Abstract: We introduce core damage evaluation guidelines, and apply Westinghouse's CDAG method to EPR units to study the core damage in severe accidents. CDAG evaluates the core damage degree mainly by judging of two parameters, namely, the containment radiation monitoring value (CRM) and the core outlet thermocouple reading (CET). We discusse the reasons for the differences between CRM and CET in the core damage estimation. The analysis results show that: 1) CDAG is suitable for the core damage evaluation in severe accidents for EPR units; 2) CDAG can reflect the real-time release fraction of fission products in reactors, so as to quickly support the emergency organizations' decision-making; 3) The conservative calculation results of CRM and CET settings based on the EPR design show a reasonable trend and range; 4) Factors such as the releasing way, fuel burn-up, and RCS fission product retention have a great impact on the core damage estimation results.

Key words: Core damage assessment, CDAG, CRM, CET