الفهرس 
THE INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
During this research, the effectiveness of theAP1000 passive safety system was verified, by using the Adaptive System Thermal-hydraulics (ASYST-VER3) as new analysis code. The role of all passive safety system components was evaluated by postulating the several accidents scenarios. The small break loss of the coolant accident (SBLOCA) in hot leg applied as first scenario to verifying the passive safety system (PSS). Failure of the automatic depressurization system as a single failure approach and the failure of the core makeup tank (CMT) with the automatic depressurization system failure as multiple failures approach were applied during hypothetical SBLOCA conditions. These accidents acted as confounding factors distorting the AP1000 Passive safety system. The reactor and safety system behavior during the SBLOCA with and without successful actuation of all passive safety system, and the importance and effectiveness of the automatic depressurization system and CMT system components in reducing and mitigating the consequences of the accident were investigated and evaluated. the effectiveness of these components by comparing the importunity-related issues with and without these components during the accidents was checked. The obtained results showed during the loss of coolant accident the automatic depressurization system decreased the pressure, allowing natural circulation to quench the reactor core. Also during the failure of the automatic depressurization system, 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 nonexistence of the CMT resulted in decreasing the reactor coolant system (RCS). So the ADS and CMT are considered as the overall importunity of the others passive safety system. A ten-inch-diameter SBLOCA was compared with a five-inch-diameter SBLOCA. To analyze the effectiveness of break size on the reactor temperature gradient during the hypothetical accident. The reactor pressure dropped slower during the five break aria than ten-inch break. This situation results in delays in the response of the reactor’s safety systems, which results in increasing the reactor’s temperature. Also the SBLOCA on the cold leg (SBCL) was compared to the SBLOCA on the hot leg (SB-HL). The effect of accident location on the passive safety system response was studied also. In the case of the SB-HL, the CMT system and the ADS system are affected by the RCS depressurization. The CMT was stopped several times, and the ADS delayed to ignition. All these factors led to a higher reactor temperature of the SB-HL than in the SB-CL condition. So a (ASYST-VER3), is effective and produced quantifiable findings which could be verified and validated by the other experimental data. So ASYST-VER3 code is able to analyze the reactor’s passive safety system in proportion to these scenarios. The capability of the ASYST code to analyze thermal phenomena during accident was validated by comparing its results with the corresponding using NOTRUMP code. The results showed that the code is effective and produced quantified findings and is capable to analyze the reactor passive safety system.