Behavior Of Composite And Multiple BarriersUnder Turbine Missile Impacts

For nuclear power plant life extension projects, it may be convenient and in some instances necessary to locate safety-related steel ducts and pipes outside of the main structures, exposing them to extreme environmental loads such as tornado missile impact. Examples of such applications include emergency firewater lines and Control Room vent ducts. The design of a tornado-impacted duct or pipe system requires an estimate of its dynamic response and an establishment of damage limits. These considerations are complicated by the system geometric and material nonlinearities and the local triaxiality effects on the response ductility limit. Simple, but acceptable accurate techniques for comprehensive evaluation of steel ducts under impact loads have not been established. This study presents simplified evaluation techniques for a steel duct/pipe under a heavy impact load, using fundamental concepts. The approach presented could be utilized to evaluate steel ducts/pipes against not only tornado missile impact loadings, but other types of transient loads as well. Both local and global responses of duct/pipe lines under missile impacts are evaluated. Applied impulse loadings for various types of tornado missiles are first established. A non-linear pseudo-static finite element analysis is performed in lieu of a more complicated dynamic analysis. The result is adopted for evaluation of the local ductility of ducts and pipes by using triaxial strain criteria. Global ductility and global shear checks are performed based on inelastic single-degree-of-freedom analysis methods. Pipe line design diameters and thicknesses are then determined based on the local ductility, global ductility and global shear evaluations. Accuracy of the non-linear pseudostatic analysis is discussed and a practical example using the proposed methodology is presented.

API Standard 521 new alternative method to evaluate fire relief for pressure relief device sizing and depressuring system design

Possible genetic damage in the Czech nuclear power plant workers

Probabilistic Safety Assessment (PSA) is an important tool for risk-informed integrated decision making application. Initiating events are caused by equipment failure or/and personnel error which causes disturbance to the nuclear power plant (NPP) and may lead to core damage. As the start of PSA, the quality of initiating events analysis has an important influence on safety assessment and PSA application for NPPs, and the application of operating experience of domestic and aboard are of great importance in initiating events analysis. Based on analysis experience of PSA model in design phase and operation phase for different NPPs, this paper developed a set of method for initiating events analysis of operation phase PSA model development. Combined with the referenced initiating events list, engineering evaluation, operating experience analysis and main logic diagram, a relatively complete initiating events list have been determined. According to the characteristics of the initiating events and analysis requirements for PSA applications, this paper adopted statistical analysis method or specific analysis method to determine the frequency of initiating events which could reflect the design of specific NPPs and operation level of domestic NPPs. The development and application of these initiating events analysis method, which could reflect design and operating characteristics more realistically, improved the development level of PSA model in operation phase effectively, and laid a solid foundation for PSA applications.

The design quality of the nuclear power plants (NPPs) has a direct impact on the operation and maintenance, which involves the safety and reliability of NPPs. Planning and development of the maintenance requirements of system and equipment in initial design stage of NPPs, and determination of reliability maintenance strategy compilation methods enable to fulfill good connection between design and operation of important value. After investigation and analysis, with a combination of reliability analysis method, experience feedback and common analysis approach, the methodology of reliability maintenance strategy compilation in design stage of NPPs has been initially established. And such methodology not only meets the maintenance requirements of system and equipment in design stage, but also enables to check the rationality and operability of process design from the maintenance implementation level, at the same time, it has great value in application regarding improving operational reliability of NPPs and avoiding non-essential major modification during operation of NPPs.

A predictive model (PM) has been developed for water and polymer flooding for use in screening studies and feasibility analysis. The PM requires only a fraction of the computing time of numerical simulators, but includes most of the phenomena which affect flood performance. This is accomplished by combining a two-dimensional crosssectional model (using vertical equilibrium), with areal sweep correlations, and injectivity functions which gives results (oil rate versus time) which are suitable for economic analysis. The paper presents validations of the PM against simulator, analytical, and field results. A brief sensitivity analysis concludes the paper.

A finite element computer program for the calculations of ice loads on offshore structures is developed. A brief description of the program is given and the solution techniques used to model general ice-structure interaction problems are discussed. The program is used to calculate maximum ice loads on various structures (vertical and inclined), and the calculations are compared to some laboratory and field measurements. Conclusions and recommendations for future work are suggested. INTRODUCTION During ice-structure interactions, the relative motion between the ice and the structure results in the development of forces known as "ice loads". Fixed offshore structures constructed in an ice infested environment must be strong enough to withstand the forces generated by ice. The last two-three decades have seen a considerable amount of ice related research work. The efforts have been directed towards understanding the mechanisms by which ice loads are developed, and subsequently formulate predictive methods for ice loads. Many empirical and analytical methods have been proposed for the calculation of ice loads on offshore structures. However, their application to actual ice-structure interaction problems requires considerable engineering judgements. First, empirical methods are valid only for the conditions and the geometries of the experiments. Extrapolation of empirical equations to compute ice loads on actual structures is underlined by a number of uncertainties [1]. Second, most existing analytical methods are developed for uniaxial problems (such as beam solutions). Field observations of ice-structure interactions indicate that ice fails in a complex state of stress and the use of uniaxial analytical methods results in unrealistic ice load estimations [2]. Proper application of analytical methods to calculate ice loads on actual structures is very complicated [3]. The complexity results from the high variability of ice conditions in the field. In addition, the intensity of ice loads depends to a large extent on the mechanical behaviour of ice and its mode of failure, geometry of the structure, and the relative motion between ice and the structure. When all these factors are taken into account, analytical solutions become very complicated. The complexities of ice-structure interaction problems dictate that the method of calculating ice loads on offshore structures should be numerical (finite element, discrete element, ...etc.). The universality and versatility of these methods allow for comprehensive analyses of ice-structure interaction problems, and subsequently realistic estimations of ice loads. However, numerical methods require constitutive models for the description of the mechanical behaviour of the materials involved in the interaction problem. Therefore, in order to carry out a reliable analysis, and subsequently a safe design of the structure, realistic mathematical models for the behaviour of ice, structural material, and soils of the foundation should be used. These models can be implemented into finite element computer programs (or discrete element programs), then used to analyze and design the structure against ice loads.

The energy generation industry faces new challenges and requirements. The fourth generation of nuclear power plants is developed to meet the future clean energy demand by 2030. The supercritical carbon dioxide (S–CO2) Brayton closed cycle features compactness and high efficiency, combined with short construction time, standing for higher profitability when compared to current steam cycles. In this article, a method for assessing overall viability of direct and indirect carbon dioxide cycles is described. This method comprises both thermodynamic and economic analyses. Thermodynamic and economic models have been developed to assess several cycle designs in terms of overall viability that includes thermodynamic performance and financial outcome. Each cycle has been calculated through an iterative process that takes into account the variation of the properties of the working fluid and returns temperatures, pressure, efficiency, and power generation for the given design characteristics. The economic model, on the other hand, includes the calculation of overnight cost, which is a function of the cycle choice, through the cost of the components. Furthermore, plant profitability is calculated over a given period, which depends on both overnight cost and power plant efficiency. The method has been applied on an indicative parametric analysis of two S–CO2 cycles (direct and indirect) where the capability of identifying optimum areas has been case shown. In terms of overall pressure ratio, it was found that a thermodynamically optimized cycle would not coincide with an economically optimized one, due to the effect of component costing. On the other hand, turbine entry temperature appeared to considerably improve both power output and economic outcome, even though a maximum value is dictated by thermal and mechanical resistances of materials. In overall, even though power generation train is only a subsystem in a nuclear plant, it has been demonstrated that thermodynamic cycle design can have a significant impact on maximizing the earning capacity of the plant, especially through the implementation of a novel highly dense fluid, such as the S–CO2, which bears the potential of high compactness.

In-service monitoring of piping and vessels in nuclear power plants: report on BMU Study SR 2218

Analytic study for physical protection system (PPS) in nuclear power plants (NPPs)

SummarySince the 9/11 attacks, whether nuclear power plants (NPPs) can withstand the malicious impact of large commercial aircraft has become a question that must be considered in the design phase. Refined model and fine‐scale element reflect more accurately the failure procedure and behaviour. However, due to the exceedingly complex structure of NPP, the traditional meshing method requires a substantial number of geometric operations involving point, line, area, and volume, leading to a tedious modelling process and very high computational costs, as well as making it difficult to modify and optimize the model. This paper combines the scaled boundary finite element method with the octree technique to refine nuclear engineering damage evolution analysis and establish a refined numerical model of the Generation III+ NPP, considering the detailed equipment hatch, air intake, and internal steel containment vessel structures. Subsequently, the refined damage evolution analysis of a large commercial aircraft crashing into an NPP was developed. The mesh size sensitivity, impact region shape comparison, and the influence of different impact heights were discussed. The results indicate that the cross‐scale refined meshing and analysis method provides a high‐quality discrete grid with fewer elements. Furthermore, this method is highly flexible, more accurately simulating the damage evolution and gradual destruction process. We recommend future structural optimization for the air intake and conducting detailed analyses at this location. The cross‐scale analysis method presented in this paper enables a rapid, refined simulation of a malicious impact by a large commercial aircraft. Additionally, it provides technical support for future studies of the responses of NPPs' internal structures, systems, and equipment under extreme earthquake and other disaster conditions.

The article is aimed at the enhancement of the stereometric approach to analysing economic categories and processes and investigating directions of its application in the science of security and taxation. Methodology. The methodological basis of the study consists of general scientific methods of analysis and synthesis, a comparative study of existing models of economic categories, which are based on the stereometric approach. The empirical method is used to describe the problem of using a stereometric approach to determining the economic security of an enterprise. The results of the study. The article demonstrates that modern realities increasingly require spatial thinking from economists, thus conditioning the appearance of 3D models of some economic categories in economic research papers. A number of stereometric elements have been applied by both foreign and Ukrainian scholars in the economic sphere for several decades. The article points out that no current model could claim the complete realization of the stereometric approach as an independent unidirectional array of the content of principles and methods of analysing economic categories and processes. There are also determined regularities not considered by other scientists, as well as current problems and omissions. Practical implications. There are substantiated differences between the stereometric and graphical methods of economic analysis. The stereometric approach is suggested to be meant as one of the economic analysis approaches based on visualization of economic categories and processes on the basis of geometric solids allowing qualitative and quantitative assessment of the level and dynamics of the selected array of indicators put into a single graphical model. There is revealed essence and principles of the stereometric approach use in the economy and in the science of security in particular. Economic security is treated as one of the ternary nature being resources, processes and a condition simultaneously. The article suggests a pyramid to determine economic security and proves that changes of quality, speed, and quantity of business processes expressed by changes of corresponding angles of the pyramid impact both the condition and the general level of economic security. Relevance/originality. The presented proposals on enhancing the stereometric approach create a theoretical foundation for applied research in various industries. The enhanced stereometric approach enables building a general-theoretical concept of economic security considering its connections with such notions as competitiveness and development.

A simple calibration method for structured light-based 3D profile measurement

Performance-based probabilistic capacity models for reinforced concrete and prestressed concrete protective structures subjected to missile impact

Deregulation in the electricity market has resulted in a number of challenges in the nuclear power industry. Nuclear power plants must find innovative ways to remain competitive by reducing operating costs without jeopardizing safety. Instrumentation and Control (I&C) systems not only play important roles in plant operation, but also in reducing the cost of power generation while maintaining and/or enhancing safety. Therefore, it is extremely important that I&C systems are managed efficiently and economically. With the increasing use of digital technologies, new methods are needed to solve problems associated with various aspects of digital I&C systems. Probabilistic Safety Assessment (PSA) has proved to be an effective method for safety analysis and risk-based decisions, even though challenges are still present. This paper provides an overview of PSA applications in three areas of digital I&C systems in nuclear power plants. These areas are Graded Quality Assurance, Surveillance Testing, and Instrumentation and Control System Design. In addition, PSA application in the regulation of nuclear power plants that adopt digital I&C systems is also investigated.