With the increasing fuel burnup of nuclear power plants both domestically and internationally, the consequences of reactivity-initiated accidents need to meet stricter acceptance criteria. According to the review requirements, it is necessary to identify and analyze the key parameters and phenomena affected by burnup when studying safety analysis of high burnup. Taking high burnup operation as the research premise, this study investigates fuel behavior in reactivity-initiated accidents, and analyzes the key parameters and phenomena in rod ejection accidents at high burnup by establishing the phenomenon identification and ranking table (PIRT). The analysis shows that, when conducting analysis of high burnup fuel behavior in rod ejection accidents, the key parameters and phenomena for high burnup should be considered to increase the credibility of the simulated analysis results of fuel behavior in accidents.