Large early release frequency is the probability of a significant radiation release within the early phase after an accident.

• A. False
• B. Not applicable
• C. True
• D. No release occurs

Answer: (C)

Large early release frequency measures the chance that a significant amount of radioactivity is released to the environment within the early time window after an initiating event. In PRA terms, it comes from the event tree and fault tree models that describe containment performance, mitigation actions, and timing. If containment fails or is bypassed early and the release magnitude exceeds the defined threshold, that scenario contributes to the large early release frequency. So the statement that it is the probability of a significant radiation release within the early phase after an accident is accurate. Time window definitions can vary by plant, but the essence is capturing early, large releases rather than late or small releases.