Which of the following is categorized as a passive safeguard?

A diking system is categorized as a passive safeguard because it is designed to provide a physical barrier that contains spills or leaks without requiring operator intervention or active controls to function. The primary purpose of diking is to prevent hazardous materials from spreading beyond a certain area, such as a storage tank or containment area, thereby protecting personnel, the environment, and adjacent facilities from the impact of potential releases.

In contrast, flow controllers, nitrogen inerting, and emergency shutdown systems are considered active safeguards because they require monitoring, control, or management by operators or automated systems to prevent incidents. Flow controllers actively regulate fluid movement, nitrogen inerting involves adding nitrogen to reduce flammability, and emergency shutdown systems are activated in response to specific alarms or failures to stop processes actively. These strategies depend on continual operation and human or automated response, differentiating them from the self-sustaining nature of passive safeguards like diking.