Definition:
Quantitative Risk Assessment (QRA) estimates the likelihood and consequences of hazardous events numerically. This is more work, hard to do well, and less common than a semi-quantitative (SQRA) method such as a HAZOP/LOPA.
Examples could be a LOPA with real failure data. Or a fault tree analysis or event tree analysis with quantified failure likelihoods.
Key Points:
- Supports decision-making around facility siting, mitigation measures, and risk acceptance.
- Often uses PLL, societal risk curves, and SIL evaluations.
Example:
A QRA shows that adding a second pressure relief system, using its actual failure rate data, reduces site fatality risk below acceptable thresholds.
See Also: SQRA, QLRA, PLL, uncertainty analysis
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