Risk-Based Approach - Consequence Analysis

The main purpose of the Consequence Analysis phase to be developed during the execution of a risk-based quantitative assessment is to answer the following question: “Which are the impacts of identified hazardous scenarios?” This step is critical for estimating reliable and accurate effects / consequences from Loss of Containment scenarios (LOCs), avoiding unrealistic results that would directly impact on the decision-making process. Additionally, it is essential that Consequence Analysis includes the identification and quantification of ALL potential outcomes that a hazardous release may cause. Event Tree Analysis (ETA) methodology is a valuable tool for identifying all these potential outcomes.

The present paper introduces the consequence analysis step by providing guidance on consequence modeling (i.e., source term characterization, dispersion of harmful gases/vapors, fires and explosions) and criteria for event trees development.

Introduction

Consequence Analysis is formally defined as the study intended to determine the extent of consequences and effects from a given set of episodic events. An episodic event is an undesired incident or event with potentially serious consequences that occurs without warning and/or over a relatively short period of time. For example, tank and vessel failures, automobile crashes, fires, explosions and earthquakes are all considered events.

Consequences are usually stated in an expected number of injuries, casualties or in some cases, exposure to certain levels of energy or concentrations of substances. Consequence analysis results are estimates of the statistically‐expected exposure of the target population to the hazard of interest and the safety/health effects related to that level of exposure. These estimates customarily use average meteorological conditions and population distribution and may include mitigating factors, such as evacuation and sheltering. Therefore, a substantial empirical database exists on the effects of fires and explosions regarding structures and equipment.

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