AP1000® Large Break LOCA Best-Estimate and Conservative Comparison with TRACE5 patch 4

– The AP1000® is an advanced Pressurized Water Reactor (PWR) design developed by Westinghouse Electric Company which implements passive safety systems to provide core cooling in case of accident. Within the different accidental sequences Large Break LOCAs are one of the most important sequences in the deterministic and probabilistic AP1000 safety analyses. The UPM group has performed a best-estimate and conservative LBLOCA analysis with TRACE5 patch 4. For this, a best-estimate first cycle core-model with realistic power distributions has been developed using open literature information. Thermomechanical TRACE options have also been activated and detailed fuel geometry and material properties data has been included in order to be able to analyze not only the PCT and ECR, but also other phenomena like ballooning, channel blockage and rod burst. Results show large safety margins with respect to the LOCA acceptance criteria. The analyses have been done for the actual and for the proposal of the 10CFR50.46c rule, the AP1000 passive safety systems have demonstrated a good behavior keeping the core cooled and within the acceptance criteria.