Gentilly-2 Safety Analysis for Higher Containment Leakage

Abstract

Based on well-supported methodology and current understanding of fission product behavior, we have assessed the impact of a hypothetically high containment leak rate of 5% volume per day at the design pressure of 124 kPa(g). In contrast, the leak rate previously assumed in the safety analyses was 0.5%. The predicted doses for all design basis events are well below the AECB guideline. For those events most sensitive to building leakage, the calculated doses are less than 5% of the AECB reference limit. The predicted doses are not very sensitive to the leakage - a confirmation of the defence-in-depth concept working in the G-2 containment. All natural process and engineered features combine force to stage an in-depth defence against radioactive releases to the public. Our results clearly demonstrate that a containment with a 5% leak rate retains its high effectiveness in mitigating the accident consequences to the public. We attribute this to more realistic assumptions on fission product behavior, improved analytical technique, and forgiving design of the containment system. Current knowledge indicates large margins still exist in our assessments; further reductions in predicted dose are quite feasible.