Insights of level-2 PSA to prevent and mitigate severe accidents in IPHWR

Abstract

Probabilistic safety assessment (PSA) uses a systematic approach to estimate the reliability and risk of a nuclear power plant (NPP). The level-2 PSA provides a structured assessment of the possible accident sequences that could occur following core damage and gives insights into which of the phenomena that could arise have the greatest potential to lead to containment failure or bypass resulting in a release of radioactive material to the environment. In some very low probability circumstances, severe accident sequences may result in core melting and plant damage leading to dispersal of radioactive material into the environment and thus constituting a health hazard to the public. The results of the level-2 PSA can be used to determine if sufficient provisions have been made to terminate core damage at an early stage and to prevent and mitigate the effects of the severe accident should the core damage progression continue. This gives insights into the level of robustness of the containment in providing protection for severe accidents and the adequacy of the accident management systems in protecting the containment and preventing a large release of radioactive material to the environment. PSA could find the plant vulnerabilities on severe accidents prevention and mitigation In addition, the level-2 PSAs are being used to identify any additional accident management measures that could be carried out to further mitigate the effects of a molten core. The paper discusses the relationship between Probabilistic Safety Assessment (PSA) and severe accident study and also introduce on how to apply PSA in severe accident prevention and mitigation. Some modifications or improvement as suggested based on level-2 PSA Study of KAPS 1&2 are presented in this paper.