Transport of large nuclear power plant components: experiences in mechanical design assessment

Abstract

In the course of decommissioning of power plants in Germany large nuclear components (steam generator, reactor pressure vessel) must be transported over public traffic routes to interim storage facilities, where they are dismantled or stored temporarily. Since it concerns surface contaminated objects or low specific activity materials, a safety evaluation considering the IAEA transport regulations mainly for industrial packages (type IP-2) is necessary. For these types of industrial packages the requirements from normal transport conditions are to be covered for the mechanical proof. For example, a free drop of the package from a defined height, in dependence of its mass, onto an unyielding target, and a stacking test are required. Since physical drop tests are impossible generally due to the singularity of such 'packages', a calculation has to be performed, preferably by a complex numerical analysis. The assessment of the loads takes place on the basis of local stress distributions, also with consideration of radiation induced brittleness of the material and with consideration of recent scientific investigation results. Large nuclear components have typically been transported in an unpackaged manner, so that the external shell of the component provides the packaging wall. The investigation must consider the entire component including all penetration areas such as manholes or nozzles. According to the present IAEA regulations the drop position is to be examined, which causes the maximum damage to the package. In the case of a transport under special arrangement a drop only in an attitude representing the usual handling position (administratively controlled) is necessary. If dose rate values of the package are higher than maximum allowable values for a public transport, then it is necessary that additional shielding construction units are attached to the large component.     

Optimisation of process conditions in powder injection moulding of microsystem components using robust design method Part 2 – Secondary design parameters

Abstract

Powder injection moulding (PIM) is a proper fabrication method for microsystem technology components. This paper studies the process control of PIM to create thin walled, high aspect ratio geometries, which can be easily found in microtechnology based electro chemical, mechanical and biological systems (MECS). The powder used in this study is gas atomised 316L stainless steel with a median particle size of 10 μm. The effects of reducing the thickness of high aspect ratio geometries on the secondary design parameters including the maximum wall shear stress, cooling time and standard deviations of the melt front velocity and areas are studied. The study shows process parameters including fill time, feedstock injection temperature, mould wall temperature and switchover position can be optimised using the Taguchi robust design method.     

NUMERICAL ANALYSES OF DESIGN AND ASSEMBLY FOR MAIN COMPONENTS OF BESIII

The design and manufacture of the main drift chamber(MDC) and the electro-magnetic calorimeter are most important issues in Beijing electron-positron collider upgraded projects. The whole mass of electro-magnetic calorimeter (EMC) in BESIII is 40t, thus high stiffness, strength and dynamical properties are required for the design of entire structural of electro-magnetic calorimeter. Based on numerical technique, the strength and the dynamical properties of EMC are analyzed, which provide theoretical reference for the design of entire structural of EMC. The MDC is composed of the elements with 28680 pre-stressed high-sensitive wires and during the assembly the wires are stringed layer by layer. The stretching forces of the wires vary continuously and couple with each other in the whole process. The modeling technique with high precision (especially "element birth and death") is carefully used to study the stress state during the process of assembly. So the variations of the stretching force of the wire are investigated, and several design schemes are evaluated and optimized. The research results have been adopted in the Beijing electron-positron collider's new project directly.     

Life management of creep strengthened ferritic steels in boilers and piping

Abstract

The advantages offered by creep strengthened ferritic steels can only be realised with careful control of fabrication methods. Effort will be needed during service to evaluate component performance. Direct life assessment methods can provide useful information for condition assessment provided that the methods are properly matched to the potential damage mechanisms and locations.     

Structure property correlations in hot isostatically pressed AISI-304 stainless steel

Abstract

Stainless steel components are usually fabricated by conventional manufacturing methods. This route becomes uneconomical for highly intricate shapes. Therefore, processing of AISI-304 stainless steel has been carried out by powder metallurgy and hot isostatic pressing (HIP) route. The microstructure and mechanical properties of the hipped steel produced from inert gas atomised powder were studied. The steel has shown a homogeneous and fine grained microstructure containing annealing twins and the absence of undesirable prior particle boundaries. This has led to higher yield strength, ultimate tensile strength and the ductility than that of the conventionally processed steel. The tensile deformation behaviour of hipped steel was found to be similar to that of the wrought material. Impact strength and fracture toughness of the hipped steel were superior to that of the wrought material; hence the hipped steel could be recommended for manufacture of components for critical applications.     

Hipping after sintering of titanium diboride cermets

Abstract

A new fabrication route, an alternative to glass encapsulated hipping (GEHIP), has been developed to produce dense TiB₂ cermets. Key points of this technique, based on hipping after vacuum sintering (VS + HIP), are the use of Ni₃ (Al,Ti) as binder phase and the selection of the proper amount of additions. The main advantage of VS + HIP with respect to GEHIP is the simplification of the sintering procedure which avoids the glass encapsulation step that makes it more adaptable for industrial use. Successful application of VS + HIP requires a minimum binder content about 10 vol.-% below which a significant hardness reduction is observed owing to the presence of residual porosity as compared with GEHIP. The materials produced by this technique combine low density and high stiffness with high hardness and toughness values, thus giving a set of properties especially attractive for applications where inertial loads are responsible for failure.     

An overview of 20 years' Romanian experience on packaging and components testing according to national and international regulations

Abstract

More than 20 years ago, the Institute for Nuclear Research (INR) Pitesti in Romania, through its Reliability and Testing Laboratory, was licensed by the Romanian Nuclear Regulatory Body – CNCAN to carry out qualification tests for packages intended for the transport and storage of radioactive materials. The radioactive material is placed in packaging which are designed in accordance with national and the International Atomic Energy Agency's (IAEA's) Regulations for safe transport to the disposal centre. A broad range of verification and certification tests are performed at INR on radioactive material packages or component sections, such as packages used for the transport of radioactive sources to be used for industrial or medical purposes. This paper describes some of the various tests, which have been performed, and how they relate to normal conditions and minor mishaps during transport. Quality assurance and quality control measures taken in order to meet technical specification provided by design there are also presented.     

烤烟外观质量指标量化分析初探

根据GB2635-92烤烟标准及有关研究结果,建立了初步量化的烟叶外观质量指标体系,并运用相关分析、聚类分析和主成分分析对外观质量指标进行了研究,得出烟叶外观质量指标间的量化关系,初步验证了烟叶外观质量量化指标的合理性。     

Development of steel grades for heat treated power train components: a review

Abstract

The development of new carburising steel grades by Daido Steel for heat treated transmission parts is reviewed. These developments are driven by the need for cost reduction, weight saving, fuel economy and higher mechanical performance in new car models under development in response to environmental and economic demands. The next generation of gears will be peened, then vacuum carburised to improve fatigue and impact strength in lighter components designed with smaller tooth cross-sections, and new steels giving improved performance have been developed. Case studies of new steels for pulleys (allowing shorter carburising times) and constant velocity joints are also described.