PRA uses a mathematical model of all important plant systems being used in the plant.

• A. False
• B. Only for safety systems
• C. Not relevant
• D. True

Answer: (D)

PRA builds a quantitative, probabilistic representation of how the plant’s systems operate and interact, focusing on those that can meaningfully affect risk. To do this well, it includes all systems that are risk-significant, not just the safety ones. The model captures how failures and degradations in electrical, cooling, instrumentation, control, and even some non-safety systems can influence the performance of safety features, dependencies among components, and how human actions fit into the sequences that lead to or prevent adverse outcomes. By assembling fault trees and event trees that map these interactions, PRA can quantify the chances of outcomes like core damage or radiological release under different scenarios. Since the goal is to represent how risk emerges from the whole system network, the statement that PRA uses a mathematical model of all important plant systems being used in the plant is true.