Operational Hazard Analysis of Nuclear Power Plant Based on MFM Functional Modeling and Reasoning

The reliability and operability of operator intervention is critical in ensuring the safe operations of nuclear power plants, especially in the case of sudden emergency accident conditions. In such situations, the operators are more prone to errors or mistakes due to the time-limited tasks and high phycological stress. In this paper, we present a Multilevel Flow Models (MFM) based functional framework for operational hazard analysis by integrating human factors in emergency prevention and mitigation. The operational hazard analysis involves proactive risk assessment by evaluating the operability of operator action sequences with consequence reasoning. The forward induction reasoning is adopted in MFM for predicting the potential risk impacts and consequences that are resulted from the execution of action sequence. The framework method is demonstrated with a case study of manual boration makeup under inadvertent boric dilution accident in nuclear power plants, where the MFM models of reactor coolant system (RCS), the chemical and volume control system (RCV), and the reactor water and boron injection system are established for domain knowledge representation and reasoning with a specific focus on the safety critical functional objectives of reactivity control and integrity of reactor coolant inventory. The demonstration results show that the paradigm framework is effective for enhancing operational safety through proactive hazardous effects and risk identification and preventive control capabilities.