Chapter 10. Risk Assessment (QRA)
10.1. Frequency and Consequence
Having identified a hazard, the term ‘risk analysis’ is often used to embrace two types of assessment:
• The frequency (or probability) of the event.
• The consequences of the event.
Thus, for a process plant the assessments could be:
• The probability of an accidental release of a given quantity of toxic (or flammable) material might be 1 in 10 000 years.
• The consequence, following a study of the toxic (or thermal radiation) effects and having regard to the population density, might be ‘a 1 in 10 chance of the event propagating to 40 fatalities’.
The term QRA (Quantified Risk Assessment) refers to assessing the frequency of an event and its measurable consequences (e.g. fatalities, ...
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