Quantitative Risk Assessment (QRA)

The hazards arising from explosives installations have for many years been limited by formal licensing procedures based on quantity-distance (QD) principles. These principles limit the quantities of explosives that can be present in workshops, magazines, etc. according to the proximity of nearby buildings and certain other facilities both on and off site. Explosives limits for these buildings might be further constrained following consideration of such factors as remote vs non-remote manufacture and minimal quantities for highly sensitive explosives.

The aim is to reduce the risk of an undesired event, thereby preserving personnel, materiel and infrastructure. The process is one that addresses required deviations from established minimum accepted levels of safety by: identifying the risk; analyzing it in terms of probability and consequence; mitigating the dangerous activities; having the proper authority accept and approve the risk; and, ensuring that the risk is properly monitored.

QRA Elements

• Schedule of potential major-accidents on the site (major accident scenarios).
• Description of methodology by which the major accident scenarios were identified.
• Consequences of each major accident scenario in terms of blast damage and concentration of toxic gases as a function of distance from the source.
• Estimated probability of each major accident scenario in terms of events per year and the methodology for estimation.
• Estimate individual risk of fatality as function of distance from the source.Schedule of potential major-accidents on the site (major accident scenarios).
• Description of methodology by which the major accident scenarios were identified.
• Consequences of each major accident scenario in terms of blast damage and concentration of toxic gases as a function of distance from the source.
• Estimated probability of each major accident scenario in terms of events per year and the methodology for estimation.
• Estimate individual risk of fatality as function of distance from the source.

Examples of QRA data follows: