the activity denoted “assess risk” the quantified risks are traditionally compared with criteria
on risk acceptability. If risks are acceptable no actions are in principle required. However, it
should be investigated if options may be identified which would lead to a better fulfilment of
the preferences of the decision maker. On the other hand if risk acceptance criteria are not
fulfilled an analysis of the different options for treatment of risks is necessary. This activity is
referred to in the figure as “risk treatment”.
(^) Define Context
and Criteria
Define System
Identify HazardScenarios
- what might go wrong- how can it happen
-how to control it
ConsequencesAnalysis of Analysis ofProbabilityIdentify RiskScenarios SensitivitiesAnalyseAssess RisksMonitor andReview TreatmentRiskFigure 4.9: Generic representation of the flow of risk based decision making (Australian New
Zealander code 4369 (1995)).
Risk analysis, as may be realized can be performed at various levels of detail. Therefore, for
the purpose of communicating the results of a risk analysis it is important that the degree of
detailing used for the analysis is indicated together with the analysis results. Otherwise, the
decision maker, who bases her/his decisions on the result of the risk analysis, has no means
for assessing the quality of the decision basis. In general it may be stated that the decision
analysis should be performed at a level of detail which facilitates a consistent ranking of the
different available options for risk management in accordance with their associated expected
benefit. In the same way a risk assessment should be performed at a level of detail which is
consistent with the level of detail underlying the possible given risk acceptance criteria.
In industrial applications only little consensus is available on the classification of risk
assessments. However, in the nuclear industry the following categorization has been agreed
for so-called probabilistic risk analysis (PRA) or probabilistic safety analysis (PSA).