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Quantitative Risk Assessment
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| 4.4.5 Quantitative Risk Assessment 4.4.5.1 Overview A quantitative risk assessment (QRA) is required in the safety casein order to determine the cumulative risk, compare against tolerability criteria and identify what drives that risk so that the hazards can be managed. The QRA should demonstrate that the likelihood and the consequences of each Major Accident Hazard have been assessed in a systematic manner. The methodology and the results of the QRA will be documented in the safety case and should include Methods and assumptions used Failure rate data used, which must be relevant to the application and composed of a dataset for which there is sufficient certainty in its accuracy and Justification for data in terms of o Site-specific circumstances o Processes and methods used to assess the consequences of each event and o Sensitivity of the conclusions to the assumptions made and the inherent uncertainty in the data inputs and the modelling used. For any hazard that may occur, there are likely to be a large number of possible outcomes dependent on, for example, whether emergency systems respond as intended or not, the location of an accidental hydrocarbon release and its size. The QRA should contain sufficient detail such that these variations can be considered as part of the analysis and Improve understanding of the hazards and what drives the risk from it Show where risk reduction measures could be improved and Identify whether the risk is tolerable or not. A degree of conservatism relative to the level of uncertainty in the risk assessment and its inputs should be included to ensure that the risk assessment results are robust. 4.4.5.2 Frequency Assessment The frequency assessment needs to assign a frequency to each of the events modelled in the consequence assessment (below) in away that is robust and conservative and this needs to be demonstrated in the safety case. Download 0.73 Mb. Share with your friends:
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