Thermal-hydraulic Design And Safety Analysis Of Supercritical Water Cooled Systems

The supercritical water cooled reactor(SCWR) is selected as one of the six Generation IV Nuclear Energy Systems proposed by Generation IV International Forum(GIF). And it is the only one GIF design using water as coolant which is regarded as the most promising one in the future. In the last few years, SCWR R&D activities are ongoing worldwide and great efforts are made on both experimental and theoretical investigation. In order to study the China-Europe corporation project Super Critical Water Reactor Fuel Qualification Test(SCWR-FQT), the modified system code ATHLET-SC is applied to Supercritical WAter MUlti Purpose loop(SWAMUP) thermal-hydraulic analysis and the SCWR-FQT loop accident safety analysis after the experimental validation of some related models.The validation of trans-critical transient and critical flow model in code ATHLET-SC are carried out based on the supercritical water depressurization and critical flow experiments. The calculation results show good agreement with the experiment results which means the system code ATHLET-SC has the capacity of simulating the trans-critical transient and critical flow phenomenon.Besides, another work is the pre-test calculation of the SWAMUP facility, which is important and necessary to show the feasibility of the experiment. The steady state and trans-critical transient analysis have be performed for the SWAMUP facility using the system code ATHLET-SC. The system behaviour e.g. system pressure, coolant mass flow, cladding temperature during the trans-critical process has been analysed. The effect of some important parameters such as heating power, depressurization rate on the system characteristics has also been investigated.Another important application of the ATHLET-SC code in this dissertation is the safety analysis of the SCWR-FQT loop which contains a small scale fuel assembly under the supercritical water condition. In this study, comparisons of the benchmark simulation by using APROS and TACOS with ATHLET-SC has been performed which also confirm the accuracy and reliability of ATHLET-SC code. Besides, the safety analyses of the four types of design basis accidents have been simulated, including loss of coolant accidents, trip of the primary pump, blockages of the coolant flow path and coolant shortcut inside the test fuel element. These safety analysis results shows the safety systems of the test loop are effective and the results will be used for licensing of the SCWR-FQT experimental facility.In addition, the coupled calculation between neutron-physics and thermal-hydraulic of a loss of coolant accident has been performed and discussed for SCWR-FQT loop. The effects of some important parameters such as external reactivity, reactivity coefficient for fluid temperature are also investigated.The results shows that the ATHLET-SC code has the capacity of analysing the SCWR systems. The outcomings achieved can provide safety analysis tools and results for licensing of the SCWR-FQT loop and also can give guidance for the experiment work of the loop.