Sarah Bonvicini

Risk analysis of hazardous materials transportation: evaluating uncertainty by means of fuzzy logic

This paper provides an application of fuzzy logic to the risk assessment of the transport of hazardous materials by road and pipeline in order to evaluate the uncertainties affecting both individual and societal risk estimates. In evaluating uncertainty by fuzzy logic, the uncertain input parameters are described by fuzzy numbers and calculations are performed using fuzzy arithmetic; the outputs will also be fuzzy numbers. This work is an attempt to justify some of the questions the use of fuzzy logic in the field of risk analysis stimulates. This study provides, first of all, a condensed description of the fundamentals of the mathematical procedures which perform the risk measures calculations. Then, some basic concepts about fuzzy logic and fuzzy arithmetic are introduced, after which an explanation on how the uncertain input data can be represented by fuzzy numbers is made. Finally, test results of combined uncertainty and sensitivity analysis in the risk evaluation of a toxic gas release are presented and extensively discussed, in order to show which effect each uncertain input has on the output uncertainty.

Development of a framework for the risk assessment of Na-Tech accidental events

Abstract Natural events impacting on chemical and process plants may cause severe accidents, triggering the release of relevant quantities of hazardous substances. The present study focused on the development of the tools needed to build up a general framework allowing the extension of quantitative risk assessment procedure to include the analysis of the industrial accidents caused by natural events. Specific methods and models were developed to allow the quantitative assessment of risk caused by two categories of “Na-Tech” accidents: accidents triggered by earthquakes and accidents triggered by floods. The approach allows the identification of the different damage modes expected for process equipment and of the accidental scenarios that may be triggered. The damage models developed allow the calculation of the damage probability of equipment items due to the natural events. A specific methodology was issued to take into account the consequences of the possible contemporary failure of several process units due to the impact of the natural event. The procedure allows the calculation of the overall individual and societal risk indexes including the multiple-failure scenarios caused by the impact of natural events. The overall methodology was applied to the analysis of specific case studies.

New detailed numerical procedures for calculating risk measures in hazardous materials transportation

Abstract Historical evidence has shown that accidents due to hazardous material releases during transportation can lead to consequences as heavy as those created by releases occurring at fixed plants and therefore quantified risk analysis has to be performed for transportation networks too. The calculation of risk measures, like individual and societal risk, due to transportation networks has considerable complexity and needs a great computational effort. For this application two new detailed procedures, named T rans I n and T rans S oc , for the evaluation of individual and societal risk, have been introduced, which can take into account, at the same time, different transportation modes, hazardous materials, meteorological conditions and seasonal situations, a non uniform wind probability density distribution and an accurate description of the indoor and outdoor population both on-route and off-route. In this paper, firstly, the arrangement of the input data is explained, and then the fundamentals of the methodology are described, often focusing attention on mathematical ways to perform operations saving accuracy without increasing calculation time.

HazMat transport through Messina town: from risk analysis suggestions for improving territorial safety

Abstract In this paper, after briefly outlining the main features of TRAT2, its application to the land transport of dangerous goods through the downtown of Messina is outlined. Owing to its particular location, there is a large flow of hazardous materials through the city of Messina. Many of these substances come from the greatest industrialised areas of Sicily. Goods reach the town by rail or road, and cross the Straits by ship. A complete inventory of dangerous substances, detailed in the paper, was the basis of a complete risk analysis, whose results, obtained by means of the TRAT2 software, have been analysed and discussed. From both individual risk distribution and societal risk curves the importance of parameters has been obtained and this has suggested measures to improve the safety of the urban area.

The Description of Population Vulnerability in Quantitative Risk Analysis

The description of the distribution of population in the potential impact areas of accident scenarios is of utmost importance for the assessment of the final consequences of potential accidents. Vulnerability centers (i.e., sites where the simultaneous presence of a relevant number of persons in a narrow area is anticipated) may play an important role in this framework. In this study a method for the correct and detailed description of offsite target population in potential impact areas of major accidents is developed. The method is aimed at supporting quantitative risk analysis studies, emergency planning, and land-use planning. An approach is suggested to define the population categories that should be taken into account and to provide criteria for indoor and outdoor population distribution in vulnerability centers. Case studies are also provided to understand the outcomes and the potentialities of the methodology.

Threshold-Based Approach

Escalation thresholds are widely used as a baseline approach to the assessment of the hazard posed by domino scenarios. These should be intended as conservative values of physical effects (thermal radiation, maximum overpressure, etc.) below which the escalation is deemed not credible. This chapter deals with this preliminary approach to domino hazard assessment, revising the values provided in the literature for escalation thresholds and providing suggested values based on recent results obtained in the revision of past accident data and in the modeling of equipment damage.

Quantitative assessment of risk due to major accidents triggered by lightning

Lightning is one of the most frequent accident causes in storage tank parks, and accidents triggered by lightning are the most frequent Natech event reported in past-accident analysis. In the present study, a methodology for the inclusion of accidents triggered by lightning in Quantitative Risk Assessment (QRA) was developed. A model for the assessment of lightning impact probability on process equipment and specific equipment vulnerability models were coupled to dedicated event trees, allowing the quantification of risk indexes. The methodology developed also allows the assessment of risk reduction by the implementation of different lightning protection strategies. The results obtained represent a step forward towards the introduction of risk-based design of lightning protection systems.

ARIPAR-GIS, TRAT, OPTIPATH, EHHRA-GIS

From time in all industrialised countries attention is focused on the risks due to major accidents in storage, production and transportation of dangerous chemicals. In Italy too, and specifically at the University of Bologna, relevant work has been performed in the field of risk analysis. The chief aim of the researches done in the past years has been the development of detailed techniques for the calculation of specific risk measures, implemented in user-friendly software codes. In this paper the main features of these tools will be presented, particularly highlighting the application field of each of them and the support they can give to decision-makers in risk management.

Risk analysis of the transportation of hazardous materials: An application of the TRAT2 software to Messina

Publisher Summary Safety themes associated with the transportation of hazardous materials is considered to be as important as the study of risk problems connected with fixed installations. Hazardous materials releases during transport may occur in areas that are not sufficiently controlled or protected such as zones of high population density or of natural and historical beauty. Risk analysis should address both fixed installations and transportation networks, thus, obtaining a complete area risk evaluation that represents the basis on which decision makers will establish the criteria for risk management, risk control, and land-use planning. The development of a methodology to study problems associated with the transportation of hazardous materials must be considered a very important target for risk analysis. For this scope, an innovative procedure has been created that represents the framework of the TRAT2 software. In this software, a user-friendly Windows interface allows the risk analyst to introduce, while communicating with the database, all the input data necessary to describe the case in examination. This chapter briefly outlines the main features of TRAT2 and its application to the land transport of dangerous goods through the downtown of Messina. The future improvements of TRAT2 and major research developments in hazardous materials transportation risk analysis are also discussed.

Impact of Hydrogeological Uncertainty on Estimation of Environmental Risks Posed by Hydrocarbon Transportation Networks

Ubiquitous hydrogeological uncertainty undermines the veracity of quantitative predictions of soil and groundwater contamination due to accidental hydrocarbon spills from onshore pipelines. Such predictions, therefore, must be accompanied by quantification of predictive uncertainty, especially when they are used for environmental risk assessment. We quantify the impact of parametric uncertainty on temporal evolution of two key risk indices, volumes of unsaturated and saturated soil contaminated by a surface spill of light non-aqueous-phase liquids. This is accomplished by treating the relevant uncertain parameters as random variables and deploying two alternative probabilistic models to estimate their effect on predictive uncertainty. A physics-based model is solved with a stochastic collocation method and is supplemented by a global sensitivity analysis. A second model represents the quantities of interest as polynomials of random inputs and has a virtually negligible computational cost, which enables one to explore any number of risk-related contamination scenarios. For a typical oil-spill scenario, our method can be used to identify key flow and transport parameters affecting the risk indices, to elucidate texture-dependent behavior of different soils, and to evaluate, with a degree of confidence specified by the decision-maker, the extent of contamination and the correspondent remediation costs.