Risk assessment scenario selection

The substances evaluated for risk assessment were selected on the basis of potential concerns, areas of use, and volumes sold. Four priority lists were established.42 The risk assessments looked at the environmental and human health aspects of a chemical s use under a variety of scenarios. For each scenario, one of the following three conclusions was drawn 43... 

On the other hand, in part II of this volume, a set of case studies are introduced. The application of the selected methodologies inside each one of the foresaid disciplines (e.g., risk assessment, life cycle assessment) to specific cases and countries is presented here. The results of such application are discussed as well as their reliability. Toxicological studies in Italy, risk assessment of electronic waste in China, or disposal of bearing lamps in India are some examples of selected scenarios. 

Figure 23-1 shows the hazards identification and risk assessment procedure. The procedure begins with a complete description of the process. This includes detailed PFD and P I diagrams, complete specifications on all equipment, maintenance records, operating procedures, and so forth. A hazard identification procedure is then selected (see Haz-ard Analysis subsection) to identify the hazards and their nature. This is followed by identification of all potential event sequences and potential incidents (scenarios) that can result in loss of control of energy or material. Next is an evaluation of both the consequences and the probability. The consequences are estimated by using source models (to describe the... 

From the standpoint of practical regulatory assessment, it would be desirable to reach a consensus on the selection of methods for routine use for pesticide risk assessments while recognizing that there may be scientific reasons for preferring alternative methods in particnlar cases. Such a consensus does not yet exist. Further case studies are required, covering a range of contrasting pesticides and scenarios, to evaluate the available methods more fully. While a consensus is lacking, it is important that reports on probabilistic assessments clearly explain how their methods work and why they were selected. 

One of the most critical steps in establishing the appropriate role and settings of the individual safety systems will be the risk assessment analysis, the process in which engineers consider and analyse all possible conditions in order to select the most appropriate safety concept, which ensures safe operation under all possible circumstances and scenarios (see Section 13.4). 

In implementing the risk-based waste classification system developed in this Report, the selection of exposure scenarios appropriate to waste disposal is an important technical issue that must be addressed. NCRP believes that scenarios for inadvertent intrusion into near-surface disposal facilities are appropriate in classifying waste for purposes of disposal and, further, that scenarios involving permanent occupancy of disposal sites after loss of institutional control would be appropriate (see Section 6.1.3) such scenarios are commonly used in regulating near-surface disposal of low-level radioactive waste and in risk assessments at hazardous waste sites subject to remediation under CERCLA. 

Figure 9.4 Risk assessment for an aquatic environment based on a probabilistic procedure into which the concept of varying sensitivity in multispecies communities is incorporated (Nendza, Volmer and Klein, 1990). Exposure and effects are determined separately from experimental or, if not available, QSAR data. Physico-chemical data and information on bioaccumulation and biotransformation are the input for computer simulations of transport and distribution processes that estimate the concentrations of a potential contaminant in a selected river scenario, using, for example, the EXAMS model (Bums, Cline and Lassiter, 1982). For the effects assessment, the log-normal sensitivity distribution is calculated from ecotoxicological data and the effective concentrations for the most sensitive species are determined. The exposure concentrations and toxicity data are then compared by analysis of variance to give a measure of risk for the environment. Modified from Nendza, Volmer and Klein (1990) with kind permission from Kluwer Academic Publishers, Dordrecht.

The process of risk assessment begins with a selection of events representing disruption of gas pipeline and a natural gas leak. A set of scenarios of possible gas pipeline damages and following physical effects... 

Another challenge for organizations responsible for the risk assessment of intentional acts is how to include the relevant range of possible scenarios of intentional acts. The selection of scenarios is often heavily influenced by the last incident or the current understanding of the security landscape (Karlsen lore, 2013). After the terrorist attack in Norway 22/7 2001 and the In Amenas attack the commission reports concluded that the people responsible for security had not envisioned the scenarios that materialized. 

By means of an analysis against several DRM-related criteria, the DRM project has selected TOPAZ from a list of candidate DRM methods as a suitable solution for the safety risk assessment of ATM operational scenarios. TOPAZ is an agent-based DRM method that uses Monte Carlo simulations and uncertainty evaluations to analyse the safety risk of air traffic operations up to the level of collisions. The project produced guidelines for the application of this method in SESAR context, and applied the method to a SESAR Test Case of Land vs Line-up Conflicting ATC Clearances. 

An accident scenario is one of many specific situations that might evolve at the end of an accident sequence. Here, we have considered eight accident scenarios of Vapour Cloud Explosion (VCE), Boiling Liquid Expanding Vapour Explosion (BLEVE) and toxic release events originating from different hazardous industries located in the study area (Fig. 2). The as reference scenarios were selected with an inherent assumption of having the potential of causing Maximum Credible Loss (MCL) (Khan and Abbasi, 2002) as identified on the basis of facility level risk assessment (Table 1). 

Once the possible scenarios are selected, the next step in QRA requires the estimation of their frequencies. However a review of several industry-specific risk assessment reports of MAH establishments in Haldia point to an absence of any definitive estimate of failures that could result in a major accident with potential offsite consequences. Even at a broader level, no such failure frequency statistics is also known to exist in India. As an alternative, we have used generic failure-frequency databases, such as the TNO s Purple Book, the HSE s Failure Rate and Event Database (FRED) etc. The assigned frequency for the above mentioned scenarios from the available HSE s Failure Rate and Event Database is presented in Tablel. 

In the previous section, we investigated main sources of uncertainty in the probabilistic fire load procedure. There are many parameters to be used for the risk assessment. Each parameter is uncertain and can be expressed by probability distributions. For instance, when leak size distributions are represented by uniform distribution with specific ranges. Representative values are randomly selected in accordance with their distributions. These sets of values compose the sets of representative scenarios and are also used as input for simulating time-dependent leak rate profile and radiation intensity of fire. 

The project SEMB analysed the threat potential which lEMI (intentional electromagnetic interference) poses to Cl in Austria. The non-classified study analysed freely available literature on respective events, available lEMI weapons and their cost, and the state of the art with respect to technical protective measures. In addition, an appropriate risk analysis method was developed, which was intended to support Cl providers in judging where in the infrastructure to prioritize improvements of protective measures. This paper describes the selection and adaptation of the risk analysis method, explains the effort-saving way of data capturing and shows how the risk assessment results are presented. Finally, some of the results are shown, which were obtained in the verification of the method on the basis of three vehicle convoy scenarios. The conclusions comprise a judgment on the benefit of the method and an outlook on further research planned. 

The next step is impact prediction that requires detailed quantitative information about the sources of risk agents, exposure models, the receptors and possible changes in the state of these receptors caused by the defined agents. If the CLL concept was selected for assessment ecosystem effects it should firstly be utilized for impact baseline studies or assessing the do-nothing scenario. In this context CLL calculation includes the following steps (Bashkin, 2002) ... 

In this chapter, after introducing some definitions, a systematic assessment procedure, based on the cooling failure scenario, is outlined. This scenario formulates six key questions that comprise the database for the assessment. Relying on the characteristic temperature levels arising from the scenario, criticality classes are defined. They provide a selection of the required risk-reducing... 

EPA has recently released the first volume containing the results of an effort to obtain the most reliable possible values for a variety of exposure parameters. This document, The Exposure Factors Handbook (4), covers 12 commonly considered exposure scenarios. The exposure assessment module of Risk Assistant incorporates the algorithms for calculating exposures under each of these scenarios, for all environmental media for which the scenario is applicable. The user can select any or all of the exposure scenarios that are relevant to the environmental media that are contaminated at a site. Where more than one contaminated medium could influence a scenario, the user has the option of selecting the most appropriate medium. 

Screening with QUICK RISK. For users who need to set assessment priorities for a large number of sites, QUICK RISK provides a means to accomplish the task rapidly. The user need only specify probable contaminant concentrations in environmental media, and QUICK RISK applies appropriately conservative exposure assumptions. Although only one scenario is considered for any medium, further detail is probably not needed for the initial selection of site priorities, and QUICK RISK provides for consistent evaluation. Assuming that concentration estimates were available, several hundred sites could be evaluated in a single day. 

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