assess probability and seriousness of each risk

Assessing Probability and Seriousness of Each Risk: A Crucial Step in Probabilistic Risk Assessment

Probabilistic risk assessment (PRA) is a systematic and comprehensive methodology used to evaluate risks associated with complex engineered technological entities, such as airliners or nuclear power plants, or the effects of stressors on the environment. In addition to traditional methods, PRA requires specialized analysis tools like human reliability analysis (HRA) and common-cause-failure analysis (CCF). Two common techniques employed in PRA are event tree analysis and fault tree analysis.

A critical aspect of PRA is assessing the probability and seriousness of each risk. This involves answering three basic questions:

1. How likely to occur are these undesirable consequences, or what are their probabilities or frequencies?

2. What and how severe are the potential detriments, or the adverse consequences that the technological entity (or ecological system) may be subjected to as a result of the occurrence of the initiator?

3. What can go wrong with the studied technological entity or stressor, or what are the initiators or initiating events (undesirable starting events) that lead to adverse consequence(s)?

To address these questions, PRA evaluates the likelihood and magnitude of each risk. This is achieved by considering both the probability of occurrence and the severity of the possible adverse consequences. In a PRA, risk is characterized by two quantities: the likelihood (probability) of occurrence of each consequence and the magnitude (severity) of the possible adverse consequence(s).

The total risk is defined as the expected loss, which is the sum of the products of the consequences multiplied by their probabilities. This means that the risk assessment considers not only the probability of occurrence but also the severity of the potential detriments.

In PRA, it is essential to consider the spectrum of risks across classes of events, including rare but high-consequence events. These events can dominate the overall risk and are typically controlled in licensing processes. Moreover, risk assessments are sensitive to assumptions about the rarity of such events.

Ultimately, assessing the probability and seriousness of each risk is a crucial step in PRA, as it enables the evaluation of potential detriments and the identification of measures to mitigate or eliminate them. By considering both the likelihood and magnitude of each risk, PRA provides a comprehensive framework for managing risks associated with complex technological entities and environmental stressors.

Assess probability and seriousness of each risk