Evaluation and integral analysis of ADS and CMT failures during AP1000 SBLOCA with ASYST VER 3 simulation code

Abstract This research focuses on verifying the importance of the ADS and the CMT, by using the ASYST code. We evaluated the role of these two components by postulating the failure of the ADS as a single failure approach and the failure of the CMT with ADS failure as multiple failures approach during hypothetical SBLOCA conditions. These accidents acted as confounding factors distorting the AP1000 PSS. We investigated the reactor and safety system behavior during the SBLOCA. We evaluated the importance and effectiveness of two components in reducing and mitigating the consequences of the accident. We checked the effectiveness of these components by comparing the importunity-related issues with and without these components during the accidents. We found that the ADS decreased the pressure, allowing natural circulation to quench the reactor core during the LOCA. During the failure of ADS, the vapor bubbles formed in the reactor vessel covering the fuel rods increased their temperature. The CMT borated water feeding quenched the actinides decay heat. The non-existence of the CMT resulted in decreasing the RCS. ASYST was compared to NOTRUMP to validate it capability to analyze thermal phenomena during accidents. It was found that in the AP1000, the ADS and CMT were considered as the overall importunity of the others PSS.