that field for metallic alloys (steels, aluminum alloys, and titanium alloys) is reviewed through different examples.     

Gamma titanium aluminides: Their status and future

Gamma alloys, based on the gamma titanium aluminide (y-TiAl) intermetallic compound, are emerging as a revolutionary engineering material for high-temperature structural applications. This article discusses the historical background as well as the status and future prospects of gamma alloy technology in the areas of alloy development/ design, process development, and applications.     

Flexible film systems: Current understanding and future prospects

The electrical and mechanical properties of metal films on polymer Substrates are of interest for use inflexible electronic devices and sensors. In these Systems, film deformation mechanisms are comparable to those from free-standing films but the influence of the Substrate and the Interface on the film properties is yet to be fully understood. This understanding is critical to further design improvements and advanced in situ characterization holds the promise of making this possible. With the aid of such techniques direct Observation of failure and deformation mechanisms has become possible.     

Environmentally benign manufacturing: Current practice and future trends

The consideration of environmental issues in manufacturing has taken on increased importance in terms of global competitiveness. Life-cycle assessment tools enable analysis of the environmental efficiency of industrial processes. Often these focus on the product, with standardized or customized data provided on current processing practice. Environmental management of the total materials cycle must provide tools to evaluate the effect of changes in processing or material substitutions on a global basis, where materials use, reuse, component remanufacture, and materials recycling can be considered and the overall costs and impacts assessed. In this article, two examples of net-shape processing are discussed from this total materials cycle perspective.     

Copper hydrometallurgy-current status,preliminary economics,future direction and positioning versus smelting

The heap leaching of oxide copper ores with copper cathode recovery by solvent extraction and electrowinning is now well established as a low-cost method of copper recovery. This technology has recently been applied successfully to mixed oxide and chalcocite ores, notably in Chile at Cerro Colorado, Quebrada Blanca and Zaldivar.Currently, there are significant development efforts underway to try to extend heap leaching to chalcopyrite ores.The success of heap leaching/SX/EW has also led to a revival in the development of hydrometallurgical processes to recover copper from chalcopyrite and other copper concentrates. The current status of copper hydrometallurgy is reviewed and the most commercially attractive potential applications are explored. The advantages and disadvantages of the hydrometallurgical treatment of chalcopyrite concentrates and its preliminary economics are compared with those for the current best practices in copper smelting and refining.     

Numerical modeling of a low temperature high velocity air fuel spraying process with injection of liquid and metal particles

An analysis of a low temperature high velocity air fuel (LTHVAF) thermal spray process is presented using computational fluid dynamics (CFD). The originality of the process lies in the injection of liquid (water) upstream of the powder injection to control to gas temperature and, therefore, the heat transfer to the injected particles. First, computation fluid dynamic techniques are implemented to solve the mass, momentum, and energy conservation equations in the gas phase. A turbulence model based on the renormalized group theory (RNG) is used for the turbulent flow field. The gas dynamic data are, then, used to model the behavior of the liquid droplets and particles in the gas flow field. The calculated results show that the liquid flow rate should range between 20 and 30 kg/h to achieve the optimal gas characteristics for particle treatment. They also show that particle velocity and temperature are strongly affected by particle size. At the gun exit, the particle velocity and temperature range between 700 and 300 m/s and between 900 and 400 K, respectively, for Cu and Ni particles with size distributions of 1 to 50 μm. As expected, the smaller particles have higher velocity and temperature. The metal coatings (Nickel and copper) produced by the LTHVAF spray process are characterized by low oxide content, low residual stresses, high deposition rates, and good bonding to the substrate.     

21世纪的热处理与表面工程--淬火技术的现状和未来发展

淬火技术是热处理的一个十分重要的组成部分,它能影响制造的质量、生产率和效益。本文在介绍淬火发展历史的基础上,简要评述了某些取得重要进展的技术,并指出未来将逐步发生的变革,具体包括:淬火系统的计算流体动力学建模和模拟、气淬、控时淬火、交替控时淬火、强烈淬火、金属/淬火介质界面表征方法、纳米淬火介质以及植物油淬火介质的发展等等。     

Advanced process modeling at the BCL smelter: Improving economic and environmental performance

Since 1973 Bamangwato Concessions Limited (BCL) has operated a nickel-copper smelter in Selebi-Phikwe, Botswana. The smelter treats concentrates from local mines and various custom feed concentrates. The nickel throughput capacity of this smelter is constrained by a low nickel feed grade in its primary BCL concentrate. BCL contracted Xstrata Process Support (XPS) to assist in identifying key economic drivers to maximize revenue-generating opportunities. After the disclosure of essential BCL plant performance data XPS developed and utilized advanced metallurgical modeling techniques to identify production bottlenecks, calculate Ni, Cu, and Co recoveries, manage the slag volumes, increase the custom feed capacity, and perform various feasibility analyses for key unit process operations in the BCL smelter. The methodology for developing the process model and its application in contributing to the economic bottom line are outlined in this paper.     

Aqueous-based extrusion of high solids loading ceramic pastes: Process modeling and control

A novel fabrication method known as aqueous-based extrusion fabrication (ABEF) has been developed for the manufacture of ceramic-based components in an environmentally friendly fashion. The method is based on the extrusion of ceramic pastes using water as the medium. This paper describes a machine developed for the extrusion of high solids loading ceramic pastes, investigates the dynamic behavior of the extrusion process, and develops and implements a feedback controller to regulate the extrusion force. The results demonstrate that aqueous-based ceramic extrusion processes have a very slow dynamic response, as compared to other non-compressible fluids such as water. A substantial amount of variation exists in aqueous-based ceramic extrusion processes, most notably during the transient period, and a constant ram velocity may either produce a relatively constant steady-state extrusion force or it may cause the extrusion force to steadily increase until the ram motor skips. It is demonstrated that the use of feedback control reduces the effects of process disturbances (i.e., agglomerate breakdown and air bubble release) and variations in the process as the material in the reservoir decreases, substantially decreases the time to obtain a desired extrusion force level, and dramatically improves part quality.