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Qin Zhang - One of the best experts on this subject based on the ideXlab platform.
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model event fault trees with dynamic uncertain causality graph for better Probabilistic Safety Assessment
IEEE Transactions on Reliability, 2017Co-Authors: Zhenxu Zhou, Qin ZhangAbstract:Probabilistic Safety Assessment (PSA) has been widely applied to large complex industrial systems like nuclear power plants, chemical plants, etc. Event trees (ET) and fault trees (FT) are the major tools, but dependences and logic cycles may exist among and within them, and are not well addressed, leading to even optimistic estimates. Repeated representations and calculations exist. Causalities are assumed deterministic, while sometimes they are uncertain. This paper applies dynamic uncertain causality graph (DUCG) in PSA to overcome these problems. DUCG is a newly presented approach for uncertain causality representation and Probabilistic reasoning, and has been successfully applied to online fault diagnoses of large complex industrial systems. This paper suggests to model all ETs and FTs of a target system as a single DUCG allowing uncertain causalities and avoiding repeated representations, and calculate the probabilities/frequencies of the undesired events by using the DUCG algorithm. In the calculation, the problems of dependencies and circular loops are solved. The suggested DUCG representation mode and calculation algorithm are presented and illustrated with examples. The results reveal the effectiveness and feasibility of this methodology.
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Model Event/Fault Trees With Dynamic Uncertain Causality Graph for Better Probabilistic Safety Assessment
IEEE Transactions on Reliability, 2017Co-Authors: Zhenxu Zhou, Qin ZhangAbstract:Probabilistic Safety Assessment (PSA) has been widely applied to large complex industrial systems like nuclear power plants, chemical plants, etc. Event trees (ET) and fault trees (FT) are the major tools, but dependences and logic cycles may exist among and within them, and are not well addressed, leading to even optimistic estimates. Repeated representations and calculations exist. Causalities are assumed deterministic, while sometimes they are uncertain. This paper applies dynamic uncertain causality graph (DUCG) in PSA to overcome these problems. DUCG is a newly presented approach for uncertain causality representation and Probabilistic reasoning, and has been successfully applied to online fault diagnoses of large complex industrial systems. This paper suggests to model all ETs and FTs of a target system as a single DUCG allowing uncertain causalities and avoiding repeated representations, and calculate the probabilities/frequencies of the undesired events by using the DUCG algorithm. In the calculation, the problems of dependencies and circular loops are solved. The suggested DUCG representation mode and calculation algorithm are presented and illustrated with examples. The results reveal the effectiveness and feasibility of this methodology.
Marko Čepin - One of the best experts on this subject based on the ideXlab platform.
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The extended living Probabilistic Safety Assessment
Proceedings of the Institution of Mechanical Engineers Part O: Journal of Risk and Reliability, 2019Co-Authors: Marko ČepinAbstract:The term living Probabilistic Safety Assessment was defined soon after the initial Probabilistic Safety Assessments were implemented. The objective of this article is to present the extended living...
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Application of shutdown Probabilistic Safety Assessment
Reliability Engineering & System Safety, 2018Co-Authors: Marko ČepinAbstract:Abstract Shutdown Probabilistic Safety Assessment represents an extension of Probabilistic Safety Assessment performed for other plant operating states, excluding power operation, which is covered in Probabilistic Safety Assessment. The objective is to present the method of shutdown Probabilistic Safety Assessment and its application on real nuclear power plant example model to evaluate the feasibility of the future wider use. The main methods are similar to conventional Probabilistic Safety Assessment including the fault tree analysis, the event tree analysis, the common cause failures analysis, the human reliability analysis and the Probabilistic data collection and analysis. Results interpretation reveals differences between power and other operating states Probabilistic Safety Assessment. Most of the results have been expected including notable or significant differences among the plat operating states regarding the minimal cut sets, regarding the main risk contributors, regarding the importance factors for equipment, regarding the variability of initiating events contributions which are easily explained due to the differences among the plant operating states. The results revealed a variability of durations of the plant operating states among different shutdowns, which causes large differences in risk results among different shutdowns and different overall risk. Such variability may require the adjustment of risk informed decision making methods.
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House events matrix for shutdown Probabilistic Safety Assessment
2016 International Conference on Probabilistic Methods Applied to Power Systems (PMAPS), 2016Co-Authors: Marko ČepinAbstract:Probabilistic Safety Assessment is one of the standardized ways of assessing Safety of nuclear power plants. The objective of the method is to present an extension of the fault tree in order to reduce the size of the shutdown Probabilistic Safety Assessment model. The shutdown Probabilistic Safety Assessment method is developed. The modelling for all plant operating states include consideration of 15 states, which were determined as appropriate representations of much more plant configurations in addition to the plant full power operation. For dealing with the complexity of the models and manageable size of the models for the sensitivity studies it is essential that the models optimizations are performed. House events matrix plays an important role as it reduces the number of the fault trees significantly. The results include the time dependent representation of the core damage frequency contributions weighted for their plant operating state durations over total duration of the shutdown timely through the whole shutdown. The risk of the plant during shutdown is smaller in general than in full power operation, however for certain specific plants and their specific plant operating states the risk for a short duration of time may increase beyond the risk of full steady state power operation.
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Development and application of a living Probabilistic Safety Assessment tool: Multi-objective multi-dimensional optimization of surveillance requirements in NPPs considering their ageing
Reliability Engineering & System Safety, 2014Co-Authors: Duško Kančev, Marko Čepin, Blaže GjorgievAbstract:Abstract The benefits of utilizing the Probabilistic Safety Assessment towards improvement of nuclear power plant Safety are presented in this paper. Namely, a nuclear power plant risk reduction can be achieved by risk-informed optimization of the deterministically-determined surveillance requirements. A living Probabilistic Safety Assessment tool for time-dependent risk analysis on component, system and plant level is developed. The study herein focuses on the application of this living Probabilistic Safety Assessment tool as a computer platform for multi-objective multi-dimensional optimization of the surveillance requirements of selected Safety equipment seen from the aspect of the risk-informed reasoning. The living Probabilistic Safety Assessment tool is based on a newly developed model for calculating time-dependent unavailability of ageing Safety equipment within nuclear power plants. By coupling the time-dependent unavailability model with a commercial software used for Probabilistic Safety Assessment modelling on plant level, the frames of the new platform i.e. the living Probabilistic Safety Assessment tool are established. In such way, the time-dependent core damage frequency is obtained and is further on utilized as first objective function within a multi-objective multi-dimensional optimization case study presented within this paper. The test and maintenance costs are designated as the second and the incurred dose due to performing the test and maintenance activities as the third objective function. The obtained results underline, in general, the usefulness and importance of a living Probabilistic Safety Assessment, seen as a dynamic Probabilistic Safety Assessment tool opposing the conventional, time-averaged unavailability-based, Probabilistic Safety Assessment. The results of the optimization, in particular, indicate that test intervals derived as optimal differ from the deterministically-determined ones defined within the existing technical specifications. Substantial risk reduction, supplemented with reduction in costs and dose is implicated if the selected existing surveillance test intervals are replaced with the corresponding optimal ones. By this, the benefits of applying risk-informed decision making are once more emphasized. Also, the importance of the inclusion of Safety equipment ageing in the plant long-term Probabilistic Safety Assessment is recognized.
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Advantages and difficulties with the application of methods of Probabilistic Safety Assessment to the power systems reliability
Nuclear Engineering and Design, 2012Co-Authors: Marko ČepinAbstract:Abstract The Probabilistic Safety Assessment is a standardized and widely accepted method for assessing and improving the reliability and Safety of complex technologies, which is particularly true for the nuclear and the aerospace industry. The number of its applications to reliability of power systems is increasing. The objective of the paper is to collect and present the advantages and difficulties with the application of methods of Probabilistic Safety Assessment to power systems reliability. The methods which apply the features of fault tree analysis to reliability analysis of power systems are presented and compared. The results are discussed and evaluated. The main advantages are connected with the facts that the methods are relative simple, the models are mostly available and that the data is intensively collected, evaluated and can serve as an excellent support for the quantitative part of the analyses. The difficulties are connected with different nature of components interaction within the power system compared to the Safety systems in a nuclear power plant and with the large complexity of the power system, which distinguishes the term reliability into its static and dynamic parts known as adequacy and security. The results show large impact of common cause failures. The lack of data for the evaluations in the field of common cause failures of power systems increases significantly the uncertainty of the results. The uncertainty of the results may be reduced by improved data collection and analysis similarly as it is done in the nuclear Safety.
Zhenxu Zhou - One of the best experts on this subject based on the ideXlab platform.
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model event fault trees with dynamic uncertain causality graph for better Probabilistic Safety Assessment
IEEE Transactions on Reliability, 2017Co-Authors: Zhenxu Zhou, Qin ZhangAbstract:Probabilistic Safety Assessment (PSA) has been widely applied to large complex industrial systems like nuclear power plants, chemical plants, etc. Event trees (ET) and fault trees (FT) are the major tools, but dependences and logic cycles may exist among and within them, and are not well addressed, leading to even optimistic estimates. Repeated representations and calculations exist. Causalities are assumed deterministic, while sometimes they are uncertain. This paper applies dynamic uncertain causality graph (DUCG) in PSA to overcome these problems. DUCG is a newly presented approach for uncertain causality representation and Probabilistic reasoning, and has been successfully applied to online fault diagnoses of large complex industrial systems. This paper suggests to model all ETs and FTs of a target system as a single DUCG allowing uncertain causalities and avoiding repeated representations, and calculate the probabilities/frequencies of the undesired events by using the DUCG algorithm. In the calculation, the problems of dependencies and circular loops are solved. The suggested DUCG representation mode and calculation algorithm are presented and illustrated with examples. The results reveal the effectiveness and feasibility of this methodology.
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Model Event/Fault Trees With Dynamic Uncertain Causality Graph for Better Probabilistic Safety Assessment
IEEE Transactions on Reliability, 2017Co-Authors: Zhenxu Zhou, Qin ZhangAbstract:Probabilistic Safety Assessment (PSA) has been widely applied to large complex industrial systems like nuclear power plants, chemical plants, etc. Event trees (ET) and fault trees (FT) are the major tools, but dependences and logic cycles may exist among and within them, and are not well addressed, leading to even optimistic estimates. Repeated representations and calculations exist. Causalities are assumed deterministic, while sometimes they are uncertain. This paper applies dynamic uncertain causality graph (DUCG) in PSA to overcome these problems. DUCG is a newly presented approach for uncertain causality representation and Probabilistic reasoning, and has been successfully applied to online fault diagnoses of large complex industrial systems. This paper suggests to model all ETs and FTs of a target system as a single DUCG allowing uncertain causalities and avoiding repeated representations, and calculate the probabilities/frequencies of the undesired events by using the DUCG algorithm. In the calculation, the problems of dependencies and circular loops are solved. The suggested DUCG representation mode and calculation algorithm are presented and illustrated with examples. The results reveal the effectiveness and feasibility of this methodology.
Muhammad Zubair - One of the best experts on this subject based on the ideXlab platform.
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A computer based living Probabilistic Safety Assessment (LPSA) method for nuclear power plants
Nuclear Engineering and Design, 2013Co-Authors: Muhammad Zubair, Zhang Zhijian, Iftikhar Ahmed, Muhammad AamirAbstract:Abstract To update PSA (Probabilistic Safety Assessment) model this paper presents a computer based living Probabilistic Safety Assessment (LPSA) method named as online risk monitor system (ORMS). The essential features and functions of ORMS have been described in this research. A case study of emergency diesel generator (EDG) of Daya Bay nuclear power plant (NPP) has been done; operational failure rate and demand failure probability of EDG has been calculated with the help of ORMS. The results of ORMS are well matched with data obtained from Daya Bay NPP. ORMS is capable of automatically update the online risk models and reliability parameters of equipment in time. ORMS can support in decision making process of operator and manager in nuclear power plant.
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Advancement in living Probabilistic Safety Assessment to increase Safety of nuclear power plants
Proceedings of the Institution of Mechanical Engineers Part O: Journal of Risk and Reliability, 2013Co-Authors: Muhammad ZubairAbstract:Among the energy resources, the energy obtained from nuclear power plants is very important for the prosperity of any country. Living Probabilistic Safety Assessment is a growing field that provides a high level of Safety for nuclear power plants. Living Probabilistic Safety Assessment consists of different techniques, among them this article presents a method to update reliability data. This method is based on Binomial likelihood function and its conjugate beta distribution for demand failure probability, and Poisson likelihood function and its conjugate gamma distribution for operational failure rate. The method uses generic data for beta and gamma prior distribution, which is updated by using the reliability data update method. Reliability data update is a computer-based program used to update nuclear power plant data according to changing conditions. By updating the living Probabilistic Safety Assessment it is possible to get an online risk monitor system that can be helpful in severe accident conditions, as in Fukushima accident, to make the man–machine system friendly.
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A methodology for Living Probabilistic Safety Assessment (LPSA) based on Advanced Control Room Operator Support System (ACROSS)
Annals of Nuclear Energy, 2011Co-Authors: Muhammad Zubair, Zhijian Zhang, Salah Ud-din KhanAbstract:Abstract In Probabilistic Safety Assessment (PSA) all attention is paid to analyze a system which is a time consuming effort so there is a need to develop a system network to support the analyst and to reduce manpower. To handle the physical, operational and organizational changes and to utilize the PSA information effectively the development of living Probabilistic Safety Assessment (LPSA) is essential. This paper presents a detailed methodology for LPSA. One part of this methodology is Advanced Control Room Operator Support System (ACROSS) which is helpful for updating the LPSA model. This methodology also provides help to make the control rooms in Nuclear Power Plants (NPPs) more advanced and user friendly. The study also makes recommendations for further use and development of this technique in the present and future NPPs.
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A methodology for living Probabilistic Safety Assessment (LPSA)
2010Co-Authors: Muhammad Zubair, Zhijian ZhangAbstract:The objective of this paper is to summarize the latest techniques, applications, methodologies, use of different software, and development of codes, in the field of Living Probabilistic Safety Assessment (LPSA) and Risk Monitoring (RM). The paper consists of three parts, in first part definitions, history, aims, uses of LPSA, and a new detailed model for LPSA have been explain. In second part brief introduction, worldwide use of RM, benefits and draw backs of software in RM, and in final part comparison between LPSA and RM have been discussed. The study also makes recommendations for further use and development of these two techniques in present and future NPPs.
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A Review: Advancement in Probabilistic Safety Assessment and Living Probabilistic Safety Assessment
2010 Asia-Pacific Power and Energy Engineering Conference, 2010Co-Authors: Muhammad Zubair, Zhijian Zhang, Muhammad AamirAbstract:Due to increasing demand of Electricity, every country in the world wants to construct more and more nuclear power plants and apply different advance techniques for accident prevention, Safety and reliability. Probabilistic Safety Assessment (PSA) and Living Probabilistic Safety Assessment (LPSA) are two of them, which are presented in this review paper. The paper consists of four parts, in first part latest application of PSA in second part definitions and methodology of LPSA, in third part risk monitoring and in fourth part comparison between these three, has been described.
Hong Kam Lo - One of the best experts on this subject based on the ideXlab platform.
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highway and road Probabilistic Safety Assessment based on bayesian network models
Computer-aided Civil and Infrastructure Engineering, 2017Co-Authors: Zacarias Grande, Enrique Castillo, Elena Mora, Hong Kam LoAbstract:A Bayesian network model is developed, in which all the items or Safety related elements encountered when traveling along a highway or road, such as terrain, infrastructure, light signals, speed limit signs, intersections, roundabouts, curves, tunnels, viaducts, and any other Safety relevant elements are reproduced. Since human error is the main cause of accidents, special attention is given to modeling the driver behavior variables (driver's tiredness and attention) and to how they evolve with time or travel length. The sets of conditional probabilities of variables given their parents, which permit to quantify the Bayesian network joint probability, are obtained and written as closed formulas, which allow us to identify the particular contribution of each variable to Safety and facilitate the computer implementation of the proposed method. In particular, the probabilities of incidents affecting Safety are calculated so that a Probabilistic Safety Assessment of the road can be done and its most critical elements can be identified and sorted by importance. This permits the improvement of road Safety making adequate corrections to save time and money in the maintenance program by concentrating on the most critical elements and effective investments. Some real examples of a Spanish highway and a conventional road are provided to illustrate the proposed methodology and show its advantages and performance.