Which of the following statements is false regarding event trees and layer of protection analysis (LOPA)?

Which of the following statements is false regarding event trees and layer of protection analysis (LOPA)?

• A. Layer of protection analysis only calculates the probability of the undesired harmful result.
• B. Both methods use probability multiplication from the logical 'AND' linking the intermediate events or protection layers.
• C. Event trees use probability of failure on demand while LOPA does not.
• D. LOPA tends to be a more structured form of event tree analysis.

Answer: (C)

The statement regarding the probability of failure on demand being exclusive to event trees, while LOPA does not use this concept, is a misconception. In fact, Layer of Protection Analysis (LOPA) does consider the probability of failure on demand when evaluating the risk associated with layers of protection. LOPA assesses the effectiveness of these layers by looking at their reliability, which includes calculating the probabilities of any initiated safety systems failing to function effectively when required. Event trees and LOPA both serve to analyze the same fundamental risks but do so in different ways. Event trees begin with an initiating event and explore potential outcomes based on subsequent events and actions. In contrast, LOPA provides a more structured approach by quantifying the layers of protection and evaluating their reliability against specific hazardous scenarios. By evaluating probability multiplication from logical 'AND' connections found in both methods, the interdependence of safety systems is highlighted. Therefore, LOPA can indeed incorporate concepts similar to those found in event trees, including the probability of failure on demand.

The statement regarding the probability of failure on demand being exclusive to event trees, while LOPA does not use this concept, is a misconception. In fact, Layer of Protection Analysis (LOPA) does consider the probability of failure on demand when evaluating the risk associated with layers of protection. LOPA assesses the effectiveness of these layers by looking at their reliability, which includes calculating the probabilities of any initiated safety systems failing to function effectively when required.

Event trees and LOPA both serve to analyze the same fundamental risks but do so in different ways. Event trees begin with an initiating event and explore potential outcomes based on subsequent events and actions. In contrast, LOPA provides a more structured approach by quantifying the layers of protection and evaluating their reliability against specific hazardous scenarios. By evaluating probability multiplication from logical 'AND' connections found in both methods, the interdependence of safety systems is highlighted. Therefore, LOPA can indeed incorporate concepts similar to those found in event trees, including the probability of failure on demand.