The Role of Protective System Reliability Analysis in the Study of System Safety

Safety–critical protective systems mitigate possible collateral harm to the public, when randomly occurring initiating events challenge the operational integrity of hazardous technologies. Quantifying the efficacy of protection remains a challenge to engineers and regulators responsible for safety. In this paper, we will explore the analytical relationship between protective system reliability and safety efficacy. Central to our discussions is the understanding that: Not only should protective systems be reliable over time, but they must be highly effective at the exact instants of initiating event arrivals. Extending traditional system reliability analyses to quantify the effectiveness of protective systems that are challenged by potentially catastrophic initiating events, requires identifying and redressing certain modeling pitfalls that are counterintuitive. It is our purpose, here, to reveal some of these pitfalls by appealing to well known results from system reliability theory and the theory of stochastic point processes.