Core damage frequency in PRA refers to the probability of which event?

• A. Off-site power loss
• B. Turbine trip
• C. Core damage
• D. Large early release

Answer: (C)

In PRA, core damage frequency is the probability per reactor-year that the reactor core becomes damaged due to an accident sequence. It represents the likelihood of fuel cladding and core structure sustaining damage as a result of failures in cooling, control, or mitigation across all possible initiating events. Large early release is a consequence of core damage in many models, representing events where damage leads to a large release of radioactivity; it is not the same as the probability of core damage itself. Off-site power loss and turbine trip are examples of initiating conditions that can lead to sequences, but they are not the event described by core damage frequency. So the correct concept is the probability that the core experiences damage.