Study on the Severe Accident Management Strategy against Over-Pressurization at PWRs in Korea

The containment is the last barrier against releasing radioactive materials to the environment and the public during a severe accident. Integrity of a containment is likely to be threaten due to the containment over-pressurization, came from decay heat of fission products and massive steam, when a severe accident is progressed without the appropriate accident managements or any countermeasures. Following the Fukushima accidents, Korean government carried out safety inspection for all nuclear power plants in Korea. As a result of the safety inspection, nearly 50 items for safety enhancement (so called, `Post-Fukushima enhancement') of operation Nuclear Power Plants (NPPs) were out. Among them, Filtered Containment Venting System (FCVS) was chosen as a countermeasure system for over-pressurization of containments at NPPs in Korea. Installations of FCVS for Pressurized Heavy Water Reactors (PHWRs) have been underway and for Pressurized Water Reactors (PWRs) are also in preparation. Also, the external coolant core injection systems have been installed at all NPPs in Korea as a new safety enhancement feature against severe accidents. In this study, preliminary evaluations of the FCVS operation strategy under severe accident conditions with the external coolant core injection were performed for establishment of severe accident management strategy appropriately for PWRs in Korea.