Pedro Saldanha | Univesidade Federal Fluminense - UFF (original) (raw)

Papers by Pedro Saldanha

Research paper thumbnail of A preliminary hazard analysis improving the analytical hierarchy process consistency in decision making process for site selection

Research paper thumbnail of Reliability Appraisal for a PWR Auxiliary Feed-Water System under Aging by Point Processes

This paper presents an application of an algorithm, named RUCA, developed to calculate the avilab... more This paper presents an application of an algorithm, named RUCA, developed to calculate the avilability of repairable systems, considering design and operation improvements. The system under study is statistically analyzed in order to choose the appropriate stochastic point process, which will be used in its probabilistic modeling. RUCA comprises a non-homogeneous Markov chain whose transition probability matrices are defined as functions of the rates of occurrence of failures (ROCOF) associated with significant failures, which governs transitions between the states. Presented is an application to the AFWS of a typical two-loop PWR. Results clearly show the suitability of point processes for treating aging phenomena. Also, although the number of components is not very high, the analysis is still performed in a personal computer with no further difficulties.

Research paper thumbnail of Reliability analysis of the service water pump using a dynamic approach to the Poisson non homogeneous processes

Research paper thumbnail of Reliability Analysis of Service Water Pumps by Poisson Point Processes with a Generalized Model for the Rate of Occurrence of Failures

Research paper thumbnail of A Methodology for Optimizing the Management of Spent Fuel of Nuclear Power Plants Using Dry Storage Casks

Science and Technology of Nuclear Installations, Feb 7, 2019

The management of spent nuclear fuel assemblies of nuclear reactors is a priority subject among m... more The management of spent nuclear fuel assemblies of nuclear reactors is a priority subject among member states of the International Atomic Energy Agency. For the majority of these countries, the destination of such fuel assemblies is a decision that is yet to be made and the "wait-and-see" policy is thus adopted by them. In this case, the irradiated fuel is stored in on-site spent fuel pools until the power plant is decommissioned or, when there is no more racking space in the pool, they are stored in intermediate storage facilities, which can be another pool or dry storage systems, until the final decision is made. The objective of this study is to propose a methodology that, using optimization algorithms, determines the ideal time for removal of the fuel assemblies from the spent fuel pool and to place them into dry casks for intermediate storage. In this scenario, the methodology allows for the optimal dimensioning of the designed spent fuel pools and the casks' characteristics, thus reducing the final costs for purchasing new Nuclear Power Plants (NPP), as the size and safety features of the pool could be reduced and dry casks, that would be needed anyway after the decommissioning of the plant, could be purchased with optimal costs. To demonstrate the steps involved in the proposed methodology, an example is given, one which uses the Monte Carlo N-Particle code (MCNP) to calculate the shielding requirements for a simplified model of a concrete dry cask. From the given example, it is possible to see that, using real-life data, the proposed methodology can become a valuable tool to help making nuclear energy a more attractive choice costwise.

Research paper thumbnail of Aging Evaluation for the Extension of Qualified Life of Nuclear Power Plant Equipment Through Modulated Poisson Processes

Research paper thumbnail of Models for the Reliability Analysis of Digital Instrumentation and Control Systems for Nuclear Power Plants

InTech eBooks, Oct 12, 2016

The objective of this chapter is to discuss two approaches for reliability analysis of digital in... more The objective of this chapter is to discuss two approaches for reliability analysis of digital instrumentation and control systems in nuclear power plants taking into account the regulatory side. Dynamic Flowgraph Methodology (DFM) and Markov/Cell-to-Cell Mapping Technique (CCMT) are discussed and case studies developed are presented. These case studies involve simplified control systems for a steam generator and a pressurizer of a Pressurized Water Reactor (PWR) plant for the purpose of evaluating each method. Advantages and limitations of each approach are addressed. For the DFM approach, three concerns in the literature are addressed: modeling of the system itself, incorporation of the methodology results into existing Probabilistic Safety Assessments (PSA), and identification of software failures. The Markov/CCMT, which has been used in dynamic probabilistic safety assessments, is approached by means of a simplified digitally controlled water volume control system. The Markov/CCMT methodology results in detailed data of the system reliability behavior in relation to time. However, it demands a higher computational effort than usual as the complexity (i.e., number of components and failure states) of the system increases. As a regulatory research conclusion, the methodologies presented can be used on PSA risk informed assessment, contributing to the regulatory side.

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

CRC Press eBooks, Sep 3, 2015

Research paper thumbnail of Analysis of the qualified life extension of nuclear safety systems through modulated Poisson point processes

Progress in Nuclear Energy, Sep 1, 2012

The Modulated Power Law Process (MPLP) is a three-parameter stochastic point process that can be ... more The Modulated Power Law Process (MPLP) is a three-parameter stochastic point process that can be used to describe the failure times of repairable systems. While the Non-Homogeneous Poisson Process (NHPP) or the Renewal Process (RP) implies that a system is exactly on the same condition just after a repair as just before a failure, the MPLP allows for the system to be affected both by failure and repair. For this reason this model is adequate for evaluating the recurrent events that incorporate both time trends and effects of past events such as the renewal type behavior. The purpose of this paper is to evaluate the MPLP as a model for the rate of occurrence of failures (ROCOF) of repairable systems to decide for an extension of qualified life in the context of a license renewal of a nuclear power plant. The analysis was carried out considering some field data spanning a 2300 calendar day period, which is approximately equivalent to four burn-up cycles and refueling periods. The reliability is estimated, and maintenance strategies are discussed, concerning the results of the case study presented. As a conclusion, the MPLP is adequate for modeling the rate of occurrence of failures that are time dependent, and can be used where aging mechanisms are present in the operation of repairable systems. This means that equipment characteristics that are important may be inserted into the model and the results can help make decisions in the context of maintenance programs, as is the case with the maintenance rule concept that has been proposed by the U.S. Nuclear Regulatory Commission and has just been implemented in nuclear power plants in Brazil, for instance. The difficulty with data acquisition for applying point processes is discussed throughout.

Research paper thumbnail of A DFM/ATHEANA human failure analysis of a digital control system for a pressurizer

Research paper thumbnail of Importance measures for performance shaping factors of human reliability analysis

Process Safety Progress, 2022

The crew of a nuclear‐powered submarine under development in Brasil plays an important role in it... more The crew of a nuclear‐powered submarine under development in Brasil plays an important role in its safety. For this reason, crew members must be trained in procedures against undesired events. However, information that would help to accurately decrease human error probability (HEP) on board nuclear‐powered submarines is not available in the literature. Therefore, a methodology is required to obtain this information. This study introduces importance measures to evaluate the contribution of performance shaping factors (PSFs) and their levels to HEP. Importance measures Fussell‐Vesely, risk reduction worth, risk achievement worth, and Birnbaum importance, commonly used in probabilistic safety assessment, are introduced to identify PSFs and PSF levels that contribute the most to HEP. The proposed approach is focused on identifying HEP's main contributors, oriented toward decision‐making. The methodology uses the PSFs established in the Standardized Plant Analysis Risk‐Human Reliabil...

Research paper thumbnail of Geometrically induced singular behavior of entanglement

Research paper thumbnail of On probability models for the unavailability analysis of safety systems under aging phenomena

Progress in Nuclear Energy, 1999

This paper presents and discusses three probability models for approaching aging of a component. ... more This paper presents and discusses three probability models for approaching aging of a component. NRC and IAEA views of aging phenomena are reviewed and discussed. Repair is approached in the first model by stochastic point processes, and a statistical dynamical model is employed to allow for Bayesian forecasting. A discussion on repairable systems terminology is presented because much controversy may

Research paper thumbnail of Regulatory activities in the field of instrumentation and control and operator support systems of ANGRA 1, 2 and 3 NPPs - 2007's status report from Brazil

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

Safety and Reliability of Complex Engineered Systems, 2015

Research paper thumbnail of Reliability Analysis of Service Water Pumps by Poisson Point Processes with a Generalized Model for the Rate of Occurrence of Failures

Advances in Safety and Reliability, 1997

Research paper thumbnail of An application of non-homogeneous Poisson point processes to the reliability analysis of service water pumps

Nuclear Engineering and Design, 2001

The purpose of this paper is to present an application of the non-homogeneous Poisson point proce... more The purpose of this paper is to present an application of the non-homogeneous Poisson point process to the study of the rates of occurrence of failures (ROCOF) when they are time dependent, and the times between failures are neither independent nor identically distributed. The application concerns the analysis of the reliability of service water pumps of a typical PWR nuclear

Research paper thumbnail of On probability models for the unavailability analysis of safety systems under aging phenomena

Progress in Nuclear Energy, 1999

This paper presents and discusses three probability models for approaching aging of a component. ... more This paper presents and discusses three probability models for approaching aging of a component. NRC and IAEA views of aging phenomena are reviewed and discussed. Repair is approached in the first model by stochastic point processes, and a statistical dynamical model is employed to allow for Bayesian forecasting. A discussion on repairable systems terminology is presented because much controversy may

Research paper thumbnail of LWR Safety Analysis and Licensing and Implications for Advanced Reactors

Nuclear Power - Operation, Safety and Environment, 2011

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

Research paper thumbnail of A preliminary hazard analysis improving the analytical hierarchy process consistency in decision making process for site selection

Research paper thumbnail of Reliability Appraisal for a PWR Auxiliary Feed-Water System under Aging by Point Processes

This paper presents an application of an algorithm, named RUCA, developed to calculate the avilab... more This paper presents an application of an algorithm, named RUCA, developed to calculate the avilability of repairable systems, considering design and operation improvements. The system under study is statistically analyzed in order to choose the appropriate stochastic point process, which will be used in its probabilistic modeling. RUCA comprises a non-homogeneous Markov chain whose transition probability matrices are defined as functions of the rates of occurrence of failures (ROCOF) associated with significant failures, which governs transitions between the states. Presented is an application to the AFWS of a typical two-loop PWR. Results clearly show the suitability of point processes for treating aging phenomena. Also, although the number of components is not very high, the analysis is still performed in a personal computer with no further difficulties.

Research paper thumbnail of Reliability analysis of the service water pump using a dynamic approach to the Poisson non homogeneous processes

Research paper thumbnail of Reliability Analysis of Service Water Pumps by Poisson Point Processes with a Generalized Model for the Rate of Occurrence of Failures

Research paper thumbnail of A Methodology for Optimizing the Management of Spent Fuel of Nuclear Power Plants Using Dry Storage Casks

Science and Technology of Nuclear Installations, Feb 7, 2019

The management of spent nuclear fuel assemblies of nuclear reactors is a priority subject among m... more The management of spent nuclear fuel assemblies of nuclear reactors is a priority subject among member states of the International Atomic Energy Agency. For the majority of these countries, the destination of such fuel assemblies is a decision that is yet to be made and the "wait-and-see" policy is thus adopted by them. In this case, the irradiated fuel is stored in on-site spent fuel pools until the power plant is decommissioned or, when there is no more racking space in the pool, they are stored in intermediate storage facilities, which can be another pool or dry storage systems, until the final decision is made. The objective of this study is to propose a methodology that, using optimization algorithms, determines the ideal time for removal of the fuel assemblies from the spent fuel pool and to place them into dry casks for intermediate storage. In this scenario, the methodology allows for the optimal dimensioning of the designed spent fuel pools and the casks' characteristics, thus reducing the final costs for purchasing new Nuclear Power Plants (NPP), as the size and safety features of the pool could be reduced and dry casks, that would be needed anyway after the decommissioning of the plant, could be purchased with optimal costs. To demonstrate the steps involved in the proposed methodology, an example is given, one which uses the Monte Carlo N-Particle code (MCNP) to calculate the shielding requirements for a simplified model of a concrete dry cask. From the given example, it is possible to see that, using real-life data, the proposed methodology can become a valuable tool to help making nuclear energy a more attractive choice costwise.

Research paper thumbnail of Aging Evaluation for the Extension of Qualified Life of Nuclear Power Plant Equipment Through Modulated Poisson Processes

Research paper thumbnail of Models for the Reliability Analysis of Digital Instrumentation and Control Systems for Nuclear Power Plants

InTech eBooks, Oct 12, 2016

The objective of this chapter is to discuss two approaches for reliability analysis of digital in... more The objective of this chapter is to discuss two approaches for reliability analysis of digital instrumentation and control systems in nuclear power plants taking into account the regulatory side. Dynamic Flowgraph Methodology (DFM) and Markov/Cell-to-Cell Mapping Technique (CCMT) are discussed and case studies developed are presented. These case studies involve simplified control systems for a steam generator and a pressurizer of a Pressurized Water Reactor (PWR) plant for the purpose of evaluating each method. Advantages and limitations of each approach are addressed. For the DFM approach, three concerns in the literature are addressed: modeling of the system itself, incorporation of the methodology results into existing Probabilistic Safety Assessments (PSA), and identification of software failures. The Markov/CCMT, which has been used in dynamic probabilistic safety assessments, is approached by means of a simplified digitally controlled water volume control system. The Markov/CCMT methodology results in detailed data of the system reliability behavior in relation to time. However, it demands a higher computational effort than usual as the complexity (i.e., number of components and failure states) of the system increases. As a regulatory research conclusion, the methodologies presented can be used on PSA risk informed assessment, contributing to the regulatory side.

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

CRC Press eBooks, Sep 3, 2015

Research paper thumbnail of Analysis of the qualified life extension of nuclear safety systems through modulated Poisson point processes

Progress in Nuclear Energy, Sep 1, 2012

The Modulated Power Law Process (MPLP) is a three-parameter stochastic point process that can be ... more The Modulated Power Law Process (MPLP) is a three-parameter stochastic point process that can be used to describe the failure times of repairable systems. While the Non-Homogeneous Poisson Process (NHPP) or the Renewal Process (RP) implies that a system is exactly on the same condition just after a repair as just before a failure, the MPLP allows for the system to be affected both by failure and repair. For this reason this model is adequate for evaluating the recurrent events that incorporate both time trends and effects of past events such as the renewal type behavior. The purpose of this paper is to evaluate the MPLP as a model for the rate of occurrence of failures (ROCOF) of repairable systems to decide for an extension of qualified life in the context of a license renewal of a nuclear power plant. The analysis was carried out considering some field data spanning a 2300 calendar day period, which is approximately equivalent to four burn-up cycles and refueling periods. The reliability is estimated, and maintenance strategies are discussed, concerning the results of the case study presented. As a conclusion, the MPLP is adequate for modeling the rate of occurrence of failures that are time dependent, and can be used where aging mechanisms are present in the operation of repairable systems. This means that equipment characteristics that are important may be inserted into the model and the results can help make decisions in the context of maintenance programs, as is the case with the maintenance rule concept that has been proposed by the U.S. Nuclear Regulatory Commission and has just been implemented in nuclear power plants in Brazil, for instance. The difficulty with data acquisition for applying point processes is discussed throughout.

Research paper thumbnail of A DFM/ATHEANA human failure analysis of a digital control system for a pressurizer

Research paper thumbnail of Importance measures for performance shaping factors of human reliability analysis

Process Safety Progress, 2022

The crew of a nuclear‐powered submarine under development in Brasil plays an important role in it... more The crew of a nuclear‐powered submarine under development in Brasil plays an important role in its safety. For this reason, crew members must be trained in procedures against undesired events. However, information that would help to accurately decrease human error probability (HEP) on board nuclear‐powered submarines is not available in the literature. Therefore, a methodology is required to obtain this information. This study introduces importance measures to evaluate the contribution of performance shaping factors (PSFs) and their levels to HEP. Importance measures Fussell‐Vesely, risk reduction worth, risk achievement worth, and Birnbaum importance, commonly used in probabilistic safety assessment, are introduced to identify PSFs and PSF levels that contribute the most to HEP. The proposed approach is focused on identifying HEP's main contributors, oriented toward decision‐making. The methodology uses the PSFs established in the Standardized Plant Analysis Risk‐Human Reliabil...

Research paper thumbnail of Geometrically induced singular behavior of entanglement

Research paper thumbnail of On probability models for the unavailability analysis of safety systems under aging phenomena

Progress in Nuclear Energy, 1999

This paper presents and discusses three probability models for approaching aging of a component. ... more This paper presents and discusses three probability models for approaching aging of a component. NRC and IAEA views of aging phenomena are reviewed and discussed. Repair is approached in the first model by stochastic point processes, and a statistical dynamical model is employed to allow for Bayesian forecasting. A discussion on repairable systems terminology is presented because much controversy may

Research paper thumbnail of Regulatory activities in the field of instrumentation and control and operator support systems of ANGRA 1, 2 and 3 NPPs - 2007's status report from Brazil

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

Safety and Reliability of Complex Engineered Systems, 2015

Research paper thumbnail of Reliability Analysis of Service Water Pumps by Poisson Point Processes with a Generalized Model for the Rate of Occurrence of Failures

Advances in Safety and Reliability, 1997

Research paper thumbnail of An application of non-homogeneous Poisson point processes to the reliability analysis of service water pumps

Nuclear Engineering and Design, 2001

The purpose of this paper is to present an application of the non-homogeneous Poisson point proce... more The purpose of this paper is to present an application of the non-homogeneous Poisson point process to the study of the rates of occurrence of failures (ROCOF) when they are time dependent, and the times between failures are neither independent nor identically distributed. The application concerns the analysis of the reliability of service water pumps of a typical PWR nuclear

Research paper thumbnail of On probability models for the unavailability analysis of safety systems under aging phenomena

Progress in Nuclear Energy, 1999

This paper presents and discusses three probability models for approaching aging of a component. ... more This paper presents and discusses three probability models for approaching aging of a component. NRC and IAEA views of aging phenomena are reviewed and discussed. Repair is approached in the first model by stochastic point processes, and a statistical dynamical model is employed to allow for Bayesian forecasting. A discussion on repairable systems terminology is presented because much controversy may

Research paper thumbnail of LWR Safety Analysis and Licensing and Implications for Advanced Reactors

Nuclear Power - Operation, Safety and Environment, 2011

Research paper thumbnail of Human-Machine Interface (HMI) scenario quantification performed by ATHEANA, A Technique for Human Error Analysis

Research paper thumbnail of RELIABILITY APPRAISAL FOR A PWR AUXILIARY FEED-WATER SYSTEM UNDER AGING BY POINT PROCESSES ID Number: D5-A2-BR

SMIRT , 1999

This paper presents an application of an algorithm, named RUCA, developed to calculate the avilab... more This paper presents an application of an algorithm, named RUCA, developed to calculate the avilability of repairable systems, considering design and operation improvements. The system under study is statistically analyzed in order to choose the appropriate stochastic point process, which will be used in its probabilistic modeling. RUCA comprises a non-homogeneous Markov chain whose transition probability matrices are defined as functions of the rates of occurrence of failures (ROCOF) associated with significant failures, which governs transitions between the states. Presented is an application to the AFWS of a typical two-loop PWR. Results clearly show the suitability of point processes for treating aging phenomena. Also, although the number of components is not very high, the analysis is still performed in a personal computer with no further difficulties.