What is QRA and how does it relate to LOPA?

• A. QRA is a qualitative risk assessment, while LOPA is quantitative.
• B. QRA is a numerical risk estimate; LOPA is a simplified screening QRA used to check if risk reduction meets risk tolerance.
• C. QRA is a design tool; LOPA is a maintenance tool.
• D. QRA is used only for chemical plants; LOPA only for oil and gas.

Answer: (B)

In this area, QRA provides a numerical estimate of risk for defined hazard scenarios, typically turning initiating-event frequencies and potential consequences into an annual risk figure or other quantitative risk metric. LOPA uses the same risk-based mindset but keeps it simple: it looks at the initiating event frequency and the failure probabilities of independent protection layers to estimate residual risk, without building a full fault/ event-tree model. It’s a screening tool designed to show whether existing safeguards reduce risk to an acceptable level defined by risk targets. If the residual risk still exceeds the tolerance, you either add protection layers or move to a more detailed QRA for a deeper evaluation. So, QRA is a numerical risk estimate, while LOPA is a simplified screening approach to verify risk reduction against risk tolerance.