Level 1: Analysis of the probability of occurrence of certain critical events in a nuclear
power plant.
Level 2: Analysis of the probability of occurrence and the consequences of certain
critical events in a nuclear power plant.
Level 3: As for level 2, but in addition including the effect of humans and the loss of
human lives when this might occur.
Whether this classification is also useful in other application areas can be discussed, but the
idea of classifying the levels of risk analysis is under any circumstances a useful one.
4.6 Techniques for System Identification
The identification of exposures, events and scenarios which potentially may lead to
consequences must consider all possible adverse consequences for:
Personnel
Environment
Economy.
This aim is hardly realizable in practice but should be attempted to the furthest extent in
accordance with all the existing knowledge. Scenario identification is therefore in essence
concerned about ensuring that all existing knowledge is identified and taken into account.
A scenario is typically referred to as an event or a sequence of events leading to consequences
for a considered engineered facility or activity. As outlined in Section 4.4 failures may thus
represent a diversity of events such as the collapse of a building structure, the flooding of a
construction site and an explosion in a tunnel. In Figures 4.10-4.13 a number of different
types of “failures” are shown.