Abstract
Under normal full power operation, the entrance isolation valve of Safety Injection & Residual Heat Removal (RIS-RHR) system may be opened by mistake, resulting in a full pressure Interfacing Systems Loss of Coolant Accident (ISLOCA). Once the fuel rod is damaged, the radioactive nuclides in the primary coolant will increase greatly. At the same time, high temperature and high pressure conditions will lead to abnormal leakage of RIS-RHR system located in safeguard building. Radioactive nuclides in primary coolant bypass to the outside of containment due to the abnormal leakage, resulting in unacceptable radioactive consequences. In this study, a best estimate code LOCUST developed independently by CGNPC is used to calculate thermal hydraulic conditions in the core region, which is used as the boundary condition for fuel rod performance evaluation. Then a fuel rod evaluation model was used to analyze the cladding damage. Finally, the radioactive consequence was given based on the reasonable hypothesis of leakage. Results showed that the top of the core was uncovered temporarily, but the cladding could remain intact during the whole accident process and the radioactive consequence was within the acceptable range. It was proved that the RIS-RHR system was reasonable in design and could withstand the consequence of full pressure ISLOCA accident.
