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Sample records for tree probabilistic risk

  1. Probabilistic risk assessment using event tables and the BNL [Brookhaven National Laboratory] event-tree analyzer

    International Nuclear Information System (INIS)

    Fullwood, R.R.; Shier, W.G.

    1989-01-01

    Probabilistic risk analysis (PRA) is being used to study design alternatives for the advanced neutron source research reactor being designed at Oak Ridge National Laboratory for operation in the 1990s. Major communication paths between the designers and the safety analysts are accident discussions supported by event tables, event-tree graphics, and accident sequence probabilities. The BETA code used in conjunction with a word processor provides this linkage. This paper describes the process, features of the BETA, how it works, and some examples of usage

  2. Probabilistic risk analysis and fault trees: Initial discussion of application to identification of risk at a wellhead

    Science.gov (United States)

    Rodak, C.; Silliman, S.

    2012-02-01

    Wellhead protection is of critical importance for managing groundwater resources. While a number of previous authors have addressed questions related to uncertainties in advective capture zones, methods for addressing wellhead protection in the presence of uncertainty in the chemistry of groundwater contaminants, the relationship between land-use and contaminant sources, and the impact on health of the receiving population are limited. It is herein suggested that probabilistic risk analysis (PRA) combined with fault trees (FT) provides a structure whereby chemical transport can be combined with uncertainties in source, chemistry, and health impact to assess the probability of negative health outcomes in the population. As such, PRA-FT provides a new strategy for the identification of areas of probabilistically high human health risk. Application of this approach is demonstrated through a simplified case study involving flow to a well in an unconfined aquifer with heterogeneity in aquifer properties and contaminant sources.

  3. Fault trees and the impact of human variability on probabilistic risk analysis

    International Nuclear Information System (INIS)

    1983-01-01

    It has long been recognized that human reliability is an important factor in probabilistic risk analysis. In the field, this is true in a direct operational sense as well as in the areas of installation and maintenance. The interest in quantification arises from the desire to achieve optimum design in the human factors sense (operability-maintainability) and from the need to include human reliability considerations in probabilistic risk analysis to achieve complete and valid risk evaluation. In order to integrate human reliability into the system analysis, it is necessary to consider two questions. These relate to the way that human functions fit into the existing analytical models and methods as well as the nature of human failure mechanisms, modes and failure (error) rates

  4. Probabilistic Risk Assessment of Hydraulic Fracturing in Unconventional Reservoirs by Means of Fault Tree Analysis: An Initial Discussion

    Science.gov (United States)

    Rodak, C. M.; McHugh, R.; Wei, X.

    2016-12-01

    The development and combination of horizontal drilling and hydraulic fracturing has unlocked unconventional hydrocarbon reserves around the globe. These advances have triggered a number of concerns regarding aquifer contamination and over-exploitation, leading to scientific studies investigating potential risks posed by directional hydraulic fracturing activities. These studies, balanced with potential economic benefits of energy production, are a crucial source of information for communities considering the development of unconventional reservoirs. However, probabilistic quantification of the overall risk posed by hydraulic fracturing at the system level are rare. Here we present the concept of fault tree analysis to determine the overall probability of groundwater contamination or over-exploitation, broadly referred to as the probability of failure. The potential utility of fault tree analysis for the quantification and communication of risks is approached with a general application. However, the fault tree design is robust and can handle various combinations of regional-specific data pertaining to relevant spatial scales, geological conditions, and industry practices where available. All available data are grouped into quantity and quality-based impacts and sub-divided based on the stage of the hydraulic fracturing process in which the data is relevant as described by the USEPA. Each stage is broken down into the unique basic events required for failure; for example, to quantify the risk of an on-site spill we must consider the likelihood, magnitude, composition, and subsurface transport of the spill. The structure of the fault tree described above can be used to render a highly complex system of variables into a straightforward equation for risk calculation based on Boolean logic. This project shows the utility of fault tree analysis for the visual communication of the potential risks of hydraulic fracturing activities on groundwater resources.

  5. Arenal-type pyroclastic flows: A probabilistic event tree risk analysis

    Science.gov (United States)

    Meloy, Anthony F.

    2006-09-01

    A quantitative hazard-specific scenario-modelling risk analysis is performed at Arenal volcano, Costa Rica for the newly recognised Arenal-type pyroclastic flow (ATPF) phenomenon using an event tree framework. These flows are generated by the sudden depressurisation and fragmentation of an active basaltic andesite lava pool as a result of a partial collapse of the crater wall. The deposits of this type of flow include angular blocks and juvenile clasts, which are rarely found in other types of pyroclastic flow. An event tree analysis (ETA) is a useful tool and framework in which to analyse and graphically present the probabilities of the occurrence of many possible events in a complex system. Four event trees are created in the analysis, three of which are extended to investigate the varying individual risk faced by three generic representatives of the surrounding community: a resident, a worker, and a tourist. The raw numerical risk estimates determined by the ETA are converted into a set of linguistic expressions (i.e. VERY HIGH, HIGH, MODERATE etc.) using an established risk classification scale. Three individually tailored semi-quantitative risk maps are then created from a set of risk conversion tables to show how the risk varies for each individual in different areas around the volcano. In some cases, by relocating from the north to the south, the level of risk can be reduced by up to three classes. While the individual risk maps may be broadly applicable, and therefore of interest to the general community, the risk maps and associated probability values generated in the ETA are intended to be used by trained professionals and government agencies to evaluate the risk and effectively manage the long-term development of infrastructure and habitation. With the addition of fresh monitoring data, the combination of both long- and short-term event trees would provide a comprehensive and consistent method of risk analysis (both during and pre-crisis), and as such

  6. Probabilistic risk assessment: Number 219

    International Nuclear Information System (INIS)

    Bari, R.A.

    1985-01-01

    This report describes a methodology for analyzing the safety of nuclear power plants. A historical overview of plants in the US is provided, and past, present, and future nuclear safety and risk assessment are discussed. A primer on nuclear power plants is provided with a discussion of pressurized water reactors (PWR) and boiling water reactors (BWR) and their operation and containment. Probabilistic Risk Assessment (PRA), utilizing both event-tree and fault-tree analysis, is discussed as a tool in reactor safety, decision making, and communications. (FI)

  7. Probabilistic Risk Analysis and Fault Trees as Tools in Improving the Delineation of Wellhead Protection Areas: An Initial Discussion

    Science.gov (United States)

    Rodak, C. M.; Silliman, S. E.

    2010-12-01

    Delineation of a wellhead protection area (WHPA) is a critical component of managing / protecting the aquifer(s) supplying potable water to a public water-supply well. While a number of previous authors have addressed questions related to uncertainties in advective capture zones, methods for assessing WHPAs in the presence of uncertainty in the chemistry of groundwater contaminants, the relationship between land-use and contaminant sources, and the impact on health risk within the receiving population are more limited. Probabilistic risk analysis (PRA) combined with fault trees (FT) addresses this latter challenge by providing a structure whereby four key WHPA issues may be addressed: (i) uncertainty in land-use practices and chemical release, (ii) uncertainty in groundwater flow, (iii) variability in natural attenuation properties (and/or remediation) of the contaminants, and (iv) estimated health risk from contaminant arrival at a well. The potential utility of PRA-FT in this application is considered through a simplified case study involving management decisions related both to regional land use planning and local land-use zoning regulation. An application-specific fault tree is constructed to visualize and identify the events required for health risk failure at the well and a Monte Carlo approach is used to create multiple realizations of groundwater flow and chemical transport to a well in a model of a simple, unconfined aquifer. Model parameters allowed to vary during this simplified case study include hydraulic conductivity, probability of a chemical spill (related to land use variation in space), and natural attenuation through variation in rate of decay of the contaminant. Numerical results are interpreted in association with multiple land-use management scenarios as well as multiple cancer risk assumptions regarding the contaminant arriving at the well. This case study shows significant variability of health risk at the well, however general trends were

  8. Analytical solutions of linked fault tree probabilistic risk assessments using binary decision diagrams with emphasis on nuclear safety applications

    International Nuclear Information System (INIS)

    Nusbaumer, O. P. M.

    2007-01-01

    This study is concerned with the quantification of Probabilistic Risk Assessment (PRA) using linked Fault Tree (FT) models. Probabilistic Risk assessment (PRA) of Nuclear Power Plants (NPPs) complements traditional deterministic analysis; it is widely recognized as a comprehensive and structured approach to identify accident scenarios and to derive numerical estimates of the associated risk levels. PRA models as found in the nuclear industry have evolved rapidly. Increasingly, they have been broadly applied to support numerous applications on various operational and regulatory matters. Regulatory bodies in many countries require that a PRA be performed for licensing purposes. PRA has reached the point where it can considerably influence the design and operation of nuclear power plants. However, most of the tools available for quantifying large PRA models are unable to produce analytically correct results. The algorithms of such quantifiers are designed to neglect sequences when their likelihood decreases below a predefined cutoff limit. In addition, the rare event approximation (e.g. Moivre's equation) is typically implemented for the first order, ignoring the success paths and the possibility that two or more events can occur simultaneously. This is only justified in assessments where the probabilities of the basic events are low. When the events in question are failures, the first order rare event approximation is always conservative, resulting in wrong interpretation of risk importance measures. Advanced NPP PRA models typically include human errors, common cause failure groups, seismic and phenomenological basic events, where the failure probabilities may approach unity, leading to questionable results. It is accepted that current quantification tools have reached their limits, and that new quantification techniques should be investigated. A novel approach using the mathematical concept of Binary Decision Diagram (BDD) is proposed to overcome these deficiencies

  9. Calculating Adversarial Risk from Attack Trees: Control Strength and Probabilistic Attackers

    NARCIS (Netherlands)

    Pieters, Wolter; Davarynejad, Mohsen

    2015-01-01

    Attack trees are a well-known formalism for quantitative analysis of cyber attacks consisting of multiple steps and alternative paths. It is possible to derive properties of the overall attacks from properties of individual steps, such as cost for the attacker and probability of success. However, in

  10. Probabilistic risk assessment methodology

    International Nuclear Information System (INIS)

    Shinaishin, M.A.

    1988-06-01

    The objective of this work is to provide the tools necessary for clear identification of: the purpose of a Probabilistic Risk Study, the bounds and depth of the study, the proper modeling techniques to be used, the failure modes contributing to the analysis, the classical and baysian approaches for manipulating data necessary for quantification, ways for treating uncertainties, and available computer codes that may be used in performing such probabilistic analysis. In addition, it provides the means for measuring the importance of a safety feature to maintaining a level of risk at a Nuclear Power Plant and the worth of optimizing a safety system in risk reduction. In applying these techniques so that they accommodate our national resources and needs it was felt that emphasis should be put on the system reliability analysis level of PRA. Objectives of such studies could include: comparing systems' designs of the various vendors in the bedding stage, and performing grid reliability and human performance analysis using national specific data. (author)

  11. Probabilistic risk assessment methodology

    Energy Technology Data Exchange (ETDEWEB)

    Shinaishin, M A

    1988-06-15

    The objective of this work is to provide the tools necessary for clear identification of: the purpose of a Probabilistic Risk Study, the bounds and depth of the study, the proper modeling techniques to be used, the failure modes contributing to the analysis, the classical and baysian approaches for manipulating data necessary for quantification, ways for treating uncertainties, and available computer codes that may be used in performing such probabilistic analysis. In addition, it provides the means for measuring the importance of a safety feature to maintaining a level of risk at a Nuclear Power Plant and the worth of optimizing a safety system in risk reduction. In applying these techniques so that they accommodate our national resources and needs it was felt that emphasis should be put on the system reliability analysis level of PRA. Objectives of such studies could include: comparing systems' designs of the various vendors in the bedding stage, and performing grid reliability and human performance analysis using national specific data. (author)

  12. Generic event trees and the treatment of dependencies and non-proceduralized actions in a low power and shutdown Probabilistic Risk Assessment

    International Nuclear Information System (INIS)

    Forester, J.; Yakle, J.; Whitehead, D.; Darby, J.

    1993-01-01

    Sandia National Laboratories was tasked by the US Nuclear Regulatory Commission to perform a Probabilistic Risk Assessment (PRA) of a boiling water reactor (BWR) during low power and shutdown (LP ampersand S) conditions. The plant chosen for the study was Grand Gulf Nuclear Station (GGNS), a BWR 6. In performing the analysis, it was found that in comparison with full-power PRAs, the low decay heat levels present during LP ampersand S conditions result in a relatively large number of ways by which cooling can be provided to the core. In addition, because of the less stringent requirements imposed on system configurations possible is large and the availability of plant systems is more difficult to specify. These aspects of the LP ampersand S environment led to the development and use of ''generic'' event trees in performing the analysis. The use of ''generic'' event trees, in turn, had a significant impact on the nature of the human reliability analysis (HRA) that was performed. This paper describes the development of the event trees for the LP ampersand S PRA and important aspects of the resulting HRA

  13. Implications of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Cullingford, M.C.; Shah, S.M.; Gittus, J.H.

    1987-01-01

    Probabilistic risk assessment (PRA) is an analytical process that quantifies the likelihoods, consequences and associated uncertainties of the potential outcomes of postulated events. Starting with planned or normal operation, probabilistic risk assessment covers a wide range of potential accidents and considers the whole plant and the interactions of systems and human actions. Probabilistic risk assessment can be applied in safety decisions in design, licensing and operation of industrial facilities, particularly nuclear power plants. The proceedings include a review of PRA procedures, methods and technical issues in treating uncertainties, operating and licensing issues and future trends. Risk assessment for specific reactor types or components and specific risks (eg aircraft crashing onto a reactor) are used to illustrate the points raised. All 52 articles are indexed separately. (U.K.)

  14. Analytical solutions of linked fault tree probabilistic risk assessments using binary decision diagrams with emphasis on nuclear safety applications[Dissertation 17286

    Energy Technology Data Exchange (ETDEWEB)

    Nusbaumer, O. P. M

    2007-07-01

    This study is concerned with the quantification of Probabilistic Risk Assessment (PRA) using linked Fault Tree (FT) models. Probabilistic Risk assessment (PRA) of Nuclear Power Plants (NPPs) complements traditional deterministic analysis; it is widely recognized as a comprehensive and structured approach to identify accident scenarios and to derive numerical estimates of the associated risk levels. PRA models as found in the nuclear industry have evolved rapidly. Increasingly, they have been broadly applied to support numerous applications on various operational and regulatory matters. Regulatory bodies in many countries require that a PRA be performed for licensing purposes. PRA has reached the point where it can considerably influence the design and operation of nuclear power plants. However, most of the tools available for quantifying large PRA models are unable to produce analytically correct results. The algorithms of such quantifiers are designed to neglect sequences when their likelihood decreases below a predefined cutoff limit. In addition, the rare event approximation (e.g. Moivre's equation) is typically implemented for the first order, ignoring the success paths and the possibility that two or more events can occur simultaneously. This is only justified in assessments where the probabilities of the basic events are low. When the events in question are failures, the first order rare event approximation is always conservative, resulting in wrong interpretation of risk importance measures. Advanced NPP PRA models typically include human errors, common cause failure groups, seismic and phenomenological basic events, where the failure probabilities may approach unity, leading to questionable results. It is accepted that current quantification tools have reached their limits, and that new quantification techniques should be investigated. A novel approach using the mathematical concept of Binary Decision Diagram (BDD) is proposed to overcome these

  15. Probabilistic risk assessment course documentation. Volume 4. System reliability and analysis techniques sessions B/C - event trees/fault trees

    International Nuclear Information System (INIS)

    Haasl, D.; Young, J.

    1985-08-01

    This course will employ a combination of lecture material and practical problem solving in order to develop competence and understanding of th principles and techniques of event tree and fault tree analysis. The role of these techniques in the overall context of PRA will be described. The emphasis of this course will be on the basic, traditional methods of event tree and fault tree analysis

  16. Application of probabilistic risk assessment to reprocessing

    International Nuclear Information System (INIS)

    Perkins, W.C.

    1984-01-01

    The Savannah River Laboratory uses probabilistic methods of risk assessment in safety analyses of reprocessing facilities at the Savannah River Plant. This method uses both the probability of an accident and its consequence to calculate the risks from radiological, chemical, and industrial hazards. The three principal steps in such an assesment are identification of accidents, calculation of frequencies, and consequence quantification. The tools used at SRL include several databanks, logic tree methods, and computer-assisted methods for calculating both frequencies and consequences. 5 figures

  17. Advances in probabilistic risk analysis

    International Nuclear Information System (INIS)

    Hardung von Hardung, H.

    1982-01-01

    Probabilistic risk analysis can now look back upon almost a quarter century of intensive development. The early studies, whose methods and results are still referred to occasionally, however, only permitted rough estimates to be made of the probabilities of recognizable accident scenarios, failing to provide a method which could have served as a reference base in calculating the overall risk associated with nuclear power plants. The first truly solid attempt was the Rasmussen Study and, partly based on it, the German Risk Study. In those studies, probabilistic risk analysis has been given a much more precise basis. However, new methodologies have been developed in the meantime, which allow much more informative risk studies to be carried out. They have been found to be valuable tools for management decisions with respect to backfitting, reinforcement and risk limitation. Today they are mainly applied by specialized private consultants and have already found widespread application especially in the USA. (orig.) [de

  18. Probabilistic risk assessment of HTGRs

    International Nuclear Information System (INIS)

    Fleming, K.N.; Houghton, W.J.; Hannaman, G.W.; Joksimovic, V.

    1980-08-01

    Probabilistic Risk Assessment methods have been applied to gas-cooled reactors for more than a decade and to HTGRs for more than six years in the programs sponsored by the US Department of Energy. Significant advancements to the development of PRA methodology in these programs are summarized as are the specific applications of the methods to HTGRs. Emphasis here is on PRA as a tool for evaluating HTGR design options. Current work and future directions are also discussed

  19. Probabilistic risk assessment of HTGRs

    International Nuclear Information System (INIS)

    Fleming, K.N.; Houghton, W.J.; Hannaman, G.W.; Joksimovic, V.

    1981-01-01

    Probabilistic Risk Assessment methods have been applied to gas-cooled reactors for more than a decade and to HTGRs for more than six years in the programs sponsored by the U.S. Department of Energy. Significant advancements to the development of PRA methodology in these programs are summarized as are the specific applications of the methods to HTGRs. Emphasis here is on PRA as a tool for evaluating HTGR design options. Current work and future directions are also discussed. (author)

  20. Probabilistic risk assessment, Volume I

    International Nuclear Information System (INIS)

    Anon.

    1982-01-01

    This book contains 158 papers presented at the International Topical Meeting on Probabilistic Risk Assessment held by the American Nuclear Society (ANS) and the European Nuclear Society (ENS) in Port Chester, New York in 1981. The meeting was second in a series of three. The main focus of the meeting was on the safety of light water reactors. The papers discuss safety goals and risk assessment. Quantitative safety goals, risk assessment in non-nuclear technologies, and operational experience and data base are also covered. Included is an address by Dr. Chauncey Starr

  1. The characterisation and evaluation of uncertainty in probabilistic risk analysis

    International Nuclear Information System (INIS)

    Parry, G.W.; Winter, P.W.

    1980-10-01

    The sources of uncertainty in probabilistic risk analysis are discussed using the event/fault tree methodology as an example. The role of statistics in quantifying these uncertainties is investigated. A class of uncertainties is identified which is, at present, unquantifiable, using either classical or Bayesian statistics. It is argued that Bayesian statistics is the more appropriate vehicle for the probabilistic analysis of rare events and a short review is given with some discussion on the representation of ignorance. (author)

  2. Development of probabilistic risk analysis library

    International Nuclear Information System (INIS)

    Soga, Shota; Kirimoto, Yukihiro; Kanda, Kenichi

    2015-01-01

    We developed a library that is designed to perform level 1 Probabilistic Risk Analysis using Binary Decision Diagram (BDD). In particular, our goal is to develop a library that will allow Japanese electric utilities to take the advantages of BDD that can solve Event Tree (ET) and Fault Tree (FT) models analytically. Using BDD, the library supports negation in FT which allows more flexible modeling of ET/FT. The library is written by C++ within an object-oriented framework using open source software. The library itself is a header-only library so that Japanese electric utilities can take advantages of its transparency to speed up development and to build their own software for their specific needs. In this report, the basic capabilities of the library is briefly described. In addition, several applications of the library are demonstrated including validation of MCS evaluation of PRA model and evaluation of corrective and preventive maintenance considering common cause failure. (author)

  3. Software for Probabilistic Risk Reduction

    Science.gov (United States)

    Hensley, Scott; Michel, Thierry; Madsen, Soren; Chapin, Elaine; Rodriguez, Ernesto

    2004-01-01

    A computer program implements a methodology, denoted probabilistic risk reduction, that is intended to aid in planning the development of complex software and/or hardware systems. This methodology integrates two complementary prior methodologies: (1) that of probabilistic risk assessment and (2) a risk-based planning methodology, implemented in a prior computer program known as Defect Detection and Prevention (DDP), in which multiple requirements and the beneficial effects of risk-mitigation actions are taken into account. The present methodology and the software are able to accommodate both process knowledge (notably of the efficacy of development practices) and product knowledge (notably of the logical structure of a system, the development of which one seeks to plan). Estimates of the costs and benefits of a planned development can be derived. Functional and non-functional aspects of software can be taken into account, and trades made among them. It becomes possible to optimize the planning process in the sense that it becomes possible to select the best suite of process steps and design choices to maximize the expectation of success while remaining within budget.

  4. Method and system for dynamic probabilistic risk assessment

    Science.gov (United States)

    Dugan, Joanne Bechta (Inventor); Xu, Hong (Inventor)

    2013-01-01

    The DEFT methodology, system and computer readable medium extends the applicability of the PRA (Probabilistic Risk Assessment) methodology to computer-based systems, by allowing DFT (Dynamic Fault Tree) nodes as pivot nodes in the Event Tree (ET) model. DEFT includes a mathematical model and solution algorithm, supports all common PRA analysis functions and cutsets. Additional capabilities enabled by the DFT include modularization, phased mission analysis, sequence dependencies, and imperfect coverage.

  5. Dynamical systems probabilistic risk assessment

    Energy Technology Data Exchange (ETDEWEB)

    Denman, Matthew R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ames, Arlo Leroy [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-03-01

    Probabilistic Risk Assessment (PRA) is the primary tool used to risk-inform nuclear power regulatory and licensing activities. Risk-informed regulations are intended to reduce inherent conservatism in regulatory metrics (e.g., allowable operating conditions and technical specifications) which are built into the regulatory framework by quantifying both the total risk profile as well as the change in the risk profile caused by an event or action (e.g., in-service inspection procedures or power uprates). Dynamical Systems (DS) analysis has been used to understand unintended time-dependent feedbacks in both industrial and organizational settings. In dynamical systems analysis, feedback loops can be characterized and studied as a function of time to describe the changes to the reliability of plant Structures, Systems and Components (SSCs). While DS has been used in many subject areas, some even within the PRA community, it has not been applied toward creating long-time horizon, dynamic PRAs (with time scales ranging between days and decades depending upon the analysis). Understanding slowly developing dynamic effects, such as wear-out, on SSC reliabilities may be instrumental in ensuring a safely and reliably operating nuclear fleet. Improving the estimation of a plant's continuously changing risk profile will allow for more meaningful risk insights, greater stakeholder confidence in risk insights, and increased operational flexibility.

  6. Risk assessment using probabilistic standards

    International Nuclear Information System (INIS)

    Avila, R.

    2004-01-01

    A core element of risk is uncertainty represented by plural outcomes and their likelihood. No risk exists if the future outcome is uniquely known and hence guaranteed. The probability that we will die some day is equal to 1, so there would be no fatal risk if sufficiently long time frame is assumed. Equally, rain risk does not exist if there was 100% assurance of rain tomorrow, although there would be other risks induced by the rain. In a formal sense, any risk exists if, and only if, more than one outcome is expected at a future time interval. In any practical risk assessment we have to deal with uncertainties associated with the possible outcomes. One way of dealing with the uncertainties is to be conservative in the assessments. For example, we may compare the maximal exposure to a radionuclide with a conservatively chosen reference value. In this case, if the exposure is below the reference value then it is possible to assure that the risk is low. Since single values are usually compared; this approach is commonly called 'deterministic'. Its main advantage lies in the simplicity and in that it requires minimum information. However, problems arise when the reference values are actually exceeded or might be exceeded, as in the case of potential exposures, and when the costs for realizing the reference values are high. In those cases, the lack of knowledge on the degree of conservatism involved impairs a rational weighing of the risks against other interests. In this presentation we will outline an approach for dealing with uncertainties that in our opinion is more consistent. We will call it a 'fully probabilistic risk assessment'. The essence of this approach consists in measuring the risk in terms of probabilities, where the later are obtained from comparison of two probabilistic distributions, one reflecting the uncertainties in the outcomes and one reflecting the uncertainties in the reference value (standard) used for defining adverse outcomes. Our first aim

  7. Performing Probabilistic Risk Assessment Through RAVEN

    Energy Technology Data Exchange (ETDEWEB)

    A. Alfonsi; C. Rabiti; D. Mandelli; J. Cogliati; R. Kinoshita

    2013-06-01

    The Reactor Analysis and Virtual control ENviroment (RAVEN) code is a software tool that acts as the control logic driver and post-processing engine for the newly developed Thermal-Hydraulic code RELAP-7. RAVEN is now a multi-purpose Probabilistic Risk Assessment (PRA) software framework that allows dispatching different functionalities: Derive and actuate the control logic required to simulate the plant control system and operator actions (guided procedures), allowing on-line monitoring/controlling in the Phase Space Perform both Monte-Carlo sampling of random distributed events and Dynamic Event Tree based analysis Facilitate the input/output handling through a Graphical User Interface (GUI) and a post-processing data mining module

  8. Probabilistic Properties of Rectilinear Steiner Minimal Trees

    Directory of Open Access Journals (Sweden)

    V. N. Salnikov

    2015-01-01

    Full Text Available This work concerns the properties of Steiner minimal trees for the manhattan plane in the context of introducing a probability measure. This problem is important because exact algorithms to solve the Steiner problem are computationally expensive (NP-hard and the solution (especially in the case of big number of points to be connected has a diversity of practical applications. That is why the work considers a possibility to rank the possible topologies of the minimal trees with respect to a probability of their usage. For this, the known facts about the structural properties of minimal trees for selected metrics have been analyzed to see their usefulness for the problem in question. For the small amount of boundary (fixed vertices, the paper offers a way to introduce a probability measure as a corollary of proved theorem about some structural properties of the minimal trees.This work is considered to further the previous similar activity concerning a problem of searching for minimal fillings, and it is a door opener to the more general (complicated task. The stated method demonstrates the possibility to reach the final result analytically, which gives a chance of its applicability to the case of the bigger number of boundary vertices (probably, with the use of computer engineering.The introducing definition of an essential Steiner point allowed a considerable restriction of the ambiguity of initial problem solution and, at the same time, comparison of such an approach with more classical works in the field concerned. The paper also lists main barriers of classical approaches, preventing their use for the task of introducing a probability measure.In prospect, application areas of the described method are expected to be wider both in terms of system enlargement (the number of boundary vertices and in terms of other metric spaces (the Euclidean case is of especial interest. The main interest is to find the classes of topologies with significantly

  9. Binary Decision Tree Development for Probabilistic Safety Assessment Applications

    International Nuclear Information System (INIS)

    Simic, Z.; Banov, R.; Mikulicic, V.

    2008-01-01

    The aim of this article is to describe state of the development for the relatively new approach in the probabilistic safety analysis (PSA). This approach is based on the application of binary decision diagrams (BDD) representation for the logical function on the quantitative and qualitative analysis of complex systems that are presented by fault trees and event trees in the PSA applied for the nuclear power plants risk determination. Even BDD approach offers full solution comparing to the partial one from the conventional quantification approach there are still problems to be solved before new approach could be fully implemented. Major problem with full application of BDD is difficulty of getting any solution for the PSA models of certain complexity. This paper is comparing two approaches in PSA quantification. Major focus of the paper is description of in-house developed BDD application with implementation of the original algorithms. Resulting number of nodes required to represent the BDD is extremely sensitive to the chosen order of variables (i.e., basic events in PSA). The problem of finding an optimal order of variables that form the BDD falls under the class of NP-complete complexity. This paper presents an original approach to the problem of finding the initial order of variables utilized for the BDD construction by various dynamical reordering schemes. Main advantage of this approach compared to the known methods of finding the initial order is with better results in respect to the required working memory and time needed to finish the BDD construction. Developed method is compared against results from well known methods such as depth-first, breadth-first search procedures. Described method may be applied in finding of an initial order for fault trees/event trees being created from basic events by means of logical operations (e.g. negation, and, or, exclusive or). With some testing models a significant reduction of used memory has been achieved, sometimes

  10. Systems analysis approach to probabilistic modeling of fault trees

    International Nuclear Information System (INIS)

    Bartholomew, R.J.; Qualls, C.R.

    1985-01-01

    A method of probabilistic modeling of fault tree logic combined with stochastic process theory (Markov modeling) has been developed. Systems are then quantitatively analyzed probabilistically in terms of their failure mechanisms including common cause/common mode effects and time dependent failure and/or repair rate effects that include synergistic and propagational mechanisms. The modeling procedure results in a state vector set of first order, linear, inhomogeneous, differential equations describing the time dependent probabilities of failure described by the fault tree. The solutions of this Failure Mode State Variable (FMSV) model are cumulative probability distribution functions of the system. A method of appropriate synthesis of subsystems to form larger systems is developed and applied to practical nuclear power safety systems

  11. Probabilistic atlas based labeling of the cerebral vessel tree

    Science.gov (United States)

    Van de Giessen, Martijn; Janssen, Jasper P.; Brouwer, Patrick A.; Reiber, Johan H. C.; Lelieveldt, Boudewijn P. F.; Dijkstra, Jouke

    2015-03-01

    Preoperative imaging of the cerebral vessel tree is essential for planning therapy on intracranial stenoses and aneurysms. Usually, a magnetic resonance angiography (MRA) or computed tomography angiography (CTA) is acquired from which the cerebral vessel tree is segmented. Accurate analysis is helped by the labeling of the cerebral vessels, but labeling is non-trivial due to anatomical topological variability and missing branches due to acquisition issues. In recent literature, labeling the cerebral vasculature around the Circle of Willis has mainly been approached as a graph-based problem. The most successful method, however, requires the definition of all possible permutations of missing vessels, which limits application to subsets of the tree and ignores spatial information about the vessel locations. This research aims to perform labeling using probabilistic atlases that model spatial vessel and label likelihoods. A cerebral vessel tree is aligned to a probabilistic atlas and subsequently each vessel is labeled by computing the maximum label likelihood per segment from label-specific atlases. The proposed method was validated on 25 segmented cerebral vessel trees. Labeling accuracies were close to 100% for large vessels, but dropped to 50-60% for small vessels that were only present in less than 50% of the set. With this work we showed that using solely spatial information of the vessel labels, vessel segments from stable vessels (>50% presence) were reliably classified. This spatial information will form the basis for a future labeling strategy with a very loose topological model.

  12. Exploration Health Risks: Probabilistic Risk Assessment

    Science.gov (United States)

    Rhatigan, Jennifer; Charles, John; Hayes, Judith; Wren, Kiley

    2006-01-01

    Maintenance of human health on long-duration exploration missions is a primary challenge to mission designers. Indeed, human health risks are currently the largest risk contributors to the risks of evacuation or loss of the crew on long-duration International Space Station missions. We describe a quantitative assessment of the relative probabilities of occurrence of the individual risks to human safety and efficiency during space flight to augment qualitative assessments used in this field to date. Quantitative probabilistic risk assessments will allow program managers to focus resources on those human health risks most likely to occur with undesirable consequences. Truly quantitative assessments are common, even expected, in the engineering and actuarial spheres, but that capability is just emerging in some arenas of life sciences research, such as identifying and minimize the hazards to astronauts during future space exploration missions. Our expectation is that these results can be used to inform NASA mission design trade studies in the near future with the objective of preventing the higher among the human health risks. We identify and discuss statistical techniques to provide this risk quantification based on relevant sets of astronaut biomedical data from short and long duration space flights as well as relevant analog populations. We outline critical assumptions made in the calculations and discuss the rationale for these. Our efforts to date have focussed on quantifying the probabilities of medical risks that are qualitatively perceived as relatively high risks of radiation sickness, cardiac dysrhythmias, medically significant renal stone formation due to increased calcium mobilization, decompression sickness as a result of EVA (extravehicular activity), and bone fracture due to loss of bone mineral density. We present these quantitative probabilities in order-of-magnitude comparison format so that relative risk can be gauged. We address the effects of

  13. Probabilistic risk analysis and terrorism risk.

    Science.gov (United States)

    Ezell, Barry Charles; Bennett, Steven P; von Winterfeldt, Detlof; Sokolowski, John; Collins, Andrew J

    2010-04-01

    Since the terrorist attacks of September 11, 2001, and the subsequent establishment of the U.S. Department of Homeland Security (DHS), considerable efforts have been made to estimate the risks of terrorism and the cost effectiveness of security policies to reduce these risks. DHS, industry, and the academic risk analysis communities have all invested heavily in the development of tools and approaches that can assist decisionmakers in effectively allocating limited resources across the vast array of potential investments that could mitigate risks from terrorism and other threats to the homeland. Decisionmakers demand models, analyses, and decision support that are useful for this task and based on the state of the art. Since terrorism risk analysis is new, no single method is likely to meet this challenge. In this article we explore a number of existing and potential approaches for terrorism risk analysis, focusing particularly on recent discussions regarding the applicability of probabilistic and decision analytic approaches to bioterrorism risks and the Bioterrorism Risk Assessment methodology used by the DHS and criticized by the National Academies and others.

  14. Advanced Test Reactor probabilistic risk assessment

    International Nuclear Information System (INIS)

    Atkinson, S.A.; Eide, S.A.; Khericha, S.T.; Thatcher, T.A.

    1993-01-01

    This report discusses Level 1 probabilistic risk assessment (PRA) incorporating a full-scope external events analysis which has been completed for the Advanced Test Reactor (ATR) located at the Idaho National Engineering Laboratory

  15. Simplified probabilistic risk assessment in fuel reprocessing

    International Nuclear Information System (INIS)

    Solbrig, C.W.

    1993-01-01

    An evaluation was made to determine if a backup mass tracking computer would significantly reduce the probability of criticality in the fuel reprocessing of the Integral Fast Reactor. Often tradeoff studies, such as this, must be made that would greatly benefit from a Probably Risk Assessment (PRA). The major benefits of a complete PRA can often be accrued with a Simplified Probabilistic Risk Assessment (SPRA). An SPRA was performed by selecting a representative fuel reprocessing operation (moving a piece of fuel) for analysis. It showed that the benefit of adding parallel computers was small compared to the benefit which could be obtained by adding parallelism to two computer input steps and two of the weighing operations. The probability of an incorrect material moves with the basic process is estimated to be 4 out of 100 moves. The actual values of the probability numbers are considered accurate to within an order of magnitude. The most useful result of developing the fault trees accrue from the ability to determine where significant improvements in the process can be made. By including the above mentioned parallelism, the error move rate can be reduced to 1 out of 1000

  16. Probabilistic risk assessment as an aid to risk management

    International Nuclear Information System (INIS)

    Garrick, B.J.

    1982-01-01

    Probabilistic risk assessments are providing important insights into nuclear power plant safety. Their value is two-fold: first as a means of quantifying nuclear plant risk including contributors to risk, and second as an aid to risk management. A risk assessment provides an analytical plant model that can be the basis for performing meaningful decision analyses for controlling safety. It is the aspect of quantitative risk management that makes probabilistic risk assessment an important technical discipline of the future

  17. Documentation design for probabilistic risk assessment

    International Nuclear Information System (INIS)

    Parkinson, W.J.; von Herrmann, J.L.

    1985-01-01

    This paper describes a framework for documentation design of probabilistic risk assessment (PRA) and is based on the EPRI document NP-3470 ''Documentation Design for Probabilistic Risk Assessment''. The goals for PRA documentation are stated. Four audiences are identified which PRA documentation must satisfy, and the documentation consistent with the needs of the various audiences are discussed, i.e., the Summary Report, the Executive Summary, the Main Report, and Appendices. The authors recommend the documentation specifications discussed herein as guides rather than rigid definitions

  18. Quasi-Birth-Death Processes, Tree-Like QBDs, Probabilistic 1-Counter Automata, and Pushdown Systems

    NARCIS (Netherlands)

    K. Etessami (Kousha); D.K. Wojtczak (Dominik); M. Yannakakis

    2010-01-01

    textabstractWe begin by observing that (discrete-time) Quasi-Birth-Death Processes (QBDs) are equivalent, in a precise sense, to probabilistic 1-Counter Automata (p1CAs), and both Tree-Like QBDs (TL-QBDs) and Tree-Structured QBDs (TS-QBDs) are equivalent to both probabilistic Pushdown Systems

  19. Overview of the probabilistic risk assessment approach

    International Nuclear Information System (INIS)

    Reed, J.W.

    1985-01-01

    The techniques of probabilistic risk assessment (PRA) are applicable to Department of Energy facilities. The background and techniques of PRA are given with special attention to seismic, wind and flooding external events. A specific application to seismic events is provided to demonstrate the method. However, the PRA framework is applicable also to wind and external flooding. 3 references, 8 figures, 1 table

  20. PRECIS -- A probabilistic risk assessment system

    International Nuclear Information System (INIS)

    Peterson, D.M.; Knowlton, R.G. Jr.

    1996-01-01

    A series of computer tools has been developed to conduct the exposure assessment and risk characterization phases of human health risk assessments within a probabilistic framework. The tools are collectively referred to as the Probabilistic Risk Evaluation and Characterization Investigation System (PRECIS). With this system, a risk assessor can calculate the doses and risks associated with multiple environmental and exposure pathways, for both chemicals and radioactive contaminants. Exposure assessment models in the system account for transport of contaminants to receptor points from a source zone originating in unsaturated soils above the water table. In addition to performing calculations of dose and risk based on initial concentrations, PRECIS can also be used in an inverse manner to compute soil concentrations in the source area that must not be exceeded if prescribed limits on dose or risk are to be met. Such soil contaminant levels, referred to as soil guidelines, are computed for both single contaminants and chemical mixtures and can be used as action levels or cleanup levels. Probabilistic estimates of risk, dose and soil guidelines are derived using Monte Carlo techniques

  1. Comparison of event tree, fault tree and Markov methods for probabilistic safety assessment and application to accident mitigation

    International Nuclear Information System (INIS)

    James, H.; Harris, M.J.; Hall, S.F.

    1992-01-01

    Probabilistic safety assessment (PSA) is used extensively in the nuclear industry. The main stages of PSA and the traditional event tree method are described. Focussing on hydrogen explosions, an event tree model is compared to a novel Markov model and a fault tree, and unexpected implication for accident mitigation is revealed. (author)

  2. Review of the Brunswick Steam Electric Plant Probabilistic Risk Assessment

    International Nuclear Information System (INIS)

    Sattison, M.B.; Davis, P.R.; Satterwhite, D.G.; Gilmore, W.E.; Gregg, R.E.

    1989-11-01

    A review of the Brunswick Steam Electric Plant probabilistic risk Assessment was conducted with the objective of confirming the safety perspectives brought to light by the probabilistic risk assessment. The scope of the review included the entire Level I probabilistic risk assessment including external events. This is consistent with the scope of the probabilistic risk assessment. The review included an assessment of the assumptions, methods, models, and data used in the study. 47 refs., 14 figs., 15 tabs

  3. A methodology for reviewing probabilistic risk assessments

    International Nuclear Information System (INIS)

    Derby, S.L.

    1983-01-01

    The starting point for peer review of a Probabilistic Risk Assessment (PRA) is a clear understanding of how the risk estimate was prepared and of what contributions dominate the calculation. The problem facing the reviewers is how to cut through the complex details of a PRA to gain this understanding. This paper presents a structured, analytical procedure that solves this problem. The effectiveness of this solution is demonstrated by an application on the Zion Probabilistic Safety Study. The procedure found the three dominant initiating events and provided a simplified reconstruction of the calculation of the risk estimate. Significant assessments of uncertainty were also identified. If peer review disputes the accuracy of these judgments, then the revised risk estimate could significantly increase

  4. Probabilistic risk assessment and its role in plant modifications

    International Nuclear Information System (INIS)

    Diederich, A.R.; McElroy, W.F.

    1986-01-01

    Electric Utilities today have a tool available to improve management's ability to evaluate nuclear power plant modifications (MODS). Probabilistic Risk Assessment (PRA), is a tool of choice since it can be applied to a specific situation such as MOD request review, bringing the perspectives of reliability, financial risk and consequences to the public in addition to the more rigid requirements like those associated with Quality Assurance or licensing criteria. The techniques used in the PRA process revolve about the creation and manipulation of Fault Trees and Event Trees, which are used to quantify the event sequences and reliability of plant systems in a logical framework. It is through these methods that chains of sequences, or events, are understood. The degree to which plant systems are modelled in the PRA can vary depending on resources and purpose. Philadelphia Elecrtric Company's PRA modelled ten (10) major systems but this number may increase during the application and updating process

  5. Probabilistic risk analysis in chemical engineering

    International Nuclear Information System (INIS)

    Schmalz, F.

    1991-01-01

    In risk analysis in the chemical industry, recognising potential risks is considered more important than assessing their quantitative extent. Even in assessing risks, emphasis is not on the probability involved but on the possible extent. Qualitative assessment has proved valuable here. Probabilistic methods are used in individual cases where the wide implications make it essential to be able to assess the reliability of safety precautions. In this case, assessment therefore centres on the reliability of technical systems and not on the extent of a chemical risk. 7 figs

  6. Engineering aspects of probabilistic risk assessment

    International Nuclear Information System (INIS)

    vonHerrmann, J.L.; Wood, P.J.

    1984-01-01

    Over the last decade, the use of probabilistic risk assessment (PRA) in the nuclear industry has expanded significantly. In these analyses the probabilities of experiencing certain undesired events (for example, a plant accident which results in damage to the nuclear fuel) are estimated and the consequences of these events are evaluated in terms of some common measure. These probabilities and consequences are then combined to form a representation of the risk associated with the plant studied. In the relatively short history of probabilistic risk assessment of nuclear power plants, the primary motivation for these studies has been the quantitative assessment of public risk associated with a single plant or group of plants. Accordingly, the primary product of most PRAs performed to date has been a 'risk curve' in which the probability (or expected frequency) of exceeding a certain consequence level is plotted against that consequence. The most common goal of these assessments has been to demonstrate the 'acceptability' of the calculated risk by comparison of the resultant risk curve to risk curves associated with other plants or with other societal risks. Presented here are brief descriptions of some alternate applications of PRAs, a discussion of how these other applications compare or contrast with the currently popular uses of PRA, and a discussion of the relative benefits of each

  7. Insights gained through probabilistic risk assessments

    International Nuclear Information System (INIS)

    Hitchler, M.J.; Burns, N.L.; Liparulo, N.J.; Mink, F.J.

    1987-01-01

    The insights gained through a comparison of seven probabilistic risk assessments (PRA) studies (Italian PUN, Sizewell B, Ringhals 2, Millstone 3, Zion 1 and 2, Oconee 3, and Seabrook) included insights regarding the adequacy of the PRA technology utilized in the studies and the potential areas for improvement and insights regarding the adequacy of plant designs and how PRA has been utilized to enhance the design and operation of nuclear power plants

  8. Fault tree technique: advances in probabilistic and logical analysis

    International Nuclear Information System (INIS)

    Clarotti, C.A.; Amendola, A.; Contini, S.; Squellati, G.

    1982-01-01

    Fault tree reliability analysis is used for assessing the risk associated to systems of increasing complexity (phased mission systems, systems with multistate components, systems with non-monotonic structure functions). Much care must be taken to make sure that fault tree technique is not used beyond its correct validity range. To this end a critical review of mathematical foundations of reliability fault tree analysis is carried out. Limitations are enlightened and potential solutions to open problems are suggested. Moreover an overview is given on the most recent developments in the implementation of an integrated software (SALP-MP, SALP-NOT, SALP-CAFT Codes) for the analysis of a wide class of systems

  9. Probabilistic risk analysis for nuclear power plants

    International Nuclear Information System (INIS)

    Hauptmanns, U.

    1988-01-01

    Risk analysis is applied if the calculation of risk from observed failures is not possible, because events contributing substantially to risk are too seldom, as in the case of nuclear reactors. The process of analysis provides a number of benefits. Some of them are listed. After this by no means complete enumeration of possible benefits to be derived from a risk analysis. An outline of risk studiesd for PWR's with some comments on the models used are given. The presentation is indebted to the detailed treatment of the subject given in the PRA Procedures Guide. Thereafter some results of the German Risk Study, Phase B, which is under way are communicated. The paper concludes with some remarks on probabilistic considerations in licensing procedures. (orig./DG)

  10. A methodology for reviewing Probabilistic Risk Assessments

    International Nuclear Information System (INIS)

    Derby, S.L.

    1983-01-01

    The starting point for peer review of a Probabilistic Risk Assessment (PRA) is a clear understanding of how the risk estimate was prepared and of what contributions dominate the calculation. The problem facing the reviewers is how to cut through the complex details of a PRA to gain this understanding. This paper presents a structured, analytical procedure that solves this problem. The effectiveness of this solution is demonstrated by an application on the Zion Probabilistic Safety Study. The procedure found the three dominant initiating events and provided a simplified reconstruction of the calculation of the risk estimate. Significant assessments of uncertainty were also identified. If peer review disputes the accuracy of these judgments, then the revised risk estimate could significantly increase. The value of this procedure comes from having a systematic framework for the PRA review. Practical constraints limit the time and qualified people needed for an adequate review. Having the established framework from this procedure as a starting point, reviewers can focus most of their attention on the accuracy and the completeness of the calculation. Time wasted at the start of the review is reduced by first using this procedure to sort through the technical details of the PRA and to reconstruct the risk estimate from dominant contributions

  11. PRA (Probabilistic Risk Assessments) Participation versus Validation

    Science.gov (United States)

    DeMott, Diana; Banke, Richard

    2013-01-01

    Probabilistic Risk Assessments (PRAs) are performed for projects or programs where the consequences of failure are highly undesirable. PRAs primarily address the level of risk those projects or programs posed during operations. PRAs are often developed after the design has been completed. Design and operational details used to develop models include approved and accepted design information regarding equipment, components, systems and failure data. This methodology basically validates the risk parameters of the project or system design. For high risk or high dollar projects, using PRA methodologies during the design process provides new opportunities to influence the design early in the project life cycle to identify, eliminate or mitigate potential risks. Identifying risk drivers before the design has been set allows the design engineers to understand the inherent risk of their current design and consider potential risk mitigation changes. This can become an iterative process where the PRA model can be used to determine if the mitigation technique is effective in reducing risk. This can result in more efficient and cost effective design changes. PRA methodology can be used to assess the risk of design alternatives and can demonstrate how major design changes or program modifications impact the overall program or project risk. PRA has been used for the last two decades to validate risk predictions and acceptability. Providing risk information which can positively influence final system and equipment design the PRA tool can also participate in design development, providing a safe and cost effective product.

  12. Probabilistic relationships in acceptable risk studies

    International Nuclear Information System (INIS)

    Benjamin, J.R.

    1977-01-01

    Acceptable risk studies involve uncertainties in future events: consequences and associated values, the acceptability levels, and the future decision environment. Probabilistic procedures afford the basic analytical tool to study the influence of each of these parameters on the acceptable risk decision, including their interrelationships, and combinations. A series of examples are presented in the paper in increasing complexity to illustrate the principles involved and to quantify the relationships to the acceptable risk decision. The basic objective of such studies is to broaden the scientific basis of acceptable risk decision making. It is shown that rationality and consistency in decision making is facilitated by such studies and that rather simple relationships exist in many situations of interest. The variation in criteria associated with an increase in the state of knowledge or change in the level of acceptability is also discussed

  13. Probabilistic relationships in acceptable risk studies

    International Nuclear Information System (INIS)

    Benjamin, J.R.

    1977-01-01

    Acceptable risk studies involve uncertainties in future events; consequences and associated values, the acceptability levels, and the future decision environment. Probabilistic procedures afford the basic analytical tool to study the influence of each of these parameters on the acceptable risk decision, including their interrelationships, and combinations. A series of examples are presented in the paper in increasing complexity to illustrate the principles involved and to quantify the relationships to the acceptable risk decision. The basic objective of such studies is to broaden the scientific basis of acceptable risk decision making. It is shown that rationality and consistency in decision making is facilitated by such studies and that rather simple relationships exist in many situations of interest. The variation in criteria associated with an increase in the state of knowledge or change in the level of acceptability is also discussed. (Auth.)

  14. Bayesian parameter estimation in probabilistic risk assessment

    International Nuclear Information System (INIS)

    Siu, Nathan O.; Kelly, Dana L.

    1998-01-01

    Bayesian statistical methods are widely used in probabilistic risk assessment (PRA) because of their ability to provide useful estimates of model parameters when data are sparse and because the subjective probability framework, from which these methods are derived, is a natural framework to address the decision problems motivating PRA. This paper presents a tutorial on Bayesian parameter estimation especially relevant to PRA. It summarizes the philosophy behind these methods, approaches for constructing likelihood functions and prior distributions, some simple but realistic examples, and a variety of cautions and lessons regarding practical applications. References are also provided for more in-depth coverage of various topics

  15. Human reliability assessment and probabilistic risk assessment

    International Nuclear Information System (INIS)

    Embrey, D.E.; Lucas, D.A.

    1989-01-01

    Human reliability assessment (HRA) is used within Probabilistic Risk Assessment (PRA) to identify the human errors (both omission and commission) which have a significant effect on the overall safety of the system and to quantify the probability of their occurrence. There exist a variey of HRA techniques and the selection of an appropriate one is often difficult. This paper reviews a number of available HRA techniques and discusses their strengths and weaknesses. The techniques reviewed include: decompositional methods, time-reliability curves and systematic expert judgement techniques. (orig.)

  16. N reactor external events probabilistic risk assessment

    International Nuclear Information System (INIS)

    Baxter, J.T.

    1989-01-01

    An external events probabilistic risk assessment of the N Reactor has been completed. The methods used are those currently being proposed for external events analysis in NUREG-1150. Results are presented for the external hazards that survived preliminary screening. They are earthquake, fire, and external flood. Core damage frequencies for these hazards are shown to be comparable to those for commercial pressurized water reactors. Dominant fire sequences are described and related to 10 CFR 50, Appendix R design requirements. Potential remedial measures that reduce fire core damage risk are described including modifications to fire protection systems, procedure changes, and addition of new administrative controls. Dominant seismic sequences are described. The effect of non-safety support system dependencies on seismic risk is presented

  17. A Probabilistic Typhoon Risk Model for Vietnam

    Science.gov (United States)

    Haseemkunju, A.; Smith, D. F.; Brolley, J. M.

    2017-12-01

    Annually, the coastal Provinces of low-lying Mekong River delta region in the southwest to the Red River Delta region in Northern Vietnam is exposed to severe wind and flood risk from landfalling typhoons. On average, about two to three tropical cyclones with a maximum sustained wind speed of >=34 knots make landfall along the Vietnam coast. Recently, Typhoon Wutip (2013) crossed Central Vietnam as a category 2 typhoon causing significant damage to properties. As tropical cyclone risk is expected to increase with increase in exposure and population growth along the coastal Provinces of Vietnam, insurance/reinsurance, and capital markets need a comprehensive probabilistic model to assess typhoon risk in Vietnam. In 2017, CoreLogic has expanded the geographical coverage of its basin-wide Western North Pacific probabilistic typhoon risk model to estimate the economic and insured losses from landfalling and by-passing tropical cyclones in Vietnam. The updated model is based on 71 years (1945-2015) of typhoon best-track data and 10,000 years of a basin-wide simulated stochastic tracks covering eight countries including Vietnam. The model is capable of estimating damage from wind, storm surge and rainfall flooding using vulnerability models, which relate typhoon hazard to building damageability. The hazard and loss models are validated against past historical typhoons affecting Vietnam. Notable typhoons causing significant damage in Vietnam are Lola (1993), Frankie (1996), Xangsane (2006), and Ketsana (2009). The central and northern coastal provinces of Vietnam are more vulnerable to wind and flood hazard, while typhoon risk in the southern provinces are relatively low.

  18. HVAC fault tree analysis for WIPP integrated risk assessment

    International Nuclear Information System (INIS)

    Kirby, P.; Iacovino, J.

    1990-01-01

    In order to evaluate the public health risk from operation of the Waste Isolation Pilot Plant (WIPP) due to potential radioactive releases, a probabilistic risk assessment of waste handling operations was conducted. One major aspect of this risk assessment involved fault tree analysis of the plant heating, ventilation, and air conditioning (HVAC) systems, which comprise the final barrier between waste handling operations and the environment. 1 refs., 1 tab

  19. The application of probabilistic risk assessment to a LLW incinerator

    International Nuclear Information System (INIS)

    Li, K.K.; Huang, F.T.

    1993-01-01

    The 100 Kg/hr low-level radioactive waste (LLW) incinerator and the 1,500 ton supercompactor are two main vehicles in the Taiwan Power Company's Volume Reduction Center. Since the hot test of the incinerator in mid 1990, various problems associated with the original design and operating procedures were encountered. During the early stages of putting an incinerator in service, the modification and fine-tuning of the system would help future reliable operations. The probabilistic risk assessment (PRA) method was introduced to evaluate the interaction between potential system failure and its environmental impact and further help diagnose the system defects initially. The draft Level 1 system analysis was completed and the event and fault trees were constructed. Qualitatively, this approach is useful for preventing the system failure from occurring. However, Levels 2 and 3 analysis can only be done when sufficient data become available in the future

  20. 2009 Space Shuttle Probabilistic Risk Assessment Overview

    Science.gov (United States)

    Hamlin, Teri L.; Canga, Michael A.; Boyer, Roger L.; Thigpen, Eric B.

    2010-01-01

    Loss of a Space Shuttle during flight has severe consequences, including loss of a significant national asset; loss of national confidence and pride; and, most importantly, loss of human life. The Shuttle Probabilistic Risk Assessment (SPRA) is used to identify risk contributors and their significance; thus, assisting management in determining how to reduce risk. In 2006, an overview of the SPRA Iteration 2.1 was presented at PSAM 8 [1]. Like all successful PRAs, the SPRA is a living PRA and has undergone revisions since PSAM 8. The latest revision to the SPRA is Iteration 3. 1, and it will not be the last as the Shuttle program progresses and more is learned. This paper discusses the SPRA scope, overall methodology, and results, as well as provides risk insights. The scope, assumptions, uncertainties, and limitations of this assessment provide risk-informed perspective to aid management s decision-making process. In addition, this paper compares the Iteration 3.1 analysis and results to the Iteration 2.1 analysis and results presented at PSAM 8.

  1. Augmenting Probabilistic Risk Assesment with Malevolent Initiators

    International Nuclear Information System (INIS)

    Smith, Curtis; Schwieder, David

    2011-01-01

    As commonly practiced, the use of probabilistic risk assessment (PRA) in nuclear power plants only considers accident initiators such as natural hazards, equipment failures, and human error. Malevolent initiators are ignored in PRA, but are considered the domain of physical security, which uses vulnerability assessment based on an officially specified threat (design basis threat). This paper explores the implications of augmenting and extending existing PRA models by considering new and modified scenarios resulting from malevolent initiators. Teaming the augmented PRA models with conventional vulnerability assessments can cost-effectively enhance security of a nuclear power plant. This methodology is useful for operating plants, as well as in the design of new plants. For the methodology, we have proposed an approach that builds on and extends the practice of PRA for nuclear power plants for security-related issues. Rather than only considering 'random' failures, we demonstrated a framework that is able to represent and model malevolent initiating events and associated plant impacts.

  2. Probabilistic Risk Assessment (PRA): A Practical and Cost Effective Approach

    Science.gov (United States)

    Lee, Lydia L.; Ingegneri, Antonino J.; Djam, Melody

    2006-01-01

    The Lunar Reconnaissance Orbiter (LRO) is the first mission of the Robotic Lunar Exploration Program (RLEP), a space exploration venture to the Moon, Mars and beyond. The LRO mission includes spacecraft developed by NASA Goddard Space Flight Center (GSFC) and seven instruments built by GSFC, Russia, and contractors across the nation. LRO is defined as a measurement mission, not a science mission. It emphasizes the overall objectives of obtaining data to facilitate returning mankind safely to the Moon in preparation for an eventual manned mission to Mars. As the first mission in response to the President's commitment of the journey of exploring the solar system and beyond: returning to the Moon in the next decade, then venturing further into the solar system, ultimately sending humans to Mars and beyond, LRO has high-visibility to the public but limited resources and a tight schedule. This paper demonstrates how NASA's Lunar Reconnaissance Orbiter Mission project office incorporated reliability analyses in assessing risks and performing design tradeoffs to ensure mission success. Risk assessment is performed using NASA Procedural Requirements (NPR) 8705.5 - Probabilistic Risk Assessment (PRA) Procedures for NASA Programs and Projects to formulate probabilistic risk assessment (PRA). As required, a limited scope PRA is being performed for the LRO project. The PRA is used to optimize the mission design within mandated budget, manpower, and schedule constraints. The technique that LRO project office uses to perform PRA relies on the application of a component failure database to quantify the potential mission success risks. To ensure mission success in an efficient manner, low cost and tight schedule, the traditional reliability analyses, such as reliability predictions, Failure Modes and Effects Analysis (FMEA), and Fault Tree Analysis (FTA), are used to perform PRA for the large system of LRO with more than 14,000 piece parts and over 120 purchased or contractor

  3. Probabilistic risk assessment in the CPI

    International Nuclear Information System (INIS)

    Guymer, P.; Kaiser, G.D.; Mc Kelvey, T.C.; Hannaman, G.W.

    1987-01-01

    Probabilistic Risk Assessment (PRA) is a method of quantifying the frequency of occurrence and magnitude of the consequences of accidents in systems that contain hazardous materials such as toxic, flammable or explosive chemicals. The frequency and magnitude of the consequences are the basic elements in the definition of risk, often simply expressed as the product of frequency and magnitude, summed over all accident sequences. PRA is a mature technique that has been used to estimate risk for a number of industrial facilities: for example, the Canvey Island Petrochemical complex; the Port of Rotterdam; the Reactor Safety Study, the first study to put the risks associated with nuclear power into perspective; and the transportation of chlorine. PRA has been developed to a greater level of sophistication in the nuclear industry than in the chemical industry. In the nuclear area, its usefulness has been demonstrated by increased plant safety, engineering insights, and cost-saving recommendations. Data and methods have been developed to increase the level of realism of the treatment of operator actions in PRA studies. It can be stated generally that the same methods can be applied with equal success in the chemical industry. However, there are pitfalls into which the unwary nuclear-oriented PRA analyst may stumble if he does not bear in mind that there are significant differences between nuclear plants and chemical plants

  4. Probabilistic Risk Assessment to Inform Decision Making: Frequently Asked Questions

    Science.gov (United States)

    General concepts and principles of Probabilistic Risk Assessment (PRA), describe how PRA can improve the bases of Agency decisions, and provide illustrations of how PRA has been used in risk estimation and in describing the uncertainty in decision making.

  5. A Probabilistic Asteroid Impact Risk Model

    Science.gov (United States)

    Mathias, Donovan L.; Wheeler, Lorien F.; Dotson, Jessie L.

    2016-01-01

    Asteroid threat assessment requires the quantification of both the impact likelihood and resulting consequence across the range of possible events. This paper presents a probabilistic asteroid impact risk (PAIR) assessment model developed for this purpose. The model incorporates published impact frequency rates with state-of-the-art consequence assessment tools, applied within a Monte Carlo framework that generates sets of impact scenarios from uncertain parameter distributions. Explicit treatment of atmospheric entry is included to produce energy deposition rates that account for the effects of thermal ablation and object fragmentation. These energy deposition rates are used to model the resulting ground damage, and affected populations are computed for the sampled impact locations. The results for each scenario are aggregated into a distribution of potential outcomes that reflect the range of uncertain impact parameters, population densities, and strike probabilities. As an illustration of the utility of the PAIR model, the results are used to address the question of what minimum size asteroid constitutes a threat to the population. To answer this question, complete distributions of results are combined with a hypothetical risk tolerance posture to provide the minimum size, given sets of initial assumptions. Model outputs demonstrate how such questions can be answered and provide a means for interpreting the effect that input assumptions and uncertainty can have on final risk-based decisions. Model results can be used to prioritize investments to gain knowledge in critical areas or, conversely, to identify areas where additional data has little effect on the metrics of interest.

  6. Probabilistic methods in fire-risk analysis

    International Nuclear Information System (INIS)

    Brandyberry, M.D.

    1989-01-01

    The first part of this work outlines a method for assessing the frequency of ignition of a consumer product in a building and shows how the method would be used in an example scenario utilizing upholstered furniture as the product and radiant auxiliary heating devices (electric heaters, wood stoves) as the ignition source. Deterministic thermal models of the heat-transport processes are coupled with parameter uncertainty analysis of the models and with a probabilistic analysis of the events involved in a typical scenario. This leads to a distribution for the frequency of ignition for the product. In second part, fire-risk analysis as currently used in nuclear plants is outlines along with a discussion of the relevant uncertainties. The use of the computer code COMPBRN is discussed for use in the fire-growth analysis along with the use of response-surface methodology to quantify uncertainties in the code's use. Generalized response surfaces are developed for temperature versus time for a cable tray, as well as a surface for the hot gas layer temperature and depth for a room of arbitrary geometry within a typical nuclear power plant compartment. These surfaces are then used to simulate the cable tray damage time in a compartment fire experiment

  7. Reliability and Probabilistic Risk Assessment - How They Play Together

    Science.gov (United States)

    Safie, Fayssal M.; Stutts, Richard G.; Zhaofeng, Huang

    2015-01-01

    PRA methodology is one of the probabilistic analysis methods that NASA brought from the nuclear industry to assess the risk of LOM, LOV and LOC for launch vehicles. PRA is a system scenario based risk assessment that uses a combination of fault trees, event trees, event sequence diagrams, and probability and statistical data to analyze the risk of a system, a process, or an activity. It is a process designed to answer three basic questions: What can go wrong? How likely is it? What is the severity of the degradation? Since 1986, NASA, along with industry partners, has conducted a number of PRA studies to predict the overall launch vehicles risks. Planning Research Corporation conducted the first of these studies in 1988. In 1995, Science Applications International Corporation (SAIC) conducted a comprehensive PRA study. In July 1996, NASA conducted a two-year study (October 1996 - September 1998) to develop a model that provided the overall Space Shuttle risk and estimates of risk changes due to proposed Space Shuttle upgrades. After the Columbia accident, NASA conducted a PRA on the Shuttle External Tank (ET) foam. This study was the most focused and extensive risk assessment that NASA has conducted in recent years. It used a dynamic, physics-based, integrated system analysis approach to understand the integrated system risk due to ET foam loss in flight. Most recently, a PRA for Ares I launch vehicle has been performed in support of the Constellation program. Reliability, on the other hand, addresses the loss of functions. In a broader sense, reliability engineering is a discipline that involves the application of engineering principles to the design and processing of products, both hardware and software, for meeting product reliability requirements or goals. It is a very broad design-support discipline. It has important interfaces with many other engineering disciplines. Reliability as a figure of merit (i.e. the metric) is the probability that an item will

  8. Probabilistic economic frameworks for disaster risk management

    Science.gov (United States)

    Dulac, Guillaume; Forni, Marc

    2013-04-01

    range from simple elicitation of data from a subject matter expert to calibrate a probability distribution to more advanced stochastic modelling. This approach can be referred to more as a proficiency in the language of uncertainty rather than modelling per se in the sense that it allows for greater flexibility to adapt a given context. In a real decision making context, one seldom has neither time nor budget resources to investigate all of these variables thoroughly, hence the importance of being able to prioritize the level of effort among them. Under the proposed framework, this can be done in an optimised fashion. The point here consists in applying probabilistic sensitivity analysis together with the fundamentals of the economic value of information; the framework as built is well suited to such considerations, and variables can be ranked according to their contribution to risk understanding. Efforts to deal with second order uncertainties on variables prove to be valuable when dealing with the economic value of sample information.

  9. The Probabilistic Convolution Tree: Efficient Exact Bayesian Inference for Faster LC-MS/MS Protein Inference

    Science.gov (United States)

    Serang, Oliver

    2014-01-01

    Exact Bayesian inference can sometimes be performed efficiently for special cases where a function has commutative and associative symmetry of its inputs (called “causal independence”). For this reason, it is desirable to exploit such symmetry on big data sets. Here we present a method to exploit a general form of this symmetry on probabilistic adder nodes by transforming those probabilistic adder nodes into a probabilistic convolution tree with which dynamic programming computes exact probabilities. A substantial speedup is demonstrated using an illustration example that can arise when identifying splice forms with bottom-up mass spectrometry-based proteomics. On this example, even state-of-the-art exact inference algorithms require a runtime more than exponential in the number of splice forms considered. By using the probabilistic convolution tree, we reduce the runtime to and the space to where is the number of variables joined by an additive or cardinal operator. This approach, which can also be used with junction tree inference, is applicable to graphs with arbitrary dependency on counting variables or cardinalities and can be used on diverse problems and fields like forward error correcting codes, elemental decomposition, and spectral demixing. The approach also trivially generalizes to multiple dimensions. PMID:24626234

  10. Probabilistic risk criteria and their application to nuclear chemical plant design

    International Nuclear Information System (INIS)

    Arthur, T.; Barnes, D.S.; Brown, M.L.; Taig, A.R.; Johnston, B.D.; Hayns, M.

    1989-01-01

    A nuclear chemical plant safety strategy is presented. The use of risk criteria in design is demonstrated by reference to a particular area of the plant. This involves the application of Probabilistic Risk Assessment (PRA) techniques. Computer programs developed by the UK Atomic Energy Authority (UKAEA) at its Safety and Reliability Directorate (SRD) are used toe valuate and analyze the resultant fault trees. the magnitude of releases are estimated and individual and societal risks determined. The paper concludes that the application of PRA to a nuclear chemical plant can be structured in such a way as to allow a designer to work to quantitative risk targets

  11. Probabilistic fire risk assessment for Koeberg Nuclear Power Station Unit 1

    International Nuclear Information System (INIS)

    Grobbelaar, J.F.; Foster, N.A.S.; Luesse, L.J.

    1995-01-01

    A probabilistic fire risk assessment was done for Koeberg Nuclear Power Station Unit 1. Areas where fires are likely to start were identified. Equipment important to safety, as well as their power and/or control cable routes were identified in each fire confinement sector. Fire confinement sectors where internal initiating events could be caused by fire were identified. Detection failure and suppression failure fault trees and event trees were constructed. The core damage frequency associated with each fire confinement sector was calculated, and important fire confinement sectors were identified. (author)

  12. HERMES probabilistic risk assessment. Pilot study

    International Nuclear Information System (INIS)

    Parisot, F.; Munoz, J.

    1993-01-01

    The study was performed in 1989 of the contribution of probabilistic analysis for the optimal construction of system safety status in aeronautical and European nuclear industries, shows the growing trends towards incorporation of quantitative safety assessment and lead to an agreement to undertake a prototype proof study on Hermes. The main steps of the study and results are presented in the paper

  13. Simple probabilistic method for relative risk evaluation of nuclear terrorism events

    International Nuclear Information System (INIS)

    Zhang Songbai; Wu Jun

    2006-01-01

    On the basis of the event-tree and probability analysis methods, a probabilistic method of nuclear terrorism risk was built, and the risk of terrorism events was analyzed. With the statistical data for and hypothetical data for relative events, the relative probabilities of the four kinds of nuclear terrorism events were obtained, as well as the relative risks of these four kinds of nuclear terrorism events were calculated by using this probabilistic method. The illustrated case show that the descending sequence of damages from the four kinds of nuclear terrorism events for single event is as following: nuclear explosive and improvised nuclear explosive, nuclear facility attacked, and 'dirty bomb'. Under the hypothetical condition, the descending sequence of possibilities for the four kinds of nuclear terrorism events is as following: 'dirty bomb', nuclear facility attacked, improvised nuclear explosive and nuclear explosive, but the descending sequence of risks is as following: 'dirty bomb', improvised nuclear explosive, nuclear facility attacked, and nuclear explosive . (authors)

  14. Risk analysis of analytical validations by probabilistic modification of FMEA

    DEFF Research Database (Denmark)

    Barends, D.M.; Oldenhof, M.T.; Vredenbregt, M.J.

    2012-01-01

    Risk analysis is a valuable addition to validation of an analytical chemistry process, enabling not only detecting technical risks, but also risks related to human failures. Failure Mode and Effect Analysis (FMEA) can be applied, using a categorical risk scoring of the occurrence, detection...... and severity of failure modes, and calculating the Risk Priority Number (RPN) to select failure modes for correction. We propose a probabilistic modification of FMEA, replacing the categorical scoring of occurrence and detection by their estimated relative frequency and maintaining the categorical scoring...... of severity. In an example, the results of traditional FMEA of a Near Infrared (NIR) analytical procedure used for the screening of suspected counterfeited tablets are re-interpretated by this probabilistic modification of FMEA. Using this probabilistic modification of FMEA, the frequency of occurrence...

  15. Probabilistic risk assessment in nuclear power plant regulation

    Energy Technology Data Exchange (ETDEWEB)

    Wall, J B

    1980-09-01

    A specific program is recommended to utilize more effectively probabilistic risk assessment in nuclear power plant regulation. It is based upon the engineering insights from the Reactor Safety Study (WASH-1400) and some follow-on risk assessment research by USNRC. The Three Mile Island accident is briefly discussed from a risk viewpoint to illustrate a weakness in current practice. The development of a probabilistic safety goal is recommended with some suggestions on underlying principles. Some ongoing work on risk perception and the draft probabilistic safety goal being reviewed on Canada is described. Some suggestions are offered on further risk assessment research. Finally, some recent U.S. Nuclear Regulatory Commission actions are described.

  16. Safety evaluation for the LMFBR plant using probabilistic risk assessment techniques

    International Nuclear Information System (INIS)

    Kani, Y.; Aizawa, K.

    1987-01-01

    This paper presents an application of probabilistic risk assessment techniques to a typical loop-type liquid metal fast breeder reactor (LMFBR) plant in the detailed design stage. A comprehensive systems analysis has been performed to identify event sequences leading to core damage and provide insights into the importance of accident contributors. While traditional event tree/fault tree modeling was used for the analysis, this study involved a thorough investigation of initiating events and of support system faults. The qualification of accident sequences has been conducted by combining the fault trees based on the event trees and obtaining sequence cut sets with the use of the SETS code. This study also attempted to quantify the potential for operator recovery actions in the course of each accident sequence. (author)

  17. Limited probabilistic risk assessment applications in plant backfitting

    International Nuclear Information System (INIS)

    Desaedeleer, G.

    1987-01-01

    Plant backfitting programs are defined on the basis of deterministic (e.g. Systematic Evaluation Program) or probabilistic (e.g. Probabilistic Risk Assessment) approaches. Each approach provides valuable assets in defining the program and has its own advantages and disadvantages. Ideally one should combine the strong points of each approach. This chapter summarizes actual experience gained from combinations of deterministic and probabilistic approaches to define and implement PWR backfitting programs. Such combinations relate to limited applications of probabilistic techniques and are illustrated for upgrading fluid systems. These evaluations allow sound and rational optimization systems upgrade. However, the boundaries of the reliability analysis need to be clearly defined and system reliability may have to go beyond classical boundaries (e.g. identification of weak links in support systems). Also the implementation of upgrade on a system per system basis is not necessarily cost-effective. (author)

  18. Structural system reliability calculation using a probabilistic fault tree analysis method

    Science.gov (United States)

    Torng, T. Y.; Wu, Y.-T.; Millwater, H. R.

    1992-01-01

    The development of a new probabilistic fault tree analysis (PFTA) method for calculating structural system reliability is summarized. The proposed PFTA procedure includes: developing a fault tree to represent the complex structural system, constructing an approximation function for each bottom event, determining a dominant sampling sequence for all bottom events, and calculating the system reliability using an adaptive importance sampling method. PFTA is suitable for complicated structural problems that require computer-intensive computer calculations. A computer program has been developed to implement the PFTA.

  19. Risk-Informed Safety Assurance and Probabilistic Assessment of Mission-Critical Software-Intensive Systems

    Science.gov (United States)

    Guarro, Sergio B.

    2010-01-01

    This report validates and documents the detailed features and practical application of the framework for software intensive digital systems risk assessment and risk-informed safety assurance presented in the NASA PRA Procedures Guide for Managers and Practitioner. This framework, called herein the "Context-based Software Risk Model" (CSRM), enables the assessment of the contribution of software and software-intensive digital systems to overall system risk, in a manner which is entirely compatible and integrated with the format of a "standard" Probabilistic Risk Assessment (PRA), as currently documented and applied for NASA missions and applications. The CSRM also provides a risk-informed path and criteria for conducting organized and systematic digital system and software testing so that, within this risk-informed paradigm, the achievement of a quantitatively defined level of safety and mission success assurance may be targeted and demonstrated. The framework is based on the concept of context-dependent software risk scenarios and on the modeling of such scenarios via the use of traditional PRA techniques - i.e., event trees and fault trees - in combination with more advanced modeling devices such as the Dynamic Flowgraph Methodology (DFM) or other dynamic logic-modeling representations. The scenarios can be synthesized and quantified in a conditional logic and probabilistic formulation. The application of the CSRM method documented in this report refers to the MiniAERCam system designed and developed by the NASA Johnson Space Center.

  20. Bayesian uncertainty analyses of probabilistic risk models

    International Nuclear Information System (INIS)

    Pulkkinen, U.

    1989-01-01

    Applications of Bayesian principles to the uncertainty analyses are discussed in the paper. A short review of the most important uncertainties and their causes is provided. An application of the principle of maximum entropy to the determination of Bayesian prior distributions is described. An approach based on so called probabilistic structures is presented in order to develop a method of quantitative evaluation of modelling uncertainties. The method is applied to a small example case. Ideas for application areas for the proposed method are discussed

  1. Probabilistic methodology for turbine missile risk analysis

    International Nuclear Information System (INIS)

    Twisdale, L.A.; Dunn, W.L.; Frank, R.A.

    1984-01-01

    A methodology has been developed for estimation of the probabilities of turbine-generated missile damage to nuclear power plant structures and systems. Mathematical models of the missile generation, transport, and impact events have been developed and sequenced to form an integrated turbine missile simulation methodology. Probabilistic Monte Carlo techniques are used to estimate the plant impact and damage probabilities. The methodology has been coded in the TURMIS computer code to facilitate numerical analysis and plant-specific turbine missile probability assessments. Sensitivity analyses have been performed on both the individual models and the integrated methodology, and probabilities have been estimated for a hypothetical nuclear power plant case study. (orig.)

  2. Probabilistic risk analysis of Angra-1 reactor

    International Nuclear Information System (INIS)

    Spivak, R.C.; Collussi, I.; Silva, M.C. da; Onusic Junior, J.

    1986-01-01

    The first phase of probabilistic study for safety analysis and operational analysis of Angra-1 reactor is presented. The study objectives and uses are: to support decisions about safety problems; to identify operational and/or project failures; to amplify operator qualification tests to include accidents in addition to project base; to provide informations to be used in development and/or review of operation procedures in emergency, test and maintenance procedures; to obtain experience for data collection about abnormal accurences; utilization of study results for training operators; and training of evaluation and reliability techniques for the personnel of CNEN and FURNAS. (M.C.K.) [pt

  3. Probabilistic risk assessment (PRA) reference document. Final report

    International Nuclear Information System (INIS)

    Murphy, J.A.

    1984-09-01

    This document describes the current status of probabilistic risk assessment (PRA) as practiced in the nuclear reactor regulatory process. The PRA studies that have been completed or are under way are reviewed. The levels of maturity of the methodologies used in a PRA are discussed. Insights derived from PRAs are listed. The potential uses of PRA results for regulatory purposes are discussed. This document was issued for comment in February 1984 entitled Probabilistic Risk Assessment (PRA): Status Report and Guidance for Regulatory Application. The comments received on the draft have been considered for this final version of the report

  4. Review of the Diablo Canyon probabilistic risk assessment

    International Nuclear Information System (INIS)

    Bozoki, G.E.; Fitzpatrick, R.G.; Bohn, M.P.; Sabek, M.G.; Ravindra, M.K.; Johnson, J.J.

    1994-08-01

    This report details the review of the Diablo Canyon Probabilistic Risk Assessment (DCPRA). The study was performed under contract from the Probabilistic Risk Analysis Branch, Office of Nuclear Reactor Research, USNRC by Brookhaven National Laboratory. The DCPRA is a full scope Level I effort and although the review touched on all aspects of the PRA, the internal events and seismic events received the vast majority of the review effort. The report includes a number of independent systems analyses sensitivity studies, importance analyses as well as conclusions on the adequacy of the DCPRA for use in the Diablo Canyon Long Term Seismic Program

  5. Development of reliability and probabilistic safety assessment program RiskA

    International Nuclear Information System (INIS)

    Wu, Yican

    2015-01-01

    Highlights: • There are four parts in the structure of RiskA. User input part lets users input the PSA model and some necessary data by GUI or model transformation tool. In calculation engine part, fault tree analysis, event tree analysis, uncertainty analysis, sensitivity analysis, importance analysis and failure mode and effects analysis are supplied. User output part outputs the analysis results, user customized reports and some other data. The last part includes reliability database, some other common tools and help documents. • RiskA has several advanced features. Extensible framework makes it easy to add any new functions, making RiskA to be a large platform of reliability and probabilistic safety assessment. It is very fast to analysis fault tree in RiskA because many advanced algorithm improvement were made. Many model formats can be imported and exported, which made the PSA model in the commercial software can be easily transformed to adapt RiskA platform. Web-based co-modeling let several users in different places work together whenever they are online. • The comparison between RiskA and other mature PSA codes (e.g. CAFTA, RiskSpectrum, XFTA) has demonstrated that the calculation and analysis of RiskA is correct and efficient. Based on the development of this code package, many applications of safety and reliability analysis of some research reactors and nuclear power plants were performed. The development of RiskA appears to be of realistic and potential value for academic research and practical operation safety management of nuclear power plants in China and abroad. - Abstract: PSA (probabilistic safety assessment) software, the indispensable tool in nuclear safety assessment, has been widely used. An integrated reliability and PSA program named RiskA has been developed by FDS Team. RiskA supplies several standard PSA modules including fault tree analysis, event tree analysis, uncertainty analysis, failure mode and effect analysis and reliability

  6. Obesity as a risk factor for developing functional limitation among older adults: A conditional inference tree analysis

    Science.gov (United States)

    Objective: To examine the risk factors of developing functional decline and make probabilistic predictions by using a tree-based method that allows higher order polynomials and interactions of the risk factors. Methods: The conditional inference tree analysis, a data mining approach, was used to con...

  7. Identifiability of tree-child phylogenetic networks under a probabilistic recombination-mutation model of evolution.

    Science.gov (United States)

    Francis, Andrew; Moulton, Vincent

    2018-06-07

    Phylogenetic networks are an extension of phylogenetic trees which are used to represent evolutionary histories in which reticulation events (such as recombination and hybridization) have occurred. A central question for such networks is that of identifiability, which essentially asks under what circumstances can we reliably identify the phylogenetic network that gave rise to the observed data? Recently, identifiability results have appeared for networks relative to a model of sequence evolution that generalizes the standard Markov models used for phylogenetic trees. However, these results are quite limited in terms of the complexity of the networks that are considered. In this paper, by introducing an alternative probabilistic model for evolution along a network that is based on some ground-breaking work by Thatte for pedigrees, we are able to obtain an identifiability result for a much larger class of phylogenetic networks (essentially the class of so-called tree-child networks). To prove our main theorem, we derive some new results for identifying tree-child networks combinatorially, and then adapt some techniques developed by Thatte for pedigrees to show that our combinatorial results imply identifiability in the probabilistic setting. We hope that the introduction of our new model for networks could lead to new approaches to reliably construct phylogenetic networks. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. Bayesian probabilistic network approach for managing earthquake risks of cities

    DEFF Research Database (Denmark)

    Bayraktarli, Yahya; Faber, Michael

    2011-01-01

    This paper considers the application of Bayesian probabilistic networks (BPNs) to large-scale risk based decision making in regard to earthquake risks. A recently developed risk management framework is outlined which utilises Bayesian probabilistic modelling, generic indicator based risk models...... and a fourth module on the consequences of an earthquake. Each of these modules is integrated into a BPN. Special attention is given to aggregated risk, i.e. the risk contribution from assets at multiple locations in a city subjected to the same earthquake. The application of the methodology is illustrated...... on an example considering a portfolio of reinforced concrete structures in a city located close to the western part of the North Anatolian Fault in Turkey....

  9. Developing Probabilistic Safety Performance Margins for Unknown and Underappreciated Risks

    Science.gov (United States)

    Benjamin, Allan; Dezfuli, Homayoon; Everett, Chris

    2015-01-01

    Probabilistic safety requirements currently formulated or proposed for space systems, nuclear reactor systems, nuclear weapon systems, and other types of systems that have a low-probability potential for high-consequence accidents depend on showing that the probability of such accidents is below a specified safety threshold or goal. Verification of compliance depends heavily upon synthetic modeling techniques such as PRA. To determine whether or not a system meets its probabilistic requirements, it is necessary to consider whether there are significant risks that are not fully considered in the PRA either because they are not known at the time or because their importance is not fully understood. The ultimate objective is to establish a reasonable margin to account for the difference between known risks and actual risks in attempting to validate compliance with a probabilistic safety threshold or goal. In this paper, we examine data accumulated over the past 60 years from the space program, from nuclear reactor experience, from aircraft systems, and from human reliability experience to formulate guidelines for estimating probabilistic margins to account for risks that are initially unknown or underappreciated. The formulation includes a review of the safety literature to identify the principal causes of such risks.

  10. Probabilistic risk assessment of aircraft impact on a spent nuclear fuel dry storage

    Energy Technology Data Exchange (ETDEWEB)

    Almomani, Belal, E-mail: balmomani@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Sanghoon, E-mail: shlee1222@kmu.ac.kr [Department of Mechanical and Automotive Engineering, Keimyung University, Dalgubeol-daero 1095, Dalseo-gu, Daegu (Korea, Republic of); Jang, Dongchan, E-mail: dongchan.jang@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kang, Hyun Gook, E-mail: kangh6@rpi.edu [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

    2017-01-15

    Highlights: • A new risk assessment frame is proposed for aircraft impact into an interim dry storage. • It uses event tree analysis, response-structural analysis, consequence analysis, and Monte Carlo simulation. • A case study of the proposed procedure is presented to illustrate the methodology’s application. - Abstract: This paper proposes a systematic risk evaluation framework for one of the most significant impact events on an interim dry storage facility, an aircraft crash, by using a probabilistic approach. A realistic case study that includes a specific cask model and selected impact conditions is performed to demonstrate the practical applicability of the proposed framework. An event tree analysis of an occurred aircraft crash that defines a set of impact conditions and storage cask response is constructed. The Monte-Carlo simulation is employed for the probabilistic approach in consideration of sources of uncertainty associated with the impact loads onto the internal storage casks. The parameters for representing uncertainties that are managed probabilistically include the aircraft impact velocity, the compressive strength of the reinforced concrete wall, the missile shape factor, and the facility wall thickness. Failure probabilities of the impacted wall and a single storage cask under direct mechanical impact load caused by the aircraft crash are estimated. A finite element analysis is applied to simulate the postulated direct engine impact load onto the cask body, and a source term analysis for associated releases of radioactive materials as well as an off-site consequence analysis are performed. Finally, conditional risk contribution calculations are represented by an event tree model. Case study results indicate that no severe risk is presented, as the radiological consequences do not exceed regulatory exposure limits to the public. This risk model can be used with any other representative detailed parameters and reference design concepts for

  11. Developing an event-tree probabilistic tsunami inundation model for NE Atlantic coasts: Application to case studies

    Science.gov (United States)

    Omira, Rachid; Baptista, Maria Ana; Matias, Luis

    2015-04-01

    This study constitutes the first assessment of probabilistic tsunami inundation in the NE Atlantic region, using an event-tree approach. It aims to develop a probabilistic tsunami inundation approach for the NE Atlantic coast with an application to two test sites of ASTARTE project, Tangier-Morocco and Sines-Portugal. Only tsunamis of tectonic origin are considered here, taking into account near-, regional- and far-filed sources. The multidisciplinary approach, proposed here, consists of an event-tree method that gathers seismic hazard assessment, tsunami numerical modelling, and statistical methods. It presents also a treatment of uncertainties related to source location and tidal stage in order to derive the likelihood of tsunami flood occurrence and exceedance of a specific near-shore wave height during a given return period. We derive high-resolution probabilistic maximum wave heights and flood distributions for both test-sites Tangier and Sines considering 100-, 500-, and 1000-year return periods. We find that the probability that a maximum wave height exceeds 1 m somewhere along the Sines coasts reaches about 55% for 100-year return period, and is up to 100% for 1000-year return period. Along Tangier coast, the probability of inundation occurrence (flow depth > 0m) is up to 45% for 100-year return period and reaches 96% in some near-shore costal location for 500-year return period. Acknowledgements: This work is funded by project ASTARTE - Assessment, STrategy And Risk Reduction for Tsunamis in Europe. Grant 603839, 7th FP (ENV.2013.6.4-3 ENV.2013.6.4-3).

  12. Adolescents' Heightened Risk-Seeking in a Probabilistic Gambling Task

    Science.gov (United States)

    Burnett, Stephanie; Bault, Nadege; Coricelli, Giorgio; Blakemore, Sarah-Jayne

    2010-01-01

    This study investigated adolescent males' decision-making under risk, and the emotional response to decision outcomes, using a probabilistic gambling task designed to evoke counterfactually mediated emotions (relief and regret). Participants were 20 adolescents (aged 9-11), 26 young adolescents (aged 12-15), 20 mid-adolescents (aged 15-18) and 17…

  13. HTGR containment design options: an application of probabilistic risk assessment

    International Nuclear Information System (INIS)

    1977-08-01

    Through the use of probabilistic risk assessment (PRA), it is possible to quantitatively evaluate the radiological risk associated with a given reactor design and to place such risk into perspective with alternative designs. The merits are discussed for several containment alternatives for the HTGR from the viewpoints of economics and licensability, as well as public risk. The quantification of cost savings and public risk indicates that presently acceptable public risk can be maintained and cost savings of $40 million can result from use of a vented confinement for the HTGR

  14. Use of Probabilistic Risk Assessment in Shuttle Decision Making Process

    Science.gov (United States)

    Boyer, Roger L.; Hamlin, Teri, L.

    2011-01-01

    This slide presentation reviews the use of Probabilistic Risk Assessment (PRA) to assist in the decision making for the shuttle design and operation. Probabilistic Risk Assessment (PRA) is a comprehensive, structured, and disciplined approach to identifying and analyzing risk in complex systems and/or processes that seeks answers to three basic questions: (i.e., what can go wrong? what is the likelihood of these occurring? and what are the consequences that could result if these occur?) The purpose of the Shuttle PRA (SPRA) is to provide a useful risk management tool for the Space Shuttle Program (SSP) to identify strengths and possible weaknesses in the Shuttle design and operation. SPRA was initially developed to support upgrade decisions, but has evolved into a tool that supports Flight Readiness Reviews (FRR) and near real-time flight decisions. Examples of the use of PRA for the shuttle are reviewed.

  15. Communicating risk to the public - Probabilistically impossible

    International Nuclear Information System (INIS)

    Gallina, C.O.

    1992-01-01

    As far as the general public is concerned, scientists can forget about risk perception and risk acceptance. These worthy scientific goals only confuse the one single important issue - how people perceive and accept technology. Risk is rarely accepted in the abstract by the general public. Because people would rather be assured than educated, risk can only be presented within the framework of what people will accept when they accept the technology, which (among other things) produces the aforementioned risk itself. It is in this technological environment that effective risk communication becomes extremely complex. To understand the risk, the public must understand the technology - a formidable task in itself, but one that becomes even more difficult when two additional factors are included: media attention and political influence

  16. A probabilistic quantitative risk assessment model for the long-term work zone crashes.

    Science.gov (United States)

    Meng, Qiang; Weng, Jinxian; Qu, Xiaobo

    2010-11-01

    Work zones especially long-term work zones increase traffic conflicts and cause safety problems. Proper casualty risk assessment for a work zone is of importance for both traffic safety engineers and travelers. This paper develops a novel probabilistic quantitative risk assessment (QRA) model to evaluate the casualty risk combining frequency and consequence of all accident scenarios triggered by long-term work zone crashes. The casualty risk is measured by the individual risk and societal risk. The individual risk can be interpreted as the frequency of a driver/passenger being killed or injured, and the societal risk describes the relation between frequency and the number of casualties. The proposed probabilistic QRA model consists of the estimation of work zone crash frequency, an event tree and consequence estimation models. There are seven intermediate events--age (A), crash unit (CU), vehicle type (VT), alcohol (AL), light condition (LC), crash type (CT) and severity (S)--in the event tree. Since the estimated value of probability for some intermediate event may have large uncertainty, the uncertainty can thus be characterized by a random variable. The consequence estimation model takes into account the combination effects of speed and emergency medical service response time (ERT) on the consequence of work zone crash. Finally, a numerical example based on the Southeast Michigan work zone crash data is carried out. The numerical results show that there will be a 62% decrease of individual fatality risk and 44% reduction of individual injury risk if the mean travel speed is slowed down by 20%. In addition, there will be a 5% reduction of individual fatality risk and 0.05% reduction of individual injury risk if ERT is reduced by 20%. In other words, slowing down speed is more effective than reducing ERT in the casualty risk mitigation. 2010 Elsevier Ltd. All rights reserved.

  17. A review of probabilistic risk assessment of contaminated land

    International Nuclear Information System (INIS)

    Oeberg, T.; Bergbaeck, B.

    2005-01-01

    Background, Aims and Scope. The management and decisions concerning restoration of contaminated land often require indepth risk analyses. An environmental risk assessment is generally described as proceeding in four separate steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization. The risk assessment should acknowledge and quantify the uncertainty in risk predictions. This can be achieved by applying probabilistic methods which, although they have been available for many years, are still not generally used. Risk assessment of contaminated land is an area where probabilistic methods have proved particularly useful. Many reports have appeared in the literature, mostly by North American researchers. The aim of this review is to summarize the experience gained so far, provide a number of useful examples, and suggest what may be done to promote probabilistic methods in Europe and the rest of the world. Methods. The available literature has been explored through searches in the major scientific and technical databases, WWW resources, textbooks and direct contacts with active researchers. A calculation example was created using standard simulation software. (orig.)

  18. A Study on Landslide Risk Management by Applying Fault Tree Logics

    Directory of Open Access Journals (Sweden)

    Kazmi Danish

    2017-01-01

    Full Text Available Slope stability is one of the focal areas of curiosity to geotechnical designers and also appears logical for the application of probabilistic approaches since the analysis lead to a “probability of failure”. Assessment of the existing slopes in relation with risks seems to be more meaningful when concerning with landslides. Probabilistic slope stability analysis (PSSA is the best option in covering the landslides events. The intent here is to bid a probabilistic framework for quantified risk analysis with human uncertainties. In this regard, Fault Tree Analysis is utilized and for prediction of risk levels, consequences of the failures of the reference landslides have been taken. It is concluded that logics of fault trees is best fit, to clinch additional categories of uncertainty; like human, organizational, and knowledge related. In actual, the approach has been used in bringing together engineering and management performances and personnel, to produce reliability in slope engineering practices.

  19. An integral approach to the use of probabilistic risk assessment methods

    International Nuclear Information System (INIS)

    Schwarzblat, M.; Arellano, J.

    1987-01-01

    In this chapter some of the work developed at the Instituto de Investigaciones Electricas in the area of probabilistic risk analysis are presented. In this area, work has been basically focused in the following directions: development and implementation of methods, and applications to real systems. The first part of this paper describes the area of methods development and implementation, presenting an integrated package of computer programs for fault tree analysis. In the second part some of the most important applications developed for real systems are presented. (author)

  20. Application of probabilistic risk based optimization approaches in environmental restoration

    International Nuclear Information System (INIS)

    Goldammer, W.

    1995-01-01

    The paper presents a general approach to site-specific risk assessments and optimization procedures. In order to account for uncertainties in the assessment of the current situation and future developments, optimization parameters are treated as probabilistic distributions. The assessments are performed within the framework of a cost-benefit analysis. Radiation hazards and conventional risks are treated within an integrated approach. Special consideration is given to consequences of low probability events such as, earthquakes or major floods. Risks and financial costs are combined to an overall figure of detriment allowing one to distinguish between benefits of available reclamation options. The probabilistic analysis uses a Monte Carlo simulation technique. The paper demonstrates the applicability of this approach in aiding the reclamation planning using an example from the German reclamation program for uranium mining and milling sites

  1. Risk analysis of analytical validations by probabilistic modification of FMEA.

    Science.gov (United States)

    Barends, D M; Oldenhof, M T; Vredenbregt, M J; Nauta, M J

    2012-05-01

    Risk analysis is a valuable addition to validation of an analytical chemistry process, enabling not only detecting technical risks, but also risks related to human failures. Failure Mode and Effect Analysis (FMEA) can be applied, using a categorical risk scoring of the occurrence, detection and severity of failure modes, and calculating the Risk Priority Number (RPN) to select failure modes for correction. We propose a probabilistic modification of FMEA, replacing the categorical scoring of occurrence and detection by their estimated relative frequency and maintaining the categorical scoring of severity. In an example, the results of traditional FMEA of a Near Infrared (NIR) analytical procedure used for the screening of suspected counterfeited tablets are re-interpretated by this probabilistic modification of FMEA. Using this probabilistic modification of FMEA, the frequency of occurrence of undetected failure mode(s) can be estimated quantitatively, for each individual failure mode, for a set of failure modes, and the full analytical procedure. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. A probabilistic analysis of fire-induced tree-grass coexistence in savannas.

    Science.gov (United States)

    D'Odorico, Paolo; Laio, Francesco; Ridolfi, Luca

    2006-03-01

    Fires play an important role in determining the composition and structure of vegetation in semiarid ecosystems. The study of the interactions between fire and vegetation requires a stochastic approach because of the random and unpredictable nature of fire occurrences. To this end, this article develops a minimalist probabilistic framework to investigate the impact of intermittent fire occurrences on the temporal dynamics of vegetation. This framework is used to analyze the emergence of statistically stable conditions favorable to tree-grass coexistence in savannas. It is found that these conditions can be induced and stabilized by the stochastic fire regime. A decrease in fire frequency leads to bush encroachment, while more frequent and intense fires favor savanna-to-grassland conversions. The positive feedback between fires and vegetation can convert states of tree-grass coexistence in semiarid savannas into bistable conditions, with both woodland and grassland as possible, though mutually exclusive, stable states of the system.

  3. Probabilistic risk assessment in the nuclear power industry

    International Nuclear Information System (INIS)

    Fullwood, R.R.; Hall, R.E.

    1988-01-01

    This book describes the more important improvements in risk assessment methodology developed over the last decade. The book covers the following areas - a general view of risk pertaining to nuclear power, mathematics necessary to understand the text, a concise overview of the light water reactors and their features for protecting the public, probabilities and consequences calculated to form risk assessment to the plant, and 34 applications of probabilistic risk assessment (PRA) in the power generation industry. There is a glossary of acronyms and unusual words and a list of references. (author)

  4. Probabilistic aspects of risk analyses for hazardous facilities

    International Nuclear Information System (INIS)

    Morici, A.; Valeri, A.; Zaffiro, C.

    1989-01-01

    The work described in the paper discusses the aspects of the risk analysis concerned with the use of the probabilistic methodology, in order to see how this approach may affect the risk management of industrial hazardous facilities. To this purpose reference is done to the Probabilistic Risk Assessment (PRA) of nuclear power plants. The paper points out that even though the public aversion towards nuclear risks is still far from being removed, the probabilistic approach may provide a sound support to the decision making and authorization process for any industrial activity implying risk for the environment and the public health. It is opinion of the authors that the probabilistic techniques have been developed to a great level of sophistication in the nuclear industry and provided much more experience in this field than in others. For some particular areas of the nuclear applications, such as the plant reliability and the plant response to the accidents, these techniques have reached a sufficient level of maturity and so some results have been usefully taken as a measure of the safety level of the plant itself. The use of some limited safety goals is regarded as a relevant item of the nuclear licensing process. The paper claims that it is time now that these methods would be applied with equal success to other hazardous facilities, and makes some comparative consideration on the differences of these plants with nuclear power plants in order to understand the effect of these differences on the PRA results and on the use one intends to make with them. (author)

  5. Advances in Probabilistic Risk Assessment (PRA): a look into practitioners toolbox

    International Nuclear Information System (INIS)

    Mok, J.; Kaasalainen, S.; Donnelly, K.

    2007-01-01

    The ever-increasing emphasis on the use of Probabilistic Risk Assessment (PRA) in risk-informed decision making translates into increased expectations relating to PRA applications for the groups tasked with developing and maintaining the facility PRAs. In order to succeed in meeting the demand for PRA work, it is essential to develop methodologies and tools (or utilities) that improve the efficiency with which the PRAs are processed and manipulated to obtain a solution. Examples from the Nuclear Safety Solutions (NSS) PRA Practitioners tool box include utilities for cutting logical loops, optimizing fault trees (to decrease run-times), modularizing fault trees, and converting event trees into high level fault tree logic (an important element if the PRA study is to be used to support a risk monitor such as an Equipment Out-of-Service (EOOS) Monitor). The objective of this paper is be to briefly describe the main features of these utilities, and to illustrate the value they have in terms of improving the efficiency and effectiveness of PRA development and maintenance at NSS. (author)

  6. Uncertainty propagation in probabilistic risk assessment: A comparative study

    International Nuclear Information System (INIS)

    Ahmed, S.; Metcalf, D.R.; Pegram, J.W.

    1982-01-01

    Three uncertainty propagation techniques, namely method of moments, discrete probability distribution (DPD), and Monte Carlo simulation, generally used in probabilistic risk assessment, are compared and conclusions drawn in terms of the accuracy of the results. For small uncertainty in the basic event unavailabilities, the three methods give similar results. For large uncertainty, the method of moments is in error, and the appropriate method is to propagate uncertainty in the discrete form either by DPD method without sampling or by Monte Carlo. (orig.)

  7. Risk measures in living probabilistic safety assessment

    International Nuclear Information System (INIS)

    Holmberg, J.; Niemelae, I.

    1993-05-01

    The main objectives of the study are: to define risk measures and suggested uses of them in various living PSA applications for the operational safety management and to describe specific model features required for living PSA applications. The report is based on three case studies performed within the Nordic research project Safety Evaluation by Use of Living PSA and Safety Indicators. (48 refs., 11 figs., 17 tabs.)

  8. Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis

    Science.gov (United States)

    Dezfuli, Homayoon; Kelly, Dana; Smith, Curtis; Vedros, Kurt; Galyean, William

    2009-01-01

    This document, Bayesian Inference for NASA Probabilistic Risk and Reliability Analysis, is intended to provide guidelines for the collection and evaluation of risk and reliability-related data. It is aimed at scientists and engineers familiar with risk and reliability methods and provides a hands-on approach to the investigation and application of a variety of risk and reliability data assessment methods, tools, and techniques. This document provides both: A broad perspective on data analysis collection and evaluation issues. A narrow focus on the methods to implement a comprehensive information repository. The topics addressed herein cover the fundamentals of how data and information are to be used in risk and reliability analysis models and their potential role in decision making. Understanding these topics is essential to attaining a risk informed decision making environment that is being sought by NASA requirements and procedures such as 8000.4 (Agency Risk Management Procedural Requirements), NPR 8705.05 (Probabilistic Risk Assessment Procedures for NASA Programs and Projects), and the System Safety requirements of NPR 8715.3 (NASA General Safety Program Requirements).

  9. A Probabilistic Risk Assessment For Emergency Preparedness

    International Nuclear Information System (INIS)

    Lee, Joomyung; Jae, Moosung; Ahn, Kwangil

    2013-01-01

    The importance of nuclear power plant PSA has grown up all over the world due to this incident. The main concern of this study is to develop a methodology to carry on an emergency preparedness evaluation and to set an exclusive area, or the emergency response area boundary in order to apply it to domestic reference plants. This study also focuses on evaluating the risk parameter of major nuclides through a sensitivity analysis and a safety assessment by calculating the population dose, early fatality, and cancer fatality rates. A methodology for an emergency preparedness, which can be applied to evaluate the damage of the radioactive release as well as to assess the safety of the accident scenario of a nuclear power plant, has been developed and applied for the reference plants in Korea. By applying a source term analysis, an exclusive zone based on the radioactive dose is obtained. And the results of the health effect assessment based on the release fraction of specific nuclides to public with an effective emergency response activity have been simulated. A methodology utilizing the Level 3 PSA with the actual emergency response activities has been developed and applied to typical nuclear accident situations. The plausible standard for performing an emergency plan is suggested and the valuable information regarding emergency preparedness has been produced in this study. For further works, the sensitivity study on important parameters will be performed to simulate the actual severe accident situations such as sheltering, evacuation, and emergency response activities

  10. Dealing with uncertainty arising out of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Solomon, K.A.; Kastenberg, W.E.; Nelson, P.F.

    1984-03-01

    In addressing the area of safety goal implementation, the question of uncertainty arises. This report suggests that the Nuclear Regulatory Commission (NRC) should examine how other regulatory organizations have addressed the issue. Several examples are given from the chemical industry, and comparisons are made to nuclear power risks. Recommendations are made as to various considerations that the NRC should require in probabilistic risk assessments in order to properly treat uncertainties in the implementation of the safety goal policy. 40 references, 7 figures, 5 tables

  11. Probabilistic risk assessment framework for structural systems under multiple hazards using Bayesian statistics

    International Nuclear Information System (INIS)

    Kwag, Shinyoung; Gupta, Abhinav

    2017-01-01

    Highlights: • This study presents the development of Bayesian framework for probabilistic risk assessment (PRA) of structural systems under multiple hazards. • The concepts of Bayesian network and Bayesian inference are combined by mapping the traditionally used fault trees into a Bayesian network. • The proposed mapping allows for consideration of dependencies as well as correlations between events. • Incorporation of Bayesian inference permits a novel way for exploration of a scenario that is likely to result in a system level “vulnerability.” - Abstract: Conventional probabilistic risk assessment (PRA) methodologies (USNRC, 1983; IAEA, 1992; EPRI, 1994; Ellingwood, 2001) conduct risk assessment for different external hazards by considering each hazard separately and independent of each other. The risk metric for a specific hazard is evaluated by a convolution of the fragility and the hazard curves. The fragility curve for basic event is obtained by using empirical, experimental, and/or numerical simulation data for a particular hazard. Treating each hazard as an independently can be inappropriate in some cases as certain hazards are statistically correlated or dependent. Examples of such correlated events include but are not limited to flooding induced fire, seismically induced internal or external flooding, or even seismically induced fire. In the current practice, system level risk and consequence sequences are typically calculated using logic trees to express the causative relationship between events. In this paper, we present the results from a study on multi-hazard risk assessment that is conducted using a Bayesian network (BN) with Bayesian inference. The framework can consider statistical dependencies among risks from multiple hazards, allows updating by considering the newly available data/information at any level, and provide a novel way to explore alternative failure scenarios that may exist due to vulnerabilities.

  12. Probabilistic risk assessment framework for structural systems under multiple hazards using Bayesian statistics

    Energy Technology Data Exchange (ETDEWEB)

    Kwag, Shinyoung [North Carolina State University, Raleigh, NC 27695 (United States); Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Gupta, Abhinav, E-mail: agupta1@ncsu.edu [North Carolina State University, Raleigh, NC 27695 (United States)

    2017-04-15

    Highlights: • This study presents the development of Bayesian framework for probabilistic risk assessment (PRA) of structural systems under multiple hazards. • The concepts of Bayesian network and Bayesian inference are combined by mapping the traditionally used fault trees into a Bayesian network. • The proposed mapping allows for consideration of dependencies as well as correlations between events. • Incorporation of Bayesian inference permits a novel way for exploration of a scenario that is likely to result in a system level “vulnerability.” - Abstract: Conventional probabilistic risk assessment (PRA) methodologies (USNRC, 1983; IAEA, 1992; EPRI, 1994; Ellingwood, 2001) conduct risk assessment for different external hazards by considering each hazard separately and independent of each other. The risk metric for a specific hazard is evaluated by a convolution of the fragility and the hazard curves. The fragility curve for basic event is obtained by using empirical, experimental, and/or numerical simulation data for a particular hazard. Treating each hazard as an independently can be inappropriate in some cases as certain hazards are statistically correlated or dependent. Examples of such correlated events include but are not limited to flooding induced fire, seismically induced internal or external flooding, or even seismically induced fire. In the current practice, system level risk and consequence sequences are typically calculated using logic trees to express the causative relationship between events. In this paper, we present the results from a study on multi-hazard risk assessment that is conducted using a Bayesian network (BN) with Bayesian inference. The framework can consider statistical dependencies among risks from multiple hazards, allows updating by considering the newly available data/information at any level, and provide a novel way to explore alternative failure scenarios that may exist due to vulnerabilities.

  13. Probabilistic risk assessment course documentation. Volume 5. System reliability and analysis techniques Session D - quantification

    International Nuclear Information System (INIS)

    Lofgren, E.V.

    1985-08-01

    This course in System Reliability and Analysis Techniques focuses on the probabilistic quantification of accident sequences and the link between accident sequences and consequences. Other sessions in this series focus on the quantification of system reliability and the development of event trees and fault trees. This course takes the viewpoint that event tree sequences or combinations of system failures and success are available and that Boolean equations for system fault trees have been developed and are available. 93 figs., 11 tabs

  14. Monte Carlo Simulation of Markov, Semi-Markov, and Generalized Semi- Markov Processes in Probabilistic Risk Assessment

    Science.gov (United States)

    English, Thomas

    2005-01-01

    A standard tool of reliability analysis used at NASA-JSC is the event tree. An event tree is simply a probability tree, with the probabilities determining the next step through the tree specified at each node. The nodal probabilities are determined by a reliability study of the physical system at work for a particular node. The reliability study performed at a node is typically referred to as a fault tree analysis, with the potential of a fault tree existing.for each node on the event tree. When examining an event tree it is obvious why the event tree/fault tree approach has been adopted. Typical event trees are quite complex in nature, and the event tree/fault tree approach provides a systematic and organized approach to reliability analysis. The purpose of this study was two fold. Firstly, we wanted to explore the possibility that a semi-Markov process can create dependencies between sojourn times (the times it takes to transition from one state to the next) that can decrease the uncertainty when estimating time to failures. Using a generalized semi-Markov model, we studied a four element reliability model and were able to demonstrate such sojourn time dependencies. Secondly, we wanted to study the use of semi-Markov processes to introduce a time variable into the event tree diagrams that are commonly developed in PRA (Probabilistic Risk Assessment) analyses. Event tree end states which change with time are more representative of failure scenarios than are the usual static probability-derived end states.

  15. Probabilistic Risk Assessment Procedures Guide for NASA Managers and Practitioners (Second Edition)

    Science.gov (United States)

    Stamatelatos,Michael; Dezfuli, Homayoon; Apostolakis, George; Everline, Chester; Guarro, Sergio; Mathias, Donovan; Mosleh, Ali; Paulos, Todd; Riha, David; Smith, Curtis; hide

    2011-01-01

    Probabilistic Risk Assessment (PRA) is a comprehensive, structured, and logical analysis method aimed at identifying and assessing risks in complex technological systems for the purpose of cost-effectively improving their safety and performance. NASA's objective is to better understand and effectively manage risk, and thus more effectively ensure mission and programmatic success, and to achieve and maintain high safety standards at NASA. NASA intends to use risk assessment in its programs and projects to support optimal management decision making for the improvement of safety and program performance. In addition to using quantitative/probabilistic risk assessment to improve safety and enhance the safety decision process, NASA has incorporated quantitative risk assessment into its system safety assessment process, which until now has relied primarily on a qualitative representation of risk. Also, NASA has recently adopted the Risk-Informed Decision Making (RIDM) process [1-1] as a valuable addition to supplement existing deterministic and experience-based engineering methods and tools. Over the years, NASA has been a leader in most of the technologies it has employed in its programs. One would think that PRA should be no exception. In fact, it would be natural for NASA to be a leader in PRA because, as a technology pioneer, NASA uses risk assessment and management implicitly or explicitly on a daily basis. NASA has probabilistic safety requirements (thresholds and goals) for crew transportation system missions to the International Space Station (ISS) [1-2]. NASA intends to have probabilistic requirements for any new human spaceflight transportation system acquisition. Methods to perform risk and reliability assessment in the early 1960s originated in U.S. aerospace and missile programs. Fault tree analysis (FTA) is an example. It would have been a reasonable extrapolation to expect that NASA would also become the world leader in the application of PRA. That was

  16. Uncertainty analysis in the applications of nuclear probabilistic risk assessment

    International Nuclear Information System (INIS)

    Le Duy, T.D.

    2011-01-01

    The aim of this thesis is to propose an approach to model parameter and model uncertainties affecting the results of risk indicators used in the applications of nuclear Probabilistic Risk assessment (PRA). After studying the limitations of the traditional probabilistic approach to represent uncertainty in PRA model, a new approach based on the Dempster-Shafer theory has been proposed. The uncertainty analysis process of the proposed approach consists in five main steps. The first step aims to model input parameter uncertainties by belief and plausibility functions according to the data PRA model. The second step involves the propagation of parameter uncertainties through the risk model to lay out the uncertainties associated with output risk indicators. The model uncertainty is then taken into account in the third step by considering possible alternative risk models. The fourth step is intended firstly to provide decision makers with information needed for decision making under uncertainty (parametric and model) and secondly to identify the input parameters that have significant uncertainty contributions on the result. The final step allows the process to be continued in loop by studying the updating of beliefs functions given new data. The proposed methodology was implemented on a real but simplified application of PRA model. (author)

  17. Future trends in flood risk in Indonesia - A probabilistic approach

    Science.gov (United States)

    Muis, Sanne; Guneralp, Burak; Jongman, Brenden; Ward, Philip

    2014-05-01

    Indonesia is one of the 10 most populous countries in the world and is highly vulnerable to (river) flooding. Catastrophic floods occur on a regular basis; total estimated damages were US 0.8 bn in 2010 and US 3 bn in 2013. Large parts of Greater Jakarta, the capital city, are annually subject to flooding. Flood risks (i.e. the product of hazard, exposure and vulnerability) are increasing due to rapid increases in exposure, such as strong population growth and ongoing economic development. The increase in risk may also be amplified by increasing flood hazards, such as increasing flood frequency and intensity due to climate change and land subsidence. The implementation of adaptation measures, such as the construction of dykes and strategic urban planning, may counteract these increasing trends. However, despite its importance for adaptation planning, a comprehensive assessment of current and future flood risk in Indonesia is lacking. This contribution addresses this issue and aims to provide insight into how socio-economic trends and climate change projections may shape future flood risks in Indonesia. Flood risk were calculated using an adapted version of the GLOFRIS global flood risk assessment model. Using this approach, we produced probabilistic maps of flood risks (i.e. annual expected damage) at a resolution of 30"x30" (ca. 1km x 1km at the equator). To represent flood exposure, we produced probabilistic projections of urban growth in a Monte-Carlo fashion based on probability density functions of projected population and GDP values for 2030. To represent flood hazard, inundation maps were computed using the hydrological-hydraulic component of GLOFRIS. These maps show flood inundation extent and depth for several return periods and were produced for several combinations of GCMs and future socioeconomic scenarios. Finally, the implementation of different adaptation strategies was incorporated into the model to explore to what extent adaptation may be able to

  18. Analyzing State Sequences with Probabilistic Suffix Trees: The PST R Package

    Directory of Open Access Journals (Sweden)

    Alexis Gabadinho

    2016-08-01

    Full Text Available This article presents the PST R package for categorical sequence analysis with probabilistic suffix trees (PSTs, i.e., structures that store variable-length Markov chains (VLMCs. VLMCs allow to model high-order dependencies in categorical sequences with parsimonious models based on simple estimation procedures. The package is specifically adapted to the field of social sciences, as it allows for VLMC models to be learned from sets of individual sequences possibly containing missing values; in addition, the package is extended to account for case weights. This article describes how a VLMC model is learned from one or more categorical sequences and stored in a PST. The PST can then be used for sequence prediction, i.e., to assign a probability to whole observed or artificial sequences. This feature supports data mining applications such as the extraction of typical patterns and outliers. This article also introduces original visualization tools for both the model and the outcomes of sequence prediction. Other features such as functions for pattern mining and artificial sequence generation are described as well. The PST package also allows for the computation of probabilistic divergence between two models and the fitting of segmented VLMCs, where sub-models fitted to distinct strata of the learning sample are stored in a single PST.

  19. Probabilistic risk assessment on maritime spent nuclear fuel transportation (Part II: Ship collision probability)

    International Nuclear Information System (INIS)

    Christian, Robby; Kang, Hyun Gook

    2017-01-01

    This paper proposes a methodology to assess and reduce risks of maritime spent nuclear fuel transportation with a probabilistic approach. Event trees detailing the progression of collisions leading to transport casks’ damage were constructed. Parallel and crossing collision probabilities were formulated based on the Poisson distribution. Automatic Identification System (AIS) data were processed with the Hough Transform algorithm to estimate possible intersections between the shipment route and the marine traffic. Monte Carlo simulations were done to compute collision probabilities and impact energies at each intersection. Possible safety improvement measures through a proper selection of operational transport parameters were investigated. These parameters include shipment routes, ship's cruise velocity, number of transport casks carried in a shipment, the casks’ stowage configuration and loading order on board the ship. A shipment case study is presented. Waters with high collision probabilities were identified. Effective range of cruising velocity to reduce collision risks were discovered. The number of casks in a shipment and their stowage method which gave low cask damage frequencies were obtained. The proposed methodology was successful in quantifying ship collision and cask damage frequency. It was effective in assisting decision making processes to minimize risks in maritime spent nuclear fuel transportation. - Highlights: • Proposes a probabilistic framework on the safety of spent nuclear fuel transportation by sea. • Developed a marine traffic simulation model using Generalized Hough Transform (GHT) algorithm. • A transportation case study on South Korean waters is presented. • Single-vessel risk reduction method is outlined by optimizing transport parameters.

  20. Seismic qualification of equipment by means of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Azarm, M.A.; Farahzad, P.; Boccio, J.L.

    1982-01-01

    Upon the sponsorship of the Equipment Qualification Branch (EQB) of NRC, Brookhaven National Laboratory (BNL) has utilized a risk-based approach for identifying, in a generic fashion, seismically risk-sensitive equipment. It is anticipated that the conclusions drawn therefrom and the methodology employed will, in part, reconcile some of the concerns dealing with the seismic qualification of equipment in operating plants. The approach taken augments an existing sensitivity analysis, based upon the WASH-1400 Reactor Safety Study (RSS), by accounting for seismicity and component fragility with the Kennedy model and by essentially including the requisite seismic data presented in the Zion Probabilistic Safety Study (ZPSS). Parametrically adjusting the seismic-related variables and ascertaining their effects on overall plant risk, core-melt probability, accident sequence probability, etc., allows one to identify those seismically risk-sensitive systems and equipment. This paper describes the approach taken and highlights the results obtained thus far for a hypothetical pressurized water reactor

  1. Phenomenological analyses and their application to the Defense Waste Processing Facility probabilistic safety analysis accident progression event tree. Revision 1

    International Nuclear Information System (INIS)

    Kalinich, D.A.; Thomas, J.K.; Gough, S.T.; Bailey, R.T.; Kearnaghan, D.P.

    1995-01-01

    In the Defense Waste Processing Facility (DWPF) Safety Analysis Reports (SARs) for the Savannah River Site (SRS), risk-based perspectives have been included per US Department of Energy (DOE) Order 5480.23. The NUREG-1150 Level 2/3 Probabilistic Risk Assessment (PRA) methodology was selected as the basis for calculating facility risk. The backbone of this methodology is the generation of an Accident Progression Event Tree (APET), which is solved using the EVNTRE computer code. To support the development of the DWPF APET, deterministic modeling of accident phenomena was necessary. From these analyses, (1) accident progressions were identified for inclusion into the APET; (2) branch point probabilities and any attendant parameters were quantified; and (3) the radionuclide releases to the environment from accidents were determined. The phenomena of interest for accident progressions included explosions, fires, a molten glass spill, and the response of the facility confinement system during such challenges. A variety of methodologies, from hand calculations to large system-model codes, were used in the evaluation of these phenomena

  2. A Probabilistic Analysis of Surface Water Flood Risk in London.

    Science.gov (United States)

    Jenkins, Katie; Hall, Jim; Glenis, Vassilis; Kilsby, Chris

    2017-10-30

    Flooding in urban areas during heavy rainfall, often characterized by short duration and high-intensity events, is known as "surface water flooding." Analyzing surface water flood risk is complex as it requires understanding of biophysical and human factors, such as the localized scale and nature of heavy precipitation events, characteristics of the urban area affected (including detailed topography and drainage networks), and the spatial distribution of economic and social vulnerability. Climate change is recognized as having the potential to enhance the intensity and frequency of heavy rainfall events. This study develops a methodology to link high spatial resolution probabilistic projections of hourly precipitation with detailed surface water flood depth maps and characterization of urban vulnerability to estimate surface water flood risk. It incorporates probabilistic information on the range of uncertainties in future precipitation in a changing climate. The method is applied to a case study of Greater London and highlights that both the frequency and spatial extent of surface water flood events are set to increase under future climate change. The expected annual damage from surface water flooding is estimated to be to be £171 million, £343 million, and £390 million/year under the baseline, 2030 high, and 2050 high climate change scenarios, respectively. © 2017 Society for Risk Analysis.

  3. Cutting costs through detailed probabilistic fire risk analysis

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Luiz; Huser, Asmund; Vianna, Savio [Det Norske Veritas PRINCIPIA, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    A new procedure for calculation of fire risks to offshore installations has been developed. The purposes of the procedure are to calculate the escalation and impairment frequencies to be applied in quantitative risk analyses, to optimize Passive Fire Protection (PFP) arrangement, and to optimize other fire mitigation means. The novelties of the procedure are that it uses state of the art Computational Fluid Dynamics (CFD) models to simulate fires and radiation, as well as the use of a probabilistic approach to decide the dimensioning fire loads. A CFD model of an actual platform was used to investigate the dynamic properties of a large set of jet fires, resulting in detailed knowledge of the important parameters that decide the severity of offshore fires. These results are applied to design the procedure. Potential increase in safety is further obtained for those conditions where simplified tools may have failed to predict abnormal heat loads due to geometrical effects. Using a field example it is indicated that the probabilistic approach can give significant reductions in PFP coverage with corresponding cost savings, still keeping the risk at acceptable level. (author)

  4. Probabilistic framework for product design optimization and risk management

    Science.gov (United States)

    Keski-Rahkonen, J. K.

    2018-05-01

    Probabilistic methods have gradually gained ground within engineering practices but currently it is still the industry standard to use deterministic safety margin approaches to dimensioning components and qualitative methods to manage product risks. These methods are suitable for baseline design work but quantitative risk management and product reliability optimization require more advanced predictive approaches. Ample research has been published on how to predict failure probabilities for mechanical components and furthermore to optimize reliability through life cycle cost analysis. This paper reviews the literature for existing methods and tries to harness their best features and simplify the process to be applicable in practical engineering work. Recommended process applies Monte Carlo method on top of load-resistance models to estimate failure probabilities. Furthermore, it adds on existing literature by introducing a practical framework to use probabilistic models in quantitative risk management and product life cycle costs optimization. The main focus is on mechanical failure modes due to the well-developed methods used to predict these types of failures. However, the same framework can be applied on any type of failure mode as long as predictive models can be developed.

  5. Current status and future expectation concerning probabilistic risk assessment of NPPs. 1. Features and issues of probabilistic risk assessment methodology

    International Nuclear Information System (INIS)

    Yamashita, Masahiro

    2012-01-01

    Probabilistic risk assessment (PRA) of Nuclear Power Plants (NPPs) could play an important role in assuring safety of NPPs. However PRA had not always effectively used, which was indicated in Japanese government's report on Fukushima Daiichi NPP accident. At the Risk Technical Committee (RTC) of Standards Committee of Atomic Energy Society of Japan, preparation of standards (implementing criteria) focusing on PRA methodology and investigation on basic philosophy for use of PRA had been in progress. Based on activities of RTC, a serial in three articles including this described current status and future expectation concerning probabilistic risk assessment of NPPs. This article introduced features and issues of PRA methodology related to the use of PRA. Features of PRA methodology could be shown as (1) systematic and comprehensive understanding of risk, (2) support of grading approach, (3) identification of effective safety upgrade measures and (4) quantitative understanding of effects of uncertainty. Issues of PRA methodology were (1) extension of PRA application area, (2) upgrade of PRA methodology, (3) quality assurance of PRA, (4) treatment of uncertainty and (5) quantitative evaluation criteria. (T. Tanaka)

  6. Applications of probabilistic risk analysis in nuclear criticality safety design

    International Nuclear Information System (INIS)

    Chang, J.K.

    1992-01-01

    Many documents have been prepared that try to define the scope of the criticality analysis and that suggest adding probabilistic risk analysis (PRA) to the deterministic safety analysis. The report of the US Department of Energy (DOE) AL 5481.1B suggested that an accident is credible if the occurrence probability is >1 x 10 -6 /yr. The draft DOE 5480 safety analysis report suggested that safety analyses should include the application of methods such as deterministic safety analysis, risk assessment, reliability engineering, common-cause failure analysis, human reliability analysis, and human factor safety analysis techniques. The US Nuclear Regulatory Commission (NRC) report NRC SG830.110 suggested that major safety analysis methods should include but not be limited to risk assessment, reliability engineering, and human factor safety analysis. All of these suggestions have recommended including PRA in the traditional criticality analysis

  7. Applications of nuclear safety probabilistic risk assessment to nuclear security for optimized risk mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, S.K.; Harvey, S.B. [Amec Foster Wheeler, Toronto, Ontario (Canada)

    2016-06-15

    Critical infrastructure assets such as nuclear power generating stations are potential targets for malevolent acts. Probabilistic methodologies can be applied to evaluate the real-time security risk based upon intelligence and threat levels. By employing this approach, the application of security forces and other protective measures can be optimized. Existing probabilistic safety analysis (PSA) methodologies and tools employed. in the nuclear industry can be adapted to security applications for this purpose. Existing PSA models can also be adapted and enhanced to consider total plant risk, due to nuclear safety risks as well as security risks. By creating a Probabilistic Security Model (PSM), safety and security practitioners can maximize the safety and security of the plant while minimizing the significant costs associated with security upgrades and security forces. (author)

  8. Architecture for Integrated Medical Model Dynamic Probabilistic Risk Assessment

    Science.gov (United States)

    Jaworske, D. A.; Myers, J. G.; Goodenow, D.; Young, M.; Arellano, J. D.

    2016-01-01

    Probabilistic Risk Assessment (PRA) is a modeling tool used to predict potential outcomes of a complex system based on a statistical understanding of many initiating events. Utilizing a Monte Carlo method, thousands of instances of the model are considered and outcomes are collected. PRA is considered static, utilizing probabilities alone to calculate outcomes. Dynamic Probabilistic Risk Assessment (dPRA) is an advanced concept where modeling predicts the outcomes of a complex system based not only on the probabilities of many initiating events, but also on a progression of dependencies brought about by progressing down a time line. Events are placed in a single time line, adding each event to a queue, as managed by a planner. Progression down the time line is guided by rules, as managed by a scheduler. The recently developed Integrated Medical Model (IMM) summarizes astronaut health as governed by the probabilities of medical events and mitigation strategies. Managing the software architecture process provides a systematic means of creating, documenting, and communicating a software design early in the development process. The software architecture process begins with establishing requirements and the design is then derived from the requirements.

  9. Seismic Probabilistic Risk Assessment (SPRA), approach and results

    International Nuclear Information System (INIS)

    Campbell, R.D.

    1995-01-01

    During the past 15 years there have been over 30 Seismic Probabilistic Risk Assessments (SPRAs) and Seismic Probabilistic Safety Assessments (SPSAs) conducted of Western Nuclear Power Plants, principally of US design. In this paper PRA and PSA are used interchangeably as the overall process is essentially the same. Some similar assessments have been done for reactors in Taiwan, Korea, Japan, Switzerland and Slovenia. These plants were also principally US supplied or built under US license. Since the restructuring of the governments in former Soviet Bloc countries, there has been grave concern regarding the safety of the reactors in these countries. To date there has been considerable activity in conducting partial seismic upgrades but the overall quantification of risk has not been pursued to the depth that it has in Western countries. This paper summarizes the methodology for Seismic PRA/PSA and compares results of two partially completed and two completed PRAs of soviet designed reactors to results from earlier PRAs on US Reactors. A WWER 440 and a WWER 1000 located in low seismic activity regions have completed PRAs and results show the seismic risk to be very low for both designs. For more active regions, partially completed PRAs of a WWER 440 and WWER 1000 located at the same site show the WWER 440 to have much greater seismic risk than the WWER 1000 plant. The seismic risk from the 1000 MW plant compares with the high end of seismic risk for earlier seismic PRAs in the US. Just as for most US plants, the seismic risk appears to be less than the risk from internal events if risk is measured is terms of mean core damage frequency. However, due to the lack of containment for the earlier WWER 440s, the risk to the public may be significantly greater due to the more probable scenario of an early release. The studies reported have not taken the accident sequences beyond the stage of core damage hence the public heath risk ratios are speculative. (author)

  10. Recent case studies and advancements in probabilistic risk assessment

    International Nuclear Information System (INIS)

    Garrick, B.J.

    1985-01-01

    During the period from 1977 to 1984, Pickard, Lowe and Garrick, Inc., had the lead in preparing several full scope probabilistic risk assessments for electric utilities. Five of those studies are discussed from the point of view of advancements and lessons learned. The objective and trend of these studies is toward utilization of the risk models by the plant owners as risk management tools. Advancements that have been made are in presentation ad documentation of the PRAs, generation of more understandable plant level information, and improvements in methodology to facilitate technology transfer. Specific areas of advancement are in the treatment of such issues as dependent failures, human interaction, and the uncertainty in the source term. Lessons learned cover a wide spectrum and include the importance of plant specific models for meaningful risk management, the role of external events in risk, the sensitivity of contributors to choice of risk index, and the very important finding that the public risk is extremely small. The future direction of PRA is to establish less dependence on experts for in-plant application. Computerizing the PRAs such that they can be accessed on line and interactively is the key

  11. Advanced Seismic Probabilistic Risk Assessment Demonstration Project Plan

    Energy Technology Data Exchange (ETDEWEB)

    Coleman, Justin [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-09-01

    Idaho National Laboratories (INL) has an ongoing research and development (R&D) project to remove excess conservatism from seismic probabilistic risk assessments (SPRA) calculations. These risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. This report presents a plan for improving our current traditional SPRA process using a seismic event recorded at a nuclear power plant site, with known outcomes, to improve the decision making process. SPRAs are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in general this approach has been conservative, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility).

  12. Probabilistic assessment of roadway departure risk in a curve

    Science.gov (United States)

    Rey, G.; Clair, D.; Fogli, M.; Bernardin, F.

    2011-10-01

    Roadway departure while cornering constitutes a major part of car accidents and casualties in France. Even though drastic policy about overspeeding contributes to reduce accidents, there obviously exist other factors. This article presents the construction of a probabilistic strategy for the roadway departure risk assessment. A specific vehicle dynamic model is developed in which some parameters are modelled by random variables. These parameters are deduced from a sensitivity analysis to ensure an efficient representation of the inherent uncertainties of the system. Then, structural reliability methods are employed to assess the roadway departure risk in function of the initial conditions measured at the entrance of the curve. This study is conducted within the French national road safety project SARI that aims to implement a warning systems alerting the driver in case of dangerous situation.

  13. Application of probabilistic risk assessment methodology to fusion

    International Nuclear Information System (INIS)

    Piet, S.J.

    1985-07-01

    Probabilistic Risk Assessment (PRA) tools are applied to general fusion issues in a systematic way, generally qualitatively. The potential value of PRA to general fusion safety and economic issues is discussed. Several important design insights result: possible fault interactions must be minimized (decouple fault conditions), inherently safe designs must include provision for passively handling loss of site power and loss of coolant conditions, the reliability of the vacuum boundary appears vital to maximizing facility availabilty and minimizing safety risk, and economic analyses appear to be incomplete without consideration of potential availability loss from forced outrages. A modification to PRA formalism is introduced, called the fault interaction matrix. The fault interaction matrix contains information concerning what initial fault condition could lead to other fault conditions and with what frequency. Thus, the fault interaction matrix represents a way to present and measure the degree to which a designer has decoupled possible fault conditions in his design

  14. Innovative real time simulation training and nuclear probabilistic risk assessment

    International Nuclear Information System (INIS)

    Reisinger, M.F.

    1991-01-01

    Operator errors have been an area of public concern for the safe operation of nuclear power plants since the TMI2 incident. Simply stated, nuclear plants are very complex systems and the public is skeptical of the operators' ability to comprehend and deal with the vast indications and complexities of potential nuclear power plant events. Prior to the TMI2 incident, operator errors and human factors were not included as contributing factors in the Probabilistic Risk Assessment (PRA) studies of nuclear power plant accidents. More recent efforts in nuclear risk assessment have addressed some of the human factors affecting safe nuclear plant operations. One study found four major factors having significant impact on operator effectiveness. This paper discusses human factor PRAs, new applications in simulation training and the specific potential benefits from simulation in promoting safer operation of future power plants as well as current operating power plants

  15. A perspective of PC-based probabilistic risk assessment

    International Nuclear Information System (INIS)

    Sattison, M.B.; Rasmuson, D.M.; Robinson, R.C.; Russell, K.D.; Van Siclen, V.S.

    1987-01-01

    Probabilistic risk assessment (PRA) information has been under-utilized in the past due to the large effort required to input the PRA data and the large expense of the computers needed to run PRA codes. The microcomputer-based Integrated Reliability and Risk Analysis System (IRRAS) and the System Analysis and Risk Assessment (SARA) System, under development at the Idaho National Engineering Laboratory, have greatly enhanced the ability of managers to use PRA techniques in their decision-making. IRRAS is a tool that allows an analyst to create, modify, update, and reanalyze a plant PRA to keep the risk assessment current with the plant's configuration and operation. The SARA system is used to perform sensitivity studies on the results of a PRA. This type of analysis can be used to evaluate proposed changes to a plant or its operation. The success of these two software projects demonstrate that risk information can be made readily available to those that need it. This is the first step in the development of a true risk management capability

  16. Probabilistic risk assessment methodology for risk management and regulatory applications

    International Nuclear Information System (INIS)

    See Meng Wong; Kelly, D.L.; Riley, J.E.

    1997-01-01

    This paper discusses the development and potential applications of PRA methodology for risk management and regulatory applications in the U.S. nuclear industry. The new PRA methodology centers on the development of This paper discusses the time-dependent configuration risk profile for evaluating the effectiveness of operational risk management programs at U.S. nuclear power plants. Configuration-risk profiles have been used as risk-information tools for (1) a better understanding of the impact of daily operational activities on plant safety, and (2) proactive planning of operational activities to manage risk. Trial applications of the methodology were undertaken to demonstrate that configuration-risk profiles can be developed routinely, and can be useful for various industry and regulatory applications. Lessons learned include a better understanding of the issues and characteristics of PRA models available to industry, and identifying the attributes and pitfalls in the developement of risk profiles

  17. Constellation Probabilistic Risk Assessment (PRA): Design Consideration for the Crew Exploration Vehicle

    Science.gov (United States)

    Prassinos, Peter G.; Stamatelatos, Michael G.; Young, Jonathan; Smith, Curtis

    2010-01-01

    Managed by NASA's Office of Safety and Mission Assurance, a pilot probabilistic risk analysis (PRA) of the NASA Crew Exploration Vehicle (CEV) was performed in early 2006. The PRA methods used follow the general guidance provided in the NASA PRA Procedures Guide for NASA Managers and Practitioners'. Phased-mission based event trees and fault trees are used to model a lunar sortie mission of the CEV - involving the following phases: launch of a cargo vessel and a crew vessel; rendezvous of these two vessels in low Earth orbit; transit to th$: moon; lunar surface activities; ascension &om the lunar surface; and return to Earth. The analysis is based upon assumptions, preliminary system diagrams, and failure data that may involve large uncertainties or may lack formal validation. Furthermore, some of the data used were based upon expert judgment or extrapolated from similar componentssystemsT. his paper includes a discussion of the system-level models and provides an overview of the analysis results used to identify insights into CEV risk drivers, and trade and sensitivity studies. Lastly, the PRA model was used to determine changes in risk as the system configurations or key parameters are modified.

  18. A probabilistic model for hydrokinetic turbine collision risks: exploring impacts on fish.

    Science.gov (United States)

    Hammar, Linus; Eggertsen, Linda; Andersson, Sandra; Ehnberg, Jimmy; Arvidsson, Rickard; Gullström, Martin; Molander, Sverker

    2015-01-01

    A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m), bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.

  19. A probabilistic model for hydrokinetic turbine collision risks: exploring impacts on fish.

    Directory of Open Access Journals (Sweden)

    Linus Hammar

    Full Text Available A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m, bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.

  20. Risk Management Technologies With Logic and Probabilistic Models

    CERN Document Server

    Solozhentsev, E D

    2012-01-01

    This book presents intellectual, innovative, information technologies (I3-technologies) based on logical and probabilistic (LP) risk models. The technologies presented here consider such models for structurally complex systems and processes with logical links and with random events in economics and technology.  The volume describes the following components of risk management technologies: LP-calculus; classes of LP-models of risk and efficiency; procedures for different classes; special software for different classes; examples of applications; methods for the estimation of probabilities of events based on expert information. Also described are a variety of training courses in these topics. The classes of risk models treated here are: LP-modeling, LP-classification, LP-efficiency, and LP-forecasting. Particular attention is paid to LP-models of risk of failure to resolve difficult economic and technical problems. Amongst the  discussed  procedures of I3-technologies  are the construction of  LP-models,...

  1. Advanced Test Reactor probabilistic risk assessment methodology and results summary

    International Nuclear Information System (INIS)

    Eide, S.A.; Atkinson, S.A.; Thatcher, T.A.

    1992-01-01

    The Advanced Test Reactor (ATR) probabilistic risk assessment (PRA) Level 1 report documents a comprehensive and state-of-the-art study to establish and reduce the risk associated with operation of the ATR, expressed as a mean frequency of fuel damage. The ATR Level 1 PRA effort is unique and outstanding because of its consistent and state-of-the-art treatment of all facets of the risk study, its comprehensive and cost-effective risk reduction effort while the risk baseline was being established, and its thorough and comprehensive documentation. The PRA includes many improvements to the state-of-the-art, including the following: establishment of a comprehensive generic data base for component failures, treatment of initiating event frequencies given significant plant improvements in recent years, performance of efficient identification and screening of fire and flood events using code-assisted vital area analysis, identification and treatment of significant seismic-fire-flood-wind interactions, and modeling of large loss-of-coolant accidents (LOCAs) and experiment loop ruptures leading to direct damage of the ATR core. 18 refs

  2. Exploring the uncertainties in cancer risk assessment using the integrated probabilistic risk assessment (IPRA) approach.

    Science.gov (United States)

    Slob, Wout; Bakker, Martine I; Biesebeek, Jan Dirk Te; Bokkers, Bas G H

    2014-08-01

    Current methods for cancer risk assessment result in single values, without any quantitative information on the uncertainties in these values. Therefore, single risk values could easily be overinterpreted. In this study, we discuss a full probabilistic cancer risk assessment approach in which all the generally recognized uncertainties in both exposure and hazard assessment are quantitatively characterized and probabilistically evaluated, resulting in a confidence interval for the final risk estimate. The methodology is applied to three example chemicals (aflatoxin, N-nitrosodimethylamine, and methyleugenol). These examples illustrate that the uncertainty in a cancer risk estimate may be huge, making single value estimates of cancer risk meaningless. Further, a risk based on linear extrapolation tends to be lower than the upper 95% confidence limit of a probabilistic risk estimate, and in that sense it is not conservative. Our conceptual analysis showed that there are two possible basic approaches for cancer risk assessment, depending on the interpretation of the dose-incidence data measured in animals. However, it remains unclear which of the two interpretations is the more adequate one, adding an additional uncertainty to the already huge confidence intervals for cancer risk estimates. © 2014 Society for Risk Analysis.

  3. Applications of the EBR-II Probabilistic Risk Assessment

    International Nuclear Information System (INIS)

    Roglans, J.: Ragland, W.A.; Hill, D.J.

    1993-01-01

    A Probabilistic Risk Assessment (PRA) of the Experimental Breeder Reactor 11 (EBR-11), a Department of Energy (DOE) Category A research reactor, has recently been completed at Argonne National Laboratory (ANL), and has been performed with close collaboration between PRA analysts and engineering and operations staff. A product of this Involvement of plant personnel has been a excellent acceptance of the PRA as a tool, which has already resulted In a variety of applications of the EBR-11 PRA. The EBR-11 has been used in support of plant hardware and procedure modifications and In new system design work. A new application in support of the refueling safety analysis will be completed in the near future

  4. OVERVIEW OF THE SAPHIRE PROBABILISTIC RISK ANALYSIS SOFTWARE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Curtis L.; Wood, Ted; Knudsen, James; Ma, Zhegang

    2016-10-01

    The Systems Analysis Programs for Hands-on Integrated Reliability Evaluations (SAPHIRE) is a software application developed for performing a complete probabilistic risk assessment (PRA) using a personal computer (PC) running the Microsoft Windows operating system. SAPHIRE Version 8 is funded by the U.S. Nuclear Regulatory Commission (NRC) and developed by the Idaho National Laboratory (INL). INL's primary role in this project is that of software developer and tester. However, INL also plays an important role in technology transfer by interfacing and supporting SAPHIRE users, who constitute a wide range of PRA practitioners from the NRC, national laboratories, the private sector, and foreign countries. In this paper, we provide an overview of the current technical capabilities found in SAPHIRE Version 8, including the user interface and enhanced solving algorithms.

  5. International Space Station End-of-Life Probabilistic Risk Assessment

    Science.gov (United States)

    Duncan, Gary W.

    2014-01-01

    The International Space Station (ISS) end-of-life (EOL) cycle is currently scheduled for 2020, although there are ongoing efforts to extend ISS life cycle through 2028. The EOL for the ISS will require deorbiting the ISS. This will be the largest manmade object ever to be de-orbited therefore safely deorbiting the station will be a very complex problem. This process is being planned by NASA and its international partners. Numerous factors will need to be considered to accomplish this such as target corridors, orbits, altitude, drag, maneuvering capabilities etc. The ISS EOL Probabilistic Risk Assessment (PRA) will play a part in this process by estimating the reliability of the hardware supplying the maneuvering capabilities. The PRA will model the probability of failure of the systems supplying and controlling the thrust needed to aid in the de-orbit maneuvering.

  6. Use of probabilistic risk assessment in fuel cycle facilities

    International Nuclear Information System (INIS)

    Gonzalez, Felix; Gonzalez, Michelle; Wagner, Brian

    2013-01-01

    As expressed in its Policy Statement on the Use of Probabilistic Risk Assessment (PRA) Methods in Nuclear Regulatory Activities, the U.S Nuclear Regulatory Commission has been working for decades to increase the use of PRA technology in its regulatory activities. Since the policy statement was issued in 1995, PRA has become a core component of the nuclear power plant (NPP) licensing and oversight processes. In the last several years, interest has increased in PRA technologies and their possible application to other areas including, but not limited to, spent fuel handling, fuel cycle facilities, reprocessing facilities, and advanced reactors. This paper describes the application of PRA technology currently used in NPPs and its application in other areas such as fuel cycle facilities and advanced reactors. It describes major challenges that are being faced in the application of PRA into new technical areas and possible ways to resolve them. (authors)

  7. The probabilistic approach in the licensing process and the development of probabilistic risk assessment methodology in Japan

    International Nuclear Information System (INIS)

    Togo, Y.; Sato, K.

    1981-01-01

    The probabilistic approach has long seemed to be one of the most comprehensive methods for evaluating the safety of nuclear plants. So far, most of the guidelines and criteria for licensing are based on the deterministic concept. However, there have been a few examples to which the probabilistic approach was directly applied, such as the evaluation of aircraft crashes and turbine missiles. One may find other examples of such applications. However, a much more important role is now to be played by this concept, in implementing the 52 recommendations from the lessons learned from the TMI accident. To develop the probabilistic risk assessment methodology most relevant to Japanese situations, a five-year programme plan has been adopted and is to be conducted by the Japan Atomic Research Institute from fiscal 1980. Various problems have been identified and are to be solved through this programme plan. The current status of developments is described together with activities outside the government programme. (author)

  8. Spatial interactions database development for effective probabilistic risk assessment

    International Nuclear Information System (INIS)

    Liming, J. K.; Dunn, R. F.

    2008-01-01

    In preparation for a subsequent probabilistic risk assessment (PRA) fire risk analysis update, the STP Nuclear Operating Company (STPNOC) is updating its spatial interactions database (SID). This work is being performed to support updating the spatial interactions analysis (SIA) initially performed for the original South Texas Project Electric Generating Station (STPEGS) probabilistic safely assessment (PSA) and updated in the STPEGS Level 2 PSA and IPE Report. S/A is a large-scope screening analysis performed for nuclear power plant PRA that serves as a prerequisite basis for more detailed location-dependent, hazard-spec analyses in the PRA, such as fire risk analysis, flooding risk analysis, etc. SIA is required to support the 'completeness' argument for the PRA scope. The objectives of the current SID development effort are to update the spatial interactions analysis data, to the greatest degree practical, to be consistent with the following: the as-built plant as of December 31, 2007 the in-effect STPNOC STPEGS Units 1 and 2 PRA the current technology and intent of NUREG/CR-6850 guidance for lire risk analysis database support the requirements for PRA SIA, including fire and flooding risk analysis, established by NRC Regulatory Guide 1.200 and the ASME PRA Standard (ASME RA-S-2002 updated through ASME RA-Sc-2007,) This paper presents the approach and methodology for state-of-the-art SID development and applications, including an overview of the SIA process for nuclear power plant PRA. The paper shows how current relational database technology and existing, conventional station information sources can be employed to collect, process, and analyze spatial interactions data for the plant in an effective and efficient manner to meet the often challenging requirements of industry guidelines and standards such as NUREG/CR-6850, NRC Regulatory Guide 1.200, and ASME RA-S-2002 (updated through ASME RA-Sc 2007). This paper includes tables and figures illustrating how SIA

  9. Probabilistic Risk Assessment for Astronaut Post Flight Bone Fracture

    Science.gov (United States)

    Lewandowski, Beth; Myers, Jerry; Licata, Angelo

    2015-01-01

    Introduction: Space flight potentially reduces the loading that bone can resist before fracture. This reduction in bone integrity may result from a combination of factors, the most common reported as reduction in astronaut BMD. Although evaluating the condition of bones continues to be a critical aspect of understanding space flight fracture risk, defining the loading regime, whether on earth, in microgravity, or in reduced gravity on a planetary surface, remains a significant component of estimating the fracture risks to astronauts. This presentation summarizes the concepts, development, and application of NASA's Bone Fracture Risk Module (BFxRM) to understanding pre-, post, and in mission astronaut bone fracture risk. The overview includes an assessment of contributing factors utilized in the BFxRM and illustrates how new information, such as biomechanics of space suit design or better understanding of post flight activities may influence astronaut fracture risk. Opportunities for the bone mineral research community to contribute to future model development are also discussed. Methods: To investigate the conditions in which spaceflight induced changes to bone plays a critical role in post-flight fracture probability, we implement a modified version of the NASA Bone Fracture Risk Model (BFxRM). Modifications included incorporation of variations in physiological characteristics, post-flight recovery rate, and variations in lateral fall conditions within the probabilistic simulation parameter space. The modeled fracture probability estimates for different loading scenarios at preflight and at 0 and 365 days post-flight time periods are compared. Results: For simple lateral side falls, mean post-flight fracture probability is elevated over mean preflight fracture probability due to spaceflight induced BMD loss and is not fully recovered at 365 days post-flight. In the case of more energetic falls, such as from elevated heights or with the addition of lateral movement

  10. Estimating Coextinction Risks from Epidemic Tree Death: Affiliate Lichen Communities among Diseased Host Tree Populations of Fraxinus excelsior

    Science.gov (United States)

    Jönsson, Mari T.; Thor, Göran

    2012-01-01

    At least 10% of the world’s tree species are threatened with extinction and pathogens are increasingly implicated in tree threats. Coextinction and threats to affiliates as a consequence of the loss or decline of their host trees is a poorly understood phenomenon. Ash dieback is an emerging infectious disease causing severe dieback of common ash Fraxinus excelsior throughout Europe. We utilized available empirical data on affiliate epiphytic lichen diversity (174 species and 17,800 observations) among 20 ash dieback infected host tree populations of F. excelsior on the island Gotland in the Baltic Sea, Sweden. From this, we used structured scenario projections scaled with empirical data of ash dieback disease to generate probabilistic models for estimating local and regional lichen coextinction risks. Average coextinction probabilities (Ā) were 0.38 (95% CI ±0.09) for lichens occurring on F. excelsior and 0.14 (95% CI ±0.03) when considering lichen persistence on all tree species. Ā was strongly linked to local disease incidence levels and generally increasing with lichen host specificity to F. excelsior and decreasing population size. Coextinctions reduced affiliate community viability, with significant local reductions in species richness and shifts in lichen species composition. Affiliates were projected to become locally extirpated before their hosts, illuminating the need to also consider host tree declines. Traditionally managed open wooded meadows had the highest incidence of ash dieback disease and significantly higher proportions of affiliate species projected to go extinct, compared with unmanaged closed forests and semi-open grazed sites. Most cothreatened species were not previously red-listed, which suggest that tree epidemics cause many unforeseen threats to species. Our analysis shows that epidemic tree deaths represent an insidious, mostly overlooked, threat to sessile affiliate communities in forested environments. Current conservation and

  11. Probabilistic risk assessment of earthquakes at the Rocky Flats Plant and subsequent upgrade to reduce risk

    International Nuclear Information System (INIS)

    Day, S.A.

    1989-01-01

    An analysis to determine the risk associated with earthquakes at the Rocky Flats Plant was performed. Seismic analyses and structural evaluations were used to postulate building and equipment damage and radiological releases to the environment from various magnitudes of earthquakes. Dispersion modeling and dose assessment to the public were then calculated. The frequency of occurrence of various magnitudes of earthquakes were determined from the Department of Energy natural Phenomena Hazards Modeling Project. Risk to the public was probabilistically assessed for each magnitude of earthquake and for overall seismic risk. Based on the results of this Probabilistic Risk Assessment and a cost/benefit analysis, seismic upgrades are being implemented for several plutonium-handling facilities for the purpose of risk reduction

  12. Space shuttle main propulsion pressurization system probabilistic risk assessment

    International Nuclear Information System (INIS)

    Plastiras, J.K.

    1989-01-01

    This paper reports that, in post-Challenger discussions with Congressional Committees and the National Research Council Risk Management Oversight Panel, criticism was levied against NASA because of the inability to prioritize the 1300+ single point failures. In the absence of a ranking it was difficult to determine where special effort was needed in failure evaluation, in design improvement, in management review of problems, and in flight readiness reviews. The belief was that the management system was overwhelmed by the quantity of critical hardware items that were on the Critical Items List (CIL) and that insufficient attention was paid to the items that required it. Congressional staff members from Congressman Markey's committee who have oversight responsibilities in the nuclear industry, and specifically over the nuclear power supplies for NASA's Galileo and Ulysses missions, felt very strongly that the addition of Probabilistic Risk Assessment (PRA) to the existing Failure Mode Effects Analysis/Hazard Analysis (FMEA/HA) methods was exceedingly important. Specifically, the Markey committee recognized that the inductive, qualitative component-oriented FMEA could be supplemented by the deductive, quantitative systems-oriented PRA. Furthermore, they felt that the PRA approach had matured to the extent that it could be used to assess risk, even with limited shuttle-specific failure data. NASA responded with arguments that the FMEA/HA had illuminated all significant failure modes satisfactorily and that no failure rate data base was available to support the PRA approach

  13. Biomechanical rupture risk assessment of abdominal aortic aneurysms based on a novel probabilistic rupture risk index.

    Science.gov (United States)

    Polzer, Stanislav; Gasser, T Christian

    2015-12-06

    A rupture risk assessment is critical to the clinical treatment of abdominal aortic aneurysm (AAA) patients. The biomechanical AAA rupture risk assessment quantitatively integrates many known AAA rupture risk factors but the variability of risk predictions due to model input uncertainties remains a challenging limitation. This study derives a probabilistic rupture risk index (PRRI). Specifically, the uncertainties in AAA wall thickness and wall strength were considered, and wall stress was predicted with a state-of-the-art deterministic biomechanical model. The discriminative power of PRRI was tested in a diameter-matched cohort of ruptured (n = 7) and intact (n = 7) AAAs and compared to alternative risk assessment methods. Computed PRRI at 1.5 mean arterial pressure was significantly (p = 0.041) higher in ruptured AAAs (20.21(s.d. 14.15%)) than in intact AAAs (3.71(s.d. 5.77)%). PRRI showed a high sensitivity and specificity (discriminative power of 0.837) to discriminate between ruptured and intact AAA cases. The underlying statistical representation of stochastic data of wall thickness, wall strength and peak wall stress had only negligible effects on PRRI computations. Uncertainties in AAA wall stress predictions, the wide range of reported wall strength and the stochastic nature of failure motivate a probabilistic rupture risk assessment. Advanced AAA biomechanical modelling paired with a probabilistic rupture index definition as known from engineering risk assessment seems to be superior to a purely deterministic approach. © 2015 The Author(s).

  14. Framework for probabilistic flood risk assessment in an Alpine region

    Science.gov (United States)

    Schneeberger, Klaus; Huttenlau, Matthias; Steinberger, Thomas; Achleitner, Stefan; Stötter, Johann

    2014-05-01

    Flooding is among the natural hazards that regularly cause significant losses to property and human lives. The assessment of flood risk delivers crucial information for all participants involved in flood risk management and especially for local authorities and insurance companies in order to estimate the possible flood losses. Therefore a framework for assessing flood risk has been developed and is introduced with the presented contribution. Flood risk is thereby defined as combination of the probability of flood events and of potential flood damages. The probability of occurrence is described through the spatial and temporal characterisation of flood. The potential flood damages are determined in the course of vulnerability assessment, whereas, the exposure and the vulnerability of the elements at risks are considered. Direct costs caused by flooding with the focus on residential building are analysed. The innovative part of this contribution lies on the development of a framework which takes the probability of flood events and their spatio-temporal characteristic into account. Usually the probability of flooding will be determined by means of recurrence intervals for an entire catchment without any spatial variation. This may lead to a misinterpretation of the flood risk. Within the presented framework the probabilistic flood risk assessment is based on analysis of a large number of spatial correlated flood events. Since the number of historic flood events is relatively small additional events have to be generated synthetically. This temporal extrapolation is realised by means of the method proposed by Heffernan and Tawn (2004). It is used to generate a large number of possible spatial correlated flood events within a larger catchment. The approach is based on the modelling of multivariate extremes considering the spatial dependence structure of flood events. The input for this approach are time series derived from river gauging stations. In a next step the

  15. Probabilistic seismic vulnerability and risk assessment of stone masonry structures

    Science.gov (United States)

    Abo El Ezz, Ahmad

    Earthquakes represent major natural hazards that regularly impact the built environment in seismic prone areas worldwide and cause considerable social and economic losses. The high losses incurred following the past destructive earthquakes promoted the need for assessment of the seismic vulnerability and risk of the existing buildings. Many historic buildings in the old urban centers in Eastern Canada such as Old Quebec City are built of stone masonry and represent un-measurable architectural and cultural heritage. These buildings were built to resist gravity loads only and generally offer poor resistance to lateral seismic loads. Seismic vulnerability assessment of stone masonry buildings is therefore the first necessary step in developing seismic retrofitting and pre-disaster mitigation plans. The objective of this study is to develop a set of probability-based analytical tools for efficient seismic vulnerability and uncertainty analysis of stone masonry buildings. A simplified probabilistic analytical methodology for vulnerability modelling of stone masonry building with systematic treatment of uncertainties throughout the modelling process is developed in the first part of this study. Building capacity curves are developed using a simplified mechanical model. A displacement based procedure is used to develop damage state fragility functions in terms of spectral displacement response based on drift thresholds of stone masonry walls. A simplified probabilistic seismic demand analysis is proposed to capture the combined uncertainty in capacity and demand on fragility functions. In the second part, a robust analytical procedure for the development of seismic hazard compatible fragility and vulnerability functions is proposed. The results are given by sets of seismic hazard compatible vulnerability functions in terms of structure-independent intensity measure (e.g. spectral acceleration) that can be used for seismic risk analysis. The procedure is very efficient for

  16. Level-1 seismic probabilistic risk assessment for a PWR plant

    International Nuclear Information System (INIS)

    Kondo, Keisuke; Nishio, Masahide; Fujimoto, Haruo; Ichitsuka, Akihiro

    2014-01-01

    In Japan, revised Seismic Design Guidelines for the domestic light water reactors was published on September 19, 2006. These new guidelines have introduced the purpose to confirm that residual risk resulting from earthquake that exceeds the design limit seismic ground motion (Ss) is sufficiently small, based on the probabilistic risk assessment (PRA) method, in addition to conventional deterministic design base methodology. In response to this situation, JNES had been working to improve seismic PRA (SPRA) models for individual domestic light water reactors. In case of PWR in Japan, total of 24 plants were grouped into 11 categories to develop individual SPRA model. The new regulatory rules against the Fukushima dai-ichi nuclear power plants' severe accidents occurred on March 11, 2011, are going to be enforced in July 2013 and utilities are necessary to implement additional safety measures to avoid and mitigate severe accident occurrence due to external events such as earthquake and tsunami, by referring to the results of severe accident study including SPRA. In this paper a SPRA model development for a domestic 3-loop PWR plant as part of the above-mentioned 11 categories is described. We paid special attention to how to categorize initiating events that are specific to seismic phenomena and how to confirm the effect of the simultaneous failure probability calculation model for the multiple components on the result of core damage frequency evaluation. Simultaneous failure probability for multiple components has been evaluated by power multiplier method. Then tentative level-1 seismic probabilistic risk assessment (SPRA) has been performed by the developed SPSA model with seismic hazard and fragility data. The base case was evaluated under the condition with calculated fragility data and conventional power multiplier. The difference in CDF between the case of conventional power multiplier and that of power multiplier=1 (complete dependence) was estimated to be

  17. Assessing Probabilistic Risk Assessment Approaches for Insect Biological Control Introductions.

    Science.gov (United States)

    Kaufman, Leyla V; Wright, Mark G

    2017-07-07

    The introduction of biological control agents to new environments requires host specificity tests to estimate potential non-target impacts of a prospective agent. Currently, the approach is conservative, and is based on physiological host ranges determined under captive rearing conditions, without consideration for ecological factors that may influence realized host range. We use historical data and current field data from introduced parasitoids that attack an endemic Lepidoptera species in Hawaii to validate a probabilistic risk assessment (PRA) procedure for non-target impacts. We use data on known host range and habitat use in the place of origin of the parasitoids to determine whether contemporary levels of non-target parasitism could have been predicted using PRA. Our results show that reasonable predictions of potential non-target impacts may be made if comprehensive data are available from places of origin of biological control agents, but scant data produce poor predictions. Using apparent mortality data rather than marginal attack rate estimates in PRA resulted in over-estimates of predicted non-target impact. Incorporating ecological data into PRA models improved the predictive power of the risk assessments.

  18. Assessing Probabilistic Risk Assessment Approaches for Insect Biological Control Introductions

    Directory of Open Access Journals (Sweden)

    Leyla V. Kaufman

    2017-07-01

    Full Text Available The introduction of biological control agents to new environments requires host specificity tests to estimate potential non-target impacts of a prospective agent. Currently, the approach is conservative, and is based on physiological host ranges determined under captive rearing conditions, without consideration for ecological factors that may influence realized host range. We use historical data and current field data from introduced parasitoids that attack an endemic Lepidoptera species in Hawaii to validate a probabilistic risk assessment (PRA procedure for non-target impacts. We use data on known host range and habitat use in the place of origin of the parasitoids to determine whether contemporary levels of non-target parasitism could have been predicted using PRA. Our results show that reasonable predictions of potential non-target impacts may be made if comprehensive data are available from places of origin of biological control agents, but scant data produce poor predictions. Using apparent mortality data rather than marginal attack rate estimates in PRA resulted in over-estimates of predicted non-target impact. Incorporating ecological data into PRA models improved the predictive power of the risk assessments.

  19. Results of the AP600 advanced plant probabilistic risk assessment

    International Nuclear Information System (INIS)

    Bueter, T.; Sancaktar, S.; Freeland, J.

    1997-01-01

    The AP600 Probabilistic Risk Assessment (PRA) includes detailed models of the plant systems, including the containment and containment systems that would be used to mitigate the consequences of a severe accident. The AP600 PRA includes a level 1 analysis (core damage frequency), and a level 2 analysis (environmental consequences), an assessment of the plant vulnerability to accidents caused by fire or floods, and a seismic margins analysis. Numerous sensitivities are included in the AP600 PRA including one that assumes no credit for non-safety plant systems. The core damage frequency for the AP600 of 1.7E-07/year is small compared with other PRAs performed in the nuclear industry. The AP600 large release frequency of 1.8E-08/year is also small and shows the ability of the containment systems to prevent a large release should a severe accident occur. Analyses of potential consequences to the environment from a severe accident show that a release would be small, and that containment still provides significant protection 24 hours after an assumed accident. Sensitivity analyses show that plant risk (as measured by core damage frequency and large release frequency) is not sensitive to the reliability of operator actions. 6 refs., 1 fig., 1 tab

  20. A review of NRC staff uses of probabilistic risk assessment

    Energy Technology Data Exchange (ETDEWEB)

    1994-03-01

    The NRC staff uses probabilistic risk assessment (PRA) and risk management as important elements its licensing and regulatory processes. In October 1991, the NRC`s Executive Director for Operations established the PRA Working Group to address concerns identified by the Advisory Committee on Reactor Safeguards with respect to unevenness and inconsistency in the staff`s current uses of PRA. After surveying current staff uses of PRA and identifying needed improvements, the Working Group defined a set of basic principles for staff PRA use and identified three areas for improvements: guidance development, training enhancements, and PRA methods development. For each area of improvement, the Working Group took certain actions and recommended additional work. The Working Group recommended integrating its work with other recent PRA-related activities the staff completed and improving staff interactions with PRA users in the nuclear industry. The Working Group took two key actions by developing general guidance for two uses of PRA within the NRC (that is, screening or prioritizing reactor safety issues and analyzing such issues in detail) and developing guidance on basic terms and methods important to the staff`s uses of PRA.

  1. The EBR-II Probabilistic Risk Assessment: Results and insights

    International Nuclear Information System (INIS)

    Hill, D.J.; Ragland, W.A.; Roglans, J.

    1993-01-01

    This paper summarizes the results from the recently completed EBR-II Probabilistic Risk Assessment (PRA) and provides an analysis of the source of risk of the operation of EBR-II from both internal and external initiating events. The EBR-II PRA explicitly accounts for the role of reactivity feedbacks in reducing fuel damage. The results show that the expected core damage frequency from internal initiating events at EBR-II is very low, 1. 6 10 -6 yr -1 , even with a wide definition of core damage (essentially that of exceeding Technical Specification limits). The probability of damage, primarily due to liquid metal fires, from externally initiated events (excluding earthquake) is 3.6 10 -6 yr -1 . overall these results are considerably better than results for other research reactors and the nuclear industry in general and stem from three main sources: low likelihood of loss of coolant due to low system pressure and top entry double, vessels; low likelihood of loss of decay heat removal due to reliance on passive means; and low likelihood of power/flow mismatch due to both passive feedbacks and reliability of rod scram capability

  2. A review of NRC staff uses of probabilistic risk assessment

    International Nuclear Information System (INIS)

    1994-03-01

    The NRC staff uses probabilistic risk assessment (PRA) and risk management as important elements its licensing and regulatory processes. In October 1991, the NRC's Executive Director for Operations established the PRA Working Group to address concerns identified by the Advisory Committee on Reactor Safeguards with respect to unevenness and inconsistency in the staff's current uses of PRA. After surveying current staff uses of PRA and identifying needed improvements, the Working Group defined a set of basic principles for staff PRA use and identified three areas for improvements: guidance development, training enhancements, and PRA methods development. For each area of improvement, the Working Group took certain actions and recommended additional work. The Working Group recommended integrating its work with other recent PRA-related activities the staff completed and improving staff interactions with PRA users in the nuclear industry. The Working Group took two key actions by developing general guidance for two uses of PRA within the NRC (that is, screening or prioritizing reactor safety issues and analyzing such issues in detail) and developing guidance on basic terms and methods important to the staff's uses of PRA

  3. PROBABILISTIC RISK ANALYSIS OF REMEDIATION EFFORTS IN NAPL SITES

    Science.gov (United States)

    Fernandez-Garcia, D.; de Vries, L.; Pool, M.; Sapriza, G.; Sanchez-Vila, X.; Bolster, D.; Tartakovsky, D. M.

    2009-12-01

    The release of non-aqueous phase liquids (NAPLs) such as petroleum hydrocarbons and chlorinated solvents in the subsurface is a severe source of groundwater and vapor contamination. Because these liquids are essentially immiscible due to low solubility, these contaminants get slowly dissolved in groundwater and/or volatilized in the vadoze zone threatening the environment and public health over a long period. Many remediation technologies and strategies have been developed in the last decades for restoring the water quality properties of these contaminated sites. The failure of an on-site treatment technology application is often due to the unnoticed presence of dissolved NAPL entrapped in low permeability areas (heterogeneity) and/or the remaining of substantial amounts of pure phase after remediation efforts. Full understanding of the impact of remediation efforts is complicated due to the role of many interlink physical and biochemical processes taking place through several potential pathways of exposure to multiple receptors in a highly unknown heterogeneous environment. Due to these difficulties, the design of remediation strategies and definition of remediation endpoints have been traditionally determined without quantifying the risk associated with the failure of such efforts. We conduct a probabilistic risk assessment of the likelihood of success of an on-site NAPL treatment technology that easily integrates all aspects of the problem (causes, pathways, and receptors). Thus, the methodology allows combining the probability of failure of a remediation effort due to multiple causes, each one associated to several pathways and receptors.

  4. International status of application of probabilistic risk analysis

    International Nuclear Information System (INIS)

    Cullingford, M.C.

    1984-01-01

    Probabilistic Risk Assessment (PRA) having been practised for about ten years and with more than twenty studies completed has reached a level of maturity such that the insights and other products derived from specific studies may be assessed. The first full-scale PRA studies were designed to develop the methodology and assess the overall risk from nuclear power. At present PRA is performed mostly for individual plants to identify core damage accident sequences and significant contributors to such sequences. More than 25 countries are utilizing insights from PRA, some from full-scale PRA studies and other countries by performing reliability analyses on safety systems identified as important contributors to one or more core melt sequences. Many Member States of the IAEA fall into one of three groups: those having (a) a large, (b) a medium number of reactor-years of operating experience and (c) those countries in the planning or feasibility study stages of a nuclear power programme. Of the many potential uses of PRA the decision areas of safety improvement by backfitting, development of operating procedures and as the basis of standards are felt to be important by countries of all three groups. The use of PRA in showing compliance with safety goals and for plant availability studies is held to be important only by those countries which have operating experience. The evolution of the PRA methodology has led to increased attention to quantification of uncertainties both in the probabilities and consequences. Although many products from performing a PRA do not rely upon overall risk numbers, increasing emphasis is being placed on the interpretation of uncertainties in risk numbers for use in decisions. International co-operation through exchange of information regarding experience with PRA methodology and its application to nuclear safety decisions will greatly enhance the widespread use of PRA. (author)

  5. Development of probabilistic risk assessment methodology against extreme snow for sodium-cooled fast reactor

    Energy Technology Data Exchange (ETDEWEB)

    Yamano, Hidemasa, E-mail: yamano.hidemasa@jaea.go.jp; Nishino, Hiroyuki; Kurisaka, Kenichi

    2016-11-15

    Highlights: • Snow PRA methodology was developed. • Snow hazard category was defined as the combination of daily snowfall depth (speed) and snowfall duration. • Failure probability models of snow removal action, manual operation of the air cooler dampers and the access route were developed. • Snow PRA showed less than 10{sup −6}/reactor-year of core damage frequency. - Abstract: This paper describes snow probabilistic risk assessment (PRA) methodology development through external hazard and event sequence evaluations mainly in terms of decay heat removal (DHR) function of a sodium-cooled fast reactor (SFR). Using recent 50-year weather data at a typical Japanese SFR site, snow hazard categories were set for the combination of daily snowfall depth (snowfall speed) and snowfall duration which can be calculated by dividing the snow depth by the snowfall speed. For each snow hazard category, the event sequence was evaluated by event trees which consist of several headings representing the loss of DHR. Snow removal action and manual operation of the air cooler dampers were introduced into the event trees as accident managements. Access route failure probability model was also developed for the quantification of the event tree. In this paper, the snow PRA showed less than 10{sup −6}/reactor-year of core damage frequency. The dominant snow hazard category was the combination of 1–2 m/day of snowfall speed and 0.5–0.75 day of snowfall duration. Importance and sensitivity analyses indicated a high risk contribution of the securing of the access routes.

  6. Development of probabilistic risk assessment methodology against extreme snow for sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    Yamano, Hidemasa; Nishino, Hiroyuki; Kurisaka, Kenichi

    2016-01-01

    Highlights: • Snow PRA methodology was developed. • Snow hazard category was defined as the combination of daily snowfall depth (speed) and snowfall duration. • Failure probability models of snow removal action, manual operation of the air cooler dampers and the access route were developed. • Snow PRA showed less than 10"−"6/reactor-year of core damage frequency. - Abstract: This paper describes snow probabilistic risk assessment (PRA) methodology development through external hazard and event sequence evaluations mainly in terms of decay heat removal (DHR) function of a sodium-cooled fast reactor (SFR). Using recent 50-year weather data at a typical Japanese SFR site, snow hazard categories were set for the combination of daily snowfall depth (snowfall speed) and snowfall duration which can be calculated by dividing the snow depth by the snowfall speed. For each snow hazard category, the event sequence was evaluated by event trees which consist of several headings representing the loss of DHR. Snow removal action and manual operation of the air cooler dampers were introduced into the event trees as accident managements. Access route failure probability model was also developed for the quantification of the event tree. In this paper, the snow PRA showed less than 10"−"6/reactor-year of core damage frequency. The dominant snow hazard category was the combination of 1–2 m/day of snowfall speed and 0.5–0.75 day of snowfall duration. Importance and sensitivity analyses indicated a high risk contribution of the securing of the access routes.

  7. Review of seismic probabilistic risk assessment and the use of sensitivity analysis

    International Nuclear Information System (INIS)

    Shiu, K.K.; Reed, J.W.; McCann, M.W. Jr.

    1985-01-01

    This paper presents results of sensitivity reviews performed to address a range of questions which arise in the context of seismic probabilistic risk assessment (PRA). In a seismic PRA, sensitivity evaluations can be divided into three areas: hazard, fragility, and system modeling. As a part of the review of standard boiling water reactor seismic PRA which was performed by General Electric (GE), a reassessment of the plant damage states frequency and a detailed sensitivity analysis were conducted at Brookhaven National Laboratory. The rationale for such an undertaking is that in this case: (1) the standard plant may be sited anywhere in the eastern US (i.e., in regions with safety shutdown earthquake (SSE) values equal to or less than 0.3g peak ground acceleration), (2) it may have equipment whose fragility values could vary over a wide range; and (3) there are variations in system designs outside the original defined scope. Seismic event trees and fault trees were developed to model the different system and plant accident sequences. Hazard curves which represent various sites on the east coast were obtained; alternate structure and equipment fragility data were postulated. Various combinations of hazard and fragility data were analyzed. In addition, system modeling was perturbed to examine the impact upon the final results. Orders of magnitude variation were observed in the plant damage state frequency among the different cases. 7 references, 3 figures, 2 tables

  8. Relative risk of probabilistic category learning deficits in patients with schizophrenia and their siblings

    Science.gov (United States)

    Weickert, Thomas W.; Goldberg, Terry E.; Egan, Michael F.; Apud, Jose A.; Meeter, Martijn; Myers, Catherine E.; Gluck, Mark A; Weinberger, Daniel R.

    2010-01-01

    Background While patients with schizophrenia display an overall probabilistic category learning performance deficit, the extent to which this deficit occurs in unaffected siblings of patients with schizophrenia is unknown. There are also discrepant findings regarding probabilistic category learning acquisition rate and performance in patients with schizophrenia. Methods A probabilistic category learning test was administered to 108 patients with schizophrenia, 82 unaffected siblings, and 121 healthy participants. Results Patients with schizophrenia displayed significant differences from their unaffected siblings and healthy participants with respect to probabilistic category learning acquisition rates. Although siblings on the whole failed to differ from healthy participants on strategy and quantitative indices of overall performance and learning acquisition, application of a revised learning criterion enabling classification into good and poor learners based on individual learning curves revealed significant differences between percentages of sibling and healthy poor learners: healthy (13.2%), siblings (34.1%), patients (48.1%), yielding a moderate relative risk. Conclusions These results clarify previous discrepant findings pertaining to probabilistic category learning acquisition rate in schizophrenia and provide the first evidence for the relative risk of probabilistic category learning abnormalities in unaffected siblings of patients with schizophrenia, supporting genetic underpinnings of probabilistic category learning deficits in schizophrenia. These findings also raise questions regarding the contribution of antipsychotic medication to the probabilistic category learning deficit in schizophrenia. The distinction between good and poor learning may be used to inform genetic studies designed to detect schizophrenia risk alleles. PMID:20172502

  9. A comparison of integrated safety analysis and probabilistic risk assessment

    International Nuclear Information System (INIS)

    Damon, Dennis R.; Mattern, Kevin S.

    2013-01-01

    The U.S. Nuclear Regulatory Commission conducted a comparison of two standard tools for risk informing the regulatory process, namely, the Probabilistic Risk Assessment (PRA) and the Integrated Safety Analysis (ISA). PRA is a calculation of risk metrics, such as Large Early Release Frequency (LERF), and has been used to assess the safety of all commercial power reactors. ISA is an analysis required for fuel cycle facilities (FCFs) licensed to possess potentially critical quantities of special nuclear material. A PRA is usually more detailed and uses more refined models and data than an ISA, in order to obtain reasonable quantitative estimates of risk. PRA is considered fully quantitative, while most ISAs are typically only partially quantitative. The extension of PRA methodology to augment or supplant ISAs in FCFs has long been considered. However, fuel cycle facilities have a wide variety of possible accident consequences, rather than a few surrogates like LERF or core damage as used for reactors. It has been noted that a fuel cycle PRA could be used to better focus attention on the most risk-significant structures, systems, components, and operator actions. ISA and PRA both identify accident sequences; however, their treatment is quite different. ISA's identify accidents that lead to high or intermediate consequences, as defined in 10 Code of Federal Regulations (CFR) 70, and develop a set of Items Relied on For Safety (IROFS) to assure adherence to performance criteria. PRAs identify potential accident scenarios and estimate their frequency and consequences to obtain risk metrics. It is acceptable for ISAs to provide bounding evaluations of accident consequences and likelihoods in order to establish acceptable safety; but PRA applications usually require a reasonable quantitative estimate, and often obtain metrics of uncertainty. This paper provides the background, features, and methodology associated with the PRA and ISA. The differences between the

  10. Validation of seismic probabilistic risk assessments of nuclear power plants

    International Nuclear Information System (INIS)

    Ellingwood, B.

    1994-01-01

    A seismic probabilistic risk assessment (PRA) of a nuclear plant requires identification and information regarding the seismic hazard at the plant site, dominant accident sequences leading to core damage, and structure and equipment fragilities. Uncertainties are associated with each of these ingredients of a PRA. Sources of uncertainty due to seismic hazard and assumptions underlying the component fragility modeling may be significant contributors to uncertainty in estimates of core damage probability. Design and construction errors also may be important in some instances. When these uncertainties are propagated through the PRA, the frequency distribution of core damage probability may span three orders of magnitude or more. This large variability brings into question the credibility of PRA methods and the usefulness of insights to be gained from a PRA. The sensitivity of accident sequence probabilities and high-confidence, low probability of failure (HCLPF) plant fragilities to seismic hazard and fragility modeling assumptions was examined for three nuclear power plants. Mean accident sequence probabilities were found to be relatively insensitive (by a factor of two or less) to: uncertainty in the coefficient of variation (logarithmic standard deviation) describing inherent randomness in component fragility; truncation of lower tail of fragility; uncertainty in random (non-seismic) equipment failures (e.g., diesel generators); correlation between component capacities; and functional form of fragility family. On the other hand, the accident sequence probabilities, expressed in the form of a frequency distribution, are affected significantly by the seismic hazard modeling, including slopes of seismic hazard curves and likelihoods assigned to those curves

  11. Application of database management software to probabilistic risk assessment calculations

    International Nuclear Information System (INIS)

    Wyss, G.D.

    1993-01-01

    Probabilistic risk assessment (PRA) calculations require the management and processing of large amounts of information. This data normally falls into two general categories. For example, a commercial nuclear power plant PRA study makes use of plant blueprints and system schematics, formal plant safety analysis reports, incident reports, letters, memos, handwritten notes from plant visits, and even the analyst's ''engineering judgment''. This information must be documented and cross-referenced in order to properly execute and substantiate the models used in a PRA study. The first category is composed of raw data that is accumulated from equipment testing and operational experiences. These data describe the equipment, its service or testing conditions, its failure mode, and its performance history. The second category is composed of statistical distributions. These distributions can represent probabilities, frequencies, or values of important parameters that are not time-related. Probability and frequency distributions are often obtained by fitting raw data to an appropriate statistical distribution. Database management software is used to store both types of data so that it can be readily queried, manipulated, and archived. This paper provides an overview of the information models used for storing PRA data and illustrates the implementation of these models using examples from current PRA software packages

  12. NRC Support for the Kalinin (VVER) probabilistic risk assessment

    International Nuclear Information System (INIS)

    Bley, D.; Diamond, D.J.; Chu, T.L.; Azarm, A.; Pratt, W.T.; Johnson, D.; Szukiewicz, A.; Drouin, M.; El-Bassioni, A.; Su, T.M.

    1998-01-01

    The US Nuclear Regulatory Commission (NRC) and the Federal Nuclear and Radiation Safety Authority of the Russian Federation have been working together since 1994 to carry out a probabilistic risk assessment (PRA) of a VVER-1000 in the Russian Federation. This was a recognition by both parties that this technology has had a profound effect on the discipline of nuclear reactor safety in the West and that the technology should be transferred to others so that it can be applied to Soviet-designed plants. The NRC provided funds from the Agency for International Development and technical support primarily through Brookhaven National Laboratory and its subcontractors. The latter support was carried out through workshops, by documenting the methodology to be used in a set of guides, and through periodic review of the technical activity. The result of this effort to date includes a set of procedure guides, a draft final report on the Level 1 PRA for internal events (excluding internal fires and floods), and progress reports on the fire, flood, and seismic analysis. It is the authors belief that the type of assistance provided by the NRC has been instrumental in assuring a quality product and transferring important technology for use by regulators and operators of Soviet-designed reactors. After a thorough review, the report will be finalized, lessons learned will be applied in the regulatory and operational regimes in the Russian Federation, and consideration will be given to supporting a containment analysis in order to complete a simplified Level 2 PRA

  13. POISSON, Analysis Solution of Poisson Problems in Probabilistic Risk Assessment

    International Nuclear Information System (INIS)

    Froehner, F.H.

    1986-01-01

    1 - Description of program or function: Purpose of program: Analytic treatment of two-stage Poisson problem in Probabilistic Risk Assessment. Input: estimated a-priori mean failure rate and error factor of system considered (for calculation of stage-1 prior), number of failures and operating times for similar systems (for calculation of stage-2 prior). Output: a-posteriori probability distributions on linear and logarithmic time scale (on specified time grid) and expectation values of failure rate and error factors are calculated for: - stage-1 a-priori distribution, - stage-1 a-posteriori distribution, - stage-2 a-priori distribution, - stage-2 a-posteriori distribution. 2 - Method of solution: Bayesian approach with conjugate stage-1 prior, improved with experience from similar systems to yield stage-2 prior, and likelihood function from experience with system under study (documentation see below under 10.). 3 - Restrictions on the complexity of the problem: Up to 100 similar systems (including the system considered), arbitrary number of problems (failure types) with same grid

  14. Probabilistic evaluation of uncertainties and risks in aerospace components

    Science.gov (United States)

    Shah, A. R.; Shiao, M. C.; Nagpal, V. K.; Chamis, C. C.

    1992-01-01

    This paper summarizes a methodology developed at NASA Lewis Research Center which computationally simulates the structural, material, and load uncertainties associated with Space Shuttle Main Engine (SSME) components. The methodology was applied to evaluate the scatter in static, buckling, dynamic, fatigue, and damage behavior of the SSME turbo pump blade. Also calculated are the probability densities of typical critical blade responses, such as effective stress, natural frequency, damage initiation, most probable damage path, etc. Risk assessments were performed for different failure modes, and the effect of material degradation on the fatigue and damage behaviors of a blade were calculated using a multi-factor interaction equation. Failure probabilities for different fatigue cycles were computed and the uncertainties associated with damage initiation and damage propagation due to different load cycle were quantified. Evaluations on the effects of mistuned blades on a rotor were made; uncertainties in the excitation frequency were found to significantly amplify the blade responses of a mistuned rotor. The effects of the number of blades on a rotor were studied. The autocorrelation function of displacements and the probability density function of the first passage time for deterministic and random barriers for structures subjected to random processes also were computed. A brief discussion was included on the future direction of probabilistic structural analysis.

  15. Probabilistic risk assessment for six vapour intrusion algorithms

    NARCIS (Netherlands)

    Provoost, J.; Reijnders, L.; Bronders, J.; Van Keer, I.; Govaerts, S.

    2014-01-01

    A probabilistic assessment with sensitivity analysis using Monte Carlo simulation for six vapour intrusion algorithms, used in various regulatory frameworks for contaminated land management, is presented here. In addition a deterministic approach with default parameter sets is evaluated against

  16. A High Performance Computing Approach to Tree Cover Delineation in 1-m NAIP Imagery Using a Probabilistic Learning Framework

    Science.gov (United States)

    Basu, Saikat; Ganguly, Sangram; Michaelis, Andrew; Votava, Petr; Roy, Anshuman; Mukhopadhyay, Supratik; Nemani, Ramakrishna

    2015-01-01

    Tree cover delineation is a useful instrument in deriving Above Ground Biomass (AGB) density estimates from Very High Resolution (VHR) airborne imagery data. Numerous algorithms have been designed to address this problem, but most of them do not scale to these datasets, which are of the order of terabytes. In this paper, we present a semi-automated probabilistic framework for the segmentation and classification of 1-m National Agriculture Imagery Program (NAIP) for tree-cover delineation for the whole of Continental United States, using a High Performance Computing Architecture. Classification is performed using a multi-layer Feedforward Backpropagation Neural Network and segmentation is performed using a Statistical Region Merging algorithm. The results from the classification and segmentation algorithms are then consolidated into a structured prediction framework using a discriminative undirected probabilistic graphical model based on Conditional Random Field, which helps in capturing the higher order contextual dependencies between neighboring pixels. Once the final probability maps are generated, the framework is updated and re-trained by relabeling misclassified image patches. This leads to a significant improvement in the true positive rates and reduction in false positive rates. The tree cover maps were generated for the whole state of California, spanning a total of 11,095 NAIP tiles covering a total geographical area of 163,696 sq. miles. The framework produced true positive rates of around 88% for fragmented forests and 74% for urban tree cover areas, with false positive rates lower than 2% for both landscapes. Comparative studies with the National Land Cover Data (NLCD) algorithm and the LiDAR canopy height model (CHM) showed the effectiveness of our framework for generating accurate high-resolution tree-cover maps.

  17. A High Performance Computing Approach to Tree Cover Delineation in 1-m NAIP Imagery using a Probabilistic Learning Framework

    Science.gov (United States)

    Basu, S.; Ganguly, S.; Michaelis, A.; Votava, P.; Roy, A.; Mukhopadhyay, S.; Nemani, R. R.

    2015-12-01

    Tree cover delineation is a useful instrument in deriving Above Ground Biomass (AGB) density estimates from Very High Resolution (VHR) airborne imagery data. Numerous algorithms have been designed to address this problem, but most of them do not scale to these datasets which are of the order of terabytes. In this paper, we present a semi-automated probabilistic framework for the segmentation and classification of 1-m National Agriculture Imagery Program (NAIP) for tree-cover delineation for the whole of Continental United States, using a High Performance Computing Architecture. Classification is performed using a multi-layer Feedforward Backpropagation Neural Network and segmentation is performed using a Statistical Region Merging algorithm. The results from the classification and segmentation algorithms are then consolidated into a structured prediction framework using a discriminative undirected probabilistic graphical model based on Conditional Random Field, which helps in capturing the higher order contextual dependencies between neighboring pixels. Once the final probability maps are generated, the framework is updated and re-trained by relabeling misclassified image patches. This leads to a significant improvement in the true positive rates and reduction in false positive rates. The tree cover maps were generated for the whole state of California, spanning a total of 11,095 NAIP tiles covering a total geographical area of 163,696 sq. miles. The framework produced true positive rates of around 88% for fragmented forests and 74% for urban tree cover areas, with false positive rates lower than 2% for both landscapes. Comparative studies with the National Land Cover Data (NLCD) algorithm and the LiDAR canopy height model (CHM) showed the effectiveness of our framework for generating accurate high-resolution tree-cover maps.

  18. Probabilistic Risk Assessment for Decision Making During Spacecraft Operations

    Science.gov (United States)

    Meshkat, Leila

    2009-01-01

    Decisions made during the operational phase of a space mission often have significant and immediate consequences. Without the explicit consideration of the risks involved and their representation in a solid model, it is very likely that these risks are not considered systematically in trade studies. Wrong decisions during the operational phase of a space mission can lead to immediate system failure whereas correct decisions can help recover the system even from faulty conditions. A problem of special interest is the determination of the system fault protection strategies upon the occurrence of faults within the system. Decisions regarding the fault protection strategy also heavily rely on a correct understanding of the state of the system and an integrated risk model that represents the various possible scenarios and their respective likelihoods. Probabilistic Risk Assessment (PRA) modeling is applicable to the full lifecycle of a space mission project, from concept development to preliminary design, detailed design, development and operations. The benefits and utilities of the model, however, depend on the phase of the mission for which it is used. This is because of the difference in the key strategic decisions that support each mission phase. The focus of this paper is on describing the particular methods used for PRA modeling during the operational phase of a spacecraft by gleaning insight from recently conducted case studies on two operational Mars orbiters. During operations, the key decisions relate to the commands sent to the spacecraft for any kind of diagnostics, anomaly resolution, trajectory changes, or planning. Often, faults and failures occur in the parts of the spacecraft but are contained or mitigated before they can cause serious damage. The failure behavior of the system during operations provides valuable data for updating and adjusting the related PRA models that are built primarily based on historical failure data. The PRA models, in turn

  19. Risk management on nuclear power plant. Application of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Kojima, Shigeo

    2003-01-01

    In U.S.A., nuclear safety regulation is moving to risk-informed regulation (RIR), so necessity of a standard to provide contents of probabilistic risk assessment (PRA) constructing its roots has been discussed for a long time. In 1998, the Committee on Nuclear Risk Management (CNRM) of the American Society of Mechanical Engineers (ASME) began to investigate the standard, of which last edition was published as the Standard for Probabilistic Risk Management for Nuclear Power Plant Applications: RA-S-2002 (PRMA) on April, 2002. As in the Committee, the Nuclear Regulatory Commission (NRC), electric power companies, national institutes, PRA specialists, and so on took parts to carry out many discussions with full energies of participants on risk management in U.S.A., the standard was finished after about four years' efforts. In U.S.A., risk management having already used PRA is successfully practiced, U.S.A. is at a stage with more advancing steps of the risk management than Japan is. Here was described on the standard of PRA and a concrete method of the risk management carried out at nuclear power stations. (G.K.)

  20. Using Probabilistic Models to Appraise and Decide on Sovereign Disaster Risk Financing and Insurance

    OpenAIRE

    Ley-Borrás, Roberto; Fox, Benjamin D.

    2015-01-01

    This paper presents an overview of the structure of probabilistic catastrophe risk models, discusses their importance for appraising sovereign disaster risk financing and insurance instruments and strategy, and puts forward a model and a process for improving decision making on the linked disaster risk management strategy and sovereign disaster risk financing and insurance strategy. The pa...

  1. A tiered approach for probabilistic ecological risk assessment of contaminated sites

    International Nuclear Information System (INIS)

    Zolezzi, M.; Nicolella, C.; Tarazona, J.V.

    2005-01-01

    This paper presents a tiered methodology for probabilistic ecological risk assessment. The proposed approach starts from deterministic comparison (ratio) of single exposure concentration and threshold or safe level calculated from a dose-response relationship, goes through comparison of probabilistic distributions that describe exposure values and toxicological responses of organisms to the chemical of concern, and finally determines the so called distribution-based quotients (DBQs). In order to illustrate the proposed approach, soil concentrations of 1,2,4-trichlorobenzene (1,2,4- TCB) measured in an industrial contaminated site were used for site-specific probabilistic ecological risks assessment. By using probabilistic distributions, the risk, which exceeds a level of concern for soil organisms with the deterministic approach, is associated to the presence of hot spots reaching concentrations able to affect acutely more than 50% of the soil species, while the large majority of the area presents 1,2,4- TCB concentrations below those reported as toxic [it

  2. Living PRAs [probabilistic risk analysis] made easier with IRRAS [Integrated Reliability and Risk Analysis System

    International Nuclear Information System (INIS)

    Russell, K.D.; Sattison, M.B.; Rasmuson, D.M.

    1989-01-01

    The Integrated Reliability and Risk Analysis System (IRRAS) is an integrated PRA software tool that gives the user the ability to create and analyze fault trees and accident sequences using an IBM-compatible microcomputer. This program provides functions that range from graphical fault tree and event tree construction to cut set generation and quantification. IRRAS contains all the capabilities and functions required to create, modify, reduce, and analyze event tree and fault tree models used in the analysis of complex systems and processes. IRRAS uses advanced graphic and analytical techniques to achieve the greatest possible realization of the potential of the microcomputer. When the needs of the user exceed this potential, IRRAS can call upon the power of the mainframe computer. The role of the Idaho National Engineering Laboratory if the IRRAS program is that of software developer and interface to the user community. Version 1.0 of the IRRAS program was released in February 1987 to prove the concept of performing this kind of analysis on microcomputers. This version contained many of the basic features needed for fault tree analysis and was received very well by the PRA community. Since the release of Version 1.0, many user comments and enhancements have been incorporated into the program providing a much more powerful and user-friendly system. This version is designated ''IRRAS 2.0''. Version 3.0 will contain all of the features required for efficient event tree and fault tree construction and analysis. 5 refs., 26 figs

  3. Incorporating organizational factors into Probabilistic Risk Assessment (PRA) of complex socio-technical systems: A hybrid technique formalization

    International Nuclear Information System (INIS)

    Mohaghegh, Zahra; Kazemi, Reza; Mosleh, Ali

    2009-01-01

    This paper is a result of a research with the primary purpose of extending Probabilistic Risk Assessment (PRA) modeling frameworks to include the effects of organizational factors as the deeper, more fundamental causes of accidents and incidents. There have been significant improvements in the sophistication of quantitative methods of safety and risk assessment, but the progress on techniques most suitable for organizational safety risk frameworks has been limited. The focus of this paper is on the choice of 'representational schemes' and 'techniques.' A methodology for selecting appropriate candidate techniques and their integration in the form of a 'hybrid' approach is proposed. Then an example is given through an integration of System Dynamics (SD), Bayesian Belief Network (BBN), Event Sequence Diagram (ESD), and Fault Tree (FT) in order to demonstrate the feasibility and value of hybrid techniques. The proposed hybrid approach integrates deterministic and probabilistic modeling perspectives, and provides a flexible risk management tool for complex socio-technical systems. An application of the hybrid technique is provided in the aviation safety domain, focusing on airline maintenance systems. The example demonstrates how the hybrid method can be used to analyze the dynamic effects of organizational factors on system risk

  4. Incorporating organizational factors into Probabilistic Risk Assessment (PRA) of complex socio-technical systems: A hybrid technique formalization

    Energy Technology Data Exchange (ETDEWEB)

    Mohaghegh, Zahra [Center for Risk and Reliability, University of Maryland, College Park, MD 20742 (United States)], E-mail: mohagheg@umd.edu; Kazemi, Reza; Mosleh, Ali [Center for Risk and Reliability, University of Maryland, College Park, MD 20742 (United States)

    2009-05-15

    This paper is a result of a research with the primary purpose of extending Probabilistic Risk Assessment (PRA) modeling frameworks to include the effects of organizational factors as the deeper, more fundamental causes of accidents and incidents. There have been significant improvements in the sophistication of quantitative methods of safety and risk assessment, but the progress on techniques most suitable for organizational safety risk frameworks has been limited. The focus of this paper is on the choice of 'representational schemes' and 'techniques.' A methodology for selecting appropriate candidate techniques and their integration in the form of a 'hybrid' approach is proposed. Then an example is given through an integration of System Dynamics (SD), Bayesian Belief Network (BBN), Event Sequence Diagram (ESD), and Fault Tree (FT) in order to demonstrate the feasibility and value of hybrid techniques. The proposed hybrid approach integrates deterministic and probabilistic modeling perspectives, and provides a flexible risk management tool for complex socio-technical systems. An application of the hybrid technique is provided in the aviation safety domain, focusing on airline maintenance systems. The example demonstrates how the hybrid method can be used to analyze the dynamic effects of organizational factors on system risk.

  5. Use of the Management Oversight and Risk Tree (MORT) methodology in health-physics program appraisals

    International Nuclear Information System (INIS)

    Essig, T.H.; Gilchrist, R.L.

    1981-06-01

    In January 1980, Pacific Northwest Laboratory (PNL) assumed a major role in helping the Nuclear Regulatory Commission (NRC) conduct comprehensive health physics appraisals at 47 operating nuclear power plants. These appraisals required the development of an analytical technique that permitted a deductive analysis of a health-physics program on an element-by-element basis. The technique employed was a modification of the Management Oversight and risk Tree (MORT) analytical logic methodology used in probabilistic assessments. This paper includes the method used in establishing the appraisal guidelines and assigning the proper level of importance within the analytical tree structure. The system for ensuring the proper subdivision necessary for an adequate assessment of each area (e.g., exposure controls and radioactive waste management) will also be discussed. In addition to these major subjects, the generation of specific review questions that correspond to the analytical trees is addressed

  6. Using incident response trees as a tool for risk management of online financial services.

    Science.gov (United States)

    Gorton, Dan

    2014-09-01

    The article introduces the use of probabilistic risk assessment for modeling the incident response process of online financial services. The main contribution is the creation of incident response trees, using event tree analysis, which provides us with a visual tool and a systematic way to estimate the probability of a successful incident response process against the currently known risk landscape, making it possible to measure the balance between front-end and back-end security measures. The model is presented using an illustrative example, and is then applied to the incident response process of a Swedish bank. Access to relevant data is verified and the applicability and usability of the proposed model is verified using one year of historical data. Potential advantages and possible shortcomings are discussed, referring to both the design phase and the operational phase, and future work is presented. © 2014 Society for Risk Analysis.

  7. Probabilistic inhalation risk assessment due to radioactivity released from coal fired thermal power plants

    International Nuclear Information System (INIS)

    Tiwari, M.; Ajmal, P.Y.; Bhangare, R.C.; Sahu, S.K.; Pandit, G.G.

    2014-01-01

    This paper deals with assessment of radiological risk to the general public around in the neighborhood of a 1000 MWe coal-based thermal power plant. We have used Monte Carlo simulation for characterization of uncertainty in inhalation risk due to radionuclide escaping from the stack of thermal power plant. Monte Carlo simulation treats parameters as random variables bound to a given probabilistic distribution to evaluate the distribution of the resulting output. Risk assessment is the process that estimates the likelihood of occurrence of adverse effects to humans and ecological receptors as a result of exposure to hazardous chemical, radiation, and/or biological agents. Quantitative risk characterization involves evaluating exposure estimates against a benchmark of toxicity, such as a cancer slope factor. Risk is calculated by multiplying the carcinogenic slope factor (SF) of the radionuclide by the dose an individual receives. The collective effective doses to the population living in the neighborhood of coal-based thermal power plant were calculated using Gaussian plume dispersion model. Monte Carlo Analysis is the most widely used probabilistic method in risk assessment. The MCA technique treats any uncertain parameter as random variable that obeys a given probabilistic distribution. This technique is widely used for analyzing probabilistic uncertainty. In MCA computer simulation are used to combine multiple probability distributions associated with the dose and SF depicted in risk equation. Thus we get a probabilistic distribution for the risk

  8. Developing an Event-Tree Probabilistic Tsunami Inundation Model for NE Atlantic Coasts: Application to a Case Study

    Science.gov (United States)

    Omira, R.; Matias, L.; Baptista, M. A.

    2016-12-01

    This study constitutes a preliminary assessment of probabilistic tsunami inundation in the NE Atlantic region. We developed an event-tree approach to calculate the likelihood of tsunami flood occurrence and exceedance of a specific near-shore wave height for a given exposure time. Only tsunamis of tectonic origin are considered here, taking into account local, regional, and far-field sources. The approach used here consists of an event-tree method that gathers probability models for seismic sources, tsunami numerical modeling, and statistical methods. It also includes a treatment of aleatoric uncertainties related to source location and tidal stage. Epistemic uncertainties are not addressed in this study. The methodology is applied to the coastal test-site of Sines located in the NE Atlantic coast of Portugal. We derive probabilistic high-resolution maximum wave amplitudes and flood distributions for the study test-site considering 100- and 500-year exposure times. We find that the probability that maximum wave amplitude exceeds 1 m somewhere along the Sines coasts reaches about 60 % for an exposure time of 100 years and is up to 97 % for an exposure time of 500 years. The probability of inundation occurrence (flow depth >0 m) varies between 10 % and 57 %, and from 20 % up to 95 % for 100- and 500-year exposure times, respectively. No validation has been performed here with historical tsunamis. This paper illustrates a methodology through a case study, which is not an operational assessment.

  9. Risk assessment for enterprise resource planning (ERP) system implementations: a fault tree analysis approach

    Science.gov (United States)

    Zeng, Yajun; Skibniewski, Miroslaw J.

    2013-08-01

    Enterprise resource planning (ERP) system implementations are often characterised with large capital outlay, long implementation duration, and high risk of failure. In order to avoid ERP implementation failure and realise the benefits of the system, sound risk management is the key. This paper proposes a probabilistic risk assessment approach for ERP system implementation projects based on fault tree analysis, which models the relationship between ERP system components and specific risk factors. Unlike traditional risk management approaches that have been mostly focused on meeting project budget and schedule objectives, the proposed approach intends to address the risks that may cause ERP system usage failure. The approach can be used to identify the root causes of ERP system implementation usage failure and quantify the impact of critical component failures or critical risk events in the implementation process.

  10. Optimization (Alara) and probabilistic exposures: the application of optimization criteria to the control of risks due to exposures of a probabilistic nature

    International Nuclear Information System (INIS)

    Gonzalez, A.J.

    1989-01-01

    The paper described the application of the principles of optimization recommended by the International Commission on Radiological Protection (ICRP) to the restrain of radiation risks due to exposures that may or may not be incurred and to which a probability of occurrence can be assigned. After describing the concept of probabilistic exposures, it proposes a basis for a converging policy of control for both certain and probabilistic exposures, namely the dose-risk relationship adopted for radiation protection purposes. On that basis some coherent approaches for dealing with probabilistic exposures, such as the limitation of individual risks, are discussed. The optimization of safety for reducing all risks from probabilistic exposures to as-low-as-reasonably-achievable (ALARA) levels is reviewed in full. The principles of optimization of protection are used as a basic framework and the relevant factors to be taken into account when moving to probabilistic exposures are presented. The paper also reviews the decision-aiding techniques suitable for performing optimization with particular emphasis to the multi-attribute utility-analysis technique. Finally, there is a discussion on some practical application of decision-aiding multi-attribute utility analysis to probabilistic exposures including the use of probabilistic utilities. In its final outlook, the paper emphasizes the need for standardization and solutions to generic problems, if optimization of safety is to be successful

  11. Significance of earthquake risk in nuclear power plant probabilistic risk assessments

    International Nuclear Information System (INIS)

    Sues, R.H.; Amico, P.J.; Campbell, R.D.

    1990-01-01

    During the last eight years, approximately 25 utility-sponsored probabilistic risk assessments (PRAs) have been conducted for US nuclear reactors. Of these, ten have been published, seven of which have included complete seismic risk assessment. The results of the seven published PRAs are reviewed here in order to ascertain the significance of the risk due to earthquake initiating events. While PRA methodology has been in a state of development over the past seven years, and the results are subject to interpretation (as discussed in the paper), from the review conducted it is clear that earthquake-induced initiating events are important risk contributors. It is concluded that earthquake initiating events should not be dismissed, a priori, in any nuclear plant risk assessment. (orig.)

  12. Integration of Evidence Base into a Probabilistic Risk Assessment

    Science.gov (United States)

    Saile, Lyn; Lopez, Vilma; Bickham, Grandin; Kerstman, Eric; FreiredeCarvalho, Mary; Byrne, Vicky; Butler, Douglas; Myers, Jerry; Walton, Marlei

    2011-01-01

    INTRODUCTION: A probabilistic decision support model such as the Integrated Medical Model (IMM) utilizes an immense amount of input data that necessitates a systematic, integrated approach for data collection, and management. As a result of this approach, IMM is able to forecasts medical events, resource utilization and crew health during space flight. METHODS: Inflight data is the most desirable input for the Integrated Medical Model. Non-attributable inflight data is collected from the Lifetime Surveillance for Astronaut Health study as well as the engineers, flight surgeons, and astronauts themselves. When inflight data is unavailable cohort studies, other models and Bayesian analyses are used, in addition to subject matters experts input on occasion. To determine the quality of evidence of a medical condition, the data source is categorized and assigned a level of evidence from 1-5; the highest level is one. The collected data reside and are managed in a relational SQL database with a web-based interface for data entry and review. The database is also capable of interfacing with outside applications which expands capabilities within the database itself. Via the public interface, customers can access a formatted Clinical Findings Form (CLiFF) that outlines the model input and evidence base for each medical condition. Changes to the database are tracked using a documented Configuration Management process. DISSCUSSION: This strategic approach provides a comprehensive data management plan for IMM. The IMM Database s structure and architecture has proven to support additional usages. As seen by the resources utilization across medical conditions analysis. In addition, the IMM Database s web-based interface provides a user-friendly format for customers to browse and download the clinical information for medical conditions. It is this type of functionality that will provide Exploratory Medicine Capabilities the evidence base for their medical condition list

  13. Development and application of the dynamic system doctor to nuclear reactor probabilistic risk assessments

    International Nuclear Information System (INIS)

    Kunsman, David Marvin; Aldemir, Tunc; Rutt, Benjamin; Metzroth, Kyle; Catalyurek, Umit; Denning, Richard; Hakobyan, Aram; Dunagan, Sean C.

    2008-01-01

    This LDRD project has produced a tool that makes probabilistic risk assessments (PRAs) of nuclear reactors - analyses which are very resource intensive - more efficient. PRAs of nuclear reactors are being increasingly relied on by the United States Nuclear Regulatory Commission (U.S.N.R.C.) for licensing decisions for current and advanced reactors. Yet, PRAs are produced much as they were 20 years ago. The work here applied a modern systems analysis technique to the accident progression analysis portion of the PRA; the technique was a system-independent multi-task computer driver routine. Initially, the objective of the work was to fuse the accident progression event tree (APET) portion of a PRA to the dynamic system doctor (DSD) created by Ohio State University. Instead, during the initial efforts, it was found that the DSD could be linked directly to a detailed accident progression phenomenological simulation code - the type on which APET construction and analysis relies, albeit indirectly - and thereby directly create and analyze the APET. The expanded DSD computational architecture and infrastructure that was created during this effort is called ADAPT (Analysis of Dynamic Accident Progression Trees). ADAPT is a system software infrastructure that supports execution and analysis of multiple dynamic event-tree simulations on distributed environments. A simulator abstraction layer was developed, and a generic driver was implemented for executing simulators on a distributed environment. As a demonstration of the use of the methodological tool, ADAPT was applied to quantify the likelihood of competing accident progression pathways occurring for a particular accident scenario in a particular reactor type using MELCOR, an integrated severe accident analysis code developed at Sandia. (ADAPT was intentionally created with flexibility, however, and is not limited to interacting with only one code. With minor coding changes to input files, ADAPT can be linked to other

  14. Probabilistic Approaches for Multi-Hazard Risk Assessment of Structures and Systems

    Science.gov (United States)

    Kwag, Shinyoung

    Performance assessment of structures, systems, and components for multi-hazard scenarios has received significant attention in recent years. However, the concept of multi-hazard analysis is quite broad in nature and the focus of existing literature varies across a wide range of problems. In some cases, such studies focus on hazards that either occur simultaneously or are closely correlated with each other. For example, seismically induced flooding or seismically induced fires. In other cases, multi-hazard studies relate to hazards that are not dependent or correlated but have strong likelihood of occurrence at different times during the lifetime of a structure. The current approaches for risk assessment need enhancement to account for multi-hazard risks. It must be able to account for uncertainty propagation in a systems-level analysis, consider correlation among events or failure modes, and allow integration of newly available information from continually evolving simulation models, experimental observations, and field measurements. This dissertation presents a detailed study that proposes enhancements by incorporating Bayesian networks and Bayesian updating within a performance-based probabilistic framework. The performance-based framework allows propagation of risk as well as uncertainties in the risk estimates within a systems analysis. Unlike conventional risk assessment techniques such as a fault-tree analysis, a Bayesian network can account for statistical dependencies and correlations among events/hazards. The proposed approach is extended to develop a risk-informed framework for quantitative validation and verification of high fidelity system-level simulation tools. Validation of such simulations can be quite formidable within the context of a multi-hazard risk assessment in nuclear power plants. The efficiency of this approach lies in identification of critical events, components, and systems that contribute to the overall risk. Validation of any event or

  15. Comparison between Canadian probabilistic safety assessment methods formulated by Atomic Energy of Canada limited and probabilistic risk assessment methods

    International Nuclear Information System (INIS)

    Shapiro, H.S.; Smith, J.E.

    1989-01-01

    The procedures used by Atomic Energy of Canada Limited (AECL) to perform probabilistic safety assessments (PRAs) differ somewhat from conventionally accepted probabilistic risk assessment (PRA) procedures used elsewhere. In Canada, PSA is used by AECL as an audit tool for an evolving design. The purpose is to assess the safety of the plant in engineering terms. Thus, the PSA procedures are geared toward providing engineering feedback so that necessary changes can be made to the design at an early stage, input can be made to operating procedures, and test and maintenance programs can be optimized in terms of costs. Most PRAs, by contrast, are performed in plants that are already built. Their main purpose is to establish the core melt frequency and the risk to the public due to core melt. Also, any design modification is very expensive. The differences in purpose and timing between PSA and PRA have resulted in differences in methodology and scope. The PSA procedures are used on all plants being designed by AECL

  16. Bayesian Hierarchical Structure for Quantifying Population Variability to Inform Probabilistic Health Risk Assessments.

    Science.gov (United States)

    Shao, Kan; Allen, Bruce C; Wheeler, Matthew W

    2017-10-01

    Human variability is a very important factor considered in human health risk assessment for protecting sensitive populations from chemical exposure. Traditionally, to account for this variability, an interhuman uncertainty factor is applied to lower the exposure limit. However, using a fixed uncertainty factor rather than probabilistically accounting for human variability can hardly support probabilistic risk assessment advocated by a number of researchers; new methods are needed to probabilistically quantify human population variability. We propose a Bayesian hierarchical model to quantify variability among different populations. This approach jointly characterizes the distribution of risk at background exposure and the sensitivity of response to exposure, which are commonly represented by model parameters. We demonstrate, through both an application to real data and a simulation study, that using the proposed hierarchical structure adequately characterizes variability across different populations. © 2016 Society for Risk Analysis.

  17. Hybrid causal methodology and software platform for probabilistic risk assessment and safety monitoring of socio-technical systems

    International Nuclear Information System (INIS)

    Groth, Katrina; Wang Chengdong; Mosleh, Ali

    2010-01-01

    This paper introduces an integrated framework and software platform for probabilistic risk assessment (PRA) and safety monitoring of complex socio-technical systems. An overview of the three-layer hybrid causal logic (HCL) modeling approach and corresponding algorithms, implemented in the Trilith software platform, are provided. The HCL approach enhances typical PRA methods by quantitatively including the influence of soft causal factors introduced by human and organizational aspects of a system. The framework allows different modeling techniques to be used for different aspects of the socio-technical system. The HCL approach combines the power of traditional event sequence diagram (ESD)event tree (ET) and fault tree (FT) techniques for modeling deterministic causal paths, with the flexibility of Bayesian belief networks for modeling non-deterministic cause-effect relationships among system elements (suitable for modeling human and organizational influences). Trilith enables analysts to construct HCL models and perform quantitative risk assessment and management of complex systems. The risk management capabilities included are HCL-based risk importance measures, hazard identification and ranking, precursor analysis, safety indicator monitoring, and root cause analysis. This paper describes the capabilities of the Trilith platform and power of the HCL algorithm by use of example risk models for a type of aviation accident (aircraft taking off from the wrong runway).

  18. Hybrid causal methodology and software platform for probabilistic risk assessment and safety monitoring of socio-technical systems

    Energy Technology Data Exchange (ETDEWEB)

    Groth, Katrina, E-mail: kgroth@umd.ed [Center for Risk and Reliability, 0151 Glenn L. Martin Hall, University of Maryland, College Park, MD 20742 (United States); Wang Chengdong; Mosleh, Ali [Center for Risk and Reliability, 0151 Glenn L. Martin Hall, University of Maryland, College Park, MD 20742 (United States)

    2010-12-15

    This paper introduces an integrated framework and software platform for probabilistic risk assessment (PRA) and safety monitoring of complex socio-technical systems. An overview of the three-layer hybrid causal logic (HCL) modeling approach and corresponding algorithms, implemented in the Trilith software platform, are provided. The HCL approach enhances typical PRA methods by quantitatively including the influence of soft causal factors introduced by human and organizational aspects of a system. The framework allows different modeling techniques to be used for different aspects of the socio-technical system. The HCL approach combines the power of traditional event sequence diagram (ESD)event tree (ET) and fault tree (FT) techniques for modeling deterministic causal paths, with the flexibility of Bayesian belief networks for modeling non-deterministic cause-effect relationships among system elements (suitable for modeling human and organizational influences). Trilith enables analysts to construct HCL models and perform quantitative risk assessment and management of complex systems. The risk management capabilities included are HCL-based risk importance measures, hazard identification and ranking, precursor analysis, safety indicator monitoring, and root cause analysis. This paper describes the capabilities of the Trilith platform and power of the HCL algorithm by use of example risk models for a type of aviation accident (aircraft taking off from the wrong runway).

  19. Probabilistic Modeling and Risk Assessment of Cable Icing

    DEFF Research Database (Denmark)

    Roldsgaard, Joan Hee

    This dissertation addresses the issues related to icing of structures with special emphasis on bridge cables. Cable supported bridges in cold climate suffers for ice accreting on the cables, this poses three different undesirable situations. Firstly the changed shape of the cable due to ice...... preliminary framework is modified for assessing the probability of occurrence of in-cloud and precipitation icing and its duration. Different probabilistic models are utilized for the representation of the meteorological variables and their appropriateness is evaluated both through goodness-of-fit tests...... are influencing the two icing mechanisms and their duration. The model is found to be more sensitive to changes in the discretization levels of the input variables. Thirdly the developed operational probabilistic framework for the assessment of the expected number of occurrences of ice/snow accretion on bridge...

  20. Application of probabilistic risk assessment in nuclear and environmental licensing processes of nuclear reactors in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Mata, Jonatas F.C. da; Vasconcelos, Vanderley de; Mesquita, Amir Z., E-mail: jonatasfmata@yahoo.com.br, E-mail: vasconv@cdtn.br, E-mail: amir@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    The nuclear accident at Fukushima Daiichi, occurred in Japan in 2011, brought reflections, worldwide, on the management of nuclear and environmental licensing processes of existing nuclear reactors. One of the key lessons learned in this matter, is that the studies of Probabilistic Safety Assessment and Severe Accidents are becoming essential, even in the early stage of a nuclear development project. In Brazil, Brazilian Nuclear Energy Commission, CNEN, conducts the nuclear licensing. The organism responsible for the environmental licensing is Brazilian Institute of Environment and Renewable Natural Resources, IBAMA. In the scope of the licensing processes of these two institutions, the safety analysis is essentially deterministic, complemented by probabilistic studies. The Probabilistic Safety Assessment (PSA) is the study performed to evaluate the behavior of the nuclear reactor in a sequence of events that may lead to the melting of its core. It includes both probability and consequence estimation of these events, which are called Severe Accidents, allowing to obtain the risk assessment of the plant. Thus, the possible shortcomings in the design of systems are identified, providing basis for safety assessment and improving safety. During the environmental licensing, a Quantitative Risk Analysis (QRA), including probabilistic evaluations, is required in order to support the development of the Risk Analysis Study, the Risk Management Program and the Emergency Plan. This article aims to provide an overview of probabilistic risk assessment methodologies and their applications in nuclear and environmental licensing processes of nuclear reactors in Brazil. (author)

  1. Application of probabilistic risk assessment in nuclear and environmental licensing processes of nuclear reactors in Brazil

    International Nuclear Information System (INIS)

    Mata, Jonatas F.C. da; Vasconcelos, Vanderley de; Mesquita, Amir Z.

    2015-01-01

    The nuclear accident at Fukushima Daiichi, occurred in Japan in 2011, brought reflections, worldwide, on the management of nuclear and environmental licensing processes of existing nuclear reactors. One of the key lessons learned in this matter, is that the studies of Probabilistic Safety Assessment and Severe Accidents are becoming essential, even in the early stage of a nuclear development project. In Brazil, Brazilian Nuclear Energy Commission, CNEN, conducts the nuclear licensing. The organism responsible for the environmental licensing is Brazilian Institute of Environment and Renewable Natural Resources, IBAMA. In the scope of the licensing processes of these two institutions, the safety analysis is essentially deterministic, complemented by probabilistic studies. The Probabilistic Safety Assessment (PSA) is the study performed to evaluate the behavior of the nuclear reactor in a sequence of events that may lead to the melting of its core. It includes both probability and consequence estimation of these events, which are called Severe Accidents, allowing to obtain the risk assessment of the plant. Thus, the possible shortcomings in the design of systems are identified, providing basis for safety assessment and improving safety. During the environmental licensing, a Quantitative Risk Analysis (QRA), including probabilistic evaluations, is required in order to support the development of the Risk Analysis Study, the Risk Management Program and the Emergency Plan. This article aims to provide an overview of probabilistic risk assessment methodologies and their applications in nuclear and environmental licensing processes of nuclear reactors in Brazil. (author)

  2. The importance of probabilistic evaluations in connection with risk analyses according to technical safety laws

    International Nuclear Information System (INIS)

    Mathiak, E.

    1984-01-01

    The nuclear energy sector exemplifies the essential importance to be attached to the practical application of probabilistic evaluations (e.g. probabilistic reliability analyses) in connection with the legal risk assessment of technical systems and installations. The study is making use of a triad risk analysis and tries to reconcile the natural science and legal points of view. Without changing the definitions of 'risk' and 'hazard' in the legal sense of their meaning the publication discusses their reconcilation with the laws of natural science, their interpretation and application in view of the latter. (HSCH) [de

  3. Probabilistic cumulative risk assessment of anti-androgenic pesticides in food

    DEFF Research Database (Denmark)

    Müller, Anne Kirstine; Nielsen, Elsa

    2008-01-01

    A cumulative risk assessment of three anti-androgenic pesticides vinclozolin, procymidone and prochloraz in combination has been carried out using an Integrated Probabilistic Risk Assessment (IPRA) model. In the model, variability in both exposure and sensitivity between individuals were combined...

  4. Seismic risk maps of Switzerland; description of the probabilistic method and discussion of some input parameters

    International Nuclear Information System (INIS)

    Mayer-Rosa, D.; Merz, H.A.

    1976-01-01

    The probabilistic model used in a seismic risk mapping project for Switzerland is presented. Some of its advantages and limitations are spelled out. In addition some earthquake parameters which should be carefully investigated before using them in a seismic risk analysis are discussed

  5. Probabilistic cumulative risk assessment of anti-androgenic pesticides in food.

    NARCIS (Netherlands)

    Müller, A.K.; Bosgra, S.; Boon, P.E.; van der Voet, H.; Nielsen, E.; Ladefoged, O.

    2009-01-01

    In this paper, we present a cumulative risk assessment of three anti-androgenic pesticides (vinclozolin, procymidone and prochloraz) using the relative potency factor (RPF) approach and an integrated probabilistic risk assessment (IPRA) model. RPFs for each substance were estimated for three

  6. Probabilistic cumulative risk assessment of anti-androgenic pesticides in food

    NARCIS (Netherlands)

    Muller, A.K.; Bosgra, S.; Boon, P.E.; Voet, van der H.; Nielsen, E.; Ladefoged, O.

    2009-01-01

    In this paper, we present a cumulative risk assessment of three anti-androgenic pesticides (vinclozolin, procymidone and prochloraz) using the relative potency factor (RPF) approach and an integrated probabilistic risk assessment (IPRA) model. RPFs for each substance were estimated for three

  7. Integrated probabilistic risk assessment for nanoparticles: the case of nanosilica in food

    OpenAIRE

    Jacobs, R.; Voet, van der, H.; Braak, ter, C.J.F.

    2015-01-01

    Insight into risks of nanotechnology and the use of nanoparticles is an essential condition for the social acceptance and safe use of nanotechnology. One of the problems with which the risk assessment of nanoparticles is faced is the lack of data, resulting in uncertainty in the risk assessment. We attempt to quantify some of this uncertainty by expanding a previous deterministic study on nanosilica (5?200?nm) in food into a fully integrated probabilistic risk assessment. We use the integrate...

  8. PRA (probabilistic risk analysis) in the nuclear sector. Quantifying human error and human malice

    International Nuclear Information System (INIS)

    Heyes, A.G.

    1995-01-01

    Regardless of the regulatory style chosen ('command and control' or 'functional') a vital prerequisite for coherent safety regulations in the nuclear power industry is the ability to assess accident risk. In this paper we present a critical analysis of current techniques of probabilistic risk analysis applied in the industry, with particular regard to the problems of quantifying risks arising from, or exacerbated by, human risk and/or human error. (Author)

  9. Probabilistic risk analysis and its role in regulatory activity in a developing country

    International Nuclear Information System (INIS)

    Arredondo-Sanchez, C.

    1985-01-01

    The author discusses the criterion adopted for regulatory activity in a developing country with a nuclear power plant. He describes the problems that have to be overcome as a result of changes in the regulations during construction of the plant. There is discussion of the action taken by the regulatory body when introducing the method of probabilistic risk analysis. The part played by this form of analysis in quantifying the safety objectives proposed in the USA together with its limitations and the problems involved in this methodology are examined. Lastly, the author gives an opinion on the use that probabilistic risk analysis should be put to in developing countries such as Mexico. (author)

  10. Probabilistic insurance

    OpenAIRE

    Wakker, P.P.; Thaler, R.H.; Tversky, A.

    1997-01-01

    textabstractProbabilistic insurance is an insurance policy involving a small probability that the consumer will not be reimbursed. Survey data suggest that people dislike probabilistic insurance and demand more than a 20% reduction in the premium to compensate for a 1% default risk. While these preferences are intuitively appealing they are difficult to reconcile with expected utility theory. Under highly plausible assumptions about the utility function, willingness to pay for probabilistic i...

  11. Probabilistic risk assessment of the Space Shuttle. Phase 3: A study of the potential of losing the vehicle during nominal operation. Volume 2: Integrated loss of vehicle model

    Science.gov (United States)

    Fragola, Joseph R.; Maggio, Gaspare; Frank, Michael V.; Gerez, Luis; Mcfadden, Richard H.; Collins, Erin P.; Ballesio, Jorge; Appignani, Peter L.; Karns, James J.

    1995-01-01

    The application of the probabilistic risk assessment methodology to a Space Shuttle environment, particularly to the potential of losing the Shuttle during nominal operation is addressed. The different related concerns are identified and combined to determine overall program risks. A fault tree model is used to allocate system probabilities to the subsystem level. The loss of the vehicle due to failure to contain energetic gas and debris, to maintain proper propulsion and configuration is analyzed, along with the loss due to Orbiter, external tank failure, and landing failure or error.

  12. Use of limited data to construct Bayesian networks for probabilistic risk assessment.

    Energy Technology Data Exchange (ETDEWEB)

    Groth, Katrina M.; Swiler, Laura Painton

    2013-03-01

    Probabilistic Risk Assessment (PRA) is a fundamental part of safety/quality assurance for nuclear power and nuclear weapons. Traditional PRA very effectively models complex hardware system risks using binary probabilistic models. However, traditional PRA models are not flexible enough to accommodate non-binary soft-causal factors, such as digital instrumentation&control, passive components, aging, common cause failure, and human errors. Bayesian Networks offer the opportunity to incorporate these risks into the PRA framework. This report describes the results of an early career LDRD project titled %E2%80%9CUse of Limited Data to Construct Bayesian Networks for Probabilistic Risk Assessment%E2%80%9D. The goal of the work was to establish the capability to develop Bayesian Networks from sparse data, and to demonstrate this capability by producing a data-informed Bayesian Network for use in Human Reliability Analysis (HRA) as part of nuclear power plant Probabilistic Risk Assessment (PRA). This report summarizes the research goal and major products of the research.

  13. 77 FR 29391 - An Approach for Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific...

    Science.gov (United States)

    2012-05-17

    ... NUCLEAR REGULATORY COMMISSION [NRC-2012-0110] An Approach for Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis AGENCY: Nuclear Regulatory Commission. ACTION: Draft regulatory guide; request for comment. SUMMARY: The U.S. Nuclear Regulatory...

  14. Application of probabilistic quantitative ecological risk assessment to radiological dose

    International Nuclear Information System (INIS)

    Twining, J.; Ferris, J.; Copplestone, D.; Zinger, I.

    2004-01-01

    Probabilistic ERA is becoming more accepted and applied in evaluations of environmental impacts worldwide. In a previous paper we have shown that the process can be applied in practice to routine effluent releases from a nuclear facility. However, there are practical issues that need to be addressed prior to its regulatory application for criteria setting or for site-specific ERA. Among these issues are a) appropriate data selection for both exposure and dose-response input, because there is a need to carefully characterise and filter the available dose-response data for its ecological relevance, b) A coherent approach is required to the choice of exposure scenarios, and c) there are various questions associated with treatment of exposure to mixed nuclides. In this paper we will evaluate and discuss aspects of these issues, using an illustrative case study approach. (author)

  15. Importance of properly treating human performance in probabilistic risk assessments

    International Nuclear Information System (INIS)

    Kukielka, C.A.; Butler, F.G.; Chaiko, M.A.

    1997-01-01

    A critical issue to consider when developing Advanced Reactor Systems (ARS) is the operators' ability to reliably execute Emergency Operating Procedures (EOPs) during accidents. A combined probabilistic and deterministic method for evaluating operator performance is outlined in this paper. Three questions are addressed: (1) does the operator understand the status of the plant? (2) does the operator know what to do? and (3) what are the odds of successful EOP execution? Deterministic methods are used to evaluate questions 1 and 2, and question 3 is addressed by statistical analysis. Simulator exercises are used to develop probability of response as a function of time curves for time limited operator actions. This method has been used to identify and resolve deficiencies in the plant operating procedures and the operator interface. An application is provided to the Anticipated Transient without Scram accident sequences. The results of Human Reliability Analysis are compared with the results of similar BWR analyses. 2 figs., 2 tabs

  16. Integrated probabilistic risk assessment for nanoparticles: the case of nanosilica in food.

    Science.gov (United States)

    Jacobs, Rianne; van der Voet, Hilko; Ter Braak, Cajo J F

    Insight into risks of nanotechnology and the use of nanoparticles is an essential condition for the social acceptance and safe use of nanotechnology. One of the problems with which the risk assessment of nanoparticles is faced is the lack of data, resulting in uncertainty in the risk assessment. We attempt to quantify some of this uncertainty by expanding a previous deterministic study on nanosilica (5-200 nm) in food into a fully integrated probabilistic risk assessment. We use the integrated probabilistic risk assessment method in which statistical distributions and bootstrap methods are used to quantify uncertainty and variability in the risk assessment. Due to the large amount of uncertainty present, this probabilistic method, which separates variability from uncertainty, contributed to a better understandable risk assessment. We found that quantifying the uncertainties did not increase the perceived risk relative to the outcome of the deterministic study. We pinpointed particular aspects of the hazard characterization that contributed most to the total uncertainty in the risk assessment, suggesting that further research would benefit most from obtaining more reliable data on those aspects.

  17. Integrated probabilistic risk assessment for nanoparticles: the case of nanosilica in food

    International Nuclear Information System (INIS)

    Jacobs, Rianne; Voet, Hilko van der; Braak, Cajo J. F. ter

    2015-01-01

    Insight into risks of nanotechnology and the use of nanoparticles is an essential condition for the social acceptance and safe use of nanotechnology. One of the problems with which the risk assessment of nanoparticles is faced is the lack of data, resulting in uncertainty in the risk assessment. We attempt to quantify some of this uncertainty by expanding a previous deterministic study on nanosilica (5–200 nm) in food into a fully integrated probabilistic risk assessment. We use the integrated probabilistic risk assessment method in which statistical distributions and bootstrap methods are used to quantify uncertainty and variability in the risk assessment. Due to the large amount of uncertainty present, this probabilistic method, which separates variability from uncertainty, contributed to a better understandable risk assessment. We found that quantifying the uncertainties did not increase the perceived risk relative to the outcome of the deterministic study. We pinpointed particular aspects of the hazard characterization that contributed most to the total uncertainty in the risk assessment, suggesting that further research would benefit most from obtaining more reliable data on those aspects

  18. Integrated probabilistic risk assessment for nanoparticles: the case of nanosilica in food

    Energy Technology Data Exchange (ETDEWEB)

    Jacobs, Rianne, E-mail: rianne.jacobs@wur.nl; Voet, Hilko van der; Braak, Cajo J. F. ter [Wageningen University and Research Centre, Biometris (Netherlands)

    2015-06-15

    Insight into risks of nanotechnology and the use of nanoparticles is an essential condition for the social acceptance and safe use of nanotechnology. One of the problems with which the risk assessment of nanoparticles is faced is the lack of data, resulting in uncertainty in the risk assessment. We attempt to quantify some of this uncertainty by expanding a previous deterministic study on nanosilica (5–200 nm) in food into a fully integrated probabilistic risk assessment. We use the integrated probabilistic risk assessment method in which statistical distributions and bootstrap methods are used to quantify uncertainty and variability in the risk assessment. Due to the large amount of uncertainty present, this probabilistic method, which separates variability from uncertainty, contributed to a better understandable risk assessment. We found that quantifying the uncertainties did not increase the perceived risk relative to the outcome of the deterministic study. We pinpointed particular aspects of the hazard characterization that contributed most to the total uncertainty in the risk assessment, suggesting that further research would benefit most from obtaining more reliable data on those aspects.

  19. Probabilistic risk assessment course documentation. Volume 1: PRA fundamentals

    International Nuclear Information System (INIS)

    Breeding, R.J.; Leahy, T.J.; Young, J.

    1985-08-01

    The full range of PRA topics is presented, with a special emphasis on systems analysis and PRA applications. Systems analysis topics include system modeling such as fault tree and event tree construction, failure rate data, and human Reliability. The discussion of PRA applications is centered on past and present PRA based programs, such as WASH-1400 and the Interim Reliability Evaluation Program, as well as on some of the potential future applications of PRA. The relationship of PRA to generic safety issues such as station blackout and Anticipated Transient Without Scram (ATWS) is also discussed. In addition to system modeling, the major PRA tasks of accident process analysis, and consequence analysis are presented. An explanation of the results of these activities, and the techniques by which these results are derived, forms the basis for a discussion of these topics. An additional topic which is presented in this course is the topic of PRA management, organization, and evaluation. 84 figs., 41 tabs

  20. Deterministic and probabilistic approach to determine seismic risk of nuclear power plants; a practical example

    International Nuclear Information System (INIS)

    Soriano Pena, A.; Lopez Arroyo, A.; Roesset, J.M.

    1976-01-01

    The probabilistic and deterministic approaches for calculating the seismic risk of nuclear power plants are both applied to a particular case in Southern Spain. The results obtained by both methods, when varying the input data, are presented and some conclusions drawn in relation to the applicability of the methods, their reliability and their sensitivity to change

  1. Probabilistic modeling of dietary intake of substances - The risk management question governs the method

    NARCIS (Netherlands)

    Pieters MN; Ossendorp BC; Bakker MI; Slob W; SIR

    2005-01-01

    In this report the discussion on the use of probabilistic modeling in relation to pesticide use in food crops is analyzed. Due to different policy questions the current discussion is complex and considers safety of an MRL as well as probability of a health risk. The question regarding the use of

  2. Probabilistic risk models for multiple disturbances: an example of forest insects and wildfires

    Science.gov (United States)

    Haiganoush K. Preisler; Alan A. Ager; Jane L. Hayes

    2010-01-01

    Building probabilistic risk models for highly random forest disturbances like wildfire and forest insect outbreaks is a challenging. Modeling the interactions among natural disturbances is even more difficult. In the case of wildfire and forest insects, we looked at the probability of a large fire given an insect outbreak and also the incidence of insect outbreaks...

  3. 77 FR 61446 - Proposed Revision Probabilistic Risk Assessment and Severe Accident Evaluation for New Reactors

    Science.gov (United States)

    2012-10-09

    ... Severe Accident Evaluation for New Reactors AGENCY: Nuclear Regulatory Commission. ACTION: Standard... its Standard Review Plan (SRP), Section 19.0, ``Probabilistic Risk Assessment and Severe Accident... assessment (PRA) information and severe accident assessments for new reactors submitted to support design...

  4. Innovative probabilistic risk assessment applications: barrier impairments and fracture toughness. Panel Discussion

    International Nuclear Information System (INIS)

    Osterman, Michael; Root, Steven; Li, F.; Modarres, Mohammad; Reinhart, F. Mark; Bradley, Biff; Calhoun, David J.

    2001-01-01

    Full text of publication follows: New probabilistic risk assessment (PRA) applications promise to improve the overall safety and efficiency of nuclear plant operations. This discussion will explore the use of PRA in evaluating barrier integrity with respect to the consequences of natural phenomena such as tornadoes, floods, and harsh environments. Additionally, the session will explore proposals to improve fracture toughness techniques using PRA. (authors)

  5. A review of the report ''IAEA safety targets and probabilistic risk assessment'' prepared for Greenpeace International

    International Nuclear Information System (INIS)

    1991-01-01

    At the request of the Director General, INSAG reviewed the report ''IAEA Safety Targets and Probabilistic Risk Assessment'' prepared for Greenpeace International by the Gesellschaft fuer Oekologische Forschung und Beratung mbH, Hannover, Germany. The conclusions of the report as well as the review results of INSAG experts are reproduced in this document

  6. The Terrestrial Investigation Model: A probabilistic risk assessment model for birds exposed to pesticides

    Science.gov (United States)

    One of the major recommendations of the National Academy of Science to the USEPA, NMFS and USFWS was to utilize probabilistic methods when assessing the risks of pesticides to federally listed endangered and threatened species. The Terrestrial Investigation Model (TIM, version 3....

  7. Potential for the adoption of probabilistic risk assessments by end-users and decision-makers

    DEFF Research Database (Denmark)

    Frewer, Lynn J.; Fischer, Arnout R. H.; van den Brink, Paul J.

    2008-01-01

    -user and regulatory uptake has not been, to date, extensive. A case study, utilizing the Theory of Planned Behavior, was conducted in order to identify potential determinants of end-user adoption of probabilistic risk assessments associated with the ecotoxicological impact of pesticides. Seventy potential end...

  8. Optimal Portfolio Allocation under a Probabilistic Risk Constraint and the Incentives for Financial Innovation

    NARCIS (Netherlands)

    J. Daníelsson (Jón); B.N. Jorgensen (Bjørn); C.G. de Vries (Casper); X. Yang (Xiaoguang)

    2001-01-01

    textabstractWe derive, in a complete markets environment, an investor's optimal portfolio allocation subject to both a budget constraint and a probabilistic risk constraint. We demonstrate that the set of feasible portfolios need not be connected or convex, while the number of local optima increases

  9. Report on probabilistic safety assessment (PSA) quality assurance in utilization of risk information

    International Nuclear Information System (INIS)

    2006-12-01

    Recently in Japan, introduction of nuclear safety regulations using risk information such as probabilistic safety assessment (PSA) has been considered and utilization of risk information in the rational and practical measures on safety assurance has made a progress to start with the operation or inspection area. The report compiled results of investigation and studies of PSA quality assurance in risk-informed activities in the USA. Relevant regulatory guide and standard review plan as well as issues and recommendations were reviewed for technical adequacy and advancement of probabilistic risk assessment technology in risk-informed decision making. Useful and important information to be referred as issues in PSA quality assurance was identified. (T. Tanaka)

  10. Urban trees and the risk of poor birth outcomes

    Science.gov (United States)

    Geoffrey H. Donovan; Yvonne L. Michael; David T. Butry; Amy D. Sullivan; John M. Chase

    2011-01-01

    This paper investigated whether greater tree-canopy cover is associated with reduced risk of poor birth outcomes in Portland, Oregon. Residential addresses were geocoded and linked to classified-aerial imagery to calculate tree-canopy cover in 50, 100, and 200 m buffers around each home in our sample (n=5696). Detailed data on maternal characteristics and additional...

  11. Probabilistic Insurance

    NARCIS (Netherlands)

    Wakker, P.P.; Thaler, R.H.; Tversky, A.

    1997-01-01

    Probabilistic insurance is an insurance policy involving a small probability that the consumer will not be reimbursed. Survey data suggest that people dislike probabilistic insurance and demand more than a 20% reduction in premium to compensate for a 1% default risk. These observations cannot be

  12. Probabilistic Insurance

    NARCIS (Netherlands)

    P.P. Wakker (Peter); R.H. Thaler (Richard); A. Tversky (Amos)

    1997-01-01

    textabstractProbabilistic insurance is an insurance policy involving a small probability that the consumer will not be reimbursed. Survey data suggest that people dislike probabilistic insurance and demand more than a 20% reduction in the premium to compensate for a 1% default risk. While these

  13. Survey of probabilistic methods in safety and risk assessment for nuclear power plant licensing

    International Nuclear Information System (INIS)

    1984-04-01

    After an overview about the goals and general methods of probabilistic approaches in nuclear safety the main features of probabilistic safety or risk assessment (PRA) methods are discussed. Mostly in practical applications not a full-fledged PRA is applied but rather various levels of analysis leading from unavailability assessment of systems over the more complex analysis of the probable core damage stages up to the assessment of the overall health effects on the total population from a certain practice. The various types of application are discussed in relation to their limitation and benefits for different stages of design or operation of nuclear power plants. This gives guidance for licensing staff to judge the usefulness of the various methods for their licensing decisions. Examples of the application of probabilistic methods in several countries are given. Two appendices on reliability analysis and on containment and consequence analysis provide some more details on these subjects. (author)

  14. Advanced Small Modular Reactor (SMR) Probabilistic Risk Assessment (PRA) Technical Exchange Meeting

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Curtis [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2013-09-01

    During FY13, the INL developed an advanced SMR PRA framework which has been described in the report Small Modular Reactor (SMR) Probabilistic Risk Assessment (PRA) Detailed Technical Framework Specification, INL/EXT-13-28974 (April 2013). In this framework, the various areas are considered: Probabilistic models to provide information specific to advanced SMRs Representation of specific SMR design issues such as having co-located modules and passive safety features Use of modern open-source and readily available analysis methods Internal and external events resulting in impacts to safety All-hazards considerations Methods to support the identification of design vulnerabilities Mechanistic and probabilistic data needs to support modeling and tools In order to describe this framework more fully and obtain feedback on the proposed approaches, the INL hosted a technical exchange meeting during August 2013. This report describes the outcomes of that meeting.

  15. Key attributes of the SAPHIRE risk and reliability analysis software for risk-informed probabilistic applications

    International Nuclear Information System (INIS)

    Smith, Curtis; Knudsen, James; Kvarfordt, Kellie; Wood, Ted

    2008-01-01

    The Idaho National Laboratory is a primary developer of probabilistic risk and reliability analysis (PRRA) tools, dating back over 35 years. Evolving from mainframe-based software, the current state-of-the-practice has led to the creation of the SAPHIRE software. Currently, agencies such as the Nuclear Regulatory Commission, the National Aeronautics and Aerospace Agency, the Department of Energy, and the Department of Defense use version 7 of the SAPHIRE software for many of their risk-informed activities. In order to better understand and appreciate the power of software as part of risk-informed applications, we need to recall that our current analysis methods and solution methods have built upon pioneering work done 30-40 years ago. We contrast this work with the current capabilities in the SAPHIRE analysis package. As part of this discussion, we provide information for both the typical features and special analysis capabilities, which are available. We also present the application and results typically found with state-of-the-practice PRRA models. By providing both a high-level and detailed look at the SAPHIRE software, we give a snapshot in time for the current use of software tools in a risk-informed decision arena

  16. Probabilistic Seismic Risk Assessment in Manizales, Colombia:Quantifying Losses for Insurance Purposes

    Institute of Scientific and Technical Information of China (English)

    Mario A.Salgado-Gálvez; Gabriel A.Bernal; Daniela Zuloaga; Mabel C.Marulanda; Omar-Darío Cardona; Sebastián Henao

    2017-01-01

    A fully probabilistic seismic risk assessment was developed in Manizales,Colombia,considering assets of different types.The first type includes elements that are part of the water and sewage network,and the second type includes public and private buildings.This assessment required the development of a probabilistic seismic hazard analysis that accounts for the dynamic soil response,assembling high resolution exposure databases,and the development of damage models for different types of elements.The economic appraisal of the exposed assets was developed together with specialists of the water utilities company of Manizales and the city administration.The risk assessment was performed using several Comprehensive Approach to Probabilistic Risk Assessment modules as well as the R-System,obtaining results in terms of traditional metrics such as loss exceedance curve,average annual loss,and probable maximum loss.For the case of pipelines,repair rates were also estimated.The results for the water and sewage network were used in activities related to the expansion and maintenance strategies,as well as for the exploration of financial retention and transfer alternatives using insurance schemes based on technical,probabilistic,and prospective damage and loss estimations.In the case of the buildings,the results were used in the update of the technical premium values of the existing collective insurance scheme.

  17. Application of probabilistic risk assessment to advanced liquid metal reactor designs

    International Nuclear Information System (INIS)

    Carroll, W.P.; Temme, M.I.

    1987-01-01

    The United States Department of Energy (US DOE) has been active in the development and application of probabilistic risk assessment methods within its liquid metal breeder reactor development program for the past eleven years. These methods have been applied to comparative risk evaluations, the selection of design features for reactor concepts, the selection and emphasis of research and development programs, and regulatory discussions. The application of probabilistic methods to reactors which are in the conceptual design stage presents unique data base, modeling, and timing challenges, and excellent opportunities to improve the final design. We provide here the background and insights on the experience which the US DOE liquid metal breeder reactor program has had in its application of probabilistic methods to the Clinch River Breeder Reactor Plant project, the Conceptual Design State of the Large Development Plant, and updates on this design. Plans for future applications of probabilistic risk assessment methods are also discussed. The US DOE is embarking on an innovative design program for liquid metal reactors. (author)

  18. Probabilistic risk assessment for new and existing chemicals: Example calculations

    NARCIS (Netherlands)

    Jager T; Hollander HA den; Janssen GB; Poel P van der; Rikken MGJ; Vermeire TG; ECO; CSR; LAE; CSR

    2000-01-01

    In the risk assessment methods for new and existing chemicals in the EU, "risk" is characterised by means of the deterministic quotient of exposure and effects (PEC/PNEC or Margin of Safety). From a scientific viewpoint, the uncertainty in the risk quotient should be accounted for explicitly in the

  19. Probabilistic fuzzy systems in value-at-risk estimation

    NARCIS (Netherlands)

    Almeida, R.J.; Kaymak, U.

    2009-01-01

    Value-at-risk (VaR) is a popular measure for quantifying the market risk that a financial institution faces into a single number. Owing to the complexity of financial markets, the risks associated with a portfolio varies over time. Consequently, advanced methods of VaR estimation use parametric

  20. The Constitutive Element of Probabilistic Agency in Risk

    DEFF Research Database (Denmark)

    Merkelsen, Henrik

    2011-01-01

    Defining central concepts with accuracy is crucial to any scientific discipline. A recent debate over risk definitions in this journal illustrates the far reaching consequences of divergent definitions. Aven and Renn define risk as a social construct while Rosa defines risk as an ontological fact...

  1. Scenario logic and probabilistic management of risk in business and engineering

    CERN Document Server

    Solojentsev, E D

    2005-01-01

    In this volume the methodological aspects of the scenario logic and probabilistic (LP) non-success risk management are considered. The theoretical bases of scenario non-success risk LP-management in business and engineering are also stated. Methods and algorithms for the scenario risk LP-management in problems of classification, investment and effectiveness are described. Risk LP- models and results of numerical investigations for credit risks, risk of frauds, security portfolio risk, risk of quality, accuracy, and risk in multi-stage systems reliability are given. In addition, a rather large number of new problems of estimation, analysis and management of risk are considered. Software for risk problems based on LP-methods, LP-theory, and GIE are described too. Audience This volume is intended for experts and scientists in the area of the risk in business and engineering, in problems of classification, investment and effectiveness, and post-graduates in those subject areas.

  2. Probabilistic risk analysis for the NASA space shuttle: a brief history and current work

    International Nuclear Information System (INIS)

    Pate-Cornell, Elisabeth; Dillon, Robin

    2001-01-01

    While NASA managers have always relied on risk analysis tools for the development and maintenance of space projects, quantitative and especially probabilistic techniques have been gaining acceptance in recent years. In some cases, the studies have been required, for example, to launch the Galileo spacecraft with plutonium fuel, but these successful applications have helped to demonstrate the benefits of these tools. This paper reviews the history of probabilistic risk analysis (PRA) by NASA for the space shuttle program and discusses the status of the on-going development of the Quantitative Risk Assessment System (QRAS) software that performs PRA. The goal is to have within NASA a tool that can be used when needed to update previous risk estimates and to assess the benefits of possible upgrades to the system

  3. A probabilistic assessment of health risks associated with short-term exposure to tropospheric ozone

    Energy Technology Data Exchange (ETDEWEB)

    Whitfield, R.G; Biller, W.F.; Jusko, M.J.; Keisler, J.M.

    1996-06-01

    The work described in this report is part of a larger risk assessment sponsored by the U.S. Environmental Protection Agency. Earlier efforts developed exposure-response relationships for acute health effects among populations engaged in heavy exertion. Those efforts also developed a probabilistic national ambient air quality standards exposure model and a general methodology for integrating probabilistic exposure-response relation- ships and exposure estimates to calculate overall risk results. Recently published data make it possible to model additional health endpoints (for exposure at moderate exertion), including hospital admissions. New air quality and exposure estimates for alternative national ambient air quality standards for ozone are combined with exposure-response models to produce the risk results for hospital admissions and acute health effects. Sample results explain the methodology and introduce risk output formats.

  4. Space Shuttle Probabilistic Risk Assessment (SPRA) Iteration 3.2

    Science.gov (United States)

    Boyer, Roger L.

    2010-01-01

    The Shuttle is a very reliable vehicle in comparison with other launch systems. Much of the risk posed by Shuttle operations is related to fundamental aspects of the spacecraft design and the environments in which it operates. It is unlikely that significant design improvements can be implemented to address these risks prior to the end of the Shuttle program. The model will continue to be used to identify possible emerging risk drivers and allow management to make risk-informed decisions on future missions. Potential uses of the SPRA in the future include: - Calculate risk impact of various mission contingencies (e.g. late inspection, crew rescue, etc.). - Assessing the risk impact of various trade studies (e.g. flow control valves). - Support risk analysis on mission specific events, such as in flight anomalies. - Serve as a guiding star and data source for future NASA programs.

  5. Correlation model to analyze dependent failures for probabilistic risk assessment

    International Nuclear Information System (INIS)

    Dezfuli, H.

    1985-01-01

    A methodology is formulated to study the dependent (correlated) failures of various abnormal events in nuclear power plants. This methodology uses correlation analysis is a means for predicting and quantifying the dependent failures. Appropriate techniques are also developed to incorporate the dependent failure in quantifying fault trees and accident sequences. The uncertainty associated with each estimation in all of the developed techniques is addressed and quantified. To identify the relative importance of the degree of dependency (correlation) among events and to incorporate these dependencies in the quantification phase of PRA, the interdependency between a pair of events in expressed with the aid of the correlation coefficient. For the purpose of demonstrating the methodology, the data base used in the Accident Sequence Precursor Study (ASP) was adopted and simulated to obtain distributions for the correlation coefficients. A computer program entitled Correlation Coefficient Generator (CCG) was developed to generate a distribution for each correlation coefficient. The method of bootstrap technique was employed in the CCG computer code to determine confidence limits of the estimated correlation coefficients. A second computer program designated CORRELATE was also developed to obtain probability intervals for both fault trees and accident sequences with statistically correlated failure data

  6. Probabilistic Modeling of Seismic Risk Based Design for a Dual System Structure

    OpenAIRE

    Sidi, Indra Djati

    2017-01-01

    The dual system structure concept has gained popularity in the construction of high-rise buildings over the last decades. Meanwhile, earthquake engineering design provisions for buildings have moved from the uniform hazard concept to the uniform risk concept upon recognizing the uncertainties involved in the earthquake resistance of concrete structures. In this study, a probabilistic model for the evaluation of such risk is proposed for a dual system structure consisting of shear walls or cor...

  7. Probabilistic cumulative risk assessment of anti-androgenic pesticides in food

    DEFF Research Database (Denmark)

    Müller, Anne Kirstine; Bosgra, Sieto; Boon, Polly E.

    2009-01-01

    In this paper, we present a cumulative risk assessment of three anti-androgenic pesticides (vinclozolin, procymidone and prochloraz) using the relative potency factor (RPF) approach and an integrated probabilistic risk assessment (IPRA) model. RPFs for each substance were estimated for three......) and the fraction of individuals with IMoEs vinclozolin, procymidone and prochloraz is not likely to be of concern for the reproductive development of their male foetuses. However...

  8. Dynamic Positioning System (DPS) Risk Analysis Using Probabilistic Risk Assessment (PRA)

    Science.gov (United States)

    Thigpen, Eric B.; Boyer, Roger L.; Stewart, Michael A.; Fougere, Pete

    2017-01-01

    The National Aeronautics and Space Administration (NASA) Safety & Mission Assurance (S&MA) directorate at the Johnson Space Center (JSC) has applied its knowledge and experience with Probabilistic Risk Assessment (PRA) to projects in industries ranging from spacecraft to nuclear power plants. PRA is a comprehensive and structured process for analyzing risk in complex engineered systems and/or processes. The PRA process enables the user to identify potential risk contributors such as, hardware and software failure, human error, and external events. Recent developments in the oil and gas industry have presented opportunities for NASA to lend their PRA expertise to both ongoing and developmental projects within the industry. This paper provides an overview of the PRA process and demonstrates how this process was applied in estimating the probability that a Mobile Offshore Drilling Unit (MODU) operating in the Gulf of Mexico and equipped with a generically configured Dynamic Positioning System (DPS) loses location and needs to initiate an emergency disconnect. The PRA described in this paper is intended to be generic such that the vessel meets the general requirements of an International Maritime Organization (IMO) Maritime Safety Committee (MSC)/Circ. 645 Class 3 dynamically positioned vessel. The results of this analysis are not intended to be applied to any specific drilling vessel, although provisions were made to allow the analysis to be configured to a specific vessel if required.

  9. Probabilistic environmental risk characterization of pharmaceuticals in sewage treatment plant discharges.

    Science.gov (United States)

    Christensen, Anne Munch; Markussen, Bo; Baun, Anders; Halling-Sørensen, Bent

    2009-10-01

    The occurrence of pharmaceuticals in different water bodies and the findings of effects on aquatic organisms in ecotoxicity tests have raised concerns about environmental risks of pharmaceuticals in receiving waters. Due to the fact that the amount of ecotoxicological studies has increased significantly during the last decade, probabilistic approaches for risk characterization of these compounds may be feasible. This approach was evaluated by applying it to 22 human-used pharmaceuticals covering both pharmaceuticals with a high volume and high ecotoxicity, using ecotoxicological effect data from laboratory studies and comparing these to monitoring data on the effluents from sewage treatment plants in Europe and pharmaceutical sales quantities. We found that for 19 of the 22 selected pharmaceuticals the existing data were sufficient for probabilistic risk characterizations. The subsequently modeled ratios between monitored concentrations and low-effect concentrations were mostly above a factor of 100. Compared to the current paradigm for EU environmental risk assessment where a safety factor of 10 or 100 might have been used it seems that for the modeled compounds there's a low environmental risk. However, similarly calculated ratios for five pharmaceuticals (propranolol, ibuprofen, furosemide, ofloxacin, and ciprofloxacin) were below 100, while ibuprofen and ciprofloxacin are considered to be of high concern due to lack of ecotoxicity studies. This paper shows that by applying probabilistic approaches, existing data can be used to execute a comprehensive study on probability of impacts, thereby contributing to a more comprehensive environmental risk assessment of pharmaceuticals.

  10. The application of probabilistic risk assessment to inherently safe reactors

    International Nuclear Information System (INIS)

    Cave, L.; Kastenberg, W.E.

    1987-01-01

    In the development of safety goals and design criteria for 'inherently safe' reactors a question which arises is 'To what extent is PRA relevant.' To answer this question it is necessary to consider both the risk to the public and the investment risk to the utility. In this paper the factors which are likely to determine safety objectives and their allocation are presented. (orig.)

  11. Site-specific probabilistic ecological risk assessment of a volatile chlorinated hydrocarbon-contaminated tidal estuary.

    Science.gov (United States)

    Hunt, James; Birch, Gavin; Warne, Michael St J

    2010-05-01

    Groundwater contaminated with volatile chlorinated hydrocarbons (VCHs) was identified as discharging to Penrhyn Estuary, an intertidal embayment of Botany Bay, New South Wales, Australia. A screening-level hazard assessment of surface water in Penrhyn Estuary identified an unacceptable hazard to marine organisms posed by VCHs. Given the limitations of hazard assessments, the present study conducted a higher-tier, quantitative probabilistic risk assessment using the joint probability curve (JPC) method that accounted for variability in exposure and toxicity profiles to quantify risk (delta). Risk was assessed for 24 scenarios, including four areas of the estuary based on three exposure scenarios (low tide, high tide, and both low and high tides) and two toxicity scenarios (chronic no-observed-effect concentrations [NOEC] and 50% effect concentrations [EC50]). Risk (delta) was greater at low tide than at high tide and varied throughout the tidal cycle. Spatial distributions of risk in the estuary were similar using both NOEC and EC50 data. The exposure scenario including data combined from both tides was considered the most accurate representation of the ecological risk in the estuary. When assessing risk using data across both tides, the greatest risk was identified in the Springvale tributary (delta=25%)-closest to the source area-followed by the inner estuary (delta=4%) and the Floodvale tributary (delta=2%), with the lowest risk in the outer estuary (delta=0.1%), farthest from the source area. Going from the screening level ecological risk assessment (ERA) to the probabilistic ERA changed the risk from unacceptable to acceptable in 50% of exposure scenarios in two of the four areas within the estuary. The probabilistic ERA provided a more realistic assessment of risk than the screening-level hazard assessment. Copyright (c) 2010 SETAC.

  12. Probabilistic disaggregation of a spatial portfolio of exposure for natural hazard risk assessment

    DEFF Research Database (Denmark)

    Custer, Rocco; Nishijima, Kazuyoshi

    2018-01-01

    In natural hazard risk assessment situations are encountered where information on the portfolio of exposure is only available in a spatially aggregated form, hindering a precise risk assessment. Recourse might be found in the spatial disaggregation of the portfolio of exposure to the resolution...... of a portfolio of buildings in two communes in Switzerland and the results are compared to sample observations. The relevance of probabilistic disaggregation uncertainty in natural hazard risk assessment is illustrated with the example of a simple flood risk assessment....

  13. Development of a Quantitative Framework for Regulatory Risk Assessments: Probabilistic Approaches

    International Nuclear Information System (INIS)

    Wilmot, R.D.

    2003-11-01

    The Swedish regulators have been active in the field of performance assessment for many years and have developed sophisticated approaches to the development of scenarios and other aspects of assessments. These assessments have generally used dose as the assessment end-point and have been based on deterministic calculations. Recently introduced Swedish regulations have introduced a risk criterion for radioactive waste disposal: the annual risk of harmful effects after closure of a disposal facility should not exceed 10 -6 for a representative individual in the group exposed to the greatest risk. A recent review of the overall structure of risk assessments in safety cases concluded that there are a number of decisions and assumptions in the development of a risk assessment methodology that could potentially affect the calculated results. Regulatory understanding of these issues, potentially supported by independent calculations, is important in preparing for review of a proponent's risk assessment. One approach to evaluating risk in performance assessments is to use the concept of probability to express uncertainties, and to propagate these probabilities through the analysis. This report describes the various approaches available for undertaking such probabilistic analyses, both as a means of accounting for uncertainty in the determination of risk and more generally as a means of sensitivity and uncertainty analysis. The report discusses the overall nature of probabilistic analyses and how they are applied to both the calculation of risk and sensitivity analyses. Several approaches are available, including differential analysis, response surface methods and simulation. Simulation is the approach most commonly used, both in assessments for radioactive waste disposal and in other subject areas, and the report describes the key stages of this approach in detail. Decisions relating to the development of input PDFs, sampling methods (including approaches to the treatment

  14. An application of the ESD framework to the probabilistic risk assessment of dynamic systems

    International Nuclear Information System (INIS)

    Swaminathan, S.; Smidts, Carol

    2000-01-01

    Dynamic reliability is the probabilistic study of man-machine-software systems affected by an underlying physical process. The theory of probabilistic dynamics established that dynamic reliability methodologies are essentially semi-Markovian frameworks and can be expressed by an extension of the Chapman-Kolmogorov equation. The mathematical complexity associated with the assessment of dynamic systems' behaviour can be rather overwhelming for real life size systems. This is due to the fact that dynamic methodologies emphasize a component based representation rather than the sequence based representation used in the traditional Event Tree/Fault Tree framework or in the original Event Sequence Diagram (ESD) Framework. An extension of the ESD framework was proposed that facilitates capture of dynamic situations. The modeling framework is composed of events, gates, conditions, competitions and constraints which express many of the dynamic situations encountered in the evolution of accidents. The following paper illustrates an application of this extended ESD framework on a complex dynamic application. The problem at hand is an extension of a problem extensively studied in the validation of dynamic reliability algorithms, a simplified model of the fast reactor Europa. A discussion on how ESDs can help in guiding dynamic reliability simulations as well as aggregating and binning the numerous scenarios generated by dynamic reliability algorithms is provided.(author)

  15. Applications and trends of the risk probabilistic analysis

    International Nuclear Information System (INIS)

    De Loera H, M.A.; Arellano G, J.

    1997-01-01

    One of the desirable parameters to know more accurately is related with the risk level in the nuclear power plant; that is to say, how much safety is sufficient. There are several methods that estimate qualitatively the risk level; however, in complex systems as nuclear power plants, chemical plants, refineries and aeronautic systems, between others, the intuition or expert judgment are not the adequate methods for evaluation. (Author)

  16. Analyzing Phylogenetic Trees with Timed and Probabilistic Model Checking: The Lactose Persistence Case Study.

    Science.gov (United States)

    Requeno, José Ignacio; Colom, José Manuel

    2014-12-01

    Model checking is a generic verification technique that allows the phylogeneticist to focus on models and specifications instead of on implementation issues. Phylogenetic trees are considered as transition systems over which we interrogate phylogenetic questions written as formulas of temporal logic. Nonetheless, standard logics become insufficient for certain practices of phylogenetic analysis since they do not allow the inclusion of explicit time and probabilities. The aim of this paper is to extend the application of model checking techniques beyond qualitative phylogenetic properties and adapt the existing logical extensions and tools to the field of phylogeny. The introduction of time and probabilities in phylogenetic specifications is motivated by the study of a real example: the analysis of the ratio of lactose intolerance in some populations and the date of appearance of this phenotype.

  17. Probabilistic risk assessment of abalone Haliotis diversicolor supertexta exposed to waterborne zinc

    International Nuclear Information System (INIS)

    Liao Chungmin; Ling Minpei

    2004-01-01

    This paper describes a risk assessment approach that integrates predicted tissue concentrations of zinc (Zn) with a concentration-response relationship and leads to predictions of survival risk for pond abalone Haliotis diversicolor supertexta as well as to the uncertainties associated with these predictions. The models implemented include a probabilistic bioaccumulation model, which linking biokinetic and consumer-resource models, accounts for Zn exposure profile and a modified Hill model for reconstructing a dose-response profile for abalone exposed to waterborne Zn. The growth risk is assessed by hazard quotients characterized by measured water level and chronic no-observed effect concentration. Our risk analyses for H. diversicolor supertexta reared near Toucheng, Kouhu, and Anping, respectively, in north, central, and south Taiwan region indicate a relatively low likelihood that survival is being affected by waterborne Zn. Expected risks of mortality for abalone were estimated as 0.46 (Toucheng), 0.36 (Kouhu), and 0.29 (Anping). The predicted 90th-percentiles of hazard quotient for potential growth risk were estimated as 1.94 (Toucheng), 0.47 (Kouhu), and 0.51 (Anping). These findings indicate that waterborne Zn exposure poses no significant risk to pond abalone in Kouhu and Anping, yet a relative high growth risk in Toucheng is alarming. Because of a scarcity of toxicity and exposure data, the probabilistic risk assessment was based on very conservative assumptions. - A novel risk assessment method was developed for abalone

  18. Probabilistic risk assessment of abalone Haliotis diversicolor supertexta exposed to waterborne zinc

    Energy Technology Data Exchange (ETDEWEB)

    Liao Chungmin; Ling Minpei

    2004-01-01

    This paper describes a risk assessment approach that integrates predicted tissue concentrations of zinc (Zn) with a concentration-response relationship and leads to predictions of survival risk for pond abalone Haliotis diversicolor supertexta as well as to the uncertainties associated with these predictions. The models implemented include a probabilistic bioaccumulation model, which linking biokinetic and consumer-resource models, accounts for Zn exposure profile and a modified Hill model for reconstructing a dose-response profile for abalone exposed to waterborne Zn. The growth risk is assessed by hazard quotients characterized by measured water level and chronic no-observed effect concentration. Our risk analyses for H. diversicolor supertexta reared near Toucheng, Kouhu, and Anping, respectively, in north, central, and south Taiwan region indicate a relatively low likelihood that survival is being affected by waterborne Zn. Expected risks of mortality for abalone were estimated as 0.46 (Toucheng), 0.36 (Kouhu), and 0.29 (Anping). The predicted 90th-percentiles of hazard quotient for potential growth risk were estimated as 1.94 (Toucheng), 0.47 (Kouhu), and 0.51 (Anping). These findings indicate that waterborne Zn exposure poses no significant risk to pond abalone in Kouhu and Anping, yet a relative high growth risk in Toucheng is alarming. Because of a scarcity of toxicity and exposure data, the probabilistic risk assessment was based on very conservative assumptions. - A novel risk assessment method was developed for abalone.

  19. Hazardous waste transportation risk assessment: Benefits of a combined deterministic and probabilistic Monte Carlo approach in expressing risk uncertainty

    International Nuclear Information System (INIS)

    Policastro, A.J.; Lazaro, M.A.; Cowen, M.A.; Hartmann, H.M.; Dunn, W.E.; Brown, D.F.

    1995-01-01

    This paper presents a combined deterministic and probabilistic methodology for modeling hazardous waste transportation risk and expressing the uncertainty in that risk. Both the deterministic and probabilistic methodologies are aimed at providing tools useful in the evaluation of alternative management scenarios for US Department of Energy (DOE) hazardous waste treatment, storage, and disposal (TSD). The probabilistic methodology can be used to provide perspective on and quantify uncertainties in deterministic predictions. The methodology developed has been applied to 63 DOE shipments made in fiscal year 1992, which contained poison by inhalation chemicals that represent an inhalation risk to the public. Models have been applied to simulate shipment routes, truck accident rates, chemical spill probabilities, spill/release rates, dispersion, population exposure, and health consequences. The simulation presented in this paper is specific to trucks traveling from DOE sites to their commercial TSD facilities, but the methodology is more general. Health consequences are presented as the number of people with potentially life-threatening health effects. Probabilistic distributions were developed (based on actual item data) for accident release amounts, time of day and season of the accident, and meteorological conditions

  20. Probabilistic Risk Assessment on Maritime Spent Nuclear Fuel Transportation

    Energy Technology Data Exchange (ETDEWEB)

    Christian, Robby; Kang, Hyun Gook [KAIST, Daejeon (Korea, Republic of)

    2016-05-15

    Spent nuclear fuel (SNF) management has been an indispensable issue in South Korea. Before a long term SNF solution is implemented, there exists the need to distribute the spent fuel pool storage loads. Transportation of SNF assemblies from populated pools to vacant ones may preferably be done through the maritime mode since all nuclear power plants in South Korea are located at coastal sites. To determine its feasibility, it is necessary to assess risks of the maritime SNF transportation. This work proposes a methodology to assess the risk arising from ship collisions during the transportation of SNF by sea. Its scope is limited to the damage probability of SNF packages given a collision event. The effect of transport parameters' variation to the package damage probability was investigated to obtain insights into possible ways to minimize risks. A reference vessel and transport cask are given in a case study to illustrate the methodology's application.

  1. Probabilistic methodology for estimating radiation-induced cancer risk

    International Nuclear Information System (INIS)

    Dunning, D.E. Jr.; Leggett, R.W.; Williams, L.R.

    1981-01-01

    The RICRAC computer code was developed at Oak Ridge National Laboratory to provide a versatile and convenient methodology for radiation risk assessment. The code allows as input essentially any dose pattern commonly encountered in risk assessments for either acute or chronic exposures, and it includes consideration of the age structure of the exposed population. Results produced by the analysis include the probability of one or more radiation-induced cancer deaths in a specified population, expected numbers of deaths, and expected years of life lost as a result of premature fatalities. These calculatons include consideration of competing risks of death from all other causes. The program also generates a probability frequency distribution of the expected number of cancers in any specified cohort resulting from a given radiation dose. The methods may be applied to any specified population and dose scenario

  2. On the use of judgement in probabilistic risk analysis

    Energy Technology Data Exchange (ETDEWEB)

    Apostolakis, G

    1986-05-01

    The extensive use of judgement in risk studies creates several issues related to the perception of probabilities and the value of formal theories for uncertainty analysis. The direct assessment of probability distributions may lead to biased curves that do not represent the state of knowledge of the assessors. The use of formal methods and the calibration of the analysts help alleviate some of these biases. Case studies involving the assessment of probability distributions for human error rates and for failure rates of components exemplify the importance of the careful use of expert opinions in risk studies.

  3. Probabilistic landslide hazards and risk mapping on Penang Island ...

    Indian Academy of Sciences (India)

    This paper deals with landslide hazards and risk analysis of Penang Island, Malaysia using Geo- .... require a priori knowledge of the main causes of landslides .... Soil. Rengam-bukit. 289450. 10.03. 96. 20.73. 2.07 temiang association. Selangor-kangkong. 34197. 1.18. 0. 0.00. 0.00 association. Local alluvium-. 373655.

  4. The implications of probabilistic risk assessment for safety policy

    International Nuclear Information System (INIS)

    Hayns, M.R.

    1987-01-01

    The use of PRA results in decision making requires a level of understanding on the part of the decision maker which is higher than that obtaining previously. The most important application of PRA lies not in the final results but in the intermediate results which refer to specific systems and operations. Such intermediate results are of great value either at the design stage or later during operation. One of the most 'visible' uses of PRA results is in comparing calculated plant risks with either proposed acceptability criteria, or with other plant, or even natural events. The capability to perform PRA has been established. Only the incorporation of PRA into the licensing process is lacking. The principal conclusions on the implications of PRA for safety policy are as follows: regardless of its state of development, PRA is the only means available for calculating public risk, being able to quantify risk is important in policy related to risk acceptability and to national energy policy. PRAs will be used to establish research and development priorities. Any hazardous plant can be treated using the same methods. More sophisticated methods will be used for solving engineering problems. (author)

  5. Probabilistic risk analysis: its possible use in safeguards problems

    International Nuclear Information System (INIS)

    Rasmussen, N.C.

    1976-01-01

    This paper reviews the methodology which was used in the Reactor Safety Study and in the WASH-1400 report. Its application to the safeguards problem is discussed. It is concluded that, while there are possible applications, an overall quantitative risk assessment of the safeguards issues is at present beyond the capability of the methodology

  6. Hanford Tank Farm interim storage phase probabilistic risk assessment outline

    International Nuclear Information System (INIS)

    1994-01-01

    This report is the second in a series examining the risks for the high level waste (HLW) storage facilities at the Hanford Site. The first phase of the HTF PSA effort addressed risks from Tank 101-SY, only. Tank 101-SY was selected as the initial focus of the PSA because of its propensity to periodically release (burp) a mixture of flammable and toxic gases. This report expands the evaluation of Tank 101-SY to all 177 storage tanks. The 177 tanks are arranged into 18 farms and contain the HLW accumulated over 50 years of weapons material production work. A centerpiece of the remediation activity is the effort toward developing a permanent method for disposing of the HLW tank's highly radioactive contents. One approach to risk based prioritization is to perform a PSA for the whole HLW tank farm complex to identify the highest risk tanks so that remediation planners and managers will have a more rational basis for allocating limited funds to the more critical areas. Section 3 presents the qualitative identification of generic initiators that could threaten to produce releases from one or more tanks. In section 4 a detailed accident sequence model is developed for each initiating event group. Section 5 defines the release categories to which the scenarios are assigned in the accident sequence model and presents analyses of the airborne and liquid source terms resulting from different release scenarios. The conditional consequences measured by worker or public exposure to radionuclides or hazardous chemicals and economic costs of cleanup and repair are analyzed in section 6. The results from all the previous sections are integrated to produce unconditional risk curves in frequency of exceedance format

  7. Hanford Tank Farm interim storage phase probabilistic risk assessment outline

    Energy Technology Data Exchange (ETDEWEB)

    1994-05-19

    This report is the second in a series examining the risks for the high level waste (HLW) storage facilities at the Hanford Site. The first phase of the HTF PSA effort addressed risks from Tank 101-SY, only. Tank 101-SY was selected as the initial focus of the PSA because of its propensity to periodically release (burp) a mixture of flammable and toxic gases. This report expands the evaluation of Tank 101-SY to all 177 storage tanks. The 177 tanks are arranged into 18 farms and contain the HLW accumulated over 50 years of weapons material production work. A centerpiece of the remediation activity is the effort toward developing a permanent method for disposing of the HLW tank`s highly radioactive contents. One approach to risk based prioritization is to perform a PSA for the whole HLW tank farm complex to identify the highest risk tanks so that remediation planners and managers will have a more rational basis for allocating limited funds to the more critical areas. Section 3 presents the qualitative identification of generic initiators that could threaten to produce releases from one or more tanks. In section 4 a detailed accident sequence model is developed for each initiating event group. Section 5 defines the release categories to which the scenarios are assigned in the accident sequence model and presents analyses of the airborne and liquid source terms resulting from different release scenarios. The conditional consequences measured by worker or public exposure to radionuclides or hazardous chemicals and economic costs of cleanup and repair are analyzed in section 6. The results from all the previous sections are integrated to produce unconditional risk curves in frequency of exceedance format.

  8. An Overview of Risk Quantification Issues for Digitalized Nuclear Power Plants using a Static Fault Tree

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun Gook; Kim, Man Cheol; Lee, Seung Jun; Lee, Ho Jung; Eom, Heung Seop; Chol, Jong Gyun; Jang, Seung Cheol [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-08-15

    Risk caused by safety-critical instrumentation and control (I and C) systems considerably affects overall plant risk. As digitalization of safety-critical systems in nuclear power plants progresses, a risk model of a digitalized safety system is required and must be included in a plant safety model in order to assess this risk effect on the plant. Unique features of a digital system cause some challenges in risk modeling. This article aims at providing an overview of the issues related to the development of a static fault-tree-based risk model. We categorize the complicated issues of digital system probabilistic risk assessment (PRA) into four groups based on their characteristics: hardware module issues, software issues, system issues, and safety function issues. Quantification of the effect of these issues dominates the quality of a developed risk model. Recent research activities for addressing various issues, such as the modeling framework of a software-based system, the software failure probability and the fault coverage of a self monitoring mechanism, are discussed. Although these issues are interrelated and affect each other, the categorized and systematic approach suggested here will provide a proper insight for analyzing risk from a digital system

  9. Probabilistic disaggregation model with application to natural hazard risk assessment of portfolios

    DEFF Research Database (Denmark)

    Custer, Rocco; Nishijima, Kazuyoshi

    In natural hazard risk assessment, a resolution mismatch between hazard data and aggregated exposure data is often observed. A possible solution to this issue is the disaggregation of exposure data to match the spatial resolution of hazard data. Disaggregation models available in literature...... disaggregation model that considers the uncertainty in the disaggregation, taking basis in the scaled Dirichlet distribution. The proposed probabilistic disaggregation model is applied to a portfolio of residential buildings in the Canton Bern, Switzerland, subject to flood risk. Thereby, the model is verified...... are usually deterministic and make use of auxiliary indicator, such as land cover, to spatially distribute exposures. As the dependence between auxiliary indicator and disaggregated number of exposures is generally imperfect, uncertainty arises in disaggregation. This paper therefore proposes a probabilistic...

  10. Tolerability of risk, safety assessment principles and their implications for probabilistic safety analysis

    International Nuclear Information System (INIS)

    Ewing, D.J.F.; Campbell, J.F.

    1994-01-01

    This paper gives a regulatory view of probabilistic safety assessment as seen by the Nuclear Installations Inspectorate (NII) and in the light of the general regulatory risk aims set out in the Health and Safety Executive's (HSE) The tolerability of risk from nuclear power stations (TOR) and in Safety assessment principles for nuclear plants (SAPs), prepared by NII on behalf of the HSE. Both of these publications were revised and republished in 1992. This paper describes the SAPs, together with the historical background, the motivation for review, the effects of the Sizewell and Hinkley Point C public inquiries, changes since the original versions, comparison with international standards and use in assessment. For new plant, probabilistic safety analysis (PSA) is seen as an essential tool in balancing the safety of the design and in demonstrating compliance with TOR and the SAPs. (Author)

  11. A fuzzy-based reliability approach to evaluate basic events of fault tree analysis for nuclear power plant probabilistic safety assessment

    International Nuclear Information System (INIS)

    Purba, Julwan Hendry

    2014-01-01

    Highlights: • We propose a fuzzy-based reliability approach to evaluate basic event reliabilities. • It implements the concepts of failure possibilities and fuzzy sets. • Experts evaluate basic event failure possibilities using qualitative words. • Triangular fuzzy numbers mathematically represent qualitative failure possibilities. • It is a very good alternative for conventional reliability approach. - Abstract: Fault tree analysis has been widely utilized as a tool for nuclear power plant probabilistic safety assessment. This analysis can be completed only if all basic events of the system fault tree have their quantitative failure rates or failure probabilities. However, it is difficult to obtain those failure data due to insufficient data, environment changing or new components. This study proposes a fuzzy-based reliability approach to evaluate basic events of system fault trees whose failure precise probability distributions of their lifetime to failures are not available. It applies the concept of failure possibilities to qualitatively evaluate basic events and the concept of fuzzy sets to quantitatively represent the corresponding failure possibilities. To demonstrate the feasibility and the effectiveness of the proposed approach, the actual basic event failure probabilities collected from the operational experiences of the David–Besse design of the Babcock and Wilcox reactor protection system fault tree are used to benchmark the failure probabilities generated by the proposed approach. The results confirm that the proposed fuzzy-based reliability approach arises as a suitable alternative for the conventional probabilistic reliability approach when basic events do not have the corresponding quantitative historical failure data for determining their reliability characteristics. Hence, it overcomes the limitation of the conventional fault tree analysis for nuclear power plant probabilistic safety assessment

  12. An evaluation of the reliability and usefulness of external-initiator PRA [probabilistic risk analysis] methodologies

    International Nuclear Information System (INIS)

    Budnitz, R.J.; Lambert, H.E.

    1990-01-01

    The discipline of probabilistic risk analysis (PRA) has become so mature in recent years that it is now being used routinely to assist decision-making throughout the nuclear industry. This includes decision-making that affects design, construction, operation, maintenance, and regulation. Unfortunately, not all sub-areas within the larger discipline of PRA are equally ''mature,'' and therefore the many different types of engineering insights from PRA are not all equally reliable. 93 refs., 4 figs., 1 tab

  13. An evaluation of the reliability and usefulness of external-initiator PRA (probabilistic risk analysis) methodologies

    Energy Technology Data Exchange (ETDEWEB)

    Budnitz, R.J.; Lambert, H.E. (Future Resources Associates, Inc., Berkeley, CA (USA))

    1990-01-01

    The discipline of probabilistic risk analysis (PRA) has become so mature in recent years that it is now being used routinely to assist decision-making throughout the nuclear industry. This includes decision-making that affects design, construction, operation, maintenance, and regulation. Unfortunately, not all sub-areas within the larger discipline of PRA are equally mature,'' and therefore the many different types of engineering insights from PRA are not all equally reliable. 93 refs., 4 figs., 1 tab.

  14. Approach to modeling of human performance for purposes of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Swain, A.D.

    1983-01-01

    This paper describes the general approach taken in NUREG/CR-1278 to model human performance in sufficienct detail to permit probabilistic risk assessments of nuclear power plant operations. To show the basis for the more specific models in the above NUREG, a simplified model of the human component in man-machine systems is presented, the role of performance shaping factors is discussed, and special problems in modeling the cognitive aspect of behavior are described

  15. Probabilistic risk assessment (PRA): status report and guidance for regulatory application. Draft report for comment

    International Nuclear Information System (INIS)

    1984-02-01

    This document describes the current status of the methodologies used in probabilistic risk assessment (PRA) and provides guidance for the application of the results of PRAs to the nuclear reactor regulatory process. The PRA studies that have been completed or are underway are reviewed. The levels of maturity of the methodologies used in a PRA are discussed. Insights derived from PRAs are listed. The potential uses of PRA results for regulatory purposes are discussed

  16. Seismic, high wind, tornado, and probabilistic risk assessment of the high flux isotope reactor

    International Nuclear Information System (INIS)

    Harris, S.P.; Hashimoto, P.S.; Dizon, J.O.; Hashimoto, P.S.

    1989-01-01

    Natural phenomena analyses were performed on the High Flux Isotope Reactor (HFIR). Deterministic and probabilistic evaluations were made to determine the risks resulting from earthquakes, high winds, and tornadoes. Analytic methods in conjunction with field evaluations and an earthquake experience data base evaluation methods were used to provide more realistic results in a shorter amount of time. Plant modifications completed in preparation for HFIR restart and potential future enhancements are discussed

  17. Seismic, high wind, tornado, and probabilistic risk assessments of the High Flux Isotope Reactor

    International Nuclear Information System (INIS)

    Harris, S.P.; Stover, R.L.; Hashimoto, P.S.; Dizon, J.O.

    1989-01-01

    Natural phenomena analyses were performed on the High Flux Isotope Reactor (HFIR) Deterministic and probabilistic evaluations were made to determine the risks resulting from earthquakes, high winds, and tornadoes. Analytic methods in conjunction with field evaluations and an earthquake experience data base evaluation methods were used to provide more realistic results in a shorter amount of time. Plant modifications completed in preparation for HFIR restart and potential future enhancements are discussed. 5 figs

  18. Application of Bayesian network to the probabilistic risk assessment of nuclear waste disposal

    International Nuclear Information System (INIS)

    Lee, Chang-Ju; Lee, Kun Jai

    2006-01-01

    The scenario in a risk analysis can be defined as the propagating feature of specific initiating event which can go to a wide range of undesirable consequences. If we take various scenarios into consideration, the risk analysis becomes more complex than do without them. A lot of risk analyses have been performed to actually estimate a risk profile under both uncertain future states of hazard sources and undesirable scenarios. Unfortunately, in case of considering specific systems such as a radioactive waste disposal facility, since the behaviour of future scenarios is hardly predicted without special reasoning process, we cannot estimate their risk only with a traditional risk analysis methodology. Moreover, we believe that the sources of uncertainty at future states can be reduced pertinently by setting up dependency relationships interrelating geological, hydrological, and ecological aspects of the site with all the scenarios. It is then required current methodology of uncertainty analysis of the waste disposal facility be revisited under this belief. In order to consider the effects predicting from an evolution of environmental conditions of waste disposal facilities, this paper proposes a quantitative assessment framework integrating the inference process of Bayesian network to the traditional probabilistic risk analysis. We developed and verified an approximate probabilistic inference program for the specific Bayesian network using a bounded-variance likelihood weighting algorithm. Ultimately, specific models, including a model for uncertainty propagation of relevant parameters were developed with a comparison of variable-specific effects due to the occurrence of diverse altered evolution scenarios (AESs). After providing supporting information to get a variety of quantitative expectations about the dependency relationship between domain variables and AESs, we could connect the results of probabilistic inference from the Bayesian network with the consequence

  19. A probabilistic topic model for clinical risk stratification from electronic health records.

    Science.gov (United States)

    Huang, Zhengxing; Dong, Wei; Duan, Huilong

    2015-12-01

    Risk stratification aims to provide physicians with the accurate assessment of a patient's clinical risk such that an individualized prevention or management strategy can be developed and delivered. Existing risk stratification techniques mainly focus on predicting the overall risk of an individual patient in a supervised manner, and, at the cohort level, often offer little insight beyond a flat score-based segmentation from the labeled clinical dataset. To this end, in this paper, we propose a new approach for risk stratification by exploring a large volume of electronic health records (EHRs) in an unsupervised fashion. Along this line, this paper proposes a novel probabilistic topic modeling framework called probabilistic risk stratification model (PRSM) based on Latent Dirichlet Allocation (LDA). The proposed PRSM recognizes a patient clinical state as a probabilistic combination of latent sub-profiles, and generates sub-profile-specific risk tiers of patients from their EHRs in a fully unsupervised fashion. The achieved stratification results can be easily recognized as high-, medium- and low-risk, respectively. In addition, we present an extension of PRSM, called weakly supervised PRSM (WS-PRSM) by incorporating minimum prior information into the model, in order to improve the risk stratification accuracy, and to make our models highly portable to risk stratification tasks of various diseases. We verify the effectiveness of the proposed approach on a clinical dataset containing 3463 coronary heart disease (CHD) patient instances. Both PRSM and WS-PRSM were compared with two established supervised risk stratification algorithms, i.e., logistic regression and support vector machine, and showed the effectiveness of our models in risk stratification of CHD in terms of the Area Under the receiver operating characteristic Curve (AUC) analysis. As well, in comparison with PRSM, WS-PRSM has over 2% performance gain, on the experimental dataset, demonstrating that

  20. Obesity as a risk factor for developing functional limitation among older adults: A conditional inference tree analysis.

    Science.gov (United States)

    Cheng, Feon W; Gao, Xiang; Bao, Le; Mitchell, Diane C; Wood, Craig; Sliwinski, Martin J; Smiciklas-Wright, Helen; Still, Christopher D; Rolston, David D K; Jensen, Gordon L

    2017-07-01

    To examine the risk factors of developing functional decline and make probabilistic predictions by using a tree-based method that allows higher order polynomials and interactions of the risk factors. The conditional inference tree analysis, a data mining approach, was used to construct a risk stratification algorithm for developing functional limitation based on BMI and other potential risk factors for disability in 1,951 older adults without functional limitations at baseline (baseline age 73.1 ± 4.2 y). We also analyzed the data with multivariate stepwise logistic regression and compared the two approaches (e.g., cross-validation). Over a mean of 9.2 ± 1.7 years of follow-up, 221 individuals developed functional limitation. Higher BMI, age, and comorbidity were consistently identified as significant risk factors for functional decline using both methods. Based on these factors, individuals were stratified into four risk groups via the conditional inference tree analysis. Compared to the low-risk group, all other groups had a significantly higher risk of developing functional limitation. The odds ratio comparing two extreme categories was 9.09 (95% confidence interval: 4.68, 17.6). Higher BMI, age, and comorbid disease were consistently identified as significant risk factors for functional decline among older individuals across all approaches and analyses. © 2017 The Obesity Society.

  1. Alternative measures of risk of extreme events in decision trees

    International Nuclear Information System (INIS)

    Frohwein, H.I.; Lambert, J.H.; Haimes, Y.Y.

    1999-01-01

    A need for a methodology to control the extreme events, defined as low-probability, high-consequence incidents, in sequential decisions is identified. A variety of alternative and complementary measures of the risk of extreme events are examined for their usability as objective functions in sequential decisions, represented as single- or multiple-objective decision trees. Earlier work had addressed difficulties, related to non-separability, with the minimization of some measures of the risk of extreme events in sequential decisions. In an extension of these results, it is shown how some non-separable measures of the risk of extreme events can be interpreted in terms of separable constituents of risk, thereby enabling a wider class of measures of the risk of extreme events to be handled in a straightforward manner in a decision tree. Also for extreme events, results are given to enable minimax- and Hurwicz-criterion analyses in decision trees. An example demonstrates the incorporation of different measures of the risk of extreme events in a multi-objective decision tree. Conceptual formulations for optimizing non-separable measures of the risk of extreme events are identified as an important area for future investigation

  2. Multi-Hazard Advanced Seismic Probabilistic Risk Assessment Tools and Applications

    International Nuclear Information System (INIS)

    Coleman, Justin L.; Bolisetti, Chandu; Veeraraghavan, Swetha; Parisi, Carlo; Prescott, Steven R.; Gupta, Abhinav

    2016-01-01

    Design of nuclear power plant (NPP) facilities to resist natural hazards has been a part of the regulatory process from the beginning of the NPP industry in the United States (US), but has evolved substantially over time. The original set of approaches and methods was entirely deterministic in nature and focused on a traditional engineering margins-based approach. However, over time probabilistic and risk-informed approaches were also developed and implemented in US Nuclear Regulatory Commission (NRC) guidance and regulation. A defense-in-depth framework has also been incorporated into US regulatory guidance over time. As a result, today, the US regulatory framework incorporates deterministic and probabilistic approaches for a range of different applications and for a range of natural hazard considerations. This framework will continue to evolve as a result of improved knowledge and newly identified regulatory needs and objectives, most notably in response to the NRC activities developed in response to the 2011 Fukushima accident in Japan. Although the US regulatory framework has continued to evolve over time, the tools, methods and data available to the US nuclear industry to meet the changing requirements have not kept pace. Notably, there is significant room for improvement in the tools and methods available for external event probabilistic risk assessment (PRA), which is the principal assessment approach used in risk-informed regulations and risk-informed decision-making applied to natural hazard assessment and design. This is particularly true if PRA is applied to natural hazards other than seismic loading. Development of a new set of tools and methods that incorporate current knowledge, modern best practice, and state-of-the-art computational resources would lead to more reliable assessment of facility risk and risk insights (e.g., the SSCs and accident sequences that are most risk-significant), with less uncertainty and reduced conservatisms.

  3. Multi-Hazard Advanced Seismic Probabilistic Risk Assessment Tools and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Coleman, Justin L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bolisetti, Chandu [Idaho National Lab. (INL), Idaho Falls, ID (United States); Veeraraghavan, Swetha [Idaho National Lab. (INL), Idaho Falls, ID (United States); Parisi, Carlo [Idaho National Lab. (INL), Idaho Falls, ID (United States); Prescott, Steven R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Gupta, Abhinav [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-09-01

    Design of nuclear power plant (NPP) facilities to resist natural hazards has been a part of the regulatory process from the beginning of the NPP industry in the United States (US), but has evolved substantially over time. The original set of approaches and methods was entirely deterministic in nature and focused on a traditional engineering margins-based approach. However, over time probabilistic and risk-informed approaches were also developed and implemented in US Nuclear Regulatory Commission (NRC) guidance and regulation. A defense-in-depth framework has also been incorporated into US regulatory guidance over time. As a result, today, the US regulatory framework incorporates deterministic and probabilistic approaches for a range of different applications and for a range of natural hazard considerations. This framework will continue to evolve as a result of improved knowledge and newly identified regulatory needs and objectives, most notably in response to the NRC activities developed in response to the 2011 Fukushima accident in Japan. Although the US regulatory framework has continued to evolve over time, the tools, methods and data available to the US nuclear industry to meet the changing requirements have not kept pace. Notably, there is significant room for improvement in the tools and methods available for external event probabilistic risk assessment (PRA), which is the principal assessment approach used in risk-informed regulations and risk-informed decision-making applied to natural hazard assessment and design. This is particularly true if PRA is applied to natural hazards other than seismic loading. Development of a new set of tools and methods that incorporate current knowledge, modern best practice, and state-of-the-art computational resources would lead to more reliable assessment of facility risk and risk insights (e.g., the SSCs and accident sequences that are most risk-significant), with less uncertainty and reduced conservatisms.

  4. Assessment and presentation of uncertainties in probabilistic risk assessment: how should this be done

    International Nuclear Information System (INIS)

    Garlick, A.R.; Holloway, N.J.

    1987-01-01

    Despite continuing improvements in probabilistic risk assessment (PRA) techniques, PRA results, particularly those including degraded core analysis, will have maximum uncertainties of several orders of magnitude. This makes the expression of results, a matter no less important than their estimation. We put forward some ideas on the assessment and expression of highly uncertain quantities, such as probabilities of outcomes of a severe accident. These do not form a consistent set, but rather a number of alternative approaches aimed at stimulating discussion. These include non-probability expressions, such as fuzzy logic or Schafer's support and plausibility which abandon the purely probabilistic expression of risk for a more flexible type of expression, in which other types of measure are possible. The 'risk equivalent plant' concepts represent the opposite approach. Since uncertainty in a risk measure is in itself a form of risk, an attempt is made to define a 'risk equivalent' which is a risk with perfectly defined parameters, regarded (by means of suitable methods of judgement) as 'equally undesirable' with the actual plant. Some guidelines are given on the use of Bayesian methods in data-free or limited data situations. (author)

  5. Ecohydrology of agroecosystems: probabilistic description of yield reduction risk under limited water availability

    Science.gov (United States)

    Vico, Giulia; Porporato, Amilcare

    2013-04-01

    Supplemental irrigation represents one of the main strategies to mitigate the effects of climate variability and stabilize yields. Irrigated agriculture currently provides 40% of food production and its relevance is expected to further increase in the near future, in face of the projected alterations of rainfall patterns and increase in food, fiber, and biofuel demand. Because of the significant investments and water requirements involved in irrigation, strategic choices are needed to preserve productivity and profitability, while maintaining a sustainable water management - a nontrivial task given the unpredictability of the rainfall forcing. To facilitate decision making under uncertainty, a widely applicable probabilistic framework is proposed. The occurrence of rainfall events and irrigation applications are linked probabilistically to crop development during the growing season and yields at harvest. Based on these linkages, the probability density function of yields and corresponding probability density function of required irrigation volumes, as well as the probability density function of yields under the most common case of limited water availability are obtained analytically, as a function of irrigation strategy, climate, soil and crop parameters. The full probabilistic description of the frequency of occurrence of yields and water requirements is a crucial tool for decision making under uncertainty, e.g., via expected utility analysis. Furthermore, the knowledge of the probability density function of yield allows us to quantify the yield reduction hydrologic risk. Two risk indices are defined and quantified: the long-term risk index, suitable for long-term irrigation strategy assessment and investment planning, and the real-time risk index, providing a rigorous probabilistic quantification of the emergence of drought conditions during a single growing season in an agricultural setting. Our approach employs relatively few parameters and is thus easily and

  6. Illstrative probabilistic biosphere model for Yucca Mountain individual risk calculations

    International Nuclear Information System (INIS)

    Wilems, R.E.

    1994-01-01

    The proposed EPA Standards for the disposal of spent fuel, high-level and transuranic radioactive waste prescribe future biosphere--one in which no sustained human activity occurs inside the controlled zone, yet sustained use of groundwater occurs just outside the controlled zone boundary. Performance assessments have generally assumed a person at this location extracts all his water needs directly from the projected contaminated plume for all of his life. Dose to this maximally-exposed individual is too conservative a measure of performance for a nuclear waste repository and does not reflect the isolation characteristics of a site. A better measure is individual risk in which uncertainties in biosphere characteristics for the longer periods of performance, for a site like Yucca Mountain only those characteristics associated with well water scenarios need be prescribed. Such a prescription of the biosphere is appropriate because the goal of the regulations is to provide indicators of future performance so the regulators can make a responsible decision regarding reasonable assurance of public health and safety

  7. Probabilistic escalation modelling

    Energy Technology Data Exchange (ETDEWEB)

    Korneliussen, G.; Eknes, M.L.; Haugen, K.; Selmer-Olsen, S. [Det Norske Veritas, Oslo (Norway)

    1997-12-31

    This paper describes how structural reliability methods may successfully be applied within quantitative risk assessment (QRA) as an alternative to traditional event tree analysis. The emphasis is on fire escalation in hydrocarbon production and processing facilities. This choice was made due to potential improvements over current QRA practice associated with both the probabilistic approach and more detailed modelling of the dynamics of escalating events. The physical phenomena important for the events of interest are explicitly modelled as functions of time. Uncertainties are represented through probability distributions. The uncertainty modelling enables the analysis to be simple when possible and detailed when necessary. The methodology features several advantages compared with traditional risk calculations based on event trees. (Author)

  8. Incorporating linguistic, probabilistic, and possibilistic information in a risk-based approach for ranking contaminated sites.

    Science.gov (United States)

    Zhang, Kejiang; Achari, Gopal; Pei, Yuansheng

    2010-10-01

    Different types of uncertain information-linguistic, probabilistic, and possibilistic-exist in site characterization. Their representation and propagation significantly influence the management of contaminated sites. In the absence of a framework with which to properly represent and integrate these quantitative and qualitative inputs together, decision makers cannot fully take advantage of the available and necessary information to identify all the plausible alternatives. A systematic methodology was developed in the present work to incorporate linguistic, probabilistic, and possibilistic information into the Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE), a subgroup of Multi-Criteria Decision Analysis (MCDA) methods for ranking contaminated sites. The identification of criteria based on the paradigm of comparative risk assessment provides a rationale for risk-based prioritization. Uncertain linguistic, probabilistic, and possibilistic information identified in characterizing contaminated sites can be properly represented as numerical values, intervals, probability distributions, and fuzzy sets or possibility distributions, and linguistic variables according to their nature. These different kinds of representation are first transformed into a 2-tuple linguistic representation domain. The propagation of hybrid uncertainties is then carried out in the same domain. This methodology can use the original site information directly as much as possible. The case study shows that this systematic methodology provides more reasonable results. © 2010 SETAC.

  9. Development of reliability databases and the particular requirements of probabilistic risk analyses

    International Nuclear Information System (INIS)

    Meslin, T.

    1989-01-01

    Nuclear utilities have an increasing need to develop reliability databases for their operating experience. The purposes of these databases are often multiple, including both equipment maintenance aspects and probabilistic risk analyses. EDF has therefore been developing experience feedback databases, including the Reliability Data Recording System (SRDF) and the Event File, as well as the history of numerous operating documents. Furthermore, since the end of 1985, EDF has been preparing a probabilistic safety analysis applied to one 1,300 MWe unit, for which a large amount of data of French origin is necessary. This data concerns both component reliability parameters and initiating event frequencies. The study has thus been an opportunity for trying out the performance databases for a specific application, as well as in-depth audits of a number of nuclear sites to make it possible to validate numerous results. Computer aided data collection is also on trial in a number of plants. After describing the EDF operating experience feedback files, we discuss the particular requirements of probabilistic risk analyses, and the resources implemented by EDF to satisfy them. (author). 5 refs

  10. Probabilistic modeling of the flows and environmental risks of nano-silica

    International Nuclear Information System (INIS)

    Wang, Yan; Kalinina, Anna; Sun, Tianyin; Nowack, Bernd

    2016-01-01

    Nano-silica, the engineered nanomaterial with one of the largest production volumes, has a wide range of applications in consumer products and industry. This study aimed to quantify the exposure of nano-silica to the environment and to assess its risk to surface waters. Concentrations were calculated for four environmental (air, soil, surface water, sediments) and two technical compartments (wastewater, solid waste) for the EU and Switzerland using probabilistic material flow modeling. The corresponding median concentration in surface water is predicted to be 0.12 μg/l in the EU (0.053–3.3 μg/l, 15/85% quantiles). The concentrations in sediments in the complete sedimentation scenario were found to be the largest among all environmental compartments, with a median annual increase of 0.43 mg/kg·y in the EU (0.19–12 mg/kg·y, 15/85% quantiles). Moreover, probabilistic species sensitivity distributions (PSSD) were computed and the risk of nano-silica in surface waters was quantified by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) distribution, which was derived from the cumulative PSSD. This assessment suggests that nano-silica currently poses no risk to aquatic organisms in surface waters. Further investigations are needed to assess the risk of nano-silica in other environmental compartments, which is currently not possible due to a lack of ecotoxicological data. - Highlights: • We quantify the exposure of nano-silica to technical systems and the environment. • The median concentration in surface waters is predicted to be 0.12 μg/L in the EU. • Probabilistic species sensitivity distributions were computed for surface waters. • The risk assessment suggests that nano-silica poses no risk to aquatic organisms.

  11. Scenario logic and probabilistic management of risk in business and engineering

    CERN Document Server

    Solojentsev, Evgueni D

    2009-01-01

    The book proposes a uniform logic and probabilistic (LP) approach to risk estimation and analysis in engineering and economics. It covers the methodological and theoretical basis of risk management at the design, test, and operation stages of economic, banking, and engineering systems with groups of incompatible events (GIE). It considers the risk LP-models in classification, investment, management of companies, bribes and corruption, analysis of risk and efficiency of social and economical processes, and management of development. Key features of this Second Edition: -Five new chapters -Treatment of the basic principles of the modern risk LP theory (the LP-calculus, the LP-methods and the risk LP-theory with GIE) using uniform methodology and terminology with a practical orientation towards both engineering and economics, for the first time in book form -Clear definitions and notations, revised sections and chapters, an extended list of references, and a new subject index -More than a hundred illustrations a...

  12. A probabilistic approach for debris impact risk with numerical simulations of debris behaviors

    International Nuclear Information System (INIS)

    Kihara, Naoto; Matsuyama, Masafumi; Fujii, Naoki

    2013-01-01

    We propose a probabilistic approach for evaluating the impact risk of tsunami debris through Monte Carlo simulations with a combined system comprising a depth-averaged two-dimensional shallow water model and a discrete element model customized to simulate the motions of floating objects such as vessels. In the proposed method, first, probabilistic tsunami hazard analysis is carried out, and the exceedance probability of tsunami height and numerous tsunami time series for various hazard levels on the offshore side of a target site are estimated. Second, a characteristic tsunami time series for each hazard level is created by cluster analysis. Third, using the Monte Carlo simulation model the debris impact probability with the buildings of interest and the exceedance probability of debris impact speed are evaluated. (author)

  13. Evaluation of the seasonal and annual abortifacient risk of western juniper trees on Oregon rangelands: Abortion risk of western juniper trees

    Science.gov (United States)

    Western juniper trees can cause late term abortions in cattle, similar to ponderosa pine trees. Analyses of western juniper trees from 35 locations across the state of Oregon suggest that western juniper trees in all areas present an abortion risk in pregnant cattle. Results from this study demonstr...

  14. Implementation of condition-dependent probabilistic risk assessment using surveillance data on passive components

    International Nuclear Information System (INIS)

    Lewandowski, Radoslaw; Denning, Richard; Aldemir, Tunc; Zhang, Jinsuo

    2016-01-01

    Highlights: • Condition-dependent probabilistic risk assessment (PRA). • Time-dependent characterization of plant-specific risk. • Containment bypass involving in secondary system piping and SCC in SG tubes. - Abstract: A great deal of surveillance data are collected for a nuclear power plant that reflect the changing condition of the plant as it ages. Although surveillance data are used to determine failure probabilities of active components for the plant’s probabilistic risk assessment (PRA) and to indicate the need for maintenance activities, they are not used in a structured manner to characterize the evolving risk of the plant. The present study explores the feasibility of using a condition-dependent PRA framework that takes a first principles approach to modeling the progression of degradation mechanisms to characterize evolving risk, periodically adapting the model to account for surveillance results. A case study is described involving a potential containment bypass accident sequence due to the progression of flow-accelerated corrosion in secondary system piping and stress corrosion cracking of steam generator tubes. In this sequence, a steam line break accompanied by failure to close of a main steam isolation valve results in depressurization of the steam generator and induces the rupture of one or more faulted steam generator tubes. The case study indicates that a condition-dependent PRA framework might be capable of providing early identification of degradation mechanisms important to plant risk.

  15. Bayesian inference in probabilistic risk assessment-The current state of the art

    International Nuclear Information System (INIS)

    Kelly, Dana L.; Smith, Curtis L.

    2009-01-01

    Markov chain Monte Carlo (MCMC) approaches to sampling directly from the joint posterior distribution of aleatory model parameters have led to tremendous advances in Bayesian inference capability in a wide variety of fields, including probabilistic risk analysis. The advent of freely available software coupled with inexpensive computing power has catalyzed this advance. This paper examines where the risk assessment community is with respect to implementing modern computational-based Bayesian approaches to inference. Through a series of examples in different topical areas, it introduces salient concepts and illustrates the practical application of Bayesian inference via MCMC sampling to a variety of important problems

  16. Application of probabilistic fracture mechanics to estimate the risk of rupture of PWR steam generator tubes

    International Nuclear Information System (INIS)

    Pitner, P.; Riffard, T.; Granger, B.

    1992-01-01

    This paper describes the COMPROMIS code developed by Electricite de France (EDF) to optimize the tube bundle maintenance of steam generators. The model, based on probabilistic fracture mechanics, makes it possible to quantify the influence of in-service inspections and maintenance work on the risk of an SG tube rupture, taking all significant parameters into account as random variables (initial defect size distribution, reliability of non-destructive detection and sizing, crack initiation and propagation, critical sizes, leak before risk of break, etc.). (authors). 5 refs., 8 figs., 3 tabs

  17. Notes for a workshop on risk analysis and decision under uncertainty. The practical use of probabilistic and Bayesian methodology inreal life risk assessment and decision problems

    Energy Technology Data Exchange (ETDEWEB)

    1979-01-01

    The use of probabilistic, and especially Bayesian, methods is explained. The concepts of risk and decision, and probability and frequency are elucidated. The mechanics of probability and probabilistic calculations is discussed. The use of the method for particular problems, such as the frequency of aircraft crashes at a specified nuclear reactor site, is illustrated. 64 figures, 20 tables. (RWR)

  18. Notes for a workshop on risk analysis and decision under uncertainty. The practical use of probabilistic and Bayesian methodology inreal life risk assessment and decision problems

    International Nuclear Information System (INIS)

    1979-01-01

    The use of probabilistic, and especially Bayesian, methods is explained. The concepts of risk and decision, and probability and frequency are elucidated. The mechanics of probability and probabilistic calculations is discussed. The use of the method for particular problems, such as the frequency of aircraft crashes at a specified nuclear reactor site, is illustrated. 64 figures, 20 tables

  19. Probabilistic Modeling Of Ocular Biomechanics In VIIP: Risk Stratification

    Science.gov (United States)

    Feola, A.; Myers, J. G.; Raykin, J.; Nelson, E. S.; Mulugeta, L.; Samuels, B.; Ethier, C. R.

    2016-01-01

    the peak strains, we ranked and then normalized these coefficients, considering that normalized values 0.5 implied a substantial influence on the range of the peak strains in the optic nerve head (ONH). IOP and ICP were found to have a major influence on the peak strains in the ONH, as did optic nerve and LC stiffness. Interestingly, the stiffness of the sclera far from the scleral canal did not have a large influence on peak strains in ONH tissues; however, the collagen fiber stiffness in the peripapillary sclera and annular ring both influenced the peak strains within the ONH. We have created a physiologically relevant model that incorporated collagen fibers to study the effects of elevated ICP. Elevated ICP resulted in strains in the optic nerve that are not predicted to occur on earth: the upright or supine conditions. We found that IOP, ICP, lamina cribrosa stiffness and optic nerve stiffness had the highest association with these extreme strains in the ONH. These extreme strains may activate mechanosensitive cells that induce tissue remodeling and are a risk factor for the development of VIIP.

  20. Insights from Guideline for Performance of Internal Flooding Probabilistic Risk Assessment (IFPRA)

    International Nuclear Information System (INIS)

    Choi, Sun Yeong; Yang, Joo Eon

    2009-01-01

    An internal flooding (IF) risk assessment refers to the quantitative probabilistic safety assessment (PSA) treatment of flooding as a result of pipe and tank breaks inside the plants, as well as from other recognized flood sources. The industry consensus standard for Internal Events Probabilistic Risk Assessment (ASME-RA-Sb-2005) includes high-level and supporting technical requirements for developing internal flooding probabilistic risk assessment (IFPRA). This industry standard is endorsed in Regulatory Guide 1.200, Revision 1 as an acceptable approach for addressing the risk contribution from IF events for risk informed applications that require U.S. Nuclear Regulatory commission (NRC) approval. In 2006, EPRI published a draft report for IFPRA that addresses the requirements of the ASME PRA consensus standard and have made efforts to refine and update the final EPRI IFPRA guideline. Westinghouse has performed an IFPRA analysis for several nuclear power plants (NPPs), such as Watts Bar and Fort Calhoun, using the draft EPRI guidelines for development of an IFPRA. Proprietary methodologies have been developed to apply the EPRI guidelines. The objectives of the draft report for IFPRA guideline are to: · Provide guidance for PSA practitioners in the performance of the elements of a PRA associated with internal flooding events consistent with the current state of the art for internal flooding PRA · Provide guidance regarding acceptable approaches that is sufficient to meeting the requirements of the ASME PRA Standard associated with internal flooding · Incorporate lessons learned in the performance of internal flooding PRAs including those identified as pilot applications of earlier drafts of this procedures guide The purpose of this paper is to present a vision for domestic nuclear power plants' IFPRA by comparing the method of the draft EPRI guidelines with the existing IFPRA method for domestic NPPs

  1. Insights from Guideline for Performance of Internal Flooding Probabilistic Risk Assessment (IFPRA)

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sun Yeong; Yang, Joo Eon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2009-10-15

    An internal flooding (IF) risk assessment refers to the quantitative probabilistic safety assessment (PSA) treatment of flooding as a result of pipe and tank breaks inside the plants, as well as from other recognized flood sources. The industry consensus standard for Internal Events Probabilistic Risk Assessment (ASME-RA-Sb-2005) includes high-level and supporting technical requirements for developing internal flooding probabilistic risk assessment (IFPRA). This industry standard is endorsed in Regulatory Guide 1.200, Revision 1 as an acceptable approach for addressing the risk contribution from IF events for risk informed applications that require U.S. Nuclear Regulatory commission (NRC) approval. In 2006, EPRI published a draft report for IFPRA that addresses the requirements of the ASME PRA consensus standard and have made efforts to refine and update the final EPRI IFPRA guideline. Westinghouse has performed an IFPRA analysis for several nuclear power plants (NPPs), such as Watts Bar and Fort Calhoun, using the draft EPRI guidelines for development of an IFPRA. Proprietary methodologies have been developed to apply the EPRI guidelines. The objectives of the draft report for IFPRA guideline are to: {center_dot} Provide guidance for PSA practitioners in the performance of the elements of a PRA associated with internal flooding events consistent with the current state of the art for internal flooding PRA {center_dot} Provide guidance regarding acceptable approaches that is sufficient to meeting the requirements of the ASME PRA Standard associated with internal flooding {center_dot} Incorporate lessons learned in the performance of internal flooding PRAs including those identified as pilot applications of earlier drafts of this procedures guide The purpose of this paper is to present a vision for domestic nuclear power plants' IFPRA by comparing the method of the draft EPRI guidelines with the existing IFPRA method for domestic NPPs.

  2. Probabilistic health risk assessment for arsenic intake through drinking groundwater in Taiwan's Pingtung Plain

    Science.gov (United States)

    Liang, C. P.; Chen, J. S.

    2017-12-01

    An abundant and inexpensive supply of groundwater is used to meet drinking, agriculture and aquaculture requirements of the residents in the Pingtung Plain. Long-term groundwater quality monitoring data indicate that the As content in groundwater in the Pingtung Plain exceeds the maximum level of 10 g/L recommended by the World Health Organization (WHO). The situation is further complicated by the fact that only 46.89% of population in the Pingtung Plain has been served with tap water, far below the national average of 92.93%. Considering there is a considerable variation in the measured concentrations, from below the detection limit (consumption rate and body weight of the individual, the conventional approach to conducting a human health risk assessment may be insufficient for health risk management. This study presents a probabilistic risk assessment for inorganic As intake through the consumption of the drinking groundwater by local residents in the Pingtung Plain. The probabilistic risk assessment for inorganic As intake through the consumption of the drinking groundwater is achieved using Monte Carlo simulation technique based on the hazard quotient (HQ) and target cancer risk (TR) established by the U.S. Environmental Protection Agency. This study demonstrates the importance of the individual variability of inorganic As intake through drinking groundwater consumption when evaluating a high exposure sub-group of the population who drink high As content groundwater.

  3. A framework to integrate software behavior into dynamic probabilistic risk assessment

    International Nuclear Information System (INIS)

    Zhu Dongfeng; Mosleh, Ali; Smidts, Carol

    2007-01-01

    Software plays an increasingly important role in modern safety-critical systems. Although, research has been done to integrate software into the classical probabilistic risk assessment (PRA) framework, current PRA practice overwhelmingly neglects the contribution of software to system risk. Dynamic probabilistic risk assessment (DPRA) is considered to be the next generation of PRA techniques. DPRA is a set of methods and techniques in which simulation models that represent the behavior of the elements of a system are exercised in order to identify risks and vulnerabilities of the system. The fact remains, however, that modeling software for use in the DPRA framework is also quite complex and very little has been done to address the question directly and comprehensively. This paper develops a methodology to integrate software contributions in the DPRA environment. The framework includes a software representation, and an approach to incorporate the software representation into the DPRA environment SimPRA. The software representation is based on multi-level objects and the paper also proposes a framework to simulate the multi-level objects in the simulation-based DPRA environment. This is a new methodology to address the state explosion problem in the DPRA environment. This study is the first systematic effort to integrate software risk contributions into DPRA environments

  4. A probabilistic risk assessment for field radiography based on expert judgment and opinion

    International Nuclear Information System (INIS)

    Jang, Han-Ki; Ryu, Hyung-Joon; Kim, Ji-Young; Lee, Jai-Ki; Cho, Kun-Woo

    2011-01-01

    A probabilistic approach was applied to assess radiation risk associated with the field radiography using gamma sources. The Delphi method based on the expert judgments and opinions was used in the process of characterization of parameters affecting risk, which are inevitably subject to large uncertainties. A mathematical approach applying the Bayesian inferences was employed for data processing to improve the Delphi results. This process consists of three phases: (1) setting prior distributions, (2) constructing the likelihood functions and (3) deriving the posterior distributions based on the likelihood functions. The approach for characterizing input parameters using the Bayesian inference is provided for improved risk estimates without intentional rejection of part of the data, which demonstrated utility of Bayesian updating of distributions of uncertain input parameters in PRA (Probabilistic Risk Assessment). The data analysis portion for PRA in field radiography is addressed for estimates of the parameters used to determine the frequencies and consequences of the various events modeled. In this study, radiological risks for the worker and the public member in the vicinity of the work place are estimated for field radiography system in Korea based on two-dimensional Monte Carlo Analysis (2D MCA). (author)

  5. Marked point process framework for living probabilistic safety assessment and risk follow-up

    International Nuclear Information System (INIS)

    Arjas, Elja; Holmberg, Jan

    1995-01-01

    We construct a model for living probabilistic safety assessment (PSA) by applying the general framework of marked point processes. The framework provides a theoretically rigorous approach for considering risk follow-up of posterior hazards. In risk follow-up, the hazard of core damage is evaluated synthetically at time points in the past, by using some observed events as logged history and combining it with re-evaluated potential hazards. There are several alternatives for doing this, of which we consider three here, calling them initiating event approach, hazard rate approach, and safety system approach. In addition, for a comparison, we consider a core damage hazard arising in risk monitoring. Each of these four definitions draws attention to a particular aspect in risk assessment, and this is reflected in the behaviour of the consequent risk importance measures. Several alternative measures are again considered. The concepts and definitions are illustrated by a numerical example

  6. Perception of Risk and Terrorism-Related Behavior Change: Dual Influences of Probabilistic Reasoning and Reality Testing

    Science.gov (United States)

    Denovan, Andrew; Dagnall, Neil; Drinkwater, Kenneth; Parker, Andrew; Clough, Peter

    2017-01-01

    The present study assessed the degree to which probabilistic reasoning performance and thinking style influenced perception of risk and self-reported levels of terrorism-related behavior change. A sample of 263 respondents, recruited via convenience sampling, completed a series of measures comprising probabilistic reasoning tasks (perception of randomness, base rate, probability, and conjunction fallacy), the Reality Testing subscale of the Inventory of Personality Organization (IPO-RT), the Domain-Specific Risk-Taking Scale, and a terrorism-related behavior change scale. Structural equation modeling examined three progressive models. Firstly, the Independence Model assumed that probabilistic reasoning, perception of risk and reality testing independently predicted terrorism-related behavior change. Secondly, the Mediation Model supposed that probabilistic reasoning and reality testing correlated, and indirectly predicted terrorism-related behavior change through perception of risk. Lastly, the Dual-Influence Model proposed that probabilistic reasoning indirectly predicted terrorism-related behavior change via perception of risk, independent of reality testing. Results indicated that performance on probabilistic reasoning tasks most strongly predicted perception of risk, and preference for an intuitive thinking style (measured by the IPO-RT) best explained terrorism-related behavior change. The combination of perception of risk with probabilistic reasoning ability in the Dual-Influence Model enhanced the predictive power of the analytical-rational route, with conjunction fallacy having a significant indirect effect on terrorism-related behavior change via perception of risk. The Dual-Influence Model possessed superior fit and reported similar predictive relations between intuitive-experiential and analytical-rational routes and terrorism-related behavior change. The discussion critically examines these findings in relation to dual-processing frameworks. This

  7. Perception of Risk and Terrorism-Related Behavior Change: Dual Influences of Probabilistic Reasoning and Reality Testing.

    Science.gov (United States)

    Denovan, Andrew; Dagnall, Neil; Drinkwater, Kenneth; Parker, Andrew; Clough, Peter

    2017-01-01

    The present study assessed the degree to which probabilistic reasoning performance and thinking style influenced perception of risk and self-reported levels of terrorism-related behavior change. A sample of 263 respondents, recruited via convenience sampling, completed a series of measures comprising probabilistic reasoning tasks (perception of randomness, base rate, probability, and conjunction fallacy), the Reality Testing subscale of the Inventory of Personality Organization (IPO-RT), the Domain-Specific Risk-Taking Scale, and a terrorism-related behavior change scale. Structural equation modeling examined three progressive models. Firstly, the Independence Model assumed that probabilistic reasoning, perception of risk and reality testing independently predicted terrorism-related behavior change. Secondly, the Mediation Model supposed that probabilistic reasoning and reality testing correlated, and indirectly predicted terrorism-related behavior change through perception of risk. Lastly, the Dual-Influence Model proposed that probabilistic reasoning indirectly predicted terrorism-related behavior change via perception of risk, independent of reality testing. Results indicated that performance on probabilistic reasoning tasks most strongly predicted perception of risk, and preference for an intuitive thinking style (measured by the IPO-RT) best explained terrorism-related behavior change. The combination of perception of risk with probabilistic reasoning ability in the Dual-Influence Model enhanced the predictive power of the analytical-rational route, with conjunction fallacy having a significant indirect effect on terrorism-related behavior change via perception of risk. The Dual-Influence Model possessed superior fit and reported similar predictive relations between intuitive-experiential and analytical-rational routes and terrorism-related behavior change. The discussion critically examines these findings in relation to dual-processing frameworks. This

  8. Perception of Risk and Terrorism-Related Behavior Change: Dual Influences of Probabilistic Reasoning and Reality Testing

    Directory of Open Access Journals (Sweden)

    Andrew Denovan

    2017-10-01

    Full Text Available The present study assessed the degree to which probabilistic reasoning performance and thinking style influenced perception of risk and self-reported levels of terrorism-related behavior change. A sample of 263 respondents, recruited via convenience sampling, completed a series of measures comprising probabilistic reasoning tasks (perception of randomness, base rate, probability, and conjunction fallacy, the Reality Testing subscale of the Inventory of Personality Organization (IPO-RT, the Domain-Specific Risk-Taking Scale, and a terrorism-related behavior change scale. Structural equation modeling examined three progressive models. Firstly, the Independence Model assumed that probabilistic reasoning, perception of risk and reality testing independently predicted terrorism-related behavior change. Secondly, the Mediation Model supposed that probabilistic reasoning and reality testing correlated, and indirectly predicted terrorism-related behavior change through perception of risk. Lastly, the Dual-Influence Model proposed that probabilistic reasoning indirectly predicted terrorism-related behavior change via perception of risk, independent of reality testing. Results indicated that performance on probabilistic reasoning tasks most strongly predicted perception of risk, and preference for an intuitive thinking style (measured by the IPO-RT best explained terrorism-related behavior change. The combination of perception of risk with probabilistic reasoning ability in the Dual-Influence Model enhanced the predictive power of the analytical-rational route, with conjunction fallacy having a significant indirect effect on terrorism-related behavior change via perception of risk. The Dual-Influence Model possessed superior fit and reported similar predictive relations between intuitive-experiential and analytical-rational routes and terrorism-related behavior change. The discussion critically examines these findings in relation to dual

  9. Probabilistic modeling of the flows and environmental risks of nano-silica.

    Science.gov (United States)

    Wang, Yan; Kalinina, Anna; Sun, Tianyin; Nowack, Bernd

    2016-03-01

    Nano-silica, the engineered nanomaterial with one of the largest production volumes, has a wide range of applications in consumer products and industry. This study aimed to quantify the exposure of nano-silica to the environment and to assess its risk to surface waters. Concentrations were calculated for four environmental (air, soil, surface water, sediments) and two technical compartments (wastewater, solid waste) for the EU and Switzerland using probabilistic material flow modeling. The corresponding median concentration in surface water is predicted to be 0.12 μg/l in the EU (0.053-3.3 μg/l, 15/85% quantiles). The concentrations in sediments in the complete sedimentation scenario were found to be the largest among all environmental compartments, with a median annual increase of 0.43 mg/kg · y in the EU (0.19-12 mg/kg · y, 15/85% quantiles). Moreover, probabilistic species sensitivity distributions (PSSD) were computed and the risk of nano-silica in surface waters was quantified by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) distribution, which was derived from the cumulative PSSD. This assessment suggests that nano-silica currently poses no risk to aquatic organisms in surface waters. Further investigations are needed to assess the risk of nano-silica in other environmental compartments, which is currently not possible due to a lack of ecotoxicological data. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. RAFT: a computer program for fault tree risk calculations

    International Nuclear Information System (INIS)

    Seybold, G.D.

    1977-11-01

    A description and user instructions are presented for RAFT, a FORTRAN computer code for calculation of a risk measure for fault tree cut sets. RAFT calculates release quantities and a risk measure based on the product of probability and release quantity for cut sets of fault trees modeling the accidental release of radioactive material from a nuclear fuel cycle facility. Cut sets and their probabilities are supplied as input to RAFT from an external fault tree analysis code. Using the total inventory available of radioactive material, along with release fractions for each event in a cut set, the release terms are calculated for each cut set. Each release term is multiplied by the cut set probability to yield the cut set risk measure. RAFT orders the dominant cut sets on the risk measure. The total risk measure of processed cut sets and their fractional contributions are supplied as output. Input options are available to eliminate redundant cut sets, apply threshold values on cut set probability and risk, and control the total number of cut sets output. Hash addressing is used to remove redundant cut sets from the analysis. Computer hardware and software restrictions are given along with a sample problem and cross-reference table of the code. Except for the use of file management utilities, RAFT is written exclusively in FORTRAN language and is operational on a Control Data, CYBER 74-18--series computer system. 4 figures

  11. Overview of seismic probabilistic risk assessment for structural analysis in nuclear facilities

    International Nuclear Information System (INIS)

    Reed, J.W.

    1989-01-01

    Probabilistic Risk Assessment (PRA) for seismic events is currently being performed for nuclear and DOE facilities. The background on seismic PRA is presented along with a basic description of the method. The seismic PRA technique is applicable to other critical facilities besides nuclear plants. The different approaches for obtained structure fragility curves are discussed and their applications to structures and equipment, in general, are addressed. It is concluded that seismic PRA is a useful technique for conducting probability analysis for a wide range of classes of structures and equipment

  12. Review process and quality assurance in the EBR-II probabilistic risk assessment

    International Nuclear Information System (INIS)

    Roglans, J.; Hill, D.J.; Ragland, W.A.

    1992-01-01

    A Probabilistic Risk Assessment (PRA) of the Experimental Breeder Reactor II (EBR-II), a Department of Energy (DOE) Category A reactor, has recently been completed at Argonne National Laboratory (ANL). Within the scope of the ANL QA Programs, a QA Plan specifically for the EBR-II PRA was developed. The QA Plan covered all aspects of the PRA development, with emphasis on the procedures for document and software control, and the internal and external review process. The effort spent in the quality assurance tasks for the EBR-II PRA has reciprocated by providing acceptance of the work and confidence in the quality of the results

  13. On the use of data and judgment in probabilistic risk and safety analysis

    International Nuclear Information System (INIS)

    Kaplan, S.

    1986-01-01

    This paper reviews the line of thought of a nuclear plant probabilistic risk analysis (PRA) identifying the points where data and judgement enter. At the ''bottom'' of the process, data and judgment are combined, using one and two stage Bayesian methods, to express what is known about the element of variables. Higher in the process, we see the use of judgment in identifying scenarios and developing almost models and specifying initiating event categories. Finally, we discuss the judgments involved in deciding to do a PRA and in applying the results. (orig.)

  14. Application of probabilistic risk assessment in the operation of Koeberg nuclear power station

    International Nuclear Information System (INIS)

    Nicholls, D.R.

    1991-01-01

    Probabilistic risk assessment (PRA) calculates the probability that a set of multiple failures could occur, the frequency with which the safety circuits will be required and the consequences of the failure of the safety systems. In this way the frequency with which major accident situations can be expected to happen, can be derived. The world history of PRA is presented, together with the South African history of PRA. The theory of PRA is explained and the application of PRA studies is described. In the last twenty years, PRA has gone from being a theoretical idea to a practical tool for assisting in plant management. 2 figs., 1 ill

  15. Probabilistic risk assessment: A look at the role of artificial intelligence

    International Nuclear Information System (INIS)

    Wang, J.; Modarres, M.; Hunt, R.N.M.

    1988-01-01

    A review of traditional Probabilistic Risk Assessment (PRA) methods used in the nuclear power industry is presented. The shortcomings of the current PRA methods are pointed out. A method of performing a PRA is proposed and is computerized. The role of artificial intelligence in developing and performing the proposed PRA approach is discussed. The proposed PRA approach is verified by comparing the results to previously performed PRAs. The comparisons have supported the adequacy and completeness of the results of the proposed model. A discussion of how the proposed method can be used as an expert system to verify plant status following loss of plant hardware is also presented. (orig.)

  16. Use of probabilistic risk assessment (PRA) in expert systems to advise nuclear plant operators and managers

    International Nuclear Information System (INIS)

    Uhrig, R.E.

    1988-01-01

    The use of expert systems in nuclear power plants to provide advice to managers, supervisors and/or operators is a concept that is rapidly gaining acceptance. Generally, expert systems rely on the expertise of human experts or knowledge that has been modified in publications, books, or regulations to provide advice under a wide variety of conditions. In this work, a probabilistic risk assessment (PRA) 3 of a nuclear power plant performed previously is used to assess the safety status of nuclear power plants and to make recommendations to the plant personnel. 5 refs., 1 fig., 2 tabs

  17. Input to the PRAST computer code used in the SRS probabilistic risk assessment

    International Nuclear Information System (INIS)

    Kearnaghan, D.P.

    1992-01-01

    The PRAST (Production Reactor Algorithm for Source Terms) computer code was developed by Westinghouse Savannah River Company and Science Application International Corporation for the quantification of source terms for the SRS Savannah River Site (SRS) Reactor Probabilistic Risk Assessment. PRAST requires as input a set of release fractions, decontamination factors, transfer fractions and source term characteristics that accurately reflect the conditions that are evaluated by PRAST. This document links the analyses which form the basis for the PRAST input parameters. In addition, it gives the distribution of the input parameters that are uncertain and considered to be important to the evaluation of the source terms to the environment

  18. Probabilistic risk benchmark of the Brazilian electrical system; Risco probabilistico de referencia do sistema eletrico brasileiro

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Neyl Hamilton Martelotta

    2002-05-01

    The main goal of this dissertation is to proceed a first numerical evaluation of the probabilistic risks magnitudes associated with the Brazilian Electrical network, considering the subsystems North, Northeast, South, Southeast and Mid West. This result is relevant because it can be used as an initial comparative reference for future reliability studies of the Brazilian Basic Grid. As a by-product, the whole set of criteria and procedures used in the work are described in detail. They may also serve as a preliminary base for future similar evaluations. (author)

  19. Probabilistic pattern of risks in company’s Quality management system

    Directory of Open Access Journals (Sweden)

    Mager Vladimir

    2017-01-01

    Full Text Available One possible approach for calculation of probabilistic rate of risks in Quality management system (QMS, which is prescribed by requirements of International Standard ISO 9001:2015, is proposed in this article. Aspects of the theory of dependability and Markov techniques are used, which are applied for evaluation of probability of failures in complicated technical systems. Representation of QMS processes as a graph with controlled discrete Markov chains is suggested, which allows to evaluate a probability of customer requirements non-fulfillment as a function of an intensity of mistakes that bring to non-conformities in QMS.

  20. Application of Bayesian network methodology to the probabilistic risk assessment of nuclear waste disposal facility

    International Nuclear Information System (INIS)

    Lee, Chang Ju

    2006-02-01

    The scenario in a risk analysis can be defined as the propagating feature of specific initiating event which can go to a wide range of undesirable consequences. If one takes various scenarios into consideration, the risk analysis becomes more complex than do without them. A lot of risk analyses have been performed to actually estimate a risk profile under both uncertain future states of hazard sources and undesirable scenarios. Unfortunately, in case of considering some stochastic passive systems such as a radioactive waste disposal facility, since the behaviour of future scenarios is hardly predicted without special reasoning process, we cannot estimate their risk only with a traditional risk analysis methodology. Moreover, it is believed that the sources of uncertainty at future states can be reduced pertinently by setting up dependency relationships interrelating geological, hydrological, and ecological aspects of the site with all the scenarios. It is then required current methodology of uncertainty analysis of the waste disposal facility be revisited under this belief. In order to consider the effects predicting from an evolution of environmental conditions of waste disposal facilities, this study proposes a quantitative assessment framework integrating the inference process of Bayesian network to the traditional probabilistic risk analysis. In this study an approximate probabilistic inference program for the specific Bayesian network developed and verified using a bounded-variance likelihood weighting algorithm. Ultimately, specific models, including a Monte-Carlo model for uncertainty propagation of relevant parameters, were developed with a comparison of variable-specific effects due to the occurrence of diverse altered evolution scenarios (AESs). After providing supporting information to get a variety of quantitative expectations about the dependency relationship between domain variables and AESs, this study could connect the results of probabilistic

  1. Review of cause-based decision tree approach for the development of domestic standard human reliability analysis procedure in low power/shutdown operation probabilistic safety assessment

    International Nuclear Information System (INIS)

    Kang, D. I.; Jung, W. D.

    2003-01-01

    We review the Cause-Based Decision Tree (CBDT) approach to decide whether we incorporate it or not for the development of domestic standard Human Reliability Analysis (HRA) procedure in low power/shutdown operation Probabilistic Safety Assessment (PSA). In this paper, we introduce the cause based decision tree approach, quantify human errors using it, and identify merits and demerits of it in comparision with previously used THERP. The review results show that it is difficult to incorporate the CBDT method for the development of domestic standard HRA procedure in low power/shutdown PSA because the CBDT method need for the subjective judgment of HRA analyst like as THERP. However, it is expected that the incorporation of the CBDT method into the development of domestic standard HRA procedure only for the comparision of quantitative HRA results will relieve the burden of development of detailed HRA procedure and will help maintain consistent quantitative HRA results

  2. Comparison of a Traditional Probabilistic Risk Assessment Approach with Advanced Safety Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Curtis L; Mandelli, Diego; Zhegang Ma

    2014-11-01

    As part of the Light Water Sustainability Program (LWRS) [1], the purpose of the Risk Informed Safety Margin Characterization (RISMC) [2] Pathway research and development (R&D) is to support plant decisions for risk-informed margin management with the aim to improve economics, reliability, and sustain safety of current NPPs. In this paper, we describe the RISMC analysis process illustrating how mechanistic and probabilistic approaches are combined in order to estimate a safety margin. We use the scenario of a “station blackout” (SBO) wherein offsite power and onsite power is lost, thereby causing a challenge to plant safety systems. We describe the RISMC approach, illustrate the station blackout modeling, and contrast this with traditional risk analysis modeling for this type of accident scenario. We also describe our approach we are using to represent advanced flooding analysis.

  3. Use of the Safety probabilistic analysis for the risk monitor before maintenance

    International Nuclear Information System (INIS)

    Gonzalez C, M.

    2004-01-01

    In this work the use of the Safety Probabilistic Analysis (APS) of the Laguna Verde Power plant to quantify the risk before maintenance is presented. Beginning to describe the nature of the Rule of Maintenance and their risk evaluations, it is planned about the paper of the APS for that purpose, and a systematic form to establish the reaches for this use open of the model is delineated. The work provides some technique details of the implantation methods of the APS like risk monitor, including the form of introducing the systems, trains and components to the user, as well as the fitness to the models and improvements to the used platform. There are covered some of the measures taken to achieve the objectives of preserving the base model approved, to facilitate the periodic realize, and to achieve acceptable times of execution for their efficient use. (Author)

  4. Review insights on the probabilistic risk assessment for the Limerick Generating Station

    International Nuclear Information System (INIS)

    1984-08-01

    In recognition of the high population density around the Limerick Generating Station site and the proposed power level, the Philadelphia Electric Company, in response to NRC staff requests, conducted and submitted between March 1981 and November 1983 a probabilistic risk assessment (PRA) on internal event contributors and a severe accident risk assessment on external event contributors to assess risks posed by operation of the plant. The applicant has developed perspectives using PRA models on the safety profile of the Limerick plant and has altered the plant design to reduce accident vulnerabilities identified in these PRAs. The staff's review of the Limerick PRA has particularly emphasized the dominant accident sequences and the resulting insights into demonstration of compliance with regulatory requirments, unique design features and major plant vulnerabilities to assess the need for any additional measures to further improve the safety of the LGS. The staff's review insights and PRA safety review conclusions are presented in this report

  5. Risk-Based Predictive Maintenance for Safety-Critical Systems by Using Probabilistic Inference

    Directory of Open Access Journals (Sweden)

    Tianhua Xu

    2013-01-01

    Full Text Available Risk-based maintenance (RBM aims to improve maintenance planning and decision making by reducing the probability and consequences of failure of equipment. A new predictive maintenance strategy that integrates dynamic evolution model and risk assessment is proposed which can be used to calculate the optimal maintenance time with minimal cost and safety constraints. The dynamic evolution model provides qualified risks by using probabilistic inference with bucket elimination and gives the prospective degradation trend of a complex system. Based on the degradation trend, an optimal maintenance time can be determined by minimizing the expected maintenance cost per time unit. The effectiveness of the proposed method is validated and demonstrated by a collision accident of high-speed trains with obstacles in the presence of safety and cost constrains.

  6. Regional probabilistic nuclear risk and vulnerability assessment by integration of mathematical modelling land GIS-analysis

    International Nuclear Information System (INIS)

    Rigina, O.; Baklanov, A.

    2002-01-01

    The Kola Peninsula, Russian Arctic exceeds all other regions in the world in the number of nuclear reactors. The study was aimed at estimating possible radiation risks to the population in the Nordic countries in case of a severe accident in the Kola Peninsula. A new approach based on probabilistic analysis of modelled possible pathways of radionuclide transport and precipitation was developed. For the general population, Finland is at most risk with respect to the Kola NPP, because of: high population density or proximity to the radiation-risk sites and relatively high probability of an airflow trajectory there, and precipitation. After considering the critical group, northern counties in Norway, Finland and Sweden appear to be most vulnerable. (au)

  7. Probabilistic Causal Analysis for System Safety Risk Assessments in Commercial Air Transport

    Science.gov (United States)

    Luxhoj, James T.

    2003-01-01

    Aviation is one of the critical modes of our national transportation system. As such, it is essential that new technologies be continually developed to ensure that a safe mode of transportation becomes even safer in the future. The NASA Aviation Safety Program (AvSP) is managing the development of new technologies and interventions aimed at reducing the fatal aviation accident rate by a factor of 5 by year 2007 and by a factor of 10 by year 2022. A portfolio assessment is currently being conducted to determine the projected impact that the new technologies and/or interventions may have on reducing aviation safety system risk. This paper reports on advanced risk analytics that combine the use of a human error taxonomy, probabilistic Bayesian Belief Networks, and case-based scenarios to assess a relative risk intensity metric. A sample case is used for illustrative purposes.

  8. Probabilistic health risk assessment of carcinogenic emissions from a MSW gasification plant.

    Science.gov (United States)

    Lonati, Giovanni; Zanoni, Francesca

    2012-09-01

    Health risk assessment due to the atmospheric emissions of carcinogenic pollutants (PCDD/Fs and Cd) from a waste gasification plant is performed by means of a probabilistic approach based on probability density functions for the description of the input data of the model parameters involved in the assessment. These functions incorporate both the epistemic and stochastic uncertainty of the input data (namely, the emission rate of the pollutants) and of all the parameters used for individual exposure assessment through the pathways of inhalation, soil ingestion and dermal contact, and diet. The uncertainty is propagated throughout the evaluation by Monte Carlo technique, resulting in the probability distribution of the individual risk. The median risk levels nearby the plant are in the 10(-8)-10(-10) range, ten-fold lower than the deterministic estimate based on precautionary values for the input data; however, the very upper percentiles (>95th) of the risk distribution can exceed the conventional 10(-6) reference value. The estimated risk is almost entirely determined by the Cd exposure through the diet; the pathways arising from PCDD/Fs exposure are without any practical significance, suggesting that the emission control should focus on Cd in order to reduce the carcinogenic risk. Risk variance decomposition shows the prevailing influence on the estimated risk of the Cd concentration at the emission stack: thus, for a more accurate risk assessment the efforts should focus primarily on the definition of its probability density function. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Probabilistic risk analysis for Test Area North Hot Shop Storage Pool Facility

    International Nuclear Information System (INIS)

    Meale, B.M.; Satterwhite, D.G.

    1990-01-01

    A storage pool facility used for storing spent fuel and radioactive debris from the Three Mile Island (TMI) accident was evaluated to determine the risk associated with its normal operations. Several hazards were identified and examined to determine if any any credible accident scenarios existed. Expected annual occurrence frequencies were calculated for hazards for which accident scenarios were identified through use of fault trees modeling techniques. Fault tree models were developed for two hazards: (1) increased radiation field and (2) spread of contamination. The models incorporated facets of the operations within the facility as well as the facility itself. 6 refs

  10. Issues related to structural aging in probabilistic risk assessment of nuclear power plants

    International Nuclear Information System (INIS)

    Ellingwood, Bruce R.

    1998-01-01

    Structural components and systems have an important safety function in nuclear power plants. Although they are essentially passive under normal operating conditions, they play a key role in mitigating the impact of extreme environmental events such as earthquakes, winds, fire and floods on plant safety. Moreover, the importance of structural components and systems in accident mitigation is amplified by common-cause effects. Reinforced concrete structural components and systems in NPPs are subject to a phenomenon known as aging, leading to time-dependent changes in strength and stiffness that may impact their ability to withstand various challenges during their service lives from operation, the environment and accidents. Time-dependent changes in structural properties as well as challenges to the system are random in nature. Accordingly, condition assessment of existing structures should be performed within a probabilistic framework. The mathematical formalism of a probabilistic risk assessment (PRA) provides a means for identifying aging structural components that may play a significant role in mitigating plant risk. Structural condition assessments supporting a decision regarding continued service can be rendered more efficient if guided by the logic of a PRA

  11. Nuclear Regulatory Commission probabilistic risk assessment implementation program: A status report

    International Nuclear Information System (INIS)

    Rubin, M.P.; Caruso, M.A.

    1996-01-01

    The US Nuclear Regulatory Commission (NRC) is undertaking a number of activities intended to increase the consideration of risk significance in its decision processes and the effective use of risk-based technologies in its regulatory activities. Although the NRC is moving toward risk-informed regulation throughout its areas of responsibilities, this paper focuses primarily on those issues associated with reactor regulation. As the NRC completed significant milestones in its development of probabilistic risk assessment (PRA) methodology and gained considerable experience in the limited application of risk assessment to selected regulatory activities, it became evident that a much broader use of risk informed approaches offered advantages to both the NRC and the US commercial nuclear industry. This desire to enhance the use of risk assessment is driven by the clear belief that application of PRA methods will result in direct improvements in nuclear power plant operational safety from the perspective of both the regulator and the plant operator. The NRC believed that an overall policy on the use of PRA methods in nuclear regulatory activities should be established so that the many potential applications of PRA could be implemented in a consistent and predictable manner that would promote regulatory stability and efficiency. This paper describes the key activities that the NRC has undertaken to implement the initial stages of an integrated risk-informed regulatory framework

  12. Probabilistic earthquake risk assessment as a tool to improve safety and explanatory adequacy

    International Nuclear Information System (INIS)

    Itoi, Tatsuya

    2015-01-01

    This paper explains the concept of probabilistic earthquake risk assessment, mainly from the viewpoint as a tool to improve safety and explanatory adequacy. The definition of risk is the expected value of undesirable effect in an engineering meaning that is likely to occur in the future, and it is defined in risk management as the triplet of scenario (what can happen), frequency, and impact. As for the earthquake risk assessment of a nuclear power plant, the fragility of structure / system / component (SSC) against earthquake (so-called earthquake fragility) is assessed, and by combining with the earthquake hazard that has been separately obtained, the occurrence frequency and impact of the accident are obtained. From the view of the authors, earthquake risk assessment is for the purpose of decision-making, and is not intended to calculate the probability in a scientifically rigorous manner. For ensuring the quality of risk assessment, the table of 'Expert utilization standards for the evaluation of epistemological uncertainty' is used. Sole quantitative risk assessment is not necessarily sufficient for risk management. It would be important to find how to build the 'framework for comprehensive decision-making.' (A.O.)

  13. Predicting the onset of psychosis in patients at clinical high risk: practical guide to probabilistic prognostic reasoning.

    Science.gov (United States)

    Fusar-Poli, P; Schultze-Lutter, F

    2016-02-01

    Prediction of psychosis in patients at clinical high risk (CHR) has become a mainstream focus of clinical and research interest worldwide. When using CHR instruments for clinical purposes, the predicted outcome is but only a probability; and, consequently, any therapeutic action following the assessment is based on probabilistic prognostic reasoning. Yet, probabilistic reasoning makes considerable demands on the clinicians. We provide here a scholarly practical guide summarising the key concepts to support clinicians with probabilistic prognostic reasoning in the CHR state. We review risk or cumulative incidence of psychosis in, person-time rate of psychosis, Kaplan-Meier estimates of psychosis risk, measures of prognostic accuracy, sensitivity and specificity in receiver operator characteristic curves, positive and negative predictive values, Bayes' theorem, likelihood ratios, potentials and limits of real-life applications of prognostic probabilistic reasoning in the CHR state. Understanding basic measures used for prognostic probabilistic reasoning is a prerequisite for successfully implementing the early detection and prevention of psychosis in clinical practice. Future refinement of these measures for CHR patients may actually influence risk management, especially as regards initiating or withholding treatment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  14. A technique of including the effect of aging of passive components in probabilistic risk assessments

    International Nuclear Information System (INIS)

    Phillips, J.H.; Weidenhamer, G.H.

    1992-01-01

    The probabilistic risk assessments (PRAS) being developed at most nuclear power plants to calculate the risk of core damage generally focus on the possible failure of active components. The possible failure of passive components is given little consideration. We are developing methods for selecting risk-significant passive components and including them in PRAS. These methods provide effective ways to prioritize passive components for inspection, and where inspection reveals aging damage, mitigation or repair can be employed to reduce the likelihood of component failure. We demonstrated a method by selecting a weld in the auxiliary feedwater (AFW) system, basing our selection on expert judgement of the likelihood of failure and on an estimate of the consequence of component failure to plant safety. We then modified and used the Piping Reliability Analysis Including Seismic Events (PRAISE) computer code to perform a probabilistic structural analysis to calculate the probability that crack growth due to aging would cause the weld to fail. The PRAISE code was modified to include the effects of changing design material properties with age and changing stress cycles. The calculation included the effects of mechanical loads and thermal transients typical of the service loads for this piping design and the effects of thermal cycling caused by a leaking check valve. However, this particular calculation showed little change in low component failure probability and plant risk for 48 years of service. However, sensitivity studies showed that if the probability of component failure is high, the effect on plant risk is significant. The success of this demonstration shows that this method could be applied to nuclear power plants. The demonstration showed the method is too involved (PRAISE takes a long time to perform the calculation and the input information is extensive) for handling a large number of passive components and therefore simpler methods are needed

  15. Nuclear power plant personnel errors in decision-making as an object of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Reer, B.

    1993-09-01

    The integration of human error - also called man-machine system analysis (MMSA) - is an essential part of probabilistic risk assessment (PRA). A new method is presented which allows for a systematic and comprehensive PRA inclusions of decision-based errors due to conflicts or similarities. For the error identification procedure, new question techniques are developed. These errors are shown to be identified by looking at retroactions caused by subordinate goals as components of the overall safety relevant goal. New quantification methods for estimating situation-specific probabilities are developed. The factors conflict and similarity are operationalized in a way that allows their quantification based on informations which are usually available in PRA. The quantification procedure uses extrapolations and interpolations based on a poor set of data related to decision-based errors. Moreover, for passive errors in decision-making a completely new approach is presented where errors are quantified via a delay initiating the required action rather than via error probabilities. The practicability of this dynamic approach is demonstrated by a probabilistic analysis of the actions required during the total loss of feedwater event at the Davis-Besse plant 1985. The extensions of the ''classical'' PRA method developed in this work are applied to a MMSA of the decay heat removal (DHR) of the ''HTR-500''. Errors in decision-making - as potential roots of extraneous acts - are taken into account in a comprehensive and systematic manner. Five additional errors are identified. However, the probabilistic quantification results a nonsignificant increase of the DHR failure probability. (orig.) [de

  16. A Probabilistic Alternative Approach to Optimal Project Profitability Based on the Value-at-Risk

    Directory of Open Access Journals (Sweden)

    Yonggu Kim

    2018-03-01

    Full Text Available This paper focuses on an investment decision-making process for sustainable development based on the profitability impact factors for overseas projects. Investors prefer to use the discounted cash-flow method. Although this method is simple and straightforward, its critical weakness is its inability to reflect the factor volatility associated with the project evaluation. To overcome this weakness, the Value-at-Risk method is used to apply the volatility of the profitability impact factors, thereby reflecting the risks and establishing decision-making criteria for risk-averse investors. Risk-averse investors can lose relatively acceptable investment opportunities to risk-neutral or risk-amenable investors due to strict investment decision-making criteria. To overcome this problem, critical factors are selected through a Monte Carlo simulation and a sensitivity analysis, and solutions to the critical-factor problems are then found by using the Theory of Inventive Problem Solving and a business version of the Project Definition Rating Index. This study examines the process of recovering investment opportunities with projects that are investment feasible and that have been rejected when applying the criterion of the Value-at-Risk method. To do this, a probabilistic alternative approach is taken. To validate this methodology, the proposed framework for an improved decision-making process is demonstrated using two actual overseas projects of a Korean steel-making company.

  17. Environmental risk assessment of white phosphorus from the use of munitions - a probabilistic approach.

    Science.gov (United States)

    Voie, Øyvind Albert; Johnsen, Arnt; Strømseng, Arnljot; Longva, Kjetil Sager

    2010-03-15

    White phosphorus (P(4)) is a highly toxic compound used in various pyrotechnic products. Ammunitions containing P(4) are widely used in military training areas where the unburned products of P(4) contaminate soil and local ponds. Traditional risk assessment methods presuppose a homogeneous spatial distribution of pollutants. The distribution of P(4) in military training areas is heterogeneous, which reduces the probability of potential receptors being exposed to the P(4) by ingestion, for example. The current approach to assess the environmental risk from the use of P(4) suggests a Bayesian network (Bn) as a risk assessment tool. The probabilistic reasoning supported by a Bn allows us to take into account the heterogeneous distribution of P(4). Furthermore, one can combine empirical data and expert knowledge, which allows the inclusion of all kinds of data that are relevant to the problem. The current work includes an example of the use of the Bn as a risk assessment tool where the risk for P(4) poisoning in humans and grazing animals at a military shooting range in Northern Norway was calculated. P(4) was detected in several craters on the range at concentrations up to 5.7g/kg. The risk to human health was considered acceptable under the current land use. The risk for grazing animals such as sheep, however, was higher, suggesting that precautionary measures may be advisable.

  18. Combining exposure and effect modeling into an integrated probabilistic environmental risk assessment for nanoparticles.

    Science.gov (United States)

    Jacobs, Rianne; Meesters, Johannes A J; Ter Braak, Cajo J F; van de Meent, Dik; van der Voet, Hilko

    2016-12-01

    There is a growing need for good environmental risk assessment of engineered nanoparticles (ENPs). Environmental risk assessment of ENPs has been hampered by lack of data and knowledge about ENPs, their environmental fate, and their toxicity. This leads to uncertainty in the risk assessment. To deal with uncertainty in the risk assessment effectively, probabilistic methods are advantageous. In the present study, the authors developed a method to model both the variability and the uncertainty in environmental risk assessment of ENPs. This method is based on the concentration ratio and the ratio of the exposure concentration to the critical effect concentration, both considered to be random. In this method, variability and uncertainty are modeled separately so as to allow the user to see which part of the total variation in the concentration ratio is attributable to uncertainty and which part is attributable to variability. The authors illustrate the use of the method with a simplified aquatic risk assessment of nano-titanium dioxide. The authors' method allows a more transparent risk assessment and can also direct further environmental and toxicological research to the areas in which it is most needed. Environ Toxicol Chem 2016;35:2958-2967. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

  19. Fuzzy-probabilistic multi agent system for breast cancer risk assessment and insurance premium assignment.

    Science.gov (United States)

    Tatari, Farzaneh; Akbarzadeh-T, Mohammad-R; Sabahi, Ahmad

    2012-12-01

    In this paper, we present an agent-based system for distributed risk assessment of breast cancer development employing fuzzy and probabilistic computing. The proposed fuzzy multi agent system consists of multiple fuzzy agents that benefit from fuzzy set theory to demonstrate their soft information (linguistic information). Fuzzy risk assessment is quantified by two linguistic variables of high and low. Through fuzzy computations, the multi agent system computes the fuzzy probabilities of breast cancer development based on various risk factors. By such ranking of high risk and low risk fuzzy probabilities, the multi agent system (MAS) decides whether the risk of breast cancer development is high or low. This information is then fed into an insurance premium adjuster in order to provide preventive decision making as well as to make appropriate adjustment of insurance premium and risk. This final step of insurance analysis also provides a numeric measure to demonstrate the utility of the approach. Furthermore, actual data are gathered from two hospitals in Mashhad during 1 year. The results are then compared with a fuzzy distributed approach. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. A probabilistic method for computing quantitative risk indexes from medical injuries compensation claims.

    Science.gov (United States)

    Dalle Carbonare, S; Folli, F; Patrini, E; Giudici, P; Bellazzi, R

    2013-01-01

    The increasing demand of health care services and the complexity of health care delivery require Health Care Organizations (HCOs) to approach clinical risk management through proper methods and tools. An important aspect of risk management is to exploit the analysis of medical injuries compensation claims in order to reduce adverse events and, at the same time, to optimize the costs of health insurance policies. This work provides a probabilistic method to estimate the risk level of a HCO by computing quantitative risk indexes from medical injury compensation claims. Our method is based on the estimate of a loss probability distribution from compensation claims data through parametric and non-parametric modeling and Monte Carlo simulations. The loss distribution can be estimated both on the whole dataset and, thanks to the application of a Bayesian hierarchical model, on stratified data. The approach allows to quantitatively assessing the risk structure of the HCO by analyzing the loss distribution and deriving its expected value and percentiles. We applied the proposed method to 206 cases of injuries with compensation requests collected from 1999 to the first semester of 2007 by the HCO of Lodi, in the Northern part of Italy. We computed the risk indexes taking into account the different clinical departments and the different hospitals involved. The approach proved to be useful to understand the HCO risk structure in terms of frequency, severity, expected and unexpected loss related to adverse events.

  1. The NUREG-1150 probabilistic risk assessment for the Sequoyah nuclear plant

    International Nuclear Information System (INIS)

    Gregory, J.J.; Breeding, R.J.; Higgins, S.J.; Shiver, A.W.; Helton, J.C.; Murfin, W.B.

    1992-01-01

    This paper summarizes the findings of the probabilistic risk assessment (PRA) for Unit 1 of the Sequoyah Nuclear Plant performed in support of NUREG-1150. The emphasis is on the 'back-end' analyses, the accident progression, source term, and consequence analyses, and the risk results obtained when the results of these analyses are combined with the accident frequency analysis. The results of this PRA indicate that the offsite risk from internal initiating events at Sequoyah are quite low with respect to the safety goals. The containment appears likely to withstand the loads that might be placed upon it if the reactor vessel fails. A good portion of the risk, in this analysis, comes from initiating events which bypass the containment. These events are estimated to have a relatively low frequency of occurrence, but their consequences are quite large. Other events that contribute to offsite risk involve early containment failures that occur during degradation of the core or near the time of vessel breach. Considerable uncertainty is associated with the risk estimates produced in this analysis. Offsite risk from external initiating events was not included in this analysis. (orig.)

  2. The NUREG-1150 probabilistic risk assessment for the Grand Gulf nuclear station

    International Nuclear Information System (INIS)

    Brown, T.D.; Breeding, R.J.; Jow, H.N.; Higgins, S.J.; Shiver, A.W.; Helton, J.C.

    1992-01-01

    This paper summarizes the findings of the probabilistic risk assessment (PRA) for Unit 1 of the Grand Gulf Nuclear Station performed in support of NUREG-1150. The emphasis is on the 'back-end' analyses, that is, the acident progression, source term, consequence analsyes, and risk results obtained when the results of these analyses are combined with the accident frequency analysis. The offsite risk from internal initiating events was found to be quite low, both with respect to the safety goals and to the other plants analyzed in NUREG-1150. The offsite risk is dominated by short-term station blackout plant damage states. The long-term blackout group and the anticiptated transients without scram (ATWS) group contribute considerably less to risk. Transients in which the power conversion system is unavailable are very minor contributors to risk. The low values for risk can be attributed to low core damage frequency, good emergency response, and plant features that reduce the potential source term. (orig.)

  3. Advances in multi-unit nuclear power plant probabilistic risk assessment

    International Nuclear Information System (INIS)

    Modarres, Mohammad; Zhou, Taotao; Massoud, Mahmoud

    2017-01-01

    The Fukushima Dai-ichi accident highlighted the importance of risks from multiple nuclear reactor unit accidents at a site. As a result, there has been considerable interest in Multi-Unit Probabilistic Risk Assessment (MUPRA) in the past few years. For considerations in nuclear safety, the MUPRA estimates measures of risk and identifies contributors to risk representing the entire site rather than the individual units in the site. In doing so, possible unit-to-unit interactions and dependencies should be modeled and accounted for in the MUPRA. In order to effectively account for these risks, six main commonality classifications—initiating events, shared connections, identical components, proximity dependencies, human dependencies, and organizational dependencies—may be used. This paper examines advances in MUPRA, offers formal definitions of multi-unit site risk measures and proposes quantitative approaches and data to account for unit-to-unit dependencies. Finally, a parametric approach for the multi-unit dependencies has been discussed and a simple example illustrates application of the proposed methodology. - Highlights: • This paper will discuss the technical aspects of an integrated MUPRA, including consideration of dependencies and assessment of the multi-unit dependency data and models for quantifying such dependencies. • The paper also provides discussions on formal definitions and metrics for multi-unit site risks. • The parametric methods are used to address multi-unit dependency situations. • A conceptual two-unit logic example is used to demonstrate the application of proposed methodology.

  4. A probabilistic seismic risk assessment procedure for nuclear power plants: (I) Methodology

    Science.gov (United States)

    Huang, Y.-N.; Whittaker, A.S.; Luco, N.

    2011-01-01

    A new procedure for probabilistic seismic risk assessment of nuclear power plants (NPPs) is proposed. This procedure modifies the current procedures using tools developed recently for performance-based earthquake engineering of buildings. The proposed procedure uses (a) response-based fragility curves to represent the capacity of structural and nonstructural components of NPPs, (b) nonlinear response-history analysis to characterize the demands on those components, and (c) Monte Carlo simulations to determine the damage state of the components. The use of response-rather than ground-motion-based fragility curves enables the curves to be independent of seismic hazard and closely related to component capacity. The use of Monte Carlo procedure enables the correlation in the responses of components to be directly included in the risk assessment. An example of the methodology is presented in a companion paper to demonstrate its use and provide the technical basis for aspects of the methodology. ?? 2011 Published by Elsevier B.V.

  5. Probabilistic commentary: the rise and fall, and rise again, of risk assessment

    International Nuclear Information System (INIS)

    Hendrie, J.M.

    1985-02-01

    Probabilistic risk assessment is mainly concerned with assessing the risks of nuclear power plants. Historically, the field of PRA began with a Senate request for a report on the safety of nuclear reactors in 1972. A quantitative report called WASH-1400 was eventually prepared and published in 1975, and in summary, it stated that nuclear reactors warranted only a low-grade concern in modern society. Criticism of this report and public perception of its results were highly visible subjects in the media, and the criticism led to the fact that PRA fell into disfavor. After Three Mile Island, it was recognized that PRA was a valuable tool for understanding such accidents, and PRA became a bit more popular again by the end of 1979. The usefulness of PRA was also supported by a German study in 1979. PRA played a significant role in the hearings on the Indian Point reactor. The present NRC regards PRA as an important tool in regulatory practice

  6. Use of probabilistic risk assessment in maintenance activities at Palo Verde

    International Nuclear Information System (INIS)

    Lindquist, R.C.; Pobst, D.S.

    1993-01-01

    Probabilistic risk assessment (PRA) is an important tool in addressing various maintenance activities. At the Palo Verde nuclear generating station (PVNGS), the PRA has been used in a variety of ways to support a wide and diverse selection of maintenance-related activities. For on-line or at-power maintenance, the PRA was used to evaluate combinations of maintenance activities possible with the 12-week or floating maintenance schedule. The maintenance schedule was evaluated to identify any higher risk, undesirable combinations of equipment outages, such as the sole steam-driven auxiliary feedwater pump and the same train emergency diesel generator. Table I is a sampling of the results from the maintenance schedule evaluation in terms of increase in conditional core damage frequency (CDF) above the base- line value due to maintenance on some important key safety systems and combinations thereof. The baseline CDF is 7.4 x 10 -7 per 72 h

  7. A probabilistic risk assessment of Oconee Unit 3. Executive highlights 60

    International Nuclear Information System (INIS)

    1984-04-01

    In 1980 the Nuclear Safety Analysis Center and Duke Power Co. joined in a project to provide the utility industry with a practical, useful example of the application of probabilistic risk assessment (PRA) methods. PRA is a structured analysis technique that accounts for all the failure possibilities that might conceivably lead to core damage. The technique uses probabilities as discriminators to determine which are most significant. The following were project objectives: to provide the host utility with an analytic model of the plant that describes and estimates the likelihood of failure combinations that could lead to core melt; to evaluate the risks to the plant and to the public; to improve utility capabilities in PRA methods and applications

  8. Licensing topical report: application of probabilistic risk assessment in the selection of design basis accidents

    International Nuclear Information System (INIS)

    Houghton, W.J.

    1980-06-01

    A probabilistic risk assessment (PRA) approach is proposed to be used to scrutinize selection of accident sequences. A technique is described in this Licensing Topical Report to identify candidates for Design Basis Accidents (DBAs) utilizing the risk assessment results. As a part of this technique, it is proposed that events with frequencies below a specified limit would not be candidates. The use of the methodology described is supplementary to the traditional, deterministic approach and may result, in some cases, in the selection of multiple failure sequences as DBAs; it may also provide a basis for not considering some traditionally postulated events as being DBAs. A process is then described for selecting a list of DBAs based on the candidates from PRA as supplementary to knowledge and judgments from past licensing practice. These DBAs would be the events considered in Chapter 15 of Safety Analysis Reports of high-temperature gas-cooled reactors

  9. Dynamic modeling of physical phenomena for probabilistic risk assessments using artificial neural networks

    International Nuclear Information System (INIS)

    Benjamin, A.S.; Paez, T.L.; Brown, N.N.

    1998-01-01

    In most probabilistic risk assessments, there is a subset of accident scenarios that involves physical challenges to the system, such as high heat rates and/or accelerations. The system's responses to these challenges may be complicated, and their prediction may require the use of long-running computer codes. To deal with the many scenarios demanded by a risk assessment, the authors have been investigating the use of artificial neural networks (ANNs) as a fast-running estimation tool. They have developed a multivariate linear spline algorithm by extending previous ANN methods that use radial basis functions. They have applied the algorithm to problems involving fires, shocks, and vibrations. They have found that within the parameter range for which it is trained, the algorithm can simulate the nonlinear responses of complex systems with high accuracy. Running times per case are less than one second

  10. EVALUATION OF MILITARY ACTIVITY IMPACT ON HUMANS THROUGH A PROBABILISTIC ECOLOGICAL RISK ASSESSMENT. EXAMPLE OF A FORMER MISSILE BASE.

    Directory of Open Access Journals (Sweden)

    Sergiy ОREL

    2015-10-01

    Full Text Available The current article provides a methodology focused on the assessment of environmental factors after termination of military activity and uses a former missile base as an example. The assessment of environmental conditions is performed through an evaluation of the risks posed by the hazardous chemicals contained by underground and surface water sources and soil to human health . Moreover, by conducting deterministic and probabilistic risk assessments, the article determines that the probabilistic assessment provides more accurate and qualitative information for decision-making on the use of environmental protection measures, which often saves financial and material resources needed for their implementation.

  11. A broad scale analysis of tree risk, mitigation and potential habitat for cavity-nesting birds

    Science.gov (United States)

    Brian Kane; Paige S. Warren; Susannah B. Lerman

    2015-01-01

    Trees in towns and cities provide habitat for wildlife. In particular, cavity-nesting birds nest in the deadand decayed stems and branches of these trees. The same dead and decayed stems and branches alsohave a greater likelihood of failure, which, in some circumstances, increases risk. We examined 1760trees in Baltimore, MD, USA and western MA, USA, assessing tree...

  12. Study on structural seismic margin and probabilistic seismic risk. Development of a structural capacity-seismic risk diagram

    International Nuclear Information System (INIS)

    Nakajima, Masato; Ohtori, Yasuki; Hirata, Kazuta

    2010-01-01

    Seismic margin is extremely important index and information when we evaluate and account seismic safety of critical structures, systems and components quantitatively. Therefore, it is required that electric power companies evaluate the seismic margin of each plant in back-check of nuclear power plants in Japan. The seismic margin of structures is usually defined as a structural capacity margin corresponding to design earthquake ground motion. However, there is little agreement as to the definition of the seismic margin and we have no knowledge about a relationship between the seismic margin and seismic risk (annual failure probability) which is obtained in PSA (Probabilistic Safety Assessment). The purpose of this report is to discuss a definition of structural seismic margin and to develop a diagram which can identify a relation between seismic margin and seismic risk. The main results of this paper are described as follows: (1) We develop seismic margin which is defined based on the fact that intensity of earthquake ground motion is more appropriate than the conventional definition (i.e., the response-based seismic margin) for the following reasons: -seismic margin based on earthquake ground motion is invariant where different typed structures are considered, -stakeholders can understand the seismic margin based on the earthquake ground motion better than the response-based one. (2) The developed seismic margin-risk diagram facilitates us to judge easily whether we need to perform detailed probabilistic risk analysis or only deterministic analysis, given that the reference risk level although information on the uncertainty parameter beta is not obtained. (3) We have performed numerical simulations based on the developed method for four sites in Japan. The structural capacity-risk diagram differs depending on each location because the diagram is greatly influenced by seismic hazard information for a target site. Furthermore, the required structural capacity

  13. Are engineered nano iron oxide particles safe? an environmental risk assessment by probabilistic exposure, effects and risk modeling.

    Science.gov (United States)

    Wang, Yan; Deng, Lei; Caballero-Guzman, Alejandro; Nowack, Bernd

    2016-12-01

    Nano iron oxide particles are beneficial to our daily lives through their use in paints, construction materials, biomedical imaging and other industrial fields. However, little is known about the possible risks associated with the current exposure level of engineered nano iron oxides (nano-FeOX) to organisms in the environment. The goal of this study was to predict the release of nano-FeOX to the environment and assess their risks for surface waters in the EU and Switzerland. The material flows of nano-FeOX to technical compartments (waste incineration and waste water treatment plants) and to the environment were calculated with a probabilistic modeling approach. The mean value of the predicted environmental concentrations (PECs) of nano-FeOX in surface waters in the EU for a worst-case scenario (no particle sedimentation) was estimated to be 28 ng/l. Using a probabilistic species sensitivity distribution, the predicted no-effect concentration (PNEC) was determined from ecotoxicological data. The risk characterization ratio, calculated by dividing the PEC by PNEC values, was used to characterize the risks. The mean risk characterization ratio was predicted to be several orders of magnitude smaller than 1 (1.4 × 10 - 4 ). Therefore, this modeling effort indicates that only a very limited risk is posed by the current release level of nano-FeOX to organisms in surface waters. However, a better understanding of the hazards of nano-FeOX to the organisms in other ecosystems (such as sediment) needs to be assessed to determine the overall risk of these particles to the environment.

  14. Probabilistic risk assessment of insecticide concentrations in agricultural surface waters: a critical appraisal.

    Science.gov (United States)

    Stehle, Sebastian; Knäbel, Anja; Schulz, Ralf

    2013-08-01

    Due to the specific modes of action and application patterns of agricultural insecticides, the insecticide exposure of agricultural surface waters is characterized by infrequent and short-term insecticide concentration peaks of high ecotoxicological relevance with implications for both monitoring and risk assessment. Here, we apply several fixed-interval strategies and an event-based sampling strategy to two generalized and two realistic insecticide exposure patterns for typical agricultural streams derived from FOCUS exposure modeling using Monte Carlo simulations. Sampling based on regular intervals was found to be inadequate for the detection of transient insecticide concentrations, whereas event-triggered sampling successfully detected all exposure incidences at substantially lower analytical costs. Our study proves that probabilistic risk assessment (PRA) concepts in their present forms are not appropriate for a thorough evaluation of insecticide exposure. Despite claims that the PRA approach uses all available data to assess exposure and enhances risk assessment realism, we demonstrate that this concept is severely biased by the amount of insecticide concentrations below detection limits and therefore by the sampling designs. Moreover, actual insecticide exposure is of almost no relevance for PRA threshold level exceedance frequencies and consequential risk assessment outcomes. Therefore, we propose a concept that features a field-relevant ecological risk analysis of agricultural insecticide surface water exposure. Our study quantifies for the first time the environmental and economic consequences of inappropriate monitoring and risk assessment concepts used for the evaluation of short-term peak surface water pollutants such as insecticides.

  15. Use of probabilistic risk assessments to define areas of possible exemption from regulatory requirements

    International Nuclear Information System (INIS)

    Thompson, C.A.; Carlson, D.; Kolaczkowski, A.; LaChance, J.

    1988-01-01

    The Risk-Based Licensing Program (RBLP) was sponsored by the Department of Energy for the purpose of establishing and demonstrating an approach for identifying potential areas for exemption from current regulatory requirements in the licensing of nuclear power plants. Such an approach could assist in the improvement of the regulatory process for both current and future nuclear plant designs. Use of the methodology could result in streamlining the regulatory process by eliminating unnecessarily detailed reviews of portions of a plant design not important to risk. The RBLP methodology utilizes probabilistic risk assessments, (PRAs), which are required of all future applicants for nuclear power plant licenses. PRA results are used as a screening tool to determine the risk significance of various plant features which are correlated to the risk importance of regulations to identify potential areas for regulatory exemption. Additional consideration is then given to non-risk factors in the final determination of exemption candidates. The RBLP methodology was demonstrated using an existing PRA. The results of the demonstration are highlighted. 10 refs

  16. An integrated probabilistic risk analysis decision support methodology for systems with multiple state variables

    International Nuclear Information System (INIS)

    Sen, P.; Tan, John K.G.; Spencer, David

    1999-01-01

    Probabilistic risk analysis (PRA) methods have been proven to be valuable in risk and reliability analysis. However, a weak link seems to exist between methods for analysing risks and those for making rational decisions. The integrated decision support system (IDSS) methodology presented in this paper attempts to address this issue in a practical manner. In consists of three phases: a PRA phase, a risk sensitivity analysis (SA) phase and an optimisation phase, which are implemented through an integrated computer software system. In the risk analysis phase the problem is analysed by the Boolean representation method (BRM), a PRA method that can deal with systems with multiple state variables and feedback loops. In the second phase the results obtained from the BRM are utilised directly to perform importance and risk SA. In the third phase, the problem is formulated as a multiple objective decision making problem in the form of multiple objective reliability optimisation. An industrial example is included. The resultant solutions of a five objective reliability optimisation are presented, on the basis of which rational decision making can be explored

  17. Probabilistic framework for assessing the arsenic exposure risk from cooked fish consumption.

    Science.gov (United States)

    Ling, Min-Pei; Wu, Chiu-Hua; Chen, Szu-Chieh; Chen, Wei-Yu; Chio, Chia-Pin; Cheng, Yi-Hsien; Liao, Chung-Min

    2014-12-01

    Geogenic arsenic (As) contamination of groundwater is a major ecological and human health problem in southwestern and northeastern coastal areas of Taiwan. Here, we present a probabilistic framework for assessing the human health risks from consuming raw and cooked fish that were cultured in groundwater As-contaminated ponds in Taiwan by linking a physiologically based pharmacokinetics model and a Weibull dose-response model. Results indicate that As levels in baked, fried, and grilled fish were higher than those of raw fish. Frying resulted in the greatest increase in As concentration, followed by grilling, with baking affecting the As concentration the least. Simulation results show that, following consumption of baked As-contaminated fish, the health risk to humans is fish is unlikely to pose a significant risk to human health. However, contaminated fish cooked by frying resulted in significant health risks, showing the highest cumulative incidence ratios of liver cancer. We also show that males have higher cumulative incidence ratio of liver cancer than females. We found that although cooking resulted in an increase for As levels in As-contaminated fish, the risk to human health of consuming baked fish is nevertheless acceptable. We suggest the adoption of baking as a cooking method and warn against frying As-contaminated fish. We conclude that the concentration of contaminants after cooking should be taken into consideration when assessing the risk to human health.

  18. Evaluation of structural fragilities for an IPEEE seismic probabilistic risk assessment study

    International Nuclear Information System (INIS)

    Ghiocel, D.M.; Wilson, P.R.; Stevenson, J.D.

    1995-01-01

    The paper presents the main issues and results of a structural fragility analysis for a Seismic Probabilistic Risk Assessment (SPRA) study of a nuclear power plant (NPP) in the Eastern US. The fragility evaluations were performed for the Reactor Building, Auxiliary Building, Intake Structure and Diesel Generator Building. The random seismic input is defined in terms of the Uniform Hazard Spectrum (UHS) earthquake on the NPP site anchored to a reference level of 0.40 g Zero Period Ground Acceleration (ZPGA). Because of the soft soil conditions new Soil-Structure Interaction (SSI) analyses were performed using the original finite element (stick) structural models and the complex frequency approach. The soil deposit randomness was described by the variations in both the low strain soil shear modules and in its dependence with the shear strain. The probabilistic SSI analyses were performed using digital simulation techniques. The critical failure modes for each structure are investigated and the fragility evaluations are discussed. Concluding remarks and recommendations for improving the quality of the structural fragility analyses are included

  19. Nuclear and isotopic techniques underpinning probabilistic ecological risk analysis in coastal marine systems

    International Nuclear Information System (INIS)

    Szymczak, R.; Twining, J.; Hollins, S.; Hughes, C.; Mazumder, D.; Alquezar, R.

    2006-01-01

    Full text: The historical operation of manufacturing, chemical and other industries in the Sydney Harbour catchment over many decades has left a legacy of high chemical contamination in the surrounding catchment, such that a recent report describes Port Jackson as one of the most contaminated harbours in the world (Birch and Taylor, 2005). The legacy in Homebush Bay is amongst the worst in the harbour and presents a considerable management problem. Elucidation of environmental processes is the key to effective ecosystem management, however few tools are available to determine their inter-relationships, rates and directions. This study has four components: (1) determination of linkages between high trophic order species and different habitats resources using stable isotopic analyses of carbon and nitrogen. These studies identify trophic cascades forming the basis for selection of biota for contaminant transfer experiments; (2) short-term (weeks - months) chronology and geochemistry of sediment cores and traps in Homebush Bay to determine rates of sedimentation and resuspension (using environmental/cosmogenic Be). Models derived from these studies provide the contaminants levels against which risk is assessed; (3) biokinetic studies using proxy radiotracer isotopes (eg. 75 Se and 109 Cd for analogous stable metals) of the uptake and trophic transfer of contaminants by specific estaurine biota. Here we identify the rates and extent to which contaminants accumulated and transferred to predators/seafoods; and (4) application of a probabilistic ecological risk assessment model (AQUARISK) set to criteria determined by stakeholder consensus. In this study we analysed the distribution of natural isotopes and redistribution of artificial isotopes injected into ecological compartments to determine the key trophic linkages and contaminant pathways in an estuarine system and contribute to improving the accuracy and specificity of a probabilistic ecological risk assessment

  20. Probabilistic risk assessment from potential exposures to the public applied for innovative nuclear installations

    International Nuclear Information System (INIS)

    Dvorzhak, Alla; Mora, Juan C.; Robles, Beatriz

    2016-01-01

    Potential exposures are those that may occur as a result of unanticipated operational performance or accidents. Potential exposure situations are probabilistic in nature because they depend on uncertain events such as equipment failure, operator errors or external initiators beyond the control of the operator. Consequently, there may exist a range of possible radiological impacts that need to be considered. In this paper a Level 3 Probabilistic Safety Assessment (PSA) for a hypothetical scenario relevant to Innovative Nuclear Energy Systems (INS) was conducted using computer code MACCS (MELCOR Accident Consequence Code Systems). The acceptability of an INS was analyzed taking into account the general requirement that relocation or evacuation measures must not be necessary beyond the site boundary. In addition, deterministic modeling of the accident consequences for the critical meteorological conditions was carried out using the JRODOS decision support system (Real-time On-line Decision Support system for off-site emergency management in Europe). The approach used for dose and risk assessment from potential exposure of accidental releases and their comparison with acceptance criteria are presented. The methodology described can be used as input to the licensing procedure and engineering design considerations to help satisfy relevant health and environmental impact criteria for fission or fusion nuclear installations. - Highlights: • PSA Level-3 based on WinMACCS code is carried out for accidental release. • Family curves of percentiles for radiation exposure doses are constructed. • Risk indicators for potential exposure are defined. • Using of risk acceptance curve criteria is proposed for decision making process.

  1. A socio-technical, probabilistic risk assessment model for surgical site infections in ambulatory surgery centers.

    Science.gov (United States)

    Bish, Ebru K; El-Amine, Hadi; Steighner, Laura A; Slonim, Anthony D

    2014-10-01

    To understand how structural and process elements may affect the risk for surgical site infections (SSIs) in the ambulatory surgery center (ASC) environment, the researchers employed a tool known as socio-technical probabilistic risk assessment (ST-PRA). ST-PRA is particularly helpful for estimating risks in outcomes that are very rare, such as the risk of SSI in ASCs. Study objectives were to (1) identify the risk factors associated with SSIs resulting from procedures performed at ASCs and (2) design an intervention to mitigate the likelihood of SSIs for the most common risk factors that were identified by the ST-PRA for a particular surgical procedure. ST-PRA was used to study the SSI risk in the ASC setting. Both quantitative and qualitative data sources were utilized, and sensitivity analysis was performed to ensure the robustness of the results. The event entitled "fail to protect the patient effectively" accounted for 51.9% of SSIs in the ambulatory care setting. Critical components of this event included several failure risk points related to skin preparation, antibiotic administration, staff training, proper response to glove punctures during surgery, and adherence to surgical preparation rules related to the wearing of jewelry, watches, and artificial nails. Assuming a 75% reduction in noncompliance on any combination of 2 of these 5 components, the risk for an SSI decreased from 0.0044 to between 0.0027 and 0.0035. An intervention that targeted the 5 major components of the major risk point was proposed, and its implications were discussed.

  2. Multi-criteria decision analysis with probabilistic risk assessment for the management of contaminated ground water

    International Nuclear Information System (INIS)

    Khadam, Ibrahim M.; Kaluarachchi, Jagath J.

    2003-01-01

    Traditionally, environmental decision analysis in subsurface contamination scenarios is performed using cost-benefit analysis. In this paper, we discuss some of the limitations associated with cost-benefit analysis, especially its definition of risk, its definition of cost of risk, and its poor ability to communicate risk-related information. This paper presents an integrated approach for management of contaminated ground water resources using health risk assessment and economic analysis through a multi-criteria decision analysis framework. The methodology introduces several important concepts and definitions in decision analysis related to subsurface contamination. These are the trade-off between population risk and individual risk, the trade-off between the residual risk and the cost of risk reduction, and cost-effectiveness as a justification for remediation. The proposed decision analysis framework integrates probabilistic health risk assessment into a comprehensive, yet simple, cost-based multi-criteria decision analysis framework. The methodology focuses on developing decision criteria that provide insight into the common questions of the decision-maker that involve a number of remedial alternatives. The paper then explores three potential approaches for alternative ranking, a structured explicit decision analysis, a heuristic approach of importance of the order of criteria, and a fuzzy logic approach based on fuzzy dominance and similarity analysis. Using formal alternative ranking procedures, the methodology seeks to present a structured decision analysis framework that can be applied consistently across many different and complex remediation settings. A simple numerical example is presented to demonstrate the proposed methodology. The results showed the importance of using an integrated approach for decision-making considering both costs and risks. Future work should focus on the application of the methodology to a variety of complex field conditions to

  3. Approximate dynamic fault tree calculations for modelling water supply risks

    International Nuclear Information System (INIS)

    Lindhe, Andreas; Norberg, Tommy; Rosén, Lars

    2012-01-01

    Traditional fault tree analysis is not always sufficient when analysing complex systems. To overcome the limitations dynamic fault tree (DFT) analysis is suggested in the literature as well as different approaches for how to solve DFTs. For added value in fault tree analysis, approximate DFT calculations based on a Markovian approach are presented and evaluated here. The approximate DFT calculations are performed using standard Monte Carlo simulations and do not require simulations of the full Markov models, which simplifies model building and in particular calculations. It is shown how to extend the calculations of the traditional OR- and AND-gates, so that information is available on the failure probability, the failure rate and the mean downtime at all levels in the fault tree. Two additional logic gates are presented that make it possible to model a system's ability to compensate for failures. This work was initiated to enable correct analyses of water supply risks. Drinking water systems are typically complex with an inherent ability to compensate for failures that is not easily modelled using traditional logic gates. The approximate DFT calculations are compared to results from simulations of the corresponding Markov models for three water supply examples. For the traditional OR- and AND-gates, and one gate modelling compensation, the errors in the results are small. For the other gate modelling compensation, the error increases with the number of compensating components. The errors are, however, in most cases acceptable with respect to uncertainties in input data. The approximate DFT calculations improve the capabilities of fault tree analysis of drinking water systems since they provide additional and important information and are simple and practically applicable.

  4. Probabilistic risk assessment modeling of digital instrumentation and control systems using two dynamic methodologies

    Energy Technology Data Exchange (ETDEWEB)

    Aldemir, T., E-mail: aldemir.1@osu.ed [Ohio State University, Nuclear Engineering Program, Columbus, OH 43210 (United States); Guarro, S. [ASCA, Inc., 1720 S. Catalina Avenue, Suite 220, Redondo Beach, CA 90277-5501 (United States); Mandelli, D. [Ohio State University, Nuclear Engineering Program, Columbus, OH 43210 (United States); Kirschenbaum, J. [Ohio State University, Department of Computer Science and Engineering, Columbus, OH 43210 (United States); Mangan, L.A. [Ohio State University, Nuclear Engineering Program, Columbus, OH 43210 (United States); Bucci, P. [Ohio State University, Department of Computer Science and Engineering, Columbus, OH 43210 (United States); Yau, M. [ASCA, Inc., 1720 S. Catalina Avenue, Suite 220, Redondo Beach, CA 90277-5501 (United States); Ekici, E. [Ohio State University, Department of Electrical and Computer Engineering, Columbus, OH 43210 (United States); Miller, D.W.; Sun, X. [Ohio State University, Nuclear Engineering Program, Columbus, OH 43210 (United States); Arndt, S.A. [U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001 (United States)

    2010-10-15

    The Markov/cell-to-cell mapping technique (CCMT) and the dynamic flowgraph methodology (DFM) are two system logic modeling methodologies that have been proposed to address the dynamic characteristics of digital instrumentation and control (I and C) systems and provide risk-analytical capabilities that supplement those provided by traditional probabilistic risk assessment (PRA) techniques for nuclear power plants. Both methodologies utilize a discrete state, multi-valued logic representation of the digital I and C system. For probabilistic quantification purposes, both techniques require the estimation of the probabilities of basic system failure modes, including digital I and C software failure modes, that appear in the prime implicants identified as contributors to a given system event of interest. As in any other system modeling process, the accuracy and predictive value of the models produced by the two techniques, depend not only on the intrinsic features of the modeling paradigm, but also and to a considerable extent on information and knowledge available to the analyst, concerning the system behavior and operation rules under normal and off-nominal conditions, and the associated controlled/monitored process dynamics. The application of the two methodologies is illustrated using a digital feedwater control system (DFWCS) similar to that of an operating pressurized water reactor. This application was carried out to demonstrate how the use of either technique, or both, can facilitate the updating of an existing nuclear power plant PRA model following an upgrade of the instrumentation and control system from analog to digital. Because of scope limitations, the focus of the demonstration of the methodologies was intentionally limited to aspects of digital I and C system behavior for which probabilistic data was on hand or could be generated within the existing project bounds of time and resources. The data used in the probabilistic quantification portion of the

  5. Associations between polygenic risk for schizophrenia and brain function during probabilistic learning in healthy individuals.

    Science.gov (United States)

    Lancaster, Thomas M; Ihssen, Niklas; Brindley, Lisa M; Tansey, Katherine E; Mantripragada, Kiran; O'Donovan, Michael C; Owen, Michael J; Linden, David E J

    2016-02-01

    A substantial proportion of schizophrenia liability can be explained by additive genetic factors. Risk profile scores (RPS) directly index risk using a summated total of common risk variants weighted by their effect. Previous studies suggest that schizophrenia RPS predict alterations to neural networks that support working memory and verbal fluency. In this study, we apply schizophrenia RPS to fMRI data to elucidate the effects of polygenic risk on functional brain networks during a probabilistic-learning neuroimaging paradigm. The neural networks recruited during this paradigm have previously been shown to be altered to unmedicated schizophrenia patients and relatives of schizophrenia patients, which may reflect genetic susceptibility. We created schizophrenia RPS using summary data from the Psychiatric Genetic Consortium (Schizophrenia Working Group) for 83 healthy individuals and explore associations between schizophrenia RPS and blood oxygen level dependency (BOLD) during periods of choice behavior (switch-stay) and reflection upon choice outcome (reward-punishment). We show that schizophrenia RPS is associated with alterations in the frontal pole (PWHOLE-BRAIN-CORRECTED  = 0.048) and the ventral striatum (PROI-CORRECTED  = 0.036), during choice behavior, but not choice outcome. We suggest that the common risk variants that increase susceptibility to schizophrenia can be associated with alterations in the neural circuitry that support the processing of changing reward contingencies. Hum Brain Mapp 37:491-500, 2016. © 2015 Wiley Periodicals, Inc. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

  6. Interpretation of risk significance of passive component aging using probabilistic structural analysis

    International Nuclear Information System (INIS)

    Phillips, J.H.; Atwood, C.L.

    1993-01-01

    The probabilistic risk assessments (PRAs) being developed at most nuclear power plants to calculate the risk of core damage generally focus on the possible failure of active components. Except as initiating events, the possible failure of passive components is given little consideration. The NRC is sponsoring a project at INEL to investigate the risk significance of passive components as they age. For this project, we developed a technique to calculate the failure probability of passive components over time, and demonstrated the technique by applying it to a weld in the auxiliary feedwater (AFW) system. A decreasing yearly rupture rate for this weld was calculated instead of the increasing rupture rate trend one might expect. We attribute this result to infant mortality; that is, most of those initial flaws that will eventually lead to rupture will do so early in life. This means that although each weld in a population may be wearing out, the population as a whole can exhibit a decreasing rupture rate. This observation has implications for passive components in commercial nuclear plants and other facilities where aging is a concern. For the population of passive components that exhibit a decreasing failure rate, risk increase is not a concern. The next step of the work is to identify the attributes that contribute to this decreasing rate, and to determine any attributes that would contribute to an increasing failure rate and thus to an increased risk

  7. Methodology for Developing a Probabilistic Risk Assessment Model of Spacecraft Rendezvous and Dockings

    Science.gov (United States)

    Farnham, Steven J., II; Garza, Joel, Jr.; Castillo, Theresa M.; Lutomski, Michael

    2011-01-01

    In 2007 NASA was preparing to send two new visiting vehicles carrying logistics and propellant to the International Space Station (ISS). These new vehicles were the European Space Agency s (ESA) Automated Transfer Vehicle (ATV), the Jules Verne, and the Japanese Aerospace and Explorations Agency s (JAXA) H-II Transfer Vehicle (HTV). The ISS Program wanted to quantify the increased risk to the ISS from these visiting vehicles. At the time, only the Shuttle, the Soyuz, and the Progress vehicles rendezvoused and docked to the ISS. The increased risk to the ISS was from an increase in vehicle traffic, thereby, increasing the potential catastrophic collision during the rendezvous and the docking or berthing of the spacecraft to the ISS. A universal method of evaluating the risk of rendezvous and docking or berthing was created by the ISS s Risk Team to accommodate the increasing number of rendezvous and docking or berthing operations due to the increasing number of different spacecraft, as well as the future arrival of commercial spacecraft. Before the first docking attempt of ESA's ATV and JAXA's HTV to the ISS, a probabilistic risk model was developed to quantitatively calculate the risk of collision of each spacecraft with the ISS. The 5 rendezvous and docking risk models (Soyuz, Progress, Shuttle, ATV, and HTV) have been used to build and refine the modeling methodology for rendezvous and docking of spacecrafts. This risk modeling methodology will be NASA s basis for evaluating the addition of future ISS visiting spacecrafts hazards, including SpaceX s Dragon, Orbital Science s Cygnus, and NASA s own Orion spacecraft. This paper will describe the methodology used for developing a visiting vehicle risk model.

  8. Probabilistic risk assessment support of emergency preparedness at the Savannah River Site

    International Nuclear Information System (INIS)

    O'Kula, K.R.; Baker, W.H.; Simpkins, A.A.; Taylor, R.P.; Wagner, K.C.; Amos, C.N.

    1992-01-01

    Integration of the Probabilistic Risk Assessment (PRA) for K Reactor operation into related technical areas at the Savannah River Site (SRS) includes coordination with several onsite organizations responsible for maintaining and upgrading emergency preparedness capabilities. Major functional categories of the PRA application are scenario development and source term algorithm enhancement. Insights and technologies from the SRS PRA have facilitated development of: (1) credible timelines for scenarios; (2) algorithms tied to plant instrumentation to provide best-estimate source terms for dose projection; and (3) expert-system logic models to implement informed counter-measures to assure onsite and offsite safety following accidental releases. The latter methodology, in particular, is readily transferable to other reactor and non-reactor facilities at SRS and represents a distinct advance relative to emergency preparedness capabilities elsewhere in the DOE complex

  9. Diablo Canyon internal events PRA [Probabilistic Risk Assessment] review: Methodology and findings

    International Nuclear Information System (INIS)

    Fitzpatrick, R.G.; Bozoki, G.; Sabek, M.

    1990-01-01

    The review of the Diablo Canyon Probabilistic Risk Assessment (DCRPA) incorporated some new and innovative approaches. These were necessitated by the unprecedented size, scope and level of detail of the DCRPA, which was submitted to the NRC for licensing purposes. This paper outlines the elements of the internal events portion of the review citing selected findings to illustrate the various approaches employed. The paper also provides a description of the extensive and comprehensive importance analysis applied by BNL to the DCRPA model. Importance calculations included: top event/function level; individual split fractions; pair importances between frontline-support and support-support systems; system importance by initiator; and others. The paper concludes with a brief discussion of the effectiveness of the applied methodology. 3 refs., 5 tabs

  10. Review of the Oconee-3 probabilistic risk assessment: external events, core damage frequency. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Hanan, N.A.; Ilberg, D.; Xue, D.; Youngblood, R.; Reed, J.W.; McCann, M.; Talwani, T.; Wreathall, J.; Kurth, P.D.; Bandyopadhyay, K.

    1986-03-01

    A review of the Oconee-3 Probabilistic Risk Assessment (OPRA) was conducted with the broad objective of evaluating qualitatively and quantitatively (as much as possible) the OPRA assessment of the important sequences that are ''externally'' generated and lead to core damage. The review included a technical assessment of the assumptions and methods used in the OPRA within its stated objective and with the limited information available. Within this scope, BNL performed a detailed reevaluation of the accident sequences generated by internal floods and earthquakes and a less detailed review (in some cases a scoping review) for the accident sequences generated by fires, tornadoes, external floods, and aircraft impact. 12 refs., 24 figs., 31 tabs.

  11. Comparison of seismic margin assessment and probabilistic risk assessment in seismic IPE

    International Nuclear Information System (INIS)

    Reed, J.W.; Kassawara, R.P.

    1993-01-01

    A comparison of technical requirements and managerial issues between seismic margin assessment (SMA) and seismic probabilistic risk assessment (SPRA) in a seismic Individual Plant Examination (IPE) is presented and related to requirements for an Unresolved Safety Issue (USI) A-46 review which is required for older nuclear power plants. Advantages and disadvantages are discussed for each approach. Technical requirements reviewed for a seismic IPE include: scope of plants covered, seismic input, scope of review, selection of equipment, required experience and training of engineers, walkdown procedure, evaluation of components, relay review, containment review, quality assurance, products, documentation requirements, and closure procedure. Managerial issues discussed include regulatory acceptability, compatibility with seismic IPE, compliance with seismic IPE requirements, ease of use by utilities, and relative cost

  12. The tsunami probabilistic risk assessment of nuclear power plant (3). Outline of tsunami fragility analysis

    International Nuclear Information System (INIS)

    Mihara, Yoshinori

    2012-01-01

    Tsunami Probabilistic Risk Assessment (PRA) standard was issued in February 2012 by Standard Committee of Atomic Energy Society of Japan (AESJ). This article detailed tsunami fragility analysis, which calculated building and structure damage probability contributing core damage and consisted of five evaluation steps: (1) selection of evaluated element and damage mode, (2) selection of evaluation procedure, (3) evaluation of actual stiffness, (4) evaluation of actual response and (5) evaluation of fragility (damage probability and others). As an application example of the standard, calculation results of tsunami fragility analysis investigation by tsunami PRA subcommittee of AESJ were shown reflecting latest knowledge of damage state caused by wave force and others acted by tsunami from the 'off the Pacific Coast of Tohoku Earthquake'. (T. Tanaka)

  13. External event Probabilistic Risk Assessment for the High Flux Isotope Reactor (HFIR)

    International Nuclear Information System (INIS)

    Flanagan, G.F.; Johnson, D.H.; Buttemer, D.; Perla, H.F.; Chien, S.H.

    1989-01-01

    The High Flux Isotope Reactor (HFIR) is a high performance isotope production and research reactor which has been in operation at Oak Ridge National Laboratory (ORNL) since 1965. In late 1986 the reactor was shut down as a result of discovery of unexpected neutron embrittlement of the reactor vessel. In January of 1988 a level 1 Probabilistic Risk Assessment (PRA) (excluding external events) was published as part of the response to the many reviews that followed the shutdown and for use by ORNL to prioritize action items intended to upgrade the safety of the reactor. A conservative estimate of the core damage frequency initiated by internal events for HFIR was 3.11 x 10 -4 . In June 1989 a draft external events initiated PRA was published. The dominant contributions from external events came from seismic, wind, and fires. The overall external event contribution to core damage frequency is about 50% of the internal event initiated contribution and is dominated by seismic events

  14. Review of the Oconee-3 probabilistic risk assessment: external events, core damage frequency. Volume 2

    International Nuclear Information System (INIS)

    Hanan, N.A.; Ilberg, D.; Xue, D.

    1986-03-01

    A review of the Oconee-3 Probabilistic Risk Assessment (OPRA) was conducted with the broad objective of evaluating qualitatively and quantitatively (as much as possible) the OPRA assessment of the important sequences that are ''externally'' generated and lead to core damage. The review included a technical assessment of the assumptions and methods used in the OPRA within its stated objective and with the limited information available. Within this scope, BNL performed a detailed reevaluation of the accident sequences generated by internal floods and earthquakes and a less detailed review (in some cases a scoping review) for the accident sequences generated by fires, tornadoes, external floods, and aircraft impact. 12 refs., 24 figs., 31 tabs

  15. Analytic Bayesian solution of the two-stage poisson-type problem in probabilistic risk analysis

    International Nuclear Information System (INIS)

    Frohner, F.H.

    1985-01-01

    The basic purpose of probabilistic risk analysis is to make inferences about the probabilities of various postulated events, with an account of all relevant information such as prior knowledge and operating experience with the specific system under study, as well as experience with other similar systems. Estimation of the failure rate of a Poisson-type system leads to an especially simple Bayesian solution in closed form if the prior probabilty implied by the invariance properties of the problem is properly taken into account. This basic simplicity persists if a more realistic prior, representing order of magnitude knowledge of the rate parameter, is employed instead. Moreover, the more realistic prior allows direct incorporation of experience gained from other similar systems, without need to postulate a statistical model for an underlying ensemble. The analytic formalism is applied to actual nuclear reactor data

  16. Probabilistic assessment of erosion and flooding risk in the northern Gulf of Mexico

    Science.gov (United States)

    Wahl, Thomas; Plant, Nathaniel G.; Long, Joseph W.

    2016-05-01

    We assess erosion and flooding risk in the northern Gulf of Mexico by identifying interdependencies among oceanographic drivers and probabilistically modeling the resulting potential for coastal change. Wave and water level observations are used to determine relationships between six hydrodynamic parameters that influence total water level and therefore erosion and flooding, through consideration of a wide range of univariate distribution functions and multivariate elliptical copulas. Using these relationships, we explore how different our interpretation of the present-day erosion/flooding risk could be if we had seen more or fewer extreme realizations of individual and combinations of parameters in the past by simulating 10,000 physically and statistically consistent sea-storm time series. We find that seasonal total water levels associated with the 100 year return period could be up to 3 m higher in summer and 0.6 m higher in winter relative to our best estimate based on the observational records. Impact hours of collision and overwash—where total water levels exceed the dune toe or dune crest elevations—could be on average 70% (collision) and 100% (overwash) larger than inferred from the observations. Our model accounts for non-stationarity in a straightforward, non-parametric way that can be applied (with little adjustments) to many other coastlines. The probabilistic model presented here, which accounts for observational uncertainty, can be applied to other coastlines where short record lengths limit the ability to identify the full range of possible wave and water level conditions that coastal mangers and planners must consider to develop sustainable management strategies.

  17. Probabilistic assessment of erosion and flooding risk in the northern Gulf of Mexico

    Science.gov (United States)

    Plant, Nathaniel G.; Wahl, Thomas; Long, Joseph W.

    2016-01-01

    We assess erosion and flooding risk in the northern Gulf of Mexico by identifying interdependencies among oceanographic drivers and probabilistically modeling the resulting potential for coastal change. Wave and water level observations are used to determine relationships between six hydrodynamic parameters that influence total water level and therefore erosion and flooding, through consideration of a wide range of univariate distribution functions and multivariate elliptical copulas. Using these relationships, we explore how different our interpretation of the present-day erosion/flooding risk could be if we had seen more or fewer extreme realizations of individual and combinations of parameters in the past by simulating 10,000 physically and statistically consistent sea-storm time series. We find that seasonal total water levels associated with the 100 year return period could be up to 3 m higher in summer and 0.6 m higher in winter relative to our best estimate based on the observational records. Impact hours of collision and overwash—where total water levels exceed the dune toe or dune crest elevations—could be on average 70% (collision) and 100% (overwash) larger than inferred from the observations. Our model accounts for non-stationarity in a straightforward, non-parametric way that can be applied (with little adjustments) to many other coastlines. The probabilistic model presented here, which accounts for observational uncertainty, can be applied to other coastlines where short record lengths limit the ability to identify the full range of possible wave and water level conditions that coastal mangers and planners must consider to develop sustainable management strategies.

  18. Incorporating probabilistic seasonal climate forecasts into river management using a risk-based framework

    Science.gov (United States)

    Sojda, Richard S.; Towler, Erin; Roberts, Mike; Rajagopalan, Balaji

    2013-01-01

    [1] Despite the influence of hydroclimate on river ecosystems, most efforts to date have focused on using climate information to predict streamflow for water supply. However, as water demands intensify and river systems are increasingly stressed, research is needed to explicitly integrate climate into streamflow forecasts that are relevant to river ecosystem management. To this end, we present a five step risk-based framework: (1) define risk tolerance, (2) develop a streamflow forecast model, (3) generate climate forecast ensembles, (4) estimate streamflow ensembles and associated risk, and (5) manage for climate risk. The framework is successfully demonstrated for an unregulated watershed in southwest Montana, where the combination of recent drought and water withdrawals has made it challenging to maintain flows needed for healthy fisheries. We put forth a generalized linear modeling (GLM) approach to develop a suite of tools that skillfully model decision-relevant low flow characteristics in terms of climate predictors. Probabilistic precipitation forecasts are used in conjunction with the GLMs, resulting in season-ahead prediction ensembles that provide the full risk profile. These tools are embedded in an end-to-end risk management framework that directly supports proactive fish conservation efforts. Results show that the use of forecasts can be beneficial to planning, especially in wet years, but historical precipitation forecasts are quite conservative (i.e., not very “sharp”). Synthetic forecasts show that a modest “sharpening” can strongly impact risk and improve skill. We emphasize that use in management depends on defining relevant environmental flows and risk tolerance, requiring local stakeholder involvement.

  19. Development and Application of a Probabilistic Risk-Benefit Assessment Model for Infant Feeding Integrating Microbiological, Nutritional, and Chemical Components.

    Science.gov (United States)

    Boué, Géraldine; Cummins, Enda; Guillou, Sandrine; Antignac, Jean-Philippe; Le Bizec, Bruno; Membré, Jeanne-Marie

    2017-12-01

    A probabilistic and interdisciplinary risk-benefit assessment (RBA) model integrating microbiological, nutritional, and chemical components was developed for infant milk, with the objective of predicting the health impact of different scenarios of consumption. Infant feeding is a particular concern of interest in RBA as breast milk and powder infant formula have both been associated with risks and benefits related to chemicals, bacteria, and nutrients, hence the model considers these three facets. Cronobacter sakazakii, dioxin-like polychlorinated biphenyls (dl-PCB), and docosahexaenoic acid (DHA) were three risk/benefit factors selected as key issues in microbiology, chemistry, and nutrition, respectively. The present model was probabilistic with variability and uncertainty separated using a second-order Monte Carlo simulation process. In this study, advantages and limitations of undertaking probabilistic and interdisciplinary RBA are discussed. In particular, the probabilistic technique was found to be powerful in dealing with missing data and to translate assumptions into quantitative inputs while taking uncertainty into account. In addition, separation of variability and uncertainty strengthened the interpretation of the model outputs by enabling better consideration and distinction of natural heterogeneity from lack of knowledge. Interdisciplinary RBA is necessary to give more structured conclusions and avoid contradictory messages to policymakers and also to consumers, leading to more decisive food recommendations. This assessment provides a conceptual development of the RBA methodology and is a robust basis on which to build upon. © 2017 Society for Risk Analysis.

  20. Probabilistic risk assessment model for allergens in food: sensitivity analysis of the minimum eliciting dose and food consumption

    NARCIS (Netherlands)

    Kruizinga, A.G.; Briggs, D.; Crevel, R.W.R.; Knulst, A.C.; Bosch, L.M.C.v.d.; Houben, G.F.

    2008-01-01

    Previously, TNO developed a probabilistic model to predict the likelihood of an allergic reaction, resulting in a quantitative assessment of the risk associated with unintended exposure to food allergens. The likelihood is estimated by including in the model the proportion of the population who is

  1. Probabilistic safety and risk assessments in the field of nuclear technology - Mode of operation, possibilities and limits

    International Nuclear Information System (INIS)

    Mertens, J.

    1993-01-01

    In this study probabilistic safety and risk assessments in the field of nuclear energy are explained. Mainly qualitative results and conclusions are presented. Explanations for often discussed aspects of such analysis reveal the procedure and reasonable limits of application. The mentioned literature contains detailed results. (orig./DG) [de

  2. Probabilistic health risk assessment for ingestion of seafood farmed in arsenic contaminated groundwater in Taiwan.

    Science.gov (United States)

    Liang, Ching-Ping; Jang, Cheng-Shin; Chen, Jui-Sheng; Wang, Sheng-Wei; Lee, Jin-Jing; Liu, Chen-Wuing

    2013-08-01

    Seafood farmed in arsenic (As)-contaminated areas is a major exposure pathway for the ingestion of inorganic As by individuals in the southwestern part of Taiwan. This study presents a probabilistic risk assessment using limited data for inorganic As intake through the consumption of the seafood by local residents in these areas. The As content and the consumption rate are both treated as probability distributions, taking into account the variability of the amount in the seafood and individual consumption habits. The Monte Carlo simulation technique is utilized to conduct an assessment of exposure due to the daily intake of inorganic As from As-contaminated seafood. Exposure is evaluated according to the provisional tolerable weekly intake (PTWI) established by the FAO/WHO and the target risk based on the US Environmental Protection Agency guidelines. The assessment results show that inorganic As intake from five types of fish (excluding mullet) and shellfish fall below the PTWI threshold values for the 95th percentiles, but exceed the target cancer risk of 10(-6). The predicted 95th percentile for inorganic As intake and lifetime cancer risks obtained in the study are both markedly higher than those obtained in previous studies in which the consumption rate of seafood considered is a deterministic value. This study demonstrates the importance of the individual variability of seafood consumption when evaluating a high exposure sub-group of the population who eat higher amounts of fish and shellfish than the average Taiwanese.

  3. Expert elicitation for deriving input data for probabilistic risk assessment of shipwrecks.

    Science.gov (United States)

    Landquist, H; Norrman, J; Lindhe, A; Norberg, T; Hassellöv, I-M; Lindgren, J F; Rosén, L

    2017-12-15

    The necessity of having a process in place for adequate risk assessment of shipwrecks that pose a threat to the marine environment is today internationally acknowledged. However, retrieving the desired data for such a risk assessment can prove challenging. One means of addressing this problem is to make use of experts' knowledge and experience. The purpose of this paper is therefore to present and analyse data for risk assessment of shipwrecks derived by expert elicitation. The main outcome is the experts' estimations of (i) the generic probability of an opening in a shipwreck due to the occurrence of a number of activities and (ii) estimations of the degree to which site-specific and wreck-specific indicators affect the probability of opening. Results show that the derived information is applicable in probabilistic shipwreck risk assessment and that the VRAKA framework now contains needed information for integrating generic and site-specific information using Bayesian updating. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. The MCRA model for probabilistic single-compound and cumulative risk assessment of pesticides.

    Science.gov (United States)

    van der Voet, Hilko; de Boer, Waldo J; Kruisselbrink, Johannes W; Goedhart, Paul W; van der Heijden, Gerie W A M; Kennedy, Marc C; Boon, Polly E; van Klaveren, Jacob D

    2015-05-01

    Pesticide risk assessment is hampered by worst-case assumptions leading to overly pessimistic assessments. On the other hand, cumulative health effects of similar pesticides are often not taken into account. This paper describes models and a web-based software system developed in the European research project ACROPOLIS. The models are appropriate for both acute and chronic exposure assessments of single compounds and of multiple compounds in cumulative assessment groups. The software system MCRA (Monte Carlo Risk Assessment) is available for stakeholders in pesticide risk assessment at mcra.rivm.nl. We describe the MCRA implementation of the methods as advised in the 2012 EFSA Guidance on probabilistic modelling, as well as more refined methods developed in the ACROPOLIS project. The emphasis is on cumulative assessments. Two approaches, sample-based and compound-based, are contrasted. It is shown that additional data on agricultural use of pesticides may give more realistic risk assessments. Examples are given of model and software validation of acute and chronic assessments, using both simulated data and comparisons against the previous release of MCRA and against the standard software DEEM-FCID used by the Environmental Protection Agency in the USA. It is shown that the EFSA Guidance pessimistic model may not always give an appropriate modelling of exposure. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  5. Modeling and Quantification of Team Performance in Human Reliability Analysis for Probabilistic Risk Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey C. JOe; Ronald L. Boring

    2014-06-01

    Probabilistic Risk Assessment (PRA) and Human Reliability Assessment (HRA) are important technical contributors to the United States (U.S.) Nuclear Regulatory Commission’s (NRC) risk-informed and performance based approach to regulating U.S. commercial nuclear activities. Furthermore, all currently operating commercial NPPs in the U.S. are required by federal regulation to be staffed with crews of operators. Yet, aspects of team performance are underspecified in most HRA methods that are widely used in the nuclear industry. There are a variety of "emergent" team cognition and teamwork errors (e.g., communication errors) that are 1) distinct from individual human errors, and 2) important to understand from a PRA perspective. The lack of robust models or quantification of team performance is an issue that affects the accuracy and validity of HRA methods and models, leading to significant uncertainty in estimating HEPs. This paper describes research that has the objective to model and quantify team dynamics and teamwork within NPP control room crews for risk informed applications, thereby improving the technical basis of HRA, which improves the risk-informed approach the NRC uses to regulate the U.S. commercial nuclear industry.

  6. Probabilistic risk analysis of mercury intake via food consumption in Spain.

    Science.gov (United States)

    Moreno-Ortega, Alicia; Moreno-Rojas, Rafael; Martínez-Álvarez, Jesús Román; González Estecha, Montserrat; Castro González, Numa Pompilio; Amaro López, Manuel Ángel

    2017-09-01

    In Spain, recently, the public institutions have given information to the population in relation to fish consumption and the risk that it poses to health from the ingestion of mercury supposedly contained in the fish. At the same time, several scientific societies have published various works in this direction. All this without there being, up to now, any study on the evaluation of a probabilistic risk from mercury due to fish and seafood intake in Spain, which is the objective of this present work. For that purpose, we took individual data from a survey of the total diet of 3000 people, whose consumption of the principal fish and seafood species (49) was estimated. We compiled individualized data (2000) on the total mercury content of those species, which were completed and validated with bibliographic statistical data. After estimating the distributions of each fish and seafood species, both of their consumption and their mercury content, a simulation was made of the distribution of mercury ingestion from fish and seafood offered by 2.6% of the Spanish population at risk of exceeding total mercury recommendations, and between 12.2% and 21.2% of those exceeding methylmercury ones. The main species responsible were tuna fish, swordfish and hake, and significant differences were identified in fish consumption between sexes and ages, although, in the risk percentage, what stands out is an increase in the latter with an increase in age. Copyright © 2017 Elsevier GmbH. All rights reserved.

  7. Fault-tree analysis for probabilistic assessment of radioactive-waste segregation: an application to a plastic clay formation at a specific site

    International Nuclear Information System (INIS)

    D'Alessandro, M.; Bonne, A.

    1982-01-01

    This study concerns a probabilistic safety analysis of potential nuclear-waste repository which may be mined into a Tertiary clay formation underlying the Nuclear Research Centre at Mol (Belgium). The value of the geological barrier has been analyzed in probabilistic terms through the application of the Fault-Tree Analysis (FTA) which can answer two main questions: how can the barrier fail (query) and what is the failure probability (query). FTA has been applied to conceptual radioactive-waste disposal systems. In this paper this methodology has been applied to a specific clay formation, to test the applicability of the procedure to a potential site. With this aim, release probabilities to three different receptors (groundwater, land surface, and atmosphere) were estimated for four different time periods. Because of obvious uncertainties in geology predictive capabilities, a probability band has been obtained. Faulting phenomena are among the main mechanisms having the potential to cause release to groundwater, whereas direct releases to land surface may be linked to various glacial phenomena; on short term, different types of human actions may be important. The overall failure probabilities seem to be sufficiently low to offer a good safety margin. (author)

  8. The probabilistic risk analysis of external hazards of an interim storage for spent nuclear fuel in Olkiluoto

    International Nuclear Information System (INIS)

    Puukka, Tiia

    2014-01-01

    Due to natural disasters occurred in the world and the experiences perceived of the Fukushima nuclear accident, the particular knowledge of the role and influence of external hazards in the safety of interim storage of spent nuclear fuel has been emphasized. For that reason it is substantial that they are included in the probabilistic risk assessment (PRA) of the interim storage facility. This is also required by the Regulatory Guides issued by The Finnish Radiation and Nuclear Safety Authority STUK. To enhance safety culture and nuclear safety in Olkiluoto, The Finnish utility Teollisuuden Voima Oyj has recently completed an analysis of external natural (seismic events are studied as a separate analysis) and unintentional human-induced risks associated with the spent fuel pool cooling and decay heat removal systems as part of the full-scope PRA study for the interim storage of spent fuel (KPA store). The analysis had four goals to achieve: (1) to determine the definition of an initiating event in the context of the KPA store, (2) to identify all potential external hazards and hazard combinations, (3) to perform a qualitative screening analysis based on frequency-strength analysis and detailed plant responses analysis and (4) to model the hazards passed the screening analysis so that model can be used as a risk analysis tool in the risk informed decision making and operating procedures. The assessment carried out included the analysis of operation procedures of decay heat removal, the study of external hazards related initiating events included in the PRA of the OL1 and OL2 nuclear power plants and their dependencies on the initiating events of the KPA store. All external hazards related initiating events were modeled using fault tree linking method. The main result and conclusion of this study was that using the screening analysis, initiating events caused by external hazards that could lead to leakage of the spent fuel pools or that could pose a threat to the

  9. Use of probabilistic risk assessment (PRA) in expert systems to advise nuclear plant operators and managers

    International Nuclear Information System (INIS)

    Uhrig, R.E.

    1988-01-01

    The use of expert systems in nuclear power plants to provide advice to managers, supervisors and/or operators is a concept that is rapidly gaining acceptance. Generally, expert systems rely on the expertise of human experts or knowledge that has been codified in publications, books, or regulations to provide advice under a wide variety of conditions. In this work, a probabilistic risk assessment (PRA) of a nuclear power plant performed previously is used to assess the safety status of nuclear power plants and to make recommendations to the plant personnel. Nuclear power plants have many redundant systems and can continue to operate when one or more of these systems is disabled or removed from service for maintenance or testing. PRAs provide a means of evaluating the risk to the public associated with the operation of nuclear power plants with components or systems out of service. While the choice of the source term and methodology in a PRA may influence the absolute probability and consequences of a core melt, the ratio of the PRA calculations for two configurations of the same plant, carried out on a consistent basis, can readily identify the increase in risk associated with going from one configuration to the other

  10. Using Statistical and Probabilistic Methods to Evaluate Health Risk Assessment: A Case Study

    Directory of Open Access Journals (Sweden)

    Hongjing Wu

    2014-06-01

    Full Text Available The toxic chemical and heavy metals within wastewater can cause serious adverse impacts on human health. Health risk assessment (HRA is an effective tool for supporting decision-making and corrective actions in water quality management. HRA can also help people understand the water quality and quantify the adverse effects of pollutants on human health. Due to the imprecision of data, measurement error and limited available information, uncertainty is inevitable in the HRA process. The purpose of this study is to integrate statistical and probabilistic methods to deal with censored and limited numbers of input data to improve the reliability of the non-cancer HRA of dermal contact exposure to contaminated river water by considering uncertainty. A case study in the Kelligrews River in St. John’s, Canada, was conducted to demonstrate the feasibility and capacity of the proposed approach. Five heavy metals were selected to evaluate the risk level, including arsenic, molybdenum, zinc, uranium and manganese. The results showed that the probability of the total hazard index of dermal exposure exceeding 1 is very low, and there is no obvious evidence of risk in the study area.

  11. Flood hazards and masonry constructions: a probabilistic framework for damage, risk and resilience at urban scale

    Directory of Open Access Journals (Sweden)

    A. Mebarki

    2012-05-01

    Full Text Available This paper deals with the failure risk of masonry constructions under the effect of floods. It is developed within a probabilistic framework, with loads and resistances considered as random variables. Two complementary approaches have been investigated for this purpose:

    – a global approach based on combined effects of several governing parameters with individual weighted contribution (material quality and geometry, presence and distance between columns, beams, openings, resistance of the soil and its slope. . .,
    – and a reliability method using the failure mechanism of masonry walls standing out-plane pressure.

    The evolution of the probability of failure of masonry constructions according to the flood water level is analysed.

    The analysis of different failure probability scenarios for masonry walls is conducted to calibrate the influence of each "vulnerability governing parameter" in the global approach that is widely used in risk assessment at the urban or regional scale.

    The global methodology is implemented in a GIS that provides the spatial distribution of damage risk for different flood scenarios. A real case is considered for the simulations, i.e. Cheffes sur Sarthe (France, for which the observed river discharge, the hydraulic load according to the Digital Terrain Model, and the structural resistance are considered as random variables. The damage probability values provided by both approaches are compared. Discussions are also developed about reduction and mitigation of the flood disaster at various scales (set of structures, city, region as well as resilience.

  12. Probabilistic risk assessment for the Sandia National Laboratories Technical Area V Liquid Waste Disposal System surface impoundments

    International Nuclear Information System (INIS)

    Dawson, L.A.; Eidson, A.F.

    1996-01-01

    A probabilistic risk assessment was completed for a former radioactive waste disposal site. The site, two unlined surface impoundment, was designed as part of the Liquid Waste Disposal System (LWDS) to receive radioactive effluent from nuclear reactors in Technical Area-V (TA-V) at Sandia National Laboratories/New Mexico (SNL/NM). First, a statistical comparison of site sampling results to natural background, using EPA methods, and a spatial distribution analysis were performed. Risk assessment was conducted with SNL/NM's Probabilistic Risk Evaluation and Characterization Investigation System model. The risk assessment indicated that contamination from several constituents might have been high enough to require remediation. However, further analysis based on expected site closure activities and recent EPA guidance indicated that No Further Action was acceptable

  13. TREATING UNCERTAINTIES IN A NUCLEAR SEISMIC PROBABILISTIC RISK ASSESSMENT BY MEANS OF THE DEMPSTER-SHAFER THEORY OF EVIDENCE

    OpenAIRE

    Lo , Chung-Kung; Pedroni , N.; Zio , Enrico

    2014-01-01

    International audience; The analyses carried out within the Seismic Probabilistic Risk Assessments (SPRAs) of Nuclear Power Plants (NPPs) are affected by significant aleatory and epistemic uncertainties. These uncertainties have to be represented and quantified coherently with the data, information and knowledge available, to provide reasonable assurance that related decisions can be taken robustly and with confidence. The amount of data, information and knowledge available for seismic risk a...

  14. Probabilistic meta-analysis of risk from the exposure to Hg in artisanal gold mining communities in Colombia

    OpenAIRE

    Miguel García, Eduardo de; Ortega Romero, Marcelo; Gómez San Martín, Amaia; Clavijo, Diana

    2014-01-01

    Colombia is one of the largest per capita mercury polluters in the world as a consequence of its artisanal gold mining activities. The severity of this problem in terms of potential health effects was evaluated by means of a probabilistic risk assessment carried out in the twelve departments (or provinces) in Colombia with the largest gold production. The two exposure pathways included in the risk assessment were inhalation of elemental Hg vapors and ingestion of fish contaminated with methyl...

  15. Probabilistic Risk Assessment of Cancer from Exposure Inorganic Arsenic in Duplicate Food by Villagers in Ronphibun, Thailand

    OpenAIRE

    Piyawat Saipan

    2010-01-01

    Ronphibun district is a district in Nakorn Si Thammarat province, within southern Thailand. This district is the site of several former tin mines that were in operation 100 years ago. Arsenic contamination caused by past mining activities remains in the area. The specific purpose of this study was conducted to assess cancer risk in people living within Ronphibun district from exposure to inorganic arsenic via duplicate food using probabilistic risk assessment. A hundred and fifty duplicate fo...

  16. MATILDA Version-2: Rough Earth TIALD Model for Laser Probabilistic Risk Assessment in Hilly Terrain - Part II

    Science.gov (United States)

    2017-07-28

    risk assessment for “unsafe” scenarios. Recently, attention in the DoD has turned to Probabilistic Risk Assessment (PRA) models [5,6] as an...corresponding to the CRA undershoot boundary. The magenta- coloured line represents the portion of the C-RX(U) circle that would contribute to the...Tertiary Precaution Surface. Undershoot related laser firing restrictions within the green- coloured C-RX(U) can be ignored. Figure 34

  17. Use of risk quotient and probabilistic approaches to assess risks of pesticides to birds

    Science.gov (United States)

    When conducting ecological risk assessments for pesticides, the United States Environmental Protection Agency typically relies upon the risk quotient (RQ). This approach is intended to be conservative in nature, making assumptions related to exposure and effects that are intended...

  18. Microbial quality of reclaimed water for urban reuses: Probabilistic risk-based investigation and recommendations.

    Science.gov (United States)

    Chhipi-Shrestha, Gyan; Hewage, Kasun; Sadiq, Rehan

    2017-01-15

    Although Canada has abundant freshwater resources, many cities still experience seasonal water shortage. Supply-side and demand-side management is a core strategy to address this water shortage. Under this strategy, reclaimed water, which the Canadian public is willing to use for non-potable purposes, is an option. However, no universal guidelines exist for reclaimed water use. Despite the federal government's long-term goal to develop guidelines for many water reuse applications, guidelines have only been prescribed for reclaimed water use in toilet and urinal flushing in Canada. At the provincial level, British Columbia (BC) has promulgated guidelines for wide applications of reclaimed water but only at broad class levels. This research has investigated and proposed probabilistic risk-based recommended values for microbial quality of reclaimed water in various non-potable urban reuses. The health risk was estimated by using quantitative microbial risk assessment. Two-dimensional Monte Carlo simulations were used in the analysis to include variability and uncertainty in input data. The proposed recommended values are based on the indicator organism E. coli. The required treatment levels for reuse were also estimated. In addition, the recommended values were successfully applied to three wastewater treatment effluents in the Okanagan Valley, BC, Canada. The health risks associated with other bacterial pathogens (Campylobacter jejuni and Salmonella spp.), virus (adenovirus, norovirus, and rotavirus), and protozoa (Cryptosporidium parvum and Giardia spp.), were also estimated. The estimated risks indicate the effectiveness of the E. coli-based water quality recommended values. Sensitivity analysis shows the pathogenic E. coli ratio and morbidity are the most sensitive input parameters for all water reuses. The proposed recommended values could be further improved by using national or regional data on water exposures, disease burden per case, and the susceptibility

  19. Implementation of a risk assessment tool based on a probabilistic safety assessment developed for radiotherapy practices

    International Nuclear Information System (INIS)

    Paz, A.; Godinez, V.; Lopez, R.

    2010-10-01

    The present work describes the implementation process and main results of the risk assessment to the radiotherapy practices with Linear Accelerators (Linac), with cobalt 60, and with brachytherapy. These evaluations were made throughout the risk assessment tool for radiotherapy practices SEVRRA (risk evaluation system for radiotherapy), developed at the Mexican National Commission in Nuclear Safety and Safeguards derived from the outcome obtained with the Probabilistic Safety Analysis developed at the Ibero-American Regulators Forum for these radiotherapy facilities. The methodology used is supported by risk matrices method, a mathematical tool that estimates the risk to the patient, radiation workers and public from mechanical failures, mis calibration of the devices, human mistakes, and so. The initiating events are defined as those undesirable events that, together with other failures, can produce a delivery of an over-dose or an under-dose of the medical prescribed dose, to the planned target volume, or a significant dose to non prescribed human organs. Initiating events frequency and reducer of its frequency (actions intended to avoid the accident) are estimated as well as robustness of barriers to those actions, such as mechanical switches, which detect and prevent the accident from occurring. The spectrum of the consequences is parameterized, and the actions performed to reduce the consequences are identified. Based on this analysis, a software tool was developed in order to simplify the evaluations to radiotherapy installations and it has been applied as a first step forward to some Mexican installations, as part of a national implementation process, the final goal is evaluation of all Mexican facilities in the near future. The main target and benefits of the SEVRRA implementation are presented in this paper. (Author)

  20. Implementation of a risk assessment tool based on a probabilistic safety assessment developed for radiotherapy practices

    Energy Technology Data Exchange (ETDEWEB)

    Paz, A.; Godinez, V.; Lopez, R., E-mail: abpaz@cnsns.gob.m [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Mexico D. F. (Mexico)

    2010-10-15

    The present work describes the implementation process and main results of the risk assessment to the radiotherapy practices with Linear Accelerators (Linac), with cobalt 60, and with brachytherapy. These evaluations were made throughout the risk assessment tool for radiotherapy practices SEVRRA (risk evaluation system for radiotherapy), developed at the Mexican National Commission in Nuclear Safety and Safeguards derived from the outcome obtained with the Probabilistic Safety Analysis developed at the Ibero-American Regulators Forum for these radiotherapy facilities. The methodology used is supported by risk matrices method, a mathematical tool that estimates the risk to the patient, radiation workers and public from mechanical failures, mis calibration of the devices, human mistakes, and so. The initiating events are defined as those undesirable events that, together with other failures, can produce a delivery of an over-dose or an under-dose of the medical prescribed dose, to the planned target volume, or a significant dose to non prescribed human organs. Initiating events frequency and reducer of its frequency (actions intended to avoid the accident) are estimated as well as robustness of barriers to those actions, such as mechanical switches, which detect and prevent the accident from occurring. The spectrum of the consequences is parameterized, and the actions performed to reduce the consequences are identified. Based on this analysis, a software tool was developed in order to simplify the evaluations to radiotherapy installations and it has been applied as a first step forward to some Mexican installations, as part of a national implementation process, the final goal is evaluation of all Mexican facilities in the near future. The main target and benefits of the SEVRRA implementation are presented in this paper. (Author)

  1. Caffeine and paraxanthine in aquatic systems: Global exposure distributions and probabilistic risk assessment.

    Science.gov (United States)

    Rodríguez-Gil, J L; Cáceres, N; Dafouz, R; Valcárcel, Y

    2018-01-15

    This study presents one of the most complete applications of probabilistic methodologies to the risk assessment of emerging contaminants. Perhaps the most data-rich of these compounds, caffeine, as well as its main metabolite (paraxanthine), were selected for this study. Information for a total of 29,132 individual caffeine and 7442 paraxanthine samples was compiled, including samples where the compounds were not detected. The inclusion of non-detect samples (as censored data) in the estimation of environmental exposure distributions (EEDs) allowed for a realistic characterization of the global presence of these compounds in aquatic systems. EEDs were compared to species sensitivity distributions (SSDs), when possible, in order to calculate joint probability curves (JPCs) to describe the risk to aquatic organisms. This way, it was determined that unacceptable environmental risk (defined as 5% of the species being potentially exposed to concentrations able to cause effects in>5% of the cases) could be expected from chronic exposure to caffeine from effluent (28.4% of the cases), surface water (6.7% of the cases) and estuary water (5.4% of the cases). Probability of exceedance of acute predicted no-effect concentrations (PNECs) for paraxanthine were higher than 5% for all assessed matrices except for drinking water and ground water, however no experimental effects data was available for paraxanthine, resulting in a precautionary deterministic hazard assessment for this compound. Given the chemical similarities between both compounds, real effect thresholds, and thus risk, for paraxanthine, would be expected to be close to those observed for caffeine. Negligible Human health risk from exposure to caffeine via drinking or groundwater is expected from the compiled data. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Probabilistic risk assessment of exposure to leucomalachite green residues from fish products.

    Science.gov (United States)

    Chu, Yung-Lin; Chimeddulam, Dalaijamts; Sheen, Lee-Yan; Wu, Kuen-Yuh

    2013-12-01

    To assess the potential risk of human exposure to carcinogenic leucomalachite green (LMG) due to fish consumption, the probabilistic risk assessment was conducted for adolescent, adult and senior adult consumers in Taiwan. The residues of LMG with the mean concentration of 13.378±20.56 μg kg(-1) (BFDA, 2009) in fish was converted into dose, considering fish intake reported for three consumer groups by NAHSIT (1993-1996) and body weight of an average individual of the group. The lifetime average and high 95th percentile dietary intakes of LMG from fish consumption for Taiwanese consumers were estimated at up to 0.0135 and 0.0451 μg kg-bw(-1) day(-1), respectively. Human equivalent dose (HED) of 2.875 mg kg-bw(-1) day(-1) obtained from a lower-bound benchmark dose (BMDL10) in mice by interspecies extrapolation was linearly extrapolated to oral cancer slope factor (CSF) of 0.035 (mgkg-bw(-1)day(-1))(-1) for humans. Although, the assumptions and methods are different, the results of lifetime cancer risk varying from 3×10(-7) to 1.6×10(-6) were comparable to those of margin of exposures (MOEs) varying from 410,000 to 4,800,000. In conclusions, Taiwanese fish consumers with the 95th percentile LADD of LMG have greater risk of liver cancer and need to an action of risk management in Taiwan. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. The development and application of an integrated radiological risk assessment procedure using time-dependent probabilistic risk analysis

    International Nuclear Information System (INIS)

    Laurens, J.M.; Thompson, B.G.J.; Sumerling, T.J.

    1990-01-01

    During the past decade, the UKDoE has funded the development of an integrated assessment procedure centred around probabilistic risk analysis (p.r.a.) using Monte Carlo simulation techniques to account for the effects of parameter value uncertainty, including those associated with temporal changes in the environment over a postclosure period of about one million years. The influence of these changes can now be incorporated explicitly into the p.r.a. simulator VANDAL (Variability ANalysis of Disposal ALternatives) briefly described here. Although a full statistically converged time-dependent p.r.a. will not be demonstrated until the current Dry Run 3 trial is complete, illustrative examples are given showing the ability of VANDAL to represent spatially complex groundwater and repository systems evolving under the influence of climatic change. 18 refs., 10 figs., 1 tab

  4. Evaluating probabilistic dengue risk forecasts from a prototype early warning system for Brazil

    Science.gov (United States)

    Lowe, Rachel; Coelho, Caio AS; Barcellos, Christovam; Carvalho, Marilia Sá; Catão, Rafael De Castro; Coelho, Giovanini E; Ramalho, Walter Massa; Bailey, Trevor C; Stephenson, David B; Rodó, Xavier

    2016-01-01

    Recently, a prototype dengue early warning system was developed to produce probabilistic forecasts of dengue risk three months ahead of the 2014 World Cup in Brazil. Here, we evaluate the categorical dengue forecasts across all microregions in Brazil, using dengue cases reported in June 2014 to validate the model. We also compare the forecast model framework to a null model, based on seasonal averages of previously observed dengue incidence. When considering the ability of the two models to predict high dengue risk across Brazil, the forecast model produced more hits and fewer missed events than the null model, with a hit rate of 57% for the forecast model compared to 33% for the null model. This early warning model framework may be useful to public health services, not only ahead of mass gatherings, but also before the peak dengue season each year, to control potentially explosive dengue epidemics. DOI: http://dx.doi.org/10.7554/eLife.11285.001 PMID:26910315

  5. Overview of methods for uncertainty analysis and sensitivity analysis in probabilistic risk assessment

    International Nuclear Information System (INIS)

    Iman, R.L.; Helton, J.C.

    1985-01-01

    Probabilistic Risk Assessment (PRA) is playing an increasingly important role in the nuclear reactor regulatory process. The assessment of uncertainties associated with PRA results is widely recognized as an important part of the analysis process. One of the major criticisms of the Reactor Safety Study was that its representation of uncertainty was inadequate. The desire for the capability to treat uncertainties with the MELCOR risk code being developed at Sandia National Laboratories is indicative of the current interest in this topic. However, as yet, uncertainty analysis and sensitivity analysis in the context of PRA is a relatively immature field. In this paper, available methods for uncertainty analysis and sensitivity analysis in a PRA are reviewed. This review first treats methods for use with individual components of a PRA and then considers how these methods could be combined in the performance of a complete PRA. In the context of this paper, the goal of uncertainty analysis is to measure the imprecision in PRA outcomes of interest, and the goal of sensitivity analysis is to identify the major contributors to this imprecision. There are a number of areas that must be considered in uncertainty analysis and sensitivity analysis for a PRA: (1) information, (2) systems analysis, (3) thermal-hydraulic phenomena/fission product behavior, (4) health and economic consequences, and (5) display of results. Each of these areas and the synthesis of them into a complete PRA are discussed

  6. Review of the Shoreham Nuclear Power Station Probabilistic Risk Assessment: internal events and core damage frequency

    International Nuclear Information System (INIS)

    Ilberg, D.; Shiu, K.; Hanan, N.; Anavim, E.

    1985-11-01

    A review of the Probabilistic Risk Assessment of the Shoreham Nuclear Power Station was conducted with the broad objective of evaluating its risks in relation to those identified in the Reactor Safety Study (WASH-1400). The scope of the review was limited to the ''front end'' part, i.e., to the evaluation of the frequencies of states in which core damage may occur. Furthermore, the review considered only internally generated accidents, consistent with the scope of the PRA. The review included an assessment of the assumptions and methods used in the Shoreham study. It also encompassed a reevaluation of the main results within the scope and general methodological framework of the Shoreham PRA, including both qualitative and quantitative analyses of accident initiators, data bases, and accident sequences which result in initiation of core damage. Specific comparisons are given between the Shoreham study, the results of the present review, and the WASH-1400 BWR, for the core damage frequency. The effect of modeling uncertainties was considered by a limited sensitivity study so as to show how the results would change if other assumptions were made. This review provides an independently assessed point value estimate of core damage frequency and describes the major contributors, by frontline systems and by accident sequences. 17 figs., 81 tabs

  7. The development and use of parametric sampling techniques for probabilistic risk assessment

    International Nuclear Information System (INIS)

    Dalrymple, G.J.; Broyd, T.W.

    1987-01-01

    In order to enable evaluation to be made of proposals for the underground disposal of low and intermediate level radioactive wastes in the United Kingdom, the Department of the Environment (DoE) research programme includes development of computer-based methods for use in a multistage assessment process. To test the adequacy of the various methods of data acquisitions and radiological assessment a mock assessment exercise is currently being conducted by the department. This paper outlines the proposed methodology which provides for the use of probabilistic modelling based upon the Atomic Energy of Canada Ltd SYVAC variability analysis approach using new models (SYVAC 'A') and data appropriate to UK conditions for a deep horizontal tunnel repository concept. This chapter describes the choice of a suitable technique for the sampling of data input to the SYVAC 'A' model and techniques for analysing the predictions of dose and risk made by the model. The sensitivity of the model predictions (risk and dose to man) to the input parameters was compared for four different methods. All four methods identified the same geological parameters as the most important. (author)

  8. The EBR-II Probabilistic Risk Assessment: lessons learned regarding passive safety

    International Nuclear Information System (INIS)

    Hill, D.J.; Ragland, W.A.; Roglans, J.

    1998-01-01

    This paper summarizes the results from the EBR-II Probabilistic Risk Assessment (PRA) and provides an analysis of the source of risk of the operation of EBR-II from both internal and external initiating events. The EBR-II PRA explicitly accounts for the role of reactivity feedbacks in reducing fuel damage. The results show that the expected core damage frequency from internal initiating events at EBR-II is very low, 1.6 10 -6 yr -1 , even with a wide definition of core damage (essentially that of exceeding Technical Specification limits). The annual frequency of damage, primarily due to liquid metal fires, from externally initiated events (excluding earthquakes) is 3.6 10 -6 yr -1 and the contribution of seismic events is 1.7 10 -5 yr -1 . Overall these results are considerably better than results for other research reactors and the nuclear industry in general and stem from three main sources: low likelihood of loss of coolant due to low system pressure and top entry double vessels; low likelihood of loss of decay heat removal due to reliance on passive means; and low likelihood of power/flow mismatch due to both passive feedbacks and reliability of rod scram capability

  9. The EBR-II Probabilistic Risk Assessment: lessons learned regarding passive safety

    Energy Technology Data Exchange (ETDEWEB)

    Hill, D J; Ragland, W A; Roglans, J

    1998-11-01

    This paper summarizes the results from the EBR-II Probabilistic Risk Assessment (PRA) and provides an analysis of the source of risk of the operation of EBR-II from both internal and external initiating events. The EBR-II PRA explicitly accounts for the role of reactivity feedbacks in reducing fuel damage. The results show that the expected core damage frequency from internal initiating events at EBR-II is very low, 1.6 10{sup -6} yr{sup -1}, even with a wide definition of core damage (essentially that of exceeding Technical Specification limits). The annual frequency of damage, primarily due to liquid metal fires, from externally initiated events (excluding earthquakes) is 3.6 10{sup -6} yr{sup -1} and the contribution of seismic events is 1.7 10{sup -5} yr{sup -1}. Overall these results are considerably better than results for other research reactors and the nuclear industry in general and stem from three main sources: low likelihood of loss of coolant due to low system pressure and top entry double vessels; low likelihood of loss of decay heat removal due to reliance on passive means; and low likelihood of power/flow mismatch due to both passive feedbacks and reliability of rod scram capability.

  10. The EBR-II probabilistic risk assessment lessons learned regarding passive safety

    International Nuclear Information System (INIS)

    Hill, D.J.; Ragland, W.A.; Roglans, J.

    1994-01-01

    This paper summarizes the results from the recently completed EBR-II Probabilistic Risk Assessment (PRA) and provides an analysis of the source of risk of the operation of EBR-II from both internal and external initiating events. The EBR-II PRA explicitly accounts for the role of reactivity feedbacks in reducing fuel damage. The results show that the expected core damage frequency from internal initiating events at EBR-II is very low, 1.6 10 -6 yr -1 , even with a wide definition of core damage (essentially that of exceeding Technical Specification limits). The annual frequency of damage, primarily due to liquid metal fires, from externally initiated events (excluding earthquakes) is 3.6 10 -6 yr -1 and the contribution of seismic events is 1.7 10 -5 yr -1 . Overall these results are considerably better than results for other research reactors and the nuclear industry in general and stem from three main sources: low likelihood of loss of coolant due to low system pressure and top entry double vessels; low likelihood of loss of decay heat removal due to reliance on passive means; and low likelihood of power/flow mismatch due to both passive feedbacks and reliability of rod scram capability

  11. Integration of human reliability analysis into the probabilistic risk assessment process: phase 1

    International Nuclear Information System (INIS)

    Bell, B.J.; Vickroy, S.C.

    1985-01-01

    The US Nuclear Regulatory Commission and Pacific Northwest Laboratory initiated a research program in 1984 to develop a testable set of analytical procedures for integrating human reliability analysis (HRA) into the probabilistic risk assessment (PRA) process to more adequately assess the overall impact of human performance on risk. In this three phase program, stand-alone HRA/PRA analytic procedures will be developed and field evaluated to provide improved methods, techniques, and models for applying quantitative and qualitative human error data which systematically integrate HRA principles, techniques, and analyses throughout the entire PRA process. Phase 1 of the program involved analysis of state-of-the-art PRAs to define the structures and processes currently in use in the industry. Phase 2 research will involve developing a new or revised PRA methodology which will enable more efficient regulation of the industry using quantitative or qualitative results of the PRA. Finally, Phase 3 will be to field test those procedures to assure that the results generated by the new methodologies will be usable and acceptable to the NRC. This paper briefly describes the first phase of the program and outlines the second

  12. Integration of human reliability analysis into the probabilistic risk assessment process: Phase 1

    International Nuclear Information System (INIS)

    Bell, B.J.; Vickroy, S.C.

    1984-10-01

    A research program was initiated to develop a testable set of analytical procedures for integrating human reliability analysis (HRA) into the probabilistic risk assessment (PRA) process to more adequately assess the overall impact of human performance on risk. In this three-phase program, stand-alone HRA/PRA analytic procedures will be developed and field evaluated to provide improved methods, techniques, and models for applying quantitative and qualitative human error data which systematically integrate HRA principles, techniques, and analyses throughout the entire PRA process. Phase 1 of the program involved analysis of state-of-the-art PRAs to define the structures and processes currently in use in the industry. Phase 2 research will involve developing a new or revised PRA methodology which will enable more efficient regulation of the industry using quantitative or qualitative results of the PRA. Finally, Phase 3 will be to field test those procedures to assure that the results generated by the new methodologies will be usable and acceptable to the NRC. This paper briefly describes the first phase of the program and outlines the second

  13. Risk-informed design of IRIS using a level-1 probabilistic risk assessment from its conceptual design phase

    International Nuclear Information System (INIS)

    Mizuno, Yuko; Ninokata, Hisashi; Finnicum, David J.

    2005-01-01

    In this study, a probabilistic risk assessment (PRA) for the International Reactor Innovative and Secure (IRIS) has been generated to address two key areas as a part of the effort for the pre-application licensing of the IRIS design. First, the IRIS PRA is supporting the evaluation of IRIS design by providing design insights as well as a solid risk basis for the pre-licensing evaluation of the IRIS design. Second, the current PRA task is beginning the preparation of the more complete PRA analyses and documentation that will be required for Design Certification. The initial IRIS PRA is an at-power, Level-1 PRA for internal events that focuses on the evaluation of the IRIS design features to support the risk-informed design of IRIS by application of the PRA insights and the risk information to the design. To accomplish the evaluation, a reasonably complete Level-1 PRA model has been developed. The use of PRA in the early stages of the design has allowed a selection of design and performance features and an optimization of the design of several systems to reduce the potential for events that could lead to core damage via both enhanced prevention and mitigation of challenges. As a result, the total core damage frequency for internal events for the IRIS design has been calculated as 1.2x10 -8 per year

  14. A probabilistic transmission and population dynamic model to assess tuberculosis infection risk.

    Science.gov (United States)

    Liao, Chung-Min; Cheng, Yi-Hsien; Lin, Yi-Jun; Hsieh, Nan-Hung; Huang, Tang-Luen; Chio, Chia-Pin; Chen, Szu-Chieh; Ling, Min-Pei

    2012-08-01

    The purpose of this study was to examine tuberculosis (TB) population dynamics and to assess potential infection risk in Taiwan. A well-established mathematical model of TB transmission built on previous models was adopted to study the potential impact of TB transmission. A probabilistic risk model was also developed to estimate site-specific risks of developing disease soon after recent primary infection, exogenous reinfection, or through endogenous reactivation (latently infected TB) among Taiwan regions. Here, we showed that the proportion of endogenous reactivation (53-67%) was larger than that of exogenous reinfection (32-47%). Our simulations showed that as epidemic reaches a steady state, age distribution of cases would finally shift toward older age groups dominated by latently infected TB cases as a result of endogenous reactivation. A comparison of age-weighted TB incidence data with our model simulation output with 95% credible intervals revealed that the predictions were in an apparent agreement with observed data. The median value of overall basic reproduction number (R₀) in eastern Taiwan ranged from 1.65 to 1.72, whereas northern Taiwan had the lowest R₀ estimate of 1.50. We found that total TB incidences in eastern Taiwan had 25-27% probabilities of total proportion of infected population exceeding 90%, whereas there were 36-66% probabilities having exceeded 20% of total proportion of infected population attributed to latently infected TB. We suggested that our Taiwan-based analysis can be extended to the context of developing countries, where TB remains a substantial cause of elderly morbidity and mortality. © 2012 Society for Risk Analysis.

  15. Uses of human reliability analysis probabilistic risk assessment results to resolve personnel performance issues that could affect safety

    International Nuclear Information System (INIS)

    O'Brien, J.N.; Spettell, C.M.

    1985-10-01

    This report is the first in a series which documents research aimed at improving the usefulness of Probabilistic Risk Assessment (PRA) results in addressing human risk issues. This first report describes the results of an assessment of how well currently available PRA data addresses human risk issues of current concern to NRC. Findings indicate that PRA data could be far more useful in addressing human risk issues with modification of the development process and documentation structure of PRAs. In addition, information from non-PRA sources could be integrated with PRA data to address many other issues. 12 tabs

  16. Trees

    Science.gov (United States)

    Al-Khaja, Nawal

    2007-01-01

    This is a thematic lesson plan for young learners about palm trees and the importance of taking care of them. The two part lesson teaches listening, reading and speaking skills. The lesson includes parts of a tree; the modal auxiliary, can; dialogues and a role play activity.

  17. Novel Threat-risk Index Using Probabilistic Risk Assessment and Human Reliability Analysis - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    George A. Beitel

    2004-02-01

    In support of a national need to improve the current state-of-the-art in alerting decision makers to the risk of terrorist attack, a quantitative approach employing scientific and engineering concepts to develop a threat-risk index was undertaken at the Idaho National Engineering and Environmental Laboratory (INEEL). As a result of this effort, a set of models has been successfully integrated into a single comprehensive model known as Quantitative Threat-Risk Index Model (QTRIM), with the capability of computing a quantitative threat-risk index on a system level, as well as for the major components of the system. Such a threat-risk index could provide a quantitative variant or basis for either prioritizing security upgrades or updating the current qualitative national color-coded terrorist threat alert.

  18. Xplicit, a novel approach in probabilistic spatiotemporally explicit exposure and risk assessment for plant protection products.

    Science.gov (United States)

    Schad, Thorsten; Schulz, Ralf

    2011-10-01

    The quantification of risk (the likelihood and extent of adverse effects) is a prerequisite in regulatory decision making for plant protection products and is the goal of the Xplicit project. In its present development stage, realism is increased in the exposure assessment (EA), first by using real-world data on, e.g., landscape factors affecting exposure, and second, by taking the variability of key factors into account. Spatial and temporal variability is explicitly addressed. Scale dependencies are taken into account, which allows for risk quantification at different scales, for example, at landscape scale, an overall picture of the potential exposure of nontarget organisms can be derived (e.g., for all off-crop habitats in a given landscape); at local scale, exposure might be relevant to assess recovery and recolonization potential; intermediate scales might best refer to population level and hence might be relevant for risk management decisions (e.g., individual off-crop habitats). The Xplicit approach is designed to comply with a central paradigm of probabilistic approaches, namely, that each individual case that is derived from the variability functions employed should represent a potential real-world case. This is mainly achieved by operating in a spatiotemporally explicit fashion. Landscape factors affecting the local exposure of habitats of nontarget species (i.e., receptors) are derived from geodatabases. Variability in time is resolved by operating at discrete time steps, with the probability of events (e.g., application) or conditions (e.g., wind conditions) defined in probability density functions (PDFs). The propagation of variability of parameters into variability of exposure and risk is done using a Monte Carlo approach. Among the outcomes are expectancy values on the realistic worst-case exposure (predicted environmental concentration [PEC]), the probability p that the PEC exceeds the ecologically acceptable concentration (EAC) for a given

  19. Analysis of the Coupled Influence of Hydraulic Conductivity and Porosity Heterogeneity on Probabilistic Risk Analysis

    Science.gov (United States)

    Libera, A.; Henri, C.; de Barros, F.

    2017-12-01

    Heterogeneities in natural porous formations, mainly manifested through the hydraulic conductivity (K) and, to a lesser degree, the porosity (Φ), largely control subsurface flow and solute transport. The influence of the heterogeneous structure of K on flow and solute transport processes has been widely studied, whereas less attention is dedicated to the joint heterogeneity of conductivity and porosity fields. Our study employs computational tools to investigate the joint effect of the spatial variabilities of K and Φ on the transport behavior of a solute plume. We explore multiple scenarios, characterized by different levels of heterogeneity of the geological system, and compare the computational results from the joint K and Φ heterogeneous system with the results originating from the generally adopted constant porosity case. In our work, we assume that the heterogeneous porosity is positively correlated to hydraulic conductivity. We perform numerical Monte Carlo simulations of conservative and reactive contaminant transport in a 3D aquifer. Contaminant mass and plume arrival times at multiple control planes and/or pumping wells operating under different extraction rates are analyzed. We employ different probabilistic metrics to quantify the risk at the monitoring locations, e.g., increased lifetime cancer risk and exceedance of Maximum Contaminant Levels (MCLs), under multiple transport scenarios (i.e., different levels of heterogeneity, conservative or reactive solutes and different contaminant species). Results show that early and late arrival times of the solute mass at the selected sensitive locations (i.e. control planes/pumping wells) as well as risk metrics are strongly influenced by the spatial variability of the Φ field.

  20. Comprehensive approach for probabilistic risk assessment (CAPRA): international initiative for disaster risk management effectiveness

    OpenAIRE

    Cardona, Omar D.; Ordaz Schroder, Mario Gustavo; Reinoso, Eduardo; Yamín, Luis; Barbat Barbat, Horia Alejandro

    2010-01-01

    Understanding disaster risk due to hazard events, such as earthquakes, creates powerful incentives for countries to develop planning options and tools to reduce potential damages. This has been the reason why CAPRA, the risk evaluation model described in this paper, was developed with the technical and financial support of the World Bank, the Inter-American Development Bank (IDB) and the International Strategy of United Nations for Disaster Reduction (ISDR). CAPRA is a techno-scientific metho...

  1. CAPRA - Comprehensive Approach to Probabilistic Risk Assessment: international initiative for risk management effectiveness

    OpenAIRE

    Cardona, Omar Darío; Ordaz, Mario G.; Reinoso, Eduardo; Yamín, Luis; Barbat Barbat, Horia Alejandro

    2012-01-01

    Understanding disaster risk due to hazard events, such as earthquakes, creates powerful incentives for countries to develop planning options and tools to reduce potential damages. This has been the reason why CAPRA, the risk evaluation model described in this paper, was developed with the technical and financial support of the World Bank, the Inter-American Development Bank (IDB) and the International Strategy of United Nations for Disaster Reduction (ISDR). CAPRA is a techno-scientific metho...

  2. Application of sensitivity analysis in nuclear power plant probabilistic risk assessment studies

    International Nuclear Information System (INIS)

    Hirschberg, S.; Knochenhauer, M.

    1986-01-01

    Nuclear power plant probabilistic risk assessment (PRA) studies utilise many models, simplifications and assumptions. Also subjective judgement is widely applied due to lack of actual data. This results in significant uncertainties. Three general types of uncertainties have been identified: (1) parameter uncertainties, (2) modelling uncertainties, and (3) completeness uncertainties. The significance of some of the modelling assumptions and simplifications cannot be investigated by assignment and propagation of parameter uncertainties. In such cases the impact of different options may (and should) be studied by performing sensitivity analyses, which concentrate on the most critical elements. This paper describes several items suitable for close examination by means of application of sensitivity analysis, when performing a level 1 PRA. Sensitivity analyses are performed with respect to: (1) boundary conditions (success criteria, credit for non-safety systems, degree of detail in modelling of support functions), (2) operator actions, (3) treatment of common cause failures (CCFs). The items of main interest are continuously identified in the course of performing a PRA study, as well as by scrutinising the final results. The practical aspects of sensitivity analysis are illustrated by several applications from a recent PRA study. The critical importance of modelling assumptions is also demonstrated by implementation of some modelling features from another level 1 PRA into the reference model. It is concluded that sensitivity analysis leads to insights important for analysts, reviewers and decision makers. (author)

  3. Probabilistic safety assessment based expert systems in support of dynamic risk assessment

    International Nuclear Information System (INIS)

    Varde, P.V.; Sharma, U.L.; Marik, S.K.; Raina, V.K.; Tikku, A.C.

    2006-01-01

    Probabilistic Safety Assessment (PSA) studies are being performed, world over as part of integrated risk assessment for Nuclear Power Plants and in many cases PSA insight is utilized in support of decision making. Though the modern plants are built with inherent safety provisions, particularly to reduce the supervisory requirements during initial period into the accident, it is always desired to develop an efficient user friendly real-time operator advisory system for handling of plant transients/emergencies which would be of immense benefit for the enhancement of operational safety of the plant. This paper discusses an integrated approach for the development of operator support system. In this approach, PSA methodology and the insight obtained from PSA has been utilized for development of knowledge based or rule based experts system. While Artificial Neural Network (ANN) approach has been employed for transient identification, rule-base expert system shell environment was used for the development of diagnostic module in this system. Attempt has been made to demonstrate that this approach offers an efficient framework for addressing requirements related to handling of real-time/dynamic scenario. (author)

  4. Probabilistic risk assessment for back-end facilities: Improving the treatment of fire and explosion scenarios

    International Nuclear Information System (INIS)

    Sunman, C.R.J.; Campbell, R.J.; Wakem, M.J.

    1996-01-01

    The nuclear reprocessing facilities at Sellafield are a key component of the International business of BNFL. The operations carried out at the site extend from the receipt and storage of irradiated fuel, chemical reprocessing, plutonium and uranium finishing, through mixed oxide fuel production. Additionally there are a wide range of supporting processes including solid waste encapsulation, vitrification, liquid waste evaporation and treatment. Decommissioning of the site's older facilities is also proceeding. The comprehensive range of these activities requires that the safety assessment team keeps up to date with developments in the field, as well as conducting and sponsoring appropriate research into methodologies and modelling in order to deliver a cost effective, timely service. This paper will review the role of Probabilistic Risk Assessment (PRA) in safety cases for operations at Sellafield and go on to describe some areas of PRA methodology development in the UK and in which BNFL is a contributor. Finally the paper will summarise some specific areas of methodology development associated with improving the modelling of fire and explosion hazards which are specific to BNFL. (author)

  5. An overview of the evolution of human reliability analysis in the context of probabilistic risk assessment

    International Nuclear Information System (INIS)

    Bley, Dennis C.; Lois, Erasmia; Kolaczkowski, Alan M.; Forester, John Alan; Wreathall, John; Cooper, Susan E.

    2009-01-01

    Since the Reactor Safety Study in the early 1970's, human reliability analysis (HRA) has been evolving towards a better ability to account for the factors and conditions that can lead humans to take unsafe actions and thereby provide better estimates of the likelihood of human error for probabilistic risk assessments (PRAs). The purpose of this paper is to provide an overview of recent reviews of operational events and advances in the behavioral sciences that have impacted the evolution of HRA methods and contributed to improvements. The paper discusses the importance of human errors in complex human-technical systems, examines why humans contribute to accidents and unsafe conditions, and discusses how lessons learned over the years have changed the perspective and approach for modeling human behavior in PRAs of complicated domains such as nuclear power plants. It is argued that it has become increasingly more important to understand and model the more cognitive aspects of human performance and to address the broader range of factors that have been shown to influence human performance in complex domains. The paper concludes by addressing the current ability of HRA to adequately predict human failure events and their likelihood

  6. An overview of the evolution of human reliability analysis in the context of probabilistic risk assessment.

    Energy Technology Data Exchange (ETDEWEB)

    Bley, Dennis C. (Buttonwood Consulting Inc., Oakton, VA); Lois, Erasmia (U.S. Nuclear Regulatory Commission, Washington, DC); Kolaczkowski, Alan M. (Science Applications International Corporation, Eugene, OR); Forester, John Alan; Wreathall, John (John Wreathall and Co., Dublin, OH); Cooper, Susan E. (U.S. Nuclear Regulatory Commission, Washington, DC)

    2009-01-01

    Since the Reactor Safety Study in the early 1970's, human reliability analysis (HRA) has been evolving towards a better ability to account for the factors and conditions that can lead humans to take unsafe actions and thereby provide better estimates of the likelihood of human error for probabilistic risk assessments (PRAs). The purpose of this paper is to provide an overview of recent reviews of operational events and advances in the behavioral sciences that have impacted the evolution of HRA methods and contributed to improvements. The paper discusses the importance of human errors in complex human-technical systems, examines why humans contribute to accidents and unsafe conditions, and discusses how lessons learned over the years have changed the perspective and approach for modeling human behavior in PRAs of complicated domains such as nuclear power plants. It is argued that it has become increasingly more important to understand and model the more cognitive aspects of human performance and to address the broader range of factors that have been shown to influence human performance in complex domains. The paper concludes by addressing the current ability of HRA to adequately predict human failure events and their likelihood.

  7. Probabilistic, meso-scale flood loss modelling

    Science.gov (United States)

    Kreibich, Heidi; Botto, Anna; Schröter, Kai; Merz, Bruno

    2016-04-01

    Flood risk analyses are an important basis for decisions on flood risk management and adaptation. However, such analyses are associated with significant uncertainty, even more if changes in risk due to global change are expected. Although uncertainty analysis and probabilistic approaches have received increased attention during the last years, they are still not standard practice for flood risk assessments and even more for flood loss modelling. State of the art in flood loss modelling is still the use of simple, deterministic approaches like stage-damage functions. Novel probabilistic, multi-variate flood loss models have been developed and validated on the micro-scale using a data-mining approach, namely bagging decision trees (Merz et al. 2013). In this presentation we demonstrate and evaluate the upscaling of the approach to the meso-scale, namely on the basis of land-use units. The model is applied in 19 municipalities which were affected during the 2002 flood by the River Mulde in Saxony, Germany (Botto et al. submitted). The application of bagging decision tree based loss models provide a probability distribution of estimated loss per municipality. Validation is undertaken on the one hand via a comparison with eight deterministic loss models including stage-damage functions as well as multi-variate models. On the other hand the results are compared with official loss data provided by the Saxon Relief Bank (SAB). The results show, that uncertainties of loss estimation remain high. Thus, the significant advantage of this probabilistic flood loss estimation approach is that it inherently provides quantitative information about the uncertainty of the prediction. References: Merz, B.; Kreibich, H.; Lall, U. (2013): Multi-variate flood damage assessment: a tree-based data-mining approach. NHESS, 13(1), 53-64. Botto A, Kreibich H, Merz B, Schröter K (submitted) Probabilistic, multi-variable flood loss modelling on the meso-scale with BT-FLEMO. Risk Analysis.

  8. Public transport risk assessment through fault tree analysis

    Directory of Open Access Journals (Sweden)

    Z. Yaghoubpour

    2016-04-01

    Full Text Available This study focused on the public transport risk assessment in District one of ​​Tehran through Fault Tree Analysis involving the three criteria of human, vehicle and road in Haddon matrix. In fact, it examined the factors contributing to the occurrence of road accidents at several urban black spots within District 1. Relying on road safety checklists and survey of experts, this study made an effort to help urban managers to assess the risks in the public transport and prevent road accidents. Finally, the risk identification and assessment of public transport in District one yielded several results to answer the research questions. The hypotheses analysis suggested that safety issues involved in public transport are concerned by urban managers. The key reactive measures are investigation of accidents, identification of causes and correction of black spots. In addition to high costs, however, the reactive measures give rise to multiple operational problems such as traffic navigation and guaranteeing user safety in every operation. The case study highlighted the same fact. The macro-level management in the metropolis of Tehran is critical. The urban road casualties and losses can be curtailed by preventive measures such as continuous assessment of road safety.

  9. A shortened version of the THERP/Handbook approach to human reliability analysis for probabilistic risk assessment

    International Nuclear Information System (INIS)

    Swain, A.D.

    1986-01-01

    The approach to human reliability analysis (HRA) known as THERP/Handbook has been applied to several probabilistic risk assessments (PRAs) of nuclear power plants (NPPs) and other complex systems. The approach is based on a thorough task analysis of the man-machine interfaces, including the interactions among the people, involved in the operations being assessed. The idea is to assess fully the underlying performance shaping factors (PSFs) and dependence effects which result either in reliable or unreliable human performance

  10. Results of the Level 1 probabilistic risk assessment (PRA) of internal events for heavy water production reactors (U)

    International Nuclear Information System (INIS)

    Tinnes, S.P.; Cramer, D.S.; Logan, V.E.; Topp, S.V.; Smith, J.A.; Brandyberry, M.D.

    1990-01-01

    This paper reports on a full-scope probabilistic risk assessment (PRA) performed for the Savannah River Site (SRS) production reactors. The Level 1 PRA for the K Reactor has been completed and includes the assessment of reactor systems response to accidents and estimates of the severe core melt frequency (SCMF). The internal events spectrum includes those events related directly to plant systems and safety functions for which transients or failures may initiate an accident

  11. Probabilistic logics and probabilistic networks

    CERN Document Server

    Haenni, Rolf; Wheeler, Gregory; Williamson, Jon; Andrews, Jill

    2014-01-01

    Probabilistic Logic and Probabilistic Networks presents a groundbreaking framework within which various approaches to probabilistic logic naturally fit. Additionally, the text shows how to develop computationally feasible methods to mesh with this framework.

  12. Flood Risk and Probabilistic Benefit Assessment to Support Management of Flood-Prone Lands: Evidence From Candaba Floodplains, Philippines

    Science.gov (United States)

    Juarez, A. M.; Kibler, K. M.; Sayama, T.; Ohara, M.

    2016-12-01

    Flood management decision-making is often supported by risk assessment, which may overlook the role of coping capacity and the potential benefits derived from direct use of flood-prone land. Alternatively, risk-benefit analysis can support floodplain management to yield maximum socio-ecological benefits for the minimum flood risk. We evaluate flood risk-probabilistic benefit tradeoffs of livelihood practices compatible with direct human use of flood-prone land (agriculture/wild fisheries) and nature conservation (wild fisheries only) in Candaba, Philippines. Located north-west to Metro Manila, Candaba area is a multi-functional landscape that provides a temporally-variable mix of possible land uses, benefits and ecosystem services of local and regional value. To characterize inundation from 1.3- to 100-year recurrence intervals we couple frequency analysis with rainfall-runoff-inundation modelling and remotely-sensed data. By combining simulated probabilistic floods with both damage and benefit functions (e.g. fish capture and rice yield with flood intensity) we estimate potential damages and benefits over varying probabilistic flood hazards. We find that although direct human uses of flood-prone land are associated with damages, for all the investigated magnitudes of flood events with different frequencies, the probabilistic benefits ( 91 million) exceed risks by a large margin ( 33 million). Even considering risk, probabilistic livelihood benefits of direct human uses far exceed benefits provided by scenarios that exclude direct "risky" human uses (difference of 85 million). In addition, we find that individual coping strategies, such as adapting crop planting periods to the flood pulse or fishing rather than cultivating rice in the wet season, minimize flood losses ( 6 million) while allowing for valuable livelihood benefits ($ 125 million) in flood-prone land. Analysis of societal benefits and local capacities to cope with regular floods demonstrate the

  13. Probabilistic risk assessment of nitrate groundwater contamination from greenhouses in Albenga plain (Liguria, Italy) using lysimeters.

    Science.gov (United States)

    Paladino, Ombretta; Seyedsalehi, Mahdi; Massabò, Marco

    2018-04-05

    The use of fertilizers in greenhouse-grown crops can pose a threat to groundwater quality and, consequently, to human beings and subterranean ecosystem, where intensive farming produces pollutants leaching. Albenga plain (Liguria, Italy) is an alluvial area of about 45km 2 historically devoted to farming. Recently the crops have evolved to greenhouses horticulture and floriculture production. In the area high levels of nitrates in groundwater have been detected. Lysimeters with three types of reconstituted soils (loamy sand, sandy clay loam and sandy loam) collected from different areas of Albenga plain were used in this study to evaluate the leaching loss of nitrate (NO 3 - ) over a period of 12weeks. Leaf lettuce (Lactuca sativa L.) was selected as a representative green-grown crop. Each of the soil samples was treated with a slow release fertilizer, simulating the real fertilizing strategy of the tillage. In order to estimate the potential risk for aquifers as well as for organisms exposed via pore water, nitrate concentrations in groundwater were evaluated by applying a simplified attenuation model to the experimental data. Results were refined and extended from comparison of single effects and exposure values (Tier I level) up to the evaluation of probabilistic distributions of exposure and related effects (Tier II, III IV levels). HHRA suggested HI >1 and about 20% probability of exceeding RfD for all the greenhouses, regardless of the soil. ERA suggested HQ>100 for all the greenhouses; 93% probability of PNEC exceedance for greenhouses containing sand clay loam. The probability of exceeding LC50 for 5% of the species was about 40% and the probability corresponding to DBQ of DEC/EC50>0.001 was >90% for all the greenhouses. The significantly high risk, related to the detected nitrate leaching loss, can be attributed to excessive and inappropriate fertigation strategies. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. The Integrated Medical Model: A Probabilistic Simulation Model Predicting In-Flight Medical Risks

    Science.gov (United States)

    Keenan, Alexandra; Young, Millennia; Saile, Lynn; Boley, Lynn; Walton, Marlei; Kerstman, Eric; Shah, Ronak; Goodenow, Debra A.; Myers, Jerry G., Jr.

    2015-01-01

    The Integrated Medical Model (IMM) is a probabilistic model that uses simulation to predict mission medical risk. Given a specific mission and crew scenario, medical events are simulated using Monte Carlo methodology to provide estimates of resource utilization, probability of evacuation, probability of loss of crew, and the amount of mission time lost due to illness. Mission and crew scenarios are defined by mission length, extravehicular activity (EVA) schedule, and crew characteristics including: sex, coronary artery calcium score, contacts, dental crowns, history of abdominal surgery, and EVA eligibility. The Integrated Medical Evidence Database (iMED) houses the model inputs for one hundred medical conditions using in-flight, analog, and terrestrial medical data. Inputs include incidence, event durations, resource utilization, and crew functional impairment. Severity of conditions is addressed by defining statistical distributions on the dichotomized best and worst-case scenarios for each condition. The outcome distributions for conditions are bounded by the treatment extremes of the fully treated scenario in which all required resources are available and the untreated scenario in which no required resources are available. Upon occurrence of a simulated medical event, treatment availability is assessed, and outcomes are generated depending on the status of the affected crewmember at the time of onset, including any pre-existing functional impairments or ongoing treatment of concurrent conditions. The main IMM outcomes, including probability of evacuation and loss of crew life, time lost due to medical events, and resource utilization, are useful in informing mission planning decisions. To date, the IMM has been used to assess mission-specific risks with and without certain crewmember characteristics, to determine the impact of eliminating certain resources from the mission medical kit, and to design medical kits that maximally benefit crew health while meeting

  15. The Integrated Medical Model: A Probabilistic Simulation Model for Predicting In-Flight Medical Risks

    Science.gov (United States)

    Keenan, Alexandra; Young, Millennia; Saile, Lynn; Boley, Lynn; Walton, Marlei; Kerstman, Eric; Shah, Ronak; Goodenow, Debra A.; Myers, Jerry G.

    2015-01-01

    The Integrated Medical Model (IMM) is a probabilistic model that uses simulation to predict mission medical risk. Given a specific mission and crew scenario, medical events are simulated using Monte Carlo methodology to provide estimates of resource utilization, probability of evacuation, probability of loss of crew, and the amount of mission time lost due to illness. Mission and crew scenarios are defined by mission length, extravehicular activity (EVA) schedule, and crew characteristics including: sex, coronary artery calcium score, contacts, dental crowns, history of abdominal surgery, and EVA eligibility. The Integrated Medical Evidence Database (iMED) houses the model inputs for one hundred medical conditions using in-flight, analog, and terrestrial medical data. Inputs include incidence, event durations, resource utilization, and crew functional impairment. Severity of conditions is addressed by defining statistical distributions on the dichotomized best and worst-case scenarios for each condition. The outcome distributions for conditions are bounded by the treatment extremes of the fully treated scenario in which all required resources are available and the untreated scenario in which no required resources are available. Upon occurrence of a simulated medical event, treatment availability is assessed, and outcomes are generated depending on the status of the affected crewmember at the time of onset, including any pre-existing functional impairments or ongoing treatment of concurrent conditions. The main IMM outcomes, including probability of evacuation and loss of crew life, time lost due to medical events, and resource utilization, are useful in informing mission planning decisions. To date, the IMM has been used to assess mission-specific risks with and without certain crewmember characteristics, to determine the impact of eliminating certain resources from the mission medical kit, and to design medical kits that maximally benefit crew health while meeting

  16. Probabilistic Risk Assessment for Bone Fracture - Bone Fracture Risk Module (BFxRM)

    Science.gov (United States)

    Licata, Angelo; Myers, Jerry G.; Lewandowski, Beth

    2013-01-01

    This presentation summarizes the concepts, development, and application of NASA's Bone Fracture Risk Module (BFxRM). The overview includes an assessmnet of strenghts and limitations of the BFxRM and proposes a numebr of discussion questions to the panel regarding future development avenues for this simulation system.

  17. Probabilistic integrated risk assessment of human exposure risk to environmental bisphenol A pollution sources.

    Science.gov (United States)

    Fu, Keng-Yen; Cheng, Yi-Hsien; Chio, Chia-Pin; Liao, Chung-Min

    2016-10-01

    Environmental bisphenol A (BPA) exposure has been linked to a variety of adverse health effects such as developmental and reproductive issues. However, establishing a clear association between BPA and the likelihood of human health is complex yet fundamentally uncertain. The purpose of this study was to assess the potential exposure risks from environmental BPA among Chinese population based on five human health outcomes, namely immune response, uterotrophic assay, cardiovascular disease (CVD), diabetes, and behavior change. We addressed these health concerns by using a stochastic integrated risk assessment approach. The BPA dose-dependent likelihood of effects was reconstructed by a series of Hill models based on animal models or epidemiological data. We developed a physiologically based pharmacokinetic (PBPK) model that allows estimation of urinary BPA concentration from external exposures. Here we showed that the daily average exposure concentrations of BPA and urinary BPA estimates were consistent with the published data. We found that BPA exposures were less likely to pose significant risks for infants (0-1 year) and adults (male and female >20 years) with human long-term BPA susceptibility in relation to multiple exposure pathways, and for informing the public of the negligible magnitude of environmental BPA pollution impacts on human health.

  18. Flood risk and adaptation strategies under climate change and urban expansion: A probabilistic analysis using global data.

    Science.gov (United States)

    Muis, Sanne; Güneralp, Burak; Jongman, Brenden; Aerts, Jeroen C J H; Ward, Philip J

    2015-12-15

    An accurate understanding of flood risk and its drivers is crucial for effective risk management. Detailed risk projections, including uncertainties, are however rarely available, particularly in developing countries. This paper presents a method that integrates recent advances in global-scale modeling of flood hazard and land change, which enables the probabilistic analysis of future trends in national-scale flood risk. We demonstrate its application to Indonesia. We develop 1000 spatially-explicit projections of urban expansion from 2000 to 2030 that account for uncertainty associated with population and economic growth projections, as well as uncertainty in where urban land change may occur. The projections show that the urban extent increases by 215%-357% (5th and 95th percentiles). Urban expansion is particularly rapid on Java, which accounts for 79% of the national increase. From 2000 to 2030, increases in exposure will elevate flood risk by, on average, 76% and 120% for river and coastal floods. While sea level rise will further increase the exposure-induced trend by 19%-37%, the response of river floods to climate change is highly uncertain. However, as urban expansion is the main driver of future risk, the implementation of adaptation measures is increasingly urgent, regardless of the wide uncertainty in climate projections. Using probabilistic urban projections, we show that spatial planning can be a very effective adaptation strategy. Our study emphasizes that global data can be used successfully for probabilistic risk assessment in data-scarce countries. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. An HVAC [heating, ventilation, and air-conditioning] fault-tree analysis for WIPP [Waste Isolation Pilot Plant] integrated risk assessment

    International Nuclear Information System (INIS)

    Kirby, P.N.; Iacovino, J.M.

    1990-01-01

    In order to evaluate the public health risk of potential radioactive releases from operation of the Waste Isolation Pilot Plant (WIPP), a probabilistic risk assessment of waste-handling operations was conducted. One major aspect of this risk assessment involved fault-tree analysis of the plant heating, ventilation, and air-conditioning (HVAC) systems, which constitute the final barrier between waste-handling operations and the environment. The WIPP site is designed to receive and store two types of waste: contact-handled transuranic (CH TRU) wastes to be shipped in 208-ell drums and remote-handled (RH) TRU wastes to be shipped in shielded casks. The identification of accident sequences for CH waste operations revealed no identified accidents that could release significant radioactive particulates to the environment without a failure in the HVAC systems. When the HVAC fault-tree results were combined with other critical system fault trees and the analysis of waste-handling accident sequences, the approximation of the overall WIPP plant risk due to airborne releases was determined to be 2.6 x 10 -7 fatalities per year for the population within a 50-mile radius of the WIPP site. This risk was demonstrated to be well below the risk of fatality from other voluntary and involuntary activities for the population within the vicinity of the WIPP

  20. Probabilistic approaches to accounting for data variability in the practical application of bioavailability in predicting aquatic risks from metals.

    Science.gov (United States)

    Ciffroy, Philippe; Charlatchka, Rayna; Ferreira, Daniel; Marang, Laura

    2013-07-01

    The biotic ligand model (BLM) theoretically enables the derivation of environmental quality standards that are based on true bioavailable fractions of metals. Several physicochemical variables (especially pH, major cations, dissolved organic carbon, and dissolved metal concentrations) must, however, be assigned to run the BLM, but they are highly variable in time and space in natural systems. This article describes probabilistic approaches for integrating such variability during the derivation of risk indexes. To describe each variable using a probability density function (PDF), several methods were combined to 1) treat censored data (i.e., data below the limit of detection), 2) incorporate the uncertainty of the solid-to-liquid partitioning of metals, and 3) detect outliers. From a probabilistic perspective, 2 alternative approaches that are based on log-normal and Γ distributions were tested to estimate the probability of the predicted environmental concentration (PEC) exceeding the predicted non-effect concentration (PNEC), i.e., p(PEC/PNEC>1). The probabilistic approach was tested on 4 real-case studies based on Cu-related data collected from stations on the Loire and Moselle rivers. The approach described in this article is based on BLM tools that are freely available for end-users (i.e., the Bio-Met software) and on accessible statistical data treatments. This approach could be used by stakeholders who are involved in risk assessments of metals for improving site-specific studies. Copyright © 2013 SETAC.

  1. Application of Probabilistic Modeling to Quantify the Reduction Levels of Hepatocellular Carcinoma Risk Attributable to Chronic Aflatoxins Exposure

    DEFF Research Database (Denmark)

    Wambui, Joseph M.; Karuri, Edward G.; Ojiambo, Julia A.

    2017-01-01

    the rural populations to HCC. A quantitative cancer risk assessment therefore quantified the levels at which potential pre- and postharvest interventions reduce the HCC risk attributable to consumption of contaminated maize and groundnuts. The assessment applied a probabilistic model to derive probability......Epidemiological studies show a definite connection between areas of high aflatoxin content and a high occurrence of human hepatocellular carcinoma (HCC). Hepatitis B virus in individuals further increases the risk of HCC. The two risk factors are prevalent in rural Kenya and continuously predispose...... distributions of HCC cases and percentage reductions levels of the risk from secondary data. Contaminated maize and groundnuts contributed to 1,847 +/- 514 and 158 +/- 52 HCC cases per annum, respectively. The total contribution of both foods to the risk was additive as it resulted in 2,000 +/- 518 cases per...

  2. Need to use probabilistic risk approach in performance assessment of waste disposal facilities

    International Nuclear Information System (INIS)

    Bonano, E.J.; Gallegos, D.P.

    1991-01-01

    Regulations governing the disposal of radioactive, hazardous, and/or mixed wastes will likely require, either directly or indirectly, that the performance of disposal facilities be assessed quantitatively. Such analyses, commonly called ''performance assessments,'' rely on the use of predictive models to arrive at a quantitative estimate of the potential impact of disposal on the environment and the safety and health of the public. It has been recognized that a suite of uncertainties affect the results of a performance assessment. These uncertainties are conventionally categorized as (1) uncertainty in the future state of the disposal system (facility and surrounding medium), (2) uncertainty in models (including conceptual models, mathematical models, and computer codes), and (3) uncertainty in data and parameters. Decisions regarding the suitability of a waste disposal facility must be made in light of these uncertainties. Hence, an approach is needed that would allow the explicit consideration of these uncertainties so that their impact on the estimated consequences of disposal can be evaluated. While most regulations for waste disposal do not prescribe the consideration of uncertainties, it is proposed that, even in such cases, a meaningful decision regarding the suitability of a waste disposal facility cannot be made without considering the impact of the attendant uncertainties. A probabilistic risk assessment (PRA) approach provides the formalism for considering the uncertainties and the technical basis that the decision makers can use in discharging their duties. A PRA methodology developed and demonstrated for the disposal of high-level radioactive waste provides a general framework for assessing the disposal of all types of wastes (radioactive, hazardous, and mixed). 15 refs., 1 fig., 1 tab

  3. Development of transient initiating event frequencies for use in probabilistic risk assessments

    International Nuclear Information System (INIS)

    Mackowiak, D.P.; Gentillon, C.D.; Smith, K.L.

    1985-05-01

    Transient initiating event frequencies are an essential input to the analysis process of a nuclear power plant probabilistic risk assessment. These frequencies describe events causing or requiring scrams. This report documents an effort to validate and update from other sources a computer-based data file developed by the Electric Power Research Institute (EPRI) describing such events at 52 United States commercial nuclear power plants. Operating information from the United States Nuclear Regulatory Commission on 24 additional plants from their date of commercial operation has been combined with the EPRI data, and the entire data base has been updated to add 1980 through 1983 events for all 76 plants. The validity of the EPRI data and data analysis methodology and the adequacy of the EPRI transient categories are examined. New transient initiating event frequencies are derived from the expanded data base using the EPRI transient categories and data display methods. Upper bounds for these frequencies are also provided. Additional analyses explore changes in the dominant transients, changes in transient outage times and their impact on plant operation, and the effects of power level and scheduled scrams on transient event frequencies. A more rigorous data analysis methodology is developed to encourage further refinement of the transient initiating event frequencies derived herein. Updating the transient event data base resulted in approx.2400 events being added to EPRI's approx.3000-event data file. The resulting frequency estimates were in most cases lower than those reported by EPRI, but no significant order-of-magnitude changes were noted. The average number of transients per year for the combined data base is 8.5 for pressurized water reactors and 7.4 for boiling water reactors

  4. Development of transient initiating event frequencies for use in probabilistic risk assessments

    Energy Technology Data Exchange (ETDEWEB)

    Mackowiak, D.P.; Gentillon, C.D.; Smith, K.L.

    1985-05-01

    Transient initiating event frequencies are an essential input to the analysis process of a nuclear power plant probabilistic risk assessment. These frequencies describe events causing or requiring scrams. This report documents an effort to validate and update from other sources a computer-based data file developed by the Electric Power Research Institute (EPRI) describing such events at 52 United States commercial nuclear power plants. Operating information from the United States Nuclear Regulatory Commission on 24 additional plants from their date of commercial operation has been combined with the EPRI data, and the entire data base has been updated to add 1980 through 1983 events for all 76 plants. The validity of the EPRI data and data analysis methodology and the adequacy of the EPRI transient categories are examined. New transient initiating event frequencies are derived from the expanded data base using the EPRI transient categories and data display methods. Upper bounds for these frequencies are also provided. Additional analyses explore changes in the dominant transients, changes in transient outage times and their impact on plant operation, and the effects of power level and scheduled scrams on transient event frequencies. A more rigorous data analysis methodology is developed to encourage further refinement of the transient initiating event frequencies derived herein. Updating the transient event data base resulted in approx.2400 events being added to EPRI's approx.3000-event data file. The resulting frequency estimates were in most cases lower than those reported by EPRI, but no significant order-of-magnitude changes were noted. The average number of transients per year for the combined data base is 8.5 for pressurized water reactors and 7.4 for boiling water reactors.

  5. A Statistical-Probabilistic Pattern for Determination of Tunnel Advance Step by Quantitative Risk Analysis

    Directory of Open Access Journals (Sweden)

    sasan ghorbani

    2017-12-01

    Full Text Available One of the main challenges faced in design and construction phases of tunneling projects is the determination of maximum allowable advance step to maximize excavation rate and reduce project delivery time. Considering the complexity of determining this factor and unexpected risks associated with inappropriate determination of that, it is necessary to employ a method which is capable of accounting for interactions among uncertain geotechnical parameters and advance step. The main objective in the present research is to undertake optimization and risk management of advance step length in water diversion tunnel at Shahriar Dam based on uncertainty of geotechnical parameters following a statistic-probabilistic approach. In the present research, in order to determine optimum advance step for excavation operation, two hybrid methods were used: strength reduction method-discrete element method- Monte Carlo simulation (SRM/DEM/MCS and strength reduction method- discrete element method- point estimate method (SRM/DEM/PEM. Moreover, Taguchi analysis was used to investigate the sensitivity of advance step to changes in statistical distribution function of input parameters under three tunneling scenarios at sections of poor to good qualities (as per RMR classification system. Final results implied the optimality of the advance step defined in scenario 2 where 2 m advance per excavation round was proposed, according to shear strain criterion and SRM/DEM/MCS, with minimum failure probability and risk of 8.05% and 75281.56 $, respectively, at 95% confidence level. Moreover, in either of normal, lognormal, and gamma distributions, as the advance step increased from Scenario 1 to 2, failure probability was observed to increase at lower rate than that observed when advance step in scenario 2 was increased to that In Scenario 3. In addition, Taguchi tests were subjected to signal-to-noise analysis and the results indicated that, considering the three statistical

  6. Probabilistic Risk Assessment of Cancer from Exposure Inorganic Arsenic in Duplicate Food by Villagers in Ronphibun, Thailand

    Directory of Open Access Journals (Sweden)

    Piyawat Saipan

    2010-07-01

    Full Text Available Ronphibun district is a district in Nakorn Si Thammarat province, within southern Thailand. This district is the site of several former tin mines that were in operation 100 years ago. Arsenic contamination caused by past mining activities remains in the area. The specific purpose of this study was conducted to assess cancer risk in people living within Ronphibun district from exposure to inorganic arsenic via duplicate food using probabilistic risk assessment. A hundred and fifty duplicate food samples were collected from participants. Inorganic arsenic concentrations are determined by hydride generation atomic absorption spectrometry. Inorganic arsenic concentrations in duplicate food ranged from 0.16 to 0.42 μg/g dry weight. The probabilistic carcinogenic risk levels were 6.76 x 10-4 and 1.74 x 10-3 based on the 50th and 95th percentile, respectively. Risk values for people in Ronphibun from exposure to inorganic arsenic remained higher than the acceptable target risk. Sensitivity analysis indicted that exposure duration and concentrations of arsenic in food were the two most influential of cancer risk estimates.

  7. Challenges in using a probabilistic safety assessment in a risk informed process (illustrated using risk informed inservice inspection)

    International Nuclear Information System (INIS)

    Chapman, James R.; Dimitrijevic, Vesna B.

    1999-01-01

    Many of the ongoing and expected uses of Probabilistic Safety Assessment (PSA) create new challenges to ensuring that the resulting conclusions are valid. This paper provides a summary of some of these challenges. Work conducted by the authors on Risk-Informed Inservice Inspection (RI-ISI) is used to illustrate these challenges. Means to address all of the challenges are not provided in detail in this paper. Several earlier papers discuss how these challenges can be addressed. References are provided for the interested reader (Chapman JR et al. In: PSA '95, vol. 1, Seoul, 1995: 177-80; Chapman JR et al. In: ICONE-IV, New Orleans, 1996; Dimitrijevic VB et al. In: Croatian Nuclear Society International Conference, Opatija, 1996: 245-54; Dimitrijevic VB et al. In: Croatian Nuclear Society International Conference, Opatija, 1996: 255-62; Dimitrijevic VB. In: Yugoslav Nuclear Society Conference, Belgrade, 1996: 53-61; O'Regan PJ et al. In: PSA '95, Seoul, vol. 1, 1995: 403-5; O'Regan PJ. In: ICONE-IV, vol. 5, New Orleans, 1996: 277-80)

  8. Combination of the deterministic and probabilistic approaches for risk-informed decision-making in US NRC regulatory guides

    International Nuclear Information System (INIS)

    Patrik, M.; Babic, P.

    2001-06-01

    The report responds to the trend where probabilistic safety analyses are attached, on a voluntary basis (as yet), to the mandatory deterministic assessment of modifications of NPP systems or operating procedures, resulting in risk-informed type documents. It contains a nearly complete Czech translation of US NRC Regulatory Guide 1.177 and presents some suggestions for improving a) PSA study applications; b) the development of NPP documents for the regulatory body; and c) the interconnection between PSA and traditional deterministic analyses as contained in the risk-informed approach. (P.A.)

  9. Probabilistic migration modelling focused on functional barrier efficiency and low migration concepts in support of risk assessment.

    Science.gov (United States)

    Brandsch, Rainer

    2017-10-01

    Migration modelling provides reliable migration estimates from food-contact materials (FCM) to food or food simulants based on mass-transfer parameters like diffusion and partition coefficients related to individual materials. In most cases, mass-transfer parameters are not readily available from the literature and for this reason are estimated with a given uncertainty. Historically, uncertainty was accounted for by introducing upper limit concepts first, turning out to be of limited applicability due to highly overestimated migration results. Probabilistic migration modelling gives the possibility to consider uncertainty of the mass-transfer parameters as well as other model inputs. With respect to a functional barrier, the most important parameters among others are the diffusion properties of the functional barrier and its thickness. A software tool that accepts distribution as inputs and is capable of applying Monte Carlo methods, i.e., random sampling from the input distributions of the relevant parameters (i.e., diffusion coefficient and layer thickness), predicts migration results with related uncertainty and confidence intervals. The capabilities of probabilistic migration modelling are presented in the view of three case studies (1) sensitivity analysis, (2) functional barrier efficiency and (3) validation by experimental testing. Based on the predicted migration by probabilistic migration modelling and related exposure estimates, safety evaluation of new materials in the context of existing or new packaging concepts is possible. Identifying associated migration risk and potential safety concerns in the early stage of packaging development is possible. Furthermore, dedicated material selection exhibiting required functional barrier efficiency under application conditions becomes feasible. Validation of the migration risk assessment by probabilistic migration modelling through a minimum of dedicated experimental testing is strongly recommended.

  10. Study of Hip Fracture Risk using Tree Structured Survival Analysis

    Directory of Open Access Journals (Sweden)

    Lu Y

    2003-01-01

    Full Text Available In dieser Studie wird das Hüftfraktur-Risiko bei postmenopausalen Frauen untersucht, indem die Frauen in verschiedene Subgruppen hinsichtlich dieses Risikos klassifiziert werden. Frauen in einer gemeinsamen Subgruppe haben ein ähnliches Risiko, hingegen in verschiedenen Subgruppen ein unterschiedliches Hüftfraktur-Risiko. Die Subgruppen wurden mittels der Tree Structured Survival Analysis (TSSA aus den Daten von 7.665 Frauen der SOF (Study of Osteoporosis Fracture ermittelt. Bei allen Studienteilnehmerinnen wurde die Knochenmineraldichte (BMD von Unterarm, Oberschenkelhals, Hüfte und Wirbelsäule gemessen. Die Zeit von der BMD-Messung bis zur Hüftfraktur wurde als Endpunkt notiert. Eine Stichprobe von 75% der Teilnehmerinnen wurde verwendet, um die prognostischen Subgruppen zu bilden (Trainings-Datensatz, während die anderen 25% als Bestätigung der Ergebnisse diente (Validierungs-Datensatz. Aufgrund des Trainings-Datensatzes konnten mittels TSSA 4 Subgruppen identifiziert werden, deren Hüftfraktur-Risiko bei einem Follow-up von im Mittel 6,5 Jahren bei 19%, 9%, 4% und 1% lag. Die Einteilung in die Subgruppen erfolgte aufgrund der Bewertung der BMD des Ward'schen Dreiecks sowie des Oberschenkelhalses und nach dem Alter. Diese Ergebnisse konnten mittels des Validierungs-Datensatzes reproduziert werden, was die Sinnhaftigkeit der Klassifizierungregeln in einem klinischen Setting bestätigte. Mittels TSSA war eine sinnvolle, aussagekräftige und reproduzierbare Identifikation von prognostischen Subgruppen, die auf dem Alter und den BMD-Werten beruhen, möglich. In this paper we studied the risk of hip fracture for post-menopausal women by classifying women into different subgroups based on their risk of hip fracture. The subgroups were generated such that all the women in a particular subgroup had relatively similar risk while women belonging to two different subgroups had rather different risks of hip fracture. We used the Tree Structured

  11. The importance of Probabilistic Safety Assessment in the careful study of risks involved to new nuclear power plant projects

    International Nuclear Information System (INIS)

    Mata, Jônatas F.C. da; Mesquita, Amir Z.

    2017-01-01

    The Fukushima Daiichi nuclear accident in Japan in 2011 has raised public fears about the actual safety of nuclear power plants in several countries. The response to this concern by government agencies and private companies has been objective and pragmatic in order to guarantee best practices in the design, construction, operation and decommissioning phases of nuclear reactors. In countries where the nucleo-electric matrix is consolidated, such as the United States, France and the United Kingdom, the safety assessment is carried out considering deterministic and probabilistic criteria. In the licensing stages of new projects, it is necessary to analyze and simulate the behavior of the nuclear power plant, when subjected to conditions that can lead to sequences of accidents. Each initiator event is studied and simulated through computational models, which allow the description and estimation of possible physical phenomena occurring in nuclear reactors. Probabilistic Safety Assessment (PSA) is fundamental in this process, as it studies in depth the sequences of events that can lead to the fusion of the nucleus of the nuclear reactor. Such sequences should be quantified in terms of probability of occurrence and your possible consequences, and organized through techniques such as Fault Tree Analysis and Event Tree Analysis. For these simulations, specialized computer codes for each type of phenomenon should be used, as well as databases based on experience gained in the operation of similar nuclear reactors. The present work will describe, in an objective way, the procedures for the realization of PSA and its applicability to the assurance of the operational reliability of the nuclear reactors, as well as a brief comparative between the approaches used in some countries traditionally users of thermonuclear energy and Brazil. By means of this analysis, it can be concluded that nuclear power is increasingly reliable and safe, being able to provide the necessary

  12. The importance of Probabilistic Safety Assessment in the careful study of risks involved to new nuclear power plant projects

    Energy Technology Data Exchange (ETDEWEB)

    Mata, Jônatas F.C. da, E-mail: jonatasfmata@yahoo.com.br [Universidade do Estado de Minas Gerais (UEMG), João Monlevade, MG (Brazil); Mesquita, Amir Z., E-mail: amir@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The Fukushima Daiichi nuclear accident in Japan in 2011 has raised public fears about the actual safety of nuclear power plants in several countries. The response to this concern by government agencies and private companies has been objective and pragmatic in order to guarantee best practices in the design, construction, operation and decommissioning phases of nuclear reactors. In countries where the nucleo-electric matrix is consolidated, such as the United States, France and the United Kingdom, the safety assessment is carried out considering deterministic and probabilistic criteria. In the licensing stages of new projects, it is necessary to analyze and simulate the behavior of the nuclear power plant, when subjected to conditions that can lead to sequences of accidents. Each initiator event is studied and simulated through computational models, which allow the description and estimation of possible physical phenomena occurring in nuclear reactors. Probabilistic Safety Assessment (PSA) is fundamental in this process, as it studies in depth the sequences of events that can lead to the fusion of the nucleus of the nuclear reactor. Such sequences should be quantified in terms of probability of occurrence and your possible consequences, and organized through techniques such as Fault Tree Analysis and Event Tree Analysis. For these simulations, specialized computer codes for each type of phenomenon should be used, as well as databases based on experience gained in the operation of similar nuclear reactors. The present work will describe, in an objective way, the procedures for the realization of PSA and its applicability to the assurance of the operational reliability of the nuclear reactors, as well as a brief comparative between the approaches used in some countries traditionally users of thermonuclear energy and Brazil. By means of this analysis, it can be concluded that nuclear power is increasingly reliable and safe, being able to provide the necessary

  13. Predicting Rib Fracture Risk With Whole-Body Finite Element Models: Development and Preliminary Evaluation of a Probabilistic Analytical Framework

    Science.gov (United States)

    Forman, Jason L.; Kent, Richard W.; Mroz, Krystoffer; Pipkorn, Bengt; Bostrom, Ola; Segui-Gomez, Maria

    2012-01-01

    This study sought to develop a strain-based probabilistic method to predict rib fracture risk with whole-body finite element (FE) models, and to describe a method to combine the results with collision exposure information to predict injury risk and potential intervention effectiveness in the field. An age-adjusted ultimate strain distribution was used to estimate local rib fracture probabilities within an FE model. These local probabilities were combined to predict injury risk and severity within the whole ribcage. The ultimate strain distribution was developed from a literature dataset of 133 tests. Frontal collision simulations were performed with the THUMS (Total HUman Model for Safety) model with four levels of delta-V and two restraints: a standard 3-point belt and a progressive 3.5–7 kN force-limited, pretensioned (FL+PT) belt. The results of three simulations (29 km/h standard, 48 km/h standard, and 48 km/h FL+PT) were compared to matched cadaver sled tests. The numbers of fractures predicted for the comparison cases were consistent with those observed experimentally. Combining these results with field exposure informantion (ΔV, NASS-CDS 1992–2002) suggests a 8.9% probability of incurring AIS3+ rib fractures for a 60 year-old restrained by a standard belt in a tow-away frontal collision with this restraint, vehicle, and occupant configuration, compared to 4.6% for the FL+PT belt. This is the first study to describe a probabilistic framework to predict rib fracture risk based on strains observed in human-body FE models. Using this analytical framework, future efforts may incorporate additional subject or collision factors for multi-variable probabilistic injury prediction. PMID:23169122

  14. A Practical Probabilistic Graphical Modeling Tool for Weighing Ecological Risk-Based Evidence

    Science.gov (United States)

    Past weight-of-evidence frameworks for adverse ecological effects have provided soft-scoring procedures for judgments based on the quality and measured attributes of evidence. Here, we provide a flexible probabilistic structure for weighing and integrating lines of evidence for e...

  15. Probabilistic risk assessment course documentation. Volume 2. Probability and statistics for PRA applications

    International Nuclear Information System (INIS)

    Iman, R.L.; Prairie, R.R.; Cramond, W.R.

    1985-08-01

    This course is intended to provide the necessary probabilistic and statistical skills to perform a PRA. Fundamental background information is reviewed, but the principal purpose is to address specific techniques used in PRAs and to illustrate them with applications. Specific examples and problems are presented for most of the topics

  16. Potential for accidents in a nuclear power plant: probabilistic risk assessment, applied statistical decision theory, and implications of such considerations to mathematics education

    International Nuclear Information System (INIS)

    Dios, R.A.

    1984-01-01

    This dissertation focuses upon the field of probabilistic risk assessment and its development. It investigates the development of probabilistic risk assessment in nuclear engineering. To provide background for its development, the related areas of population dynamics (demography), epidemiology and actuarial science are studied by presenting information upon how risk has been viewed in these areas over the years. A second major problem involves presenting an overview of the mathematical models related to risk analysis to mathematics educators and making recommendations for presenting this theory in classes of probability and statistics for mathematics and engineering majors at the undergraduate and graduate levels

  17. Utilization of a risk matrix based on Probabilistic Safety Analysis to improve nuclear safety in NPP

    International Nuclear Information System (INIS)

    Stubbe, Gerald

    2010-01-01

    The Probabilistic Safety Analysis (PSA) is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity. Risk in a PSA is defined as a feasible detrimental outcome of an initiator. Those initiators can be 'classical' transient as the loss of main feedwater, loss of the secondary heat sink, etc.. or accident (LOCA - Loss Of Coolant Accident, SGTR - Steam Generator Tube Rupture, LOOP - Loss Of Offsite Power, etc..) In a PSA, risk is characterized by two quantities: the magnitude (severity) of the possible adverse consequence, the likelihood (probability) of occurrence of each consequence. Consequences are expressed numerically (for this purpose: the core damage) and their likelihoods of occurrence are expressed as probabilities or frequencies (i.e., the number of occurrences or the probability of occurrence per unit time). The total risk is the expected loss: the sum of the products of the consequences multiplied by their probabilities. This lead to the parameter CDF: The Core Damage Frequency, which is expressed by unit of time. The main advantage of this risk calculation is to have a global, integrated, overview of the plants and their systems. This allows to have an objective and quantitative point of view on the importance of the equipments, human action, or common cause failures that can challenge the plant's safety. A total PSA model is divided in three levels: Level one, which consider the core damage; Level two, which consider the robustness of the containment; Level three, which consider the impact of the radiological release on the public. For the purpose of the risk matrix, a level one PSA is needed. The scope of a PSA model is important to have a good characterization of the plant's risk. The matrix makes more sense if you have a full scope level one model, containing, furthermore the internal events, the fire and flooding, but also seismic event (if relevant). Asymmetries are also classical in the

  18. Results of the Level 1 probabilistic risk assessment (PRA) of internal events for heavy water production reactors

    International Nuclear Information System (INIS)

    Tinnes, S.P.; Cramer, D.S.; Logan, V.E.; Topp, S.V.; Smith, J.A.; Brandyberry, M.D.

    1990-01-01

    A full-scope probabilistic risk assessment (PRA) is being performed for the Savannah River site (SRS) production reactors. The Level 1 PRA for the K Reactor has been completed and includes the assessment of reactor systems response to accidents and estimates of the severe core melt frequency (SCMF). The internal events spectrum includes those events related directly to plant systems and safety functions for which transients or failures may initiate an accident. The SRS PRA has three principal objectives: improved understanding of SRS reactor safety issues through discovery and understanding of the mechanisms involved. Improved risk management capability through tools for assessing the safety impact of both current standard operations and proposed revisions. A quantitative measure of the risks posed by SRS reactor operation to employees and the general public, to allow comparison with declared goals and other societal risks

  19. A probabilistic safety assessment of radioactive materials transport. A risk analysis of LLW package handling at harbor

    International Nuclear Information System (INIS)

    Watabe, Naohito; Suzuki, Hiroshi; Kouno, Yutaka

    1997-01-01

    The Probabilistic Safety Assessment (PSA) method for radioactive materials (RAM) transport has been developed by CRIEPI. A case study was executed for the purpose of studying the adaptability of the PSA method to LLW package handling, which is one of the processes of the actual transport. The main results of the case study were as follows; 1) Accident scenarios for falling of package were extracted from the 25 ton-crane system chart and package handling manual. 2) Protection methods for each drop accident scenario were confirmed. 3) Important points of the crane system were extracted. 4) Fault trees, which describe accident scenarios, were developed. 5) Probabilities for each basic event and the top event on fault trees were calculated. Consequently, 'falling of a package' on the package handling process by the 25 ton-crane was revealed to be extremely low. Among the four major stages of handling process, i.e. 'Rolling-up', 'Horizontal travelling' 'Rolling-down' and 'Contact with loading platform', the 'Rolling-down' process was found to be a major process with occupies more than 50% of the probability of the falling accidents. According to those results, it was concluded that PSA method is adaptable to package handling from the view points of extraction of weak points and review of the effect of vestment for facility. (author)

  20. Updating of adventitious fuel pin failure frequency in sodium-cooled fast reactors and probabilistic risk assessment on consequent severe accident in Monju

    International Nuclear Information System (INIS)

    Fukano, Yoshitaka; Kurisaka, Kenichi; Nishimura, Masahiro; Naruto, Kenichi

    2015-01-01

    Experimental studies, deterministic approaches and probabilistic risk assessments (PRAs) on local fault (LF) propagation in sodium-cooled fast reactors (SFRs) have been performed in many countries because LFs have been historically considered as one of the possible causes of severe accidents. Adventitious-fuel-pin-failures (AFPFs) have been considered to be the most dominant initiators of LFs in these PRAs because of their high frequency of occurrence during reactor operation and possibility of fuel-element-failure-propagation (FEFP). A PRA on FEFP from AFPF (FEFPA) in the Japanese prototype SFR (Monju) was performed in this study based on the state-of-the-art knowledge, reflecting the most recent operation procedures under off-normal conditions. Frequency of occurrence of AFPF in SFRs which was the initiating event of the event tree in this PRA was updated using a variety of methods based on the above-mentioned latest review on experiences of this phenomenon. As a result, the frequency of occurrence of, and the core damage frequency (CDF) from, AFPF in Monju was significantly reduced to a negligible magnitude compared with those in the existing PRAs. It was, therefore concluded that the CDF of FEFPA in Monju could be comprised in that of anticipated transient without scram or protected loss of heat sink events from both the viewpoint of occurrence probability and consequences. (author)

  1. Forecasting risk along a river basin using a probabilistic and deterministic model for environmental risk assessment of effluents through ecotoxicological evaluation and GIS.

    Science.gov (United States)

    Gutiérrez, Simón; Fernandez, Carlos; Barata, Carlos; Tarazona, José Vicente

    2009-12-20

    This work presents a computer model for Risk Assessment of Basins by Ecotoxicological Evaluation (RABETOX). The model is based on whole effluent toxicity testing and water flows along a specific river basin. It is capable of estimating the risk along a river segment using deterministic and probabilistic approaches. The Henares River Basin was selected as a case study to demonstrate the importance of seasonal hydrological variations in Mediterranean regions. As model inputs, two different ecotoxicity tests (the miniaturized Daphnia magna acute test and the D.magna feeding test) were performed on grab samples from 5 waste water treatment plant effluents. Also used as model inputs were flow data from the past 25 years, water velocity measurements and precise distance measurements using Geographical Information Systems (GIS). The model was implemented into a spreadsheet and the results were interpreted and represented using GIS in order to facilitate risk communication. To better understand the bioassays results, the effluents were screened through SPME-GC/MS analysis. The deterministic model, performed each month during one calendar year, showed a significant seasonal variation of risk while revealing that September represents the worst-case scenario with values up to 950 Risk Units. This classifies the entire area of study for the month of September as "sublethal significant risk for standard species". The probabilistic approach using Monte Carlo analysis was performed on 7 different forecast points distributed along the Henares River. A 0% probability of finding "low risk" was found at all forecast points with a more than 50% probability of finding "potential risk for sensitive species". The values obtained through both the deterministic and probabilistic approximations reveal the presence of certain substances, which might be causing sublethal effects in the aquatic species present in the Henares River.

  2. Procedures for the elicitation of expert judgements in the probabilistic risk analysis of radioactive waste repositories: an overview

    International Nuclear Information System (INIS)

    Watson, S.R.

    1992-01-01

    In modelling the consequences of a radioactive waste repository using Probabilistic Risk Analysis, it is necessary to use the judgement of experts both in assessing probabilities subjectively, and in choosing suitable analytic frameworks. This report presents the literature on these topics, first discussing the meaning of probability in PRA, and then giving an extensive review of what is known about how to elicit probabilities from experts. The report then provides an overview of the less well developed field of how best to use expertise in the construction of models for PRA. (author)

  3. Application of Probabilistic Modeling to Quantify the Reduction Levels of Hepatocellular Carcinoma Risk Attributable to Chronic Aflatoxins Exposure.

    Science.gov (United States)

    Wambui, Joseph M; Karuri, Edward G; Ojiambo, Julia A; Njage, Patrick M K

    2017-01-01

    Epidemiological studies show a definite connection between areas of high aflatoxin content and a high occurrence of human hepatocellular carcinoma (HCC). Hepatitis B virus in individuals further increases the risk of HCC. The two risk factors are prevalent in rural Kenya and continuously predispose the rural populations to HCC. A quantitative cancer risk assessment therefore quantified the levels at which potential pre- and postharvest interventions reduce the HCC risk attributable to consumption of contaminated maize and groundnuts. The assessment applied a probabilistic model to derive probability distributions of HCC cases and percentage reductions levels of the risk from secondary data. Contaminated maize and groundnuts contributed to 1,847 ± 514 and 158 ± 52 HCC cases per annum, respectively. The total contribution of both foods to the risk was additive as it resulted in 2,000 ± 518 cases per annum. Consumption and contamination levels contributed significantly to the risk whereby lower age groups were most affected. Nonetheless, pre- and postharvest interventions might reduce the risk by 23.0-83.4% and 4.8-95.1%, respectively. Therefore, chronic exposure to aflatoxins increases the HCC risk in rural Kenya, but a significant reduction of the risk can be achieved by applying specific pre- and postharvest interventions.

  4. Health risk assessment of heavy metals through the consumption of food crops fertilized by biosolids: A probabilistic-based analysis

    International Nuclear Information System (INIS)

    Hosseini Koupaie, E.; Eskicioglu, C.

    2015-01-01

    Highlights: • No potential health risk of land application of the regional biosolids. • More realistic risk assessment via probabilistic approach than that of deterministic. • Increasing the total hazard index with increasing fertilizer land application rate. • Significant effect of long-term biosolids land application of hazard index. • Greater contribution of rice ingestion than vegetable ingestion on hazard index. - Abstract: The objective of this study was to perform a probabilistic risk analysis (PRA) to assess the health risk of Cadmium (Cd), Copper (Cu), and Zinc (Zn) through the consumption of food crops grown on farm lands fertilized by biosolids. The risk analysis was conducted using 8 years of historical heavy metal data (2005–2013) of the municipal biosolids generated by a nearby treatment facility considering one-time and long-term biosolids land application scenarios for a range of 5–100 t/ha fertilizer application rate. The 95th percentile of the hazard index (HI) increased from 0.124 to 0.179 when the rate of fertilizer application increased from 5 to 100 t/ha at one-time biosolids land application. The HI at long-term biosolids land application was also found 1.3 and 1.9 times greater than that of one-time land application at fertilizer application rates of 5 and 100 t/ha, respectively. Rice ingestion had more contribution to the HI than vegetable ingestion. Cd and Cu were also found to have more contribution to the health risk associated to vegetable and rice ingestion, respectively. Results indicated no potential risk to the human health even at long-term biosolids land application scenario at 100 t/ha fertilizer application rate.

  5. Health risk assessment of heavy metals through the consumption of food crops fertilized by biosolids: A probabilistic-based analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini Koupaie, E., E-mail: ehssan.hosseini.k@gmail.com; Eskicioglu, C., E-mail: cigdem.eskicioglu@ubc.ca

    2015-12-30

    Highlights: • No potential health risk of land application of the regional biosolids. • More realistic risk assessment via probabilistic approach than that of deterministic. • Increasing the total hazard index with increasing fertilizer land application rate. • Significant effect of long-term biosolids land application of hazard index. • Greater contribution of rice ingestion than vegetable ingestion on hazard index. - Abstract: The objective of this study was to perform a probabilistic risk analysis (PRA) to assess the health risk of Cadmium (Cd), Copper (Cu), and Zinc (Zn) through the consumption of food crops grown on farm lands fertilized by biosolids. The risk analysis was conducted using 8 years of historical heavy metal data (2005–2013) of the municipal biosolids generated by a nearby treatment facility considering one-time and long-term biosolids land application scenarios for a range of 5–100 t/ha fertilizer application rate. The 95th percentile of the hazard index (HI) increased from 0.124 to 0.179 when the rate of fertilizer application increased from 5 to 100 t/ha at one-time biosolids land application. The HI at long-term biosolids land application was also found 1.3 and 1.9 times greater than that of one-time land application at fertilizer application rates of 5 and 100 t/ha, respectively. Rice ingestion had more contribution to the HI than vegetable ingestion. Cd and Cu were also found to have more contribution to the health risk associated to vegetable and rice ingestion, respectively. Results indicated no potential risk to the human health even at long-term biosolids land application scenario at 100 t/ha fertilizer application rate.

  6. Applicability of PRISM PRA Methodology to the Level II Probabilistic Safety Analysis of KALIMER-600 (I) (Core Damage Event Tree Analysis Part)

    International Nuclear Information System (INIS)

    Park, S. Y.; Kim, T. W.; Ha, K. S.; Lee, B. Y.

    2009-03-01

    The Korea Atomic Energy Research Institute (KAERI) has been developing liquid metal reactor (LMR) design technologies under a National Nuclear R and D Program. Nevertheless, there is no experience of the PSA domestically for a fast reactor with the metal fuel. Therefore, the objective of this study is to establish the methodologies of risk assessment for the reference design of KALIMER-600 reactor. An applicability of the PSA of the PRISM plant to the KALIMER-600 has been studied. The study is confined to a core damage event tree analysis which is a part of a level 2 PSA. Assuming that the accident types, which can be developed from level 1 PSA, are same as the PRISM PRA, core damage categories are defined and core damage event trees are developed for the KALIMER-600 reactor. Fission product release fractions of the core damage categories and branch probabilities of the core damage event trees are referred from the PRISM PRA temporarily. Plant specific data will be used during the detail analysis

  7. Probabilistic and possibilistic approach for assessment of radiological risk due to organically bound and tissue free water tritium

    International Nuclear Information System (INIS)

    Dahiya, Sudhir; Hegde, A.G.; Joshi, M.L.; Verma, P.C.; Kushwaha, H.S.

    2006-01-01

    This study illustrates use of two approaches namely probabilistic using Monte Carlo simulation (MCS) and possibilistic using fuzzy α-cut (FAC) to estimate the radiological cancer risk to the population from ingestion of organically bound tritium (OBT) and tissue free water tritium (TFWT) from fish consumption from the Rana Pratap Sagar Lake (RPSL), Kota. Using FAC technique, radiological cancer risk rate (year -1 ) at A αl.0 level were 1.15E-08 and 1.50E-09 for OBT and TFWT respectively from fish ingestion pathway. The radiological cancer risk rate (year -1 ) using MCS approach at 50th percentile (median) level is 1.14E-08 and 1.49E-09 for OBT and HTO respectively from ingestion of fresh water fish. (author)

  8. Using Probabilistic Methods in Water Scarcity Assessments: A First Step Towards a Water Scarcity Risk Assessment Framework

    Science.gov (United States)

    Veldkamp, Ted; Wada, Yoshihide; Aerts, Jeroen; Ward, Phillip

    2016-01-01

    Water scarcity -driven by climate change, climate variability, and socioeconomic developments- is recognized as one of the most important global risks, both in terms of likelihood and impact. Whilst a wide range of studies have assessed the role of long term climate change and socioeconomic trends on global water scarcity, the impact of variability is less well understood. Moreover, the interactions between different forcing mechanisms, and their combined effect on changes in water scarcity conditions, are often neglected. Therefore, we provide a first step towards a framework for global water scarcity risk assessments, applying probabilistic methods to estimate water scarcity risks for different return periods under current and future conditions while using multiple climate and socioeconomic scenarios.

  9. Probabilistic design of aluminum sheet drawing for reduced risk of wrinkling and fracture

    International Nuclear Information System (INIS)

    Zhang Wenfeng; Shivpuri, Rajiv

    2009-01-01

    Often, sheet drawing processes are designed to provide the geometry of the final part, and then the process parameters such as blank dimensions, blank holder forces (BHFs), press strokes and interface friction are designed and controlled to provide the greatest drawability (largest depth of draw without violating the wrinkling and thinning constraints). The exclusion of inherent process variations in this design can often lead to process designs that are unreliable and uncontrollable. In this paper, a general multi-criteria design approach is presented to quantify the uncertainties and to incorporate them into the response surface method (RSM) based model so as to conduct probabilistic optimization. A surrogate RSM model of the process mechanics is generated using FEM-based high-fidelity models and design of experiments (DOEs), and a simple linear weighted approach is used to formulate the objective function or the quality index (QI). To demonstrate this approach, deep drawing of an aluminum Hishida part is analyzed. With the predetermined blank shape, tooling design and fixed drawing depth, a probabilistic design (PD) is successfully carried out to find the optimal combination of BHF and friction coefficient under variation of material properties. The results show that with the probabilistic approach, the QI improved by 42% over the traditional deterministic design (DD). It also shows that by further reducing the variation of friction coefficient to 2%, the QI will improve further to 98.97%

  10. A mediation model to explain decision making under conditions of risk among adolescents: the role of fluid intelligence and probabilistic reasoning.

    Science.gov (United States)

    Donati, Maria Anna; Panno, Angelo; Chiesi, Francesca; Primi, Caterina

    2014-01-01

    This study tested the mediating role of probabilistic reasoning ability in the relationship between fluid intelligence and advantageous decision making among adolescents in explicit situations of risk--that is, in contexts in which information on the choice options (gains, losses, and probabilities) were explicitly presented at the beginning of the task. Participants were 282 adolescents attending high school (77% males, mean age = 17.3 years). We first measured fluid intelligence and probabilistic reasoning ability. Then, to measure decision making under explicit conditions of risk, participants performed the Game of Dice Task, in which they have to decide among different alternatives that are explicitly linked to a specific amount of gain or loss and have obvious winning probabilities that are stable over time. Analyses showed a significant positive indirect effect of fluid intelligence on advantageous decision making through probabilistic reasoning ability that acted as a mediator. Specifically, fluid intelligence may enhance ability to reason in probabilistic terms, which in turn increases the likelihood of advantageous choices when adolescents are confronted with an explicit decisional context. Findings show that in experimental paradigm settings, adolescents are able to make advantageous decisions using cognitive abilities when faced with decisions under explicit risky conditions. This study suggests that interventions designed to promote probabilistic reasoning, for example by incrementing the mathematical prerequisites necessary to reason in probabilistic terms, may have a positive effect on adolescents' decision-making abilities.

  11. Computer aided probabilistic assessment of containment integrity

    International Nuclear Information System (INIS)

    Tsai, J.C.; Touchton, R.A.

    1984-01-01

    In the probabilistic risk assessment (PRA) of a nuclear power plant, there are three probability-based techniques which are widely used for event sequence frequency quantification (including nodal probability estimation). These three techniques are the event tree analysis, the fault tree analysis and the Bayesian approach for database development. In the barrier analysis for assessing radionuclide release to the environment in a PRA study, these techniques are employed to a greater extent in estimating conditions which could lead to failure of the fuel cladding and the reactor coolant system (RCS) pressure boundary, but to a lesser degree in the containment pressure boundary failure analysis. The main reason is that containment issues are currently still in a state of flux. In this paper, the authors describe briefly the computer programs currently used by the nuclear industry to do event tree analyses, fault tree analyses and the Bayesian update. The authors discuss how these computer aided probabilistic techniques might be adopted for failure analysis of the containment pressure boundary

  12. Mixture Of Probabilistic Factor Analyzers For Market Risk Measurement: Empirical Evidence From The Tunisian Foreign Exchange Market

    Directory of Open Access Journals (Sweden)

    Mohamed Nidhal Mosbahi

    2017-05-01

    Full Text Available In this paper, we propose a new approach for Basel-Compliant Value-at-Risk (VaR estimation in financial portfolio risk management, which combines Gaussian Mixture Models with probabilistic factor analysis models. This new mixed specification provides an alternative, compact, model to handle co-movements, heterogeneity and intra-frame correlations in financial data. This results in a model which concurrently performs clustering and dimensionality reduction, and can be considered as a reduced dimension mixture of probabilistic factor analyzers. For maximum likelihood estimation we have used an iterative approach based on the Alternating Expectation Conditional Maximization (AECM algorithm. Using a set of historical data in a rolling time window, from the Tunisian foreign exchange market, the model structure as well as its parameters are determined and estimated. Then, the fitted model combined with a modified Monte-Carlo simulation algorithm was used to predict the VaR. Through a Backtesting analysis, we found that this new specification exhibits a good fit to the data compared to other competing approaches, improves the accuracy of VaR prediction, possesses more flexibility, and can avoid serious violations when a financial crisis occurs.

  13. Risk assessment methods in radiotherapy: Probabilistic safety assessment (PSA); Los metodos de analisis de riesgo en radioterapia: Analisis Probabilistico de seguridad (APS)

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez Vera, M. L.; Perez Mulas, A.; Delgado, J. M.; Barrientos Ontero, M.; Somoano, F.; Alvarez Garcia, C.; Rodriguez Marti, M.

    2011-07-01

    The understanding of accidents that have occurred in radiotherapy and the lessons learned from them are very useful to prevent repetition, but there are other risks that have not been detected to date. With a view to identifying and preventing such risks, proactive methods successfully applied in other fields, such as probabilistic safety assessment (PSA), have been developed. (Author)

  14. Probabilistic approach for assessing infants' health risks due to ingestion of nanoscale silver released from consumer products.

    Science.gov (United States)

    Pang, Chengfang; Hristozov, Danail; Zabeo, Alex; Pizzol, Lisa; Tsang, Michael P; Sayre, Phil; Marcomini, Antonio

    2017-02-01

    Silver nanoparticles (n-Ag) are widely used in consumer products and many medical applications because of their unique antibacterial properties. Their use is raising concern about potential human exposures and health effects. Therefore, it is informative to assess the potential human health risks of n-Ag in order to ensure that nanotechnology-based consumer products are deployed in a safe and sustainable way. Even though toxicity studies clearly show the potential hazard of n-Ag, there have been few attempts to integrate hazard and exposure assessments to evaluate risks. The underlying reason for this is the difficulty in characterizing exposure and the lack of toxicity studies essential for human health risk assessment (HHRA). Such data gaps introduce significant uncertainty into the risk assessment process. This study uses probabilistic methods to assess the relative uncertainty and potential risks of n-Ag exposure to infants. In this paper, we estimate the risks for infants potentially exposed to n-Ag through drinking juice or milk from sippy cups or licking baby blankets containing n-Ag. We explicitly evaluate uncertainty and variability contained in available dose-response and exposure data in order to make the risk characterization process transparent. Our results showed that individual margin of exposures for oral exposure to sippy cups and baby blankets containing n-Ag exhibited minimal risk. Copyright © 2016. Published by Elsevier Ltd.

  15. Developing EHR-driven heart failure risk prediction models using CPXR(Log) with the probabilistic loss function.

    Science.gov (United States)

    Taslimitehrani, Vahid; Dong, Guozhu; Pereira, Naveen L; Panahiazar, Maryam; Pathak, Jyotishman

    2016-04-01

    Computerized survival prediction in healthcare identifying the risk of disease mortality, helps healthcare providers to effectively manage their patients by providing appropriate treatment options. In this study, we propose to apply a classification algorithm, Contrast Pattern Aided Logistic Regression (CPXR(Log)) with the probabilistic loss function, to develop and validate prognostic risk models to predict 1, 2, and 5year survival in heart failure (HF) using data from electronic health records (EHRs) at Mayo Clinic. The CPXR(Log) constructs a pattern aided logistic regression model defined by several patterns and corresponding local logistic regression models. One of the models generated by CPXR(Log) achieved an AUC and accuracy of 0.94 and 0.91, respectively, and significantly outperformed prognostic models reported in prior studies. Data extracted from EHRs allowed incorporation of patient co-morbidities into our models which helped improve the performance of the CPXR(Log) models (15.9% AUC improvement), although did not improve the accuracy of the models built by other classifiers. We also propose a probabilistic loss function to determine the large error and small error instances. The new loss function used in the algorithm outperforms other functions used in the previous studies by 1% improvement in the AUC. This study revealed that using EHR data to build prediction models can be very challenging using existing classification methods due to the high dimensionality and complexity of EHR data. The risk models developed by CPXR(Log) also reveal that HF is a highly heterogeneous disease, i.e., different subgroups of HF patients require different types of considerations with their diagnosis and treatment. Our risk models provided two valuable insights for application of predictive modeling techniques in biomedicine: Logistic risk models often make systematic prediction errors, and it is prudent to use subgroup based prediction models such as those given by CPXR

  16. Trait acclimation mitigates mortality risks of tropical canopy trees under global warming

    Directory of Open Access Journals (Sweden)

    Frank eSterck

    2016-05-01

    Full Text Available There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area to maximize carbon gain. We simulated tree carbon gain for temperatures (25-35ºC and ambient CO2 concentrations (390-800 ppm predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10-20% and the maximum tolerated temperature by up to 2ºC, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change.

  17. Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming

    Science.gov (United States)

    Sterck, Frank; Anten, Niels P. R.; Schieving, Feike; Zuidema, Pieter A.

    2016-01-01

    There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25–35°C) and ambient CO2 concentrations (390–800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10–20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change. PMID:27242814

  18. Development of a Risk-Based Probabilistic Performance-Assessment Method for Long-Term Cover Systems - 2nd Edition

    International Nuclear Information System (INIS)

    HO, CLIFFORD K.; ARNOLD, BILL W.; COCHRAN, JOHN R.; TAIRA, RANDAL Y.

    2002-01-01

    A probabilistic, risk-based performance-assessment methodology has been developed to assist designers, regulators, and stakeholders in the selection, design, and monitoring of long-term covers for contaminated subsurface sites. This report describes the method, the software tools that were developed, and an example that illustrates the probabilistic performance-assessment method using a repository site in Monticello, Utah. At the Monticello site, a long-term cover system is being used to isolate long-lived uranium mill tailings from the biosphere. Computer models were developed to simulate relevant features, events, and processes that include water flux through the cover, source-term release, vadose-zone transport, saturated-zone transport, gas transport, and exposure pathways. The component models were then integrated into a total-system performance-assessment model, and uncertainty distributions of important input parameters were constructed and sampled in a stochastic Monte Carlo analysis. Multiple realizations were simulated using the integrated model to produce cumulative distribution functions of the performance metrics, which were used to assess cover performance for both present- and long-term future conditions. Performance metrics for this study included the water percolation reaching the uranium mill tailings, radon gas flux at the surface, groundwater concentrations, and dose. Results from uncertainty analyses, sensitivity analyses, and alternative design comparisons are presented for each of the performance metrics. The benefits from this methodology include a quantification of uncertainty, the identification of parameters most important to performance (to prioritize site characterization and monitoring activities), and the ability to compare alternative designs using probabilistic evaluations of performance (for cost savings)

  19. Parametric estimation of P(X > Y) for normal distributions in the context of probabilistic environmental risk assessment.

    Science.gov (United States)

    Jacobs, Rianne; Bekker, Andriëtte A; van der Voet, Hilko; Ter Braak, Cajo J F

    2015-01-01

    Estimating the risk, P(X > Y), in probabilistic environmental risk assessment of nanoparticles is a problem when confronted by potentially small risks and small sample sizes of the exposure concentration X and/or the effect concentration Y. This is illustrated in the motivating case study of aquatic risk assessment of nano-Ag. A non-parametric estimator based on data alone is not sufficient as it is limited by sample size. In this paper, we investigate the maximum gain possible when making strong parametric assumptions as opposed to making no parametric assumptions at all. We compare maximum likelihood and Bayesian estimators with the non-parametric estimator and study the influence of sample size and risk on the (interval) estimators via simulation. We found that the parametric estimators enable us to estimate and bound the risk for smaller sample sizes and small risks. Also, the Bayesian estimator outperforms the maximum likelihood estimators in terms of coverage and interval lengths and is, therefore, preferred in our motivating case study.

  20. Response to Yellman and Murray's comment on 'The meaning of probability in probabilistic risk analysis'

    International Nuclear Information System (INIS)

    Watson, Stephen R.

    1995-01-01

    In their comment on a recent contribution of mine, [Watson, S., The meaning of probability in probabilistic safety analysis. Reliab. Engng and System Safety, 45 (1994) 261-269.] Yellman and Murray assert that (1) I argue in favour of a realistic interpretation of probability for PSAs; (2) that the only satisfactory philosophical theory of probability is the relative frequency theory; (3) that I mean the same thing by the words 'uncertainty' and 'probability'; (4) that my argument can easily lead to the belief that the output of PSAs are meaningless. I take issue with all these points, and in this response I set out my arguments

  1. Probabilistic safety assessment of WWER440 reactors prediction, quantification and management of the risk

    CERN Document Server

    Kovacs, Zoltan

    2014-01-01

    The aim of this book is to summarize probabilistic safety assessment (PSA) of nuclear power plants with WWER440 reactors and  demonstrate that the plants are safe enough for producing energy even in light of the Fukushima accident. The book examines level 1 and 2 full power, low power and shutdown PSA, and summarizes the author's experience gained during the last 35 years in this area. It provides useful examples taken from PSA training courses the author has lectured and organized by the International Atomic Energy Agency. Such training courses were organised in Argonne National Laboratory (

  2. Probabilistic risk assessment course documentation. Volume 3. System reliability and analysis techniques, Session A - reliability

    International Nuclear Information System (INIS)

    Lofgren, E.V.

    1985-08-01

    This course in System Reliability and Analysis Techniques focuses on the quantitative estimation of reliability at the systems level. Various methods are reviewed, but the structure provided by the fault tree method is used as the basis for system reliability estimates. The principles of fault tree analysis are briefly reviewed. Contributors to system unreliability and unavailability are reviewed, models are given for quantitative evaluation, and the requirements for both generic and plant-specific data are discussed. Also covered are issues of quantifying component faults that relate to the systems context in which the components are embedded. All reliability terms are carefully defined. 44 figs., 22 tabs

  3. Phytoextraction of risk elements by willow and poplar trees.

    Science.gov (United States)

    Kacálková, Lada; Tlustoš, Pavel; Száková, Jiřina

    2015-01-01

    To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4-2.0 mg Cd.kg(-1), 78-313 mg Zn.kg(-1), 21.3-118 mg Cu.kg(-1)). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg(-1), 909 mg Zn.kg(-1), and 17.7 mg Cu.kg(-1)) compared to Populus clones (maximum 2.06 mg Cd.kg(-1), 463 mg Zn.kg(-1), and 11.8 mg Cu.kg(-1)). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.

  4. Reduced activation in the ventral striatum during probabilistic decision-making in patients in an at-risk mental state

    Science.gov (United States)

    Rausch, Franziska; Mier, Daniela; Eifler, Sarah; Fenske, Sabrina; Schirmbeck, Frederike; Englisch, Susanne; Schilling, Claudia; Meyer-Lindenberg, Andreas; Kirsch, Peter; Zink, Mathias

    2015-01-01

    Background Patients with schizophrenia display metacognitive impairments, such as hasty decision-making during probabilistic reasoning — the “jumping to conclusion” bias (JTC). Our recent fMRI study revealed reduced activations in the right ventral striatum (VS) and the ventral tegmental area (VTA) to be associated with decision-making in patients with schizophrenia. It is unclear whether these functional alterations occur in the at-risk mental state (ARMS). Methods We administered the classical beads task and fMRI among ARMS patients and healthy controls matched for age, sex, education and premorbid verbal intelligence. None of the ARMS patients was treated with antipsychotics. Both tasks request probabilistic decisions after a variable amount of stimuli. We evaluated activation during decision-making under certainty versus uncertainty and the process of final decision-making. Results We included 24 AMRS patients and 24 controls in our study. Compared with controls, ARMS patients tended to draw fewer beads and showed significantly more JTC bias in the classical beads task, mirroring findings in patients with schizophrenia. During fMRI, ARMS patients did not demonstrate JTC bias on the behavioural level, but showed a significant hypoactivation in the right VS during the decision stage. Limitations Owing to the cross-sectional design of the study, results are constrained to a better insight into the neurobiology of risk constellations, but not pre-psychotic stages. Nine of the ARMS patients were treated with antidepressants and/or lorazepam. Conclusion As in patients with schizophrenia, a striatal hypoactivation was found in ARMS patients. Confounding effects of antipsychotic medication can be excluded. Our findings indicate that error prediction signalling and reward anticipation may be linked to striatal dysfunction during prodromal stages and should be examined for their utility in predicting transition risk. PMID:25622039

  5. Endosulfan and its metabolite, endosulfan sulfate, in freshwater ecosystems of South Florida: a probabilistic aquatic ecological risk assessment.

    Science.gov (United States)

    Rand, Gary M; Carriger, John F; Gardinali, Piero R; Castro, Joffre

    2010-06-01

    Endosulfan is an insecticide-acaricide used in South Florida and is one of the remaining organochlorine insecticides registered under the Federal Insecticide Fungicide and Rodenticide Act by the U.S.EPA. The technical grade material consists of two isomers (alpha-, beta-) and the main environmental metabolite in water, sediment and tissue is endosulfan sulfate through oxidation. A comprehensive probabilistic aquatic ecological risk assessment was conducted to determine the potential risks of existing exposures to endosulfan and endosulfan sulfate in freshwaters of South Florida based on historical data (1992-2007). The assessment included hazard assessment (Tier 1) followed by probabilistic risk assessment (Tier 2). Tier 1 compared actual measured concentrations in surface freshwaters of 47 sites in South Florida from historical data to U.S.EPA numerical water quality criteria. Based on results of Tier 1, Tier 2 focused on the acute and chronic risks of endosulfan at nine sites by comparing distributions of surface water exposure concentrations of endosulfan [i.e., for total endosulfan (summation of concentrations of alpha- and beta-isomers plus the sulfate), alpha- plus beta-endosulfan, and endosulfan sulfate (alone)] with distributions of species effects from laboratory toxicity data. In Tier 2 the distribution of total endosulfan in fish tissue (whole body) from South Florida freshwaters was also used to determine the probability of exceeding a distribution of whole body residues of endosulfan producing mortality (critical lethal residues). Tier 1 showed the majority of endosulfan water quality violations in South Florida were at locations S-178 followed by S-177 in the C-111 system (southeastern boundary of Everglades National Park (ENP)). Nine surface water sampling sites were chosen for Tier 2. Tier 2 showed the highest potentially affected fraction of toxicity values (>10%) by the estimated 90th centile exposure concentration (total endosulfan) was at S-178

  6. Probabilistic Structural Analysis Program

    Science.gov (United States)

    Pai, Shantaram S.; Chamis, Christos C.; Murthy, Pappu L. N.; Stefko, George L.; Riha, David S.; Thacker, Ben H.; Nagpal, Vinod K.; Mital, Subodh K.

    2010-01-01

    NASA/NESSUS 6.2c is a general-purpose, probabilistic analysis program that computes probability of failure and probabilistic sensitivity measures of engineered systems. Because NASA/NESSUS uses highly computationally efficient and accurate analysis techniques, probabilistic solutions can be obtained even for extremely large and complex models. Once the probabilistic response is quantified, the results can be used to support risk-informed decisions regarding reliability for safety-critical and one-of-a-kind systems, as well as for maintaining a level of quality while reducing manufacturing costs for larger-quantity products. NASA/NESSUS has been successfully applied to a diverse range of problems in aerospace, gas turbine engines, biomechanics, pipelines, defense, weaponry, and infrastructure. This program combines state-of-the-art probabilistic algorithms with general-purpose structural analysis and lifting methods to compute the probabilistic response and reliability of engineered structures. Uncertainties in load, material properties, geometry, boundary conditions, and initial conditions can be simulated. The structural analysis methods include non-linear finite-element methods, heat-transfer analysis, polymer/ceramic matrix composite analysis, monolithic (conventional metallic) materials life-prediction methodologies, boundary element methods, and user-written subroutines. Several probabilistic algorithms are available such as the advanced mean value method and the adaptive importance sampling method. NASA/NESSUS 6.2c is structured in a modular format with 15 elements.

  7. Review of the severe accident risk reduction program (SARRP) containment event trees

    International Nuclear Information System (INIS)

    1986-05-01

    A part of the Severe Accident Risk Reduction Program, researchers at Sandia National Laboratories have constructed a group of containment event trees to be used in the analysis of key accident sequences for light water reactors (LWR) during postulated severe accidents. The ultimate goal of the program is to provide to the NRC staff a current assessment of the risk from severe reactor accidents for a group of five light water reactors. This review specifically focuses on the development and construction of the containment event trees and the results for containment failure probability, modes and timing. The report first gives the background on the program, the review criteria, and a summary of the observations, findings and recommendations. secondly, the individual reviews of each committee member on the event trees is presented. Finally, a review is provided on the computer model used to construct and evaluate the event trees

  8. German risk study, phase B: Results of the event tree and fault tree analysis

    International Nuclear Information System (INIS)

    Hoertner, H.

    1987-01-01

    This paper deals with the most important results of the level 1 analysis performed in Phase B of the German Risk Study and with the insights it provided. The question is raised, to what extent the results of risk analyses can be verified against available operating experience. In this respect the results of the German Risk Study will be compared with the estimates of the German Precursor Study. Finally, the results of the German investigations are briefly compared with the results of recent U.S. risk analyses. (orig.)

  9. Application of probabilistic methods to accident analysis at waste management facilities

    International Nuclear Information System (INIS)

    Banz, I.

    1986-01-01

    Probabilistic risk assessment is a technique used to systematically analyze complex technical systems, such as nuclear waste management facilities, in order to identify and measure their public health, environmental, and economic risks. Probabilistic techniques have been utilized at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, to evaluate the probability of a catastrophic waste hoist accident. A probability model was developed to represent the hoisting system, and fault trees were constructed to identify potential sequences of events that could result in a hoist accident. Quantification of the fault trees using statistics compiled by the Mine Safety and Health Administration (MSHA) indicated that the annual probability of a catastrophic hoist accident at WIPP is less than one in 60 million. This result allowed classification of a catastrophic hoist accident as ''not credible'' at WIPP per DOE definition. Potential uses of probabilistic techniques at other waste management facilities are discussed

  10. Health risk assessment of heavy metals through the consumption of food crops fertilized by biosolids: A probabilistic-based analysis.

    Science.gov (United States)

    Hosseini Koupaie, E; Eskicioglu, C

    2015-12-30

    The objective of this study was to perform a probabilistic risk analysis (PRA) to assess the health risk of Cadmium (Cd), Copper (Cu), and Zinc (Zn) through the consumption of food crops grown on farm lands fertilized by biosolids. The risk analysis was conducted using 8 years of historical heavy metal data (2005-2013) of the municipal biosolids generated by a nearby treatment facility considering one-time and long-term biosolids land application scenarios for a range of 5-100 t/ha fertilizer application rate. The 95th percentile of the hazard index (HI) increased from 0.124 to 0.179 when the rate of fertilizer application increased from 5 to 100 t/ha at one-time biosolids land application. The HI at long-term biosolids land application was also found 1.3 and 1.9 times greater than that of one-time land application at fertilizer application rates of 5 and 100 t/ha, respectively. Rice ingestion had more contribution to the HI than vegetable ingestion. Cd and Cu were also found to have more contribution to the health risk associated to vegetable and rice ingestion, respectively. Results indicated no potential risk to the human health even at long-term biosolids land application scenario at 100 t/ha fertilizer application rate. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Generalized Fragility Relationships with Local Site Conditions for Probabilistic Performance-based Seismic Risk Assessment of Bridge Inventories

    Directory of Open Access Journals (Sweden)

    Sivathayalan S.

    2012-01-01

    Full Text Available The current practice of detailed seismic risk assessment cannot be easily applied to all the bridges in a large transportation networks due to limited resources. This paper presents a new approach for seismic risk assessment of large bridge inventories in a city or national bridge network based on the framework of probabilistic performance based seismic risk assessment. To account for the influences of local site effects, a procedure to generate site-specific hazard curves that includes seismic hazard microzonation information has been developed for seismic risk assessment of bridge inventories. Simulated ground motions compatible with the site specific seismic hazard are used as input excitations in nonlinear time history analysis of representative bridges for calibration. A normalizing procedure to obtain generalized fragility relationships in terms of structural characteristic parameters of bridge span and size and longitudinal and transverse reinforcement ratios is presented. The seismic risk of bridges in a large inventory can then be easily evaluated using the normalized fragility relationships without the requirement of carrying out detailed nonlinear time history analysis.

  12. Predicting climate change extirpation risk for central and southern Appalachian forest tree species

    Science.gov (United States)

    Kevin M. Potter; William W. Hargrove; Frank H. Koch

    2010-01-01

    Climate change will likely pose a severe threat to the viability of certain forest tree species, which will be forced either to adapt to new conditions or to shift to more favorable environments if they are to survive. Several forest tree species of the central and southern Appalachians may be at particular risk, since they occur in limited high-elevation ranges and/or...

  13. Risk Factors of Falls in Community-Dwelling Older Adults: Logistic Regression Tree Analysis

    Science.gov (United States)

    Yamashita, Takashi; Noe, Douglas A.; Bailer, A. John

    2012-01-01

    Purpose of the Study: A novel logistic regression tree-based method was applied to identify fall risk factors and possible interaction effects of those risk factors. Design and Methods: A nationally representative sample of American older adults aged 65 years and older (N = 9,592) in the Health and Retirement Study 2004 and 2006 modules was used.…

  14. PRA Procedures Guide: a guide to the performance of probabilistic risk assessments for nuclear power plants. Final report, Volume 1 - Chapters 1-8

    International Nuclear Information System (INIS)

    1983-01-01

    This document, the Probabilistic Risk Assessment (PRA) Procedures Guide, is intended to provide an overview of the risk-assessment field as it exists today and to identify acceptable techniques for the systematic assessment of the risk from nuclear power plants. Topics discussed include: organization of PRA; accident-sequence definition and system modeling; human-reliability analysis; data-base development; accident-sequence quantification; physical processes of core-melt accidents; and radionuclide release and transport

  15. Millstone 3 risk evaluation report. An overall review and evaluation of the Millstone Unit 3 probabilistic safety study

    International Nuclear Information System (INIS)

    Kelly, G.; Barrett, R.; Buslik, A.

    1986-06-01

    In 1981, the US Nuclear Regulatory Commission (NRC) requested Northeast Utilities to perform a design-specific probabilistic safety study (PSS) for Millstone Nuclear Power Station, Unit No. 3 (Millstone 3). In 1983, Northeast Utilities submitted the Millstone 3 Probabilistic Safety Study for review by the NRC staff. The NRC staff prepared the Millstone 3 Risk Evaluation Report, which discusses the findings regarding the PSS. The PSS estimates that the mean annual core damage frequency due to internal and external events is 5 x 10 -5 and 2 x 10 -5 , respectively. The NRC staff's Risk Evaluation Report estimates that the mean annual core damage frequency is about 2 x 10 -4 for internal events and lies between 1 x 10 -5 and 2 x 10 -4 for external events. The NRC staff estimates that station blackout dominates internal and external event core damage frequencies. The staff recommends that Northeast Utilities perform an engineering analysis on upgrading the diesel generator lube oil cooler anchorage system and on adding a manually operated, AC-independent containment spray system. The staff also recommends that Northeast Utilities prepare two emergency procedures (loss of room cooling and relay chatter due to an earthquake) to help reduce uncertainties. (Subsequent to the completion of this document, Northeast Utilities and the NRC staff have continued a dialogue regarding station blackout from events other than earthquakes. Both Northeast Utilities and the staff have performed additional evaluations, which have drawn their results closer together. Final requirements, if any, for the prevention or mitigation of station blackout from events other than earthquakes have not yet been determined.) 26 refs., 16 tabs

  16. Probabilistic risk assessment for CO2 storage in geological forma