Abstract:
Present thesis work primarily focuses on the analysis of flow instabilities in one of the most powerful concepts under Gen.-IV nuclear reactor technology, namely the supercritical water-cooled reactor (SCWR). Safety is the primary concern in nuclear reactors and the study of flow instabilities is an important aspect of safety assessment. To facilitate the study of complex phenomena in the laboratory, a method for designing a downscaled model has been proposed here for both natural as well as forced circulation SCWR. For detailed analysis of the stability characteristics of the system, a simple but computationally inexpensive model has been developed as lumped parameter model (LPM). Using this model, linear and nonlinear stability analyses have been done for various ranges of parameter values. Instabilities in SCWR subjected to seismic effects have also been analysed by using the LPM.Nuclear power plants use the heat generated from nuclear fission in a contained environment to convert water to steam, which powers generators to produce electricity. Light water reactors (LWR) use water as coolant and moderator. SCWR is a Gen.-IV LWR. It is a concept for an advanced reactor that operates at supercritical pressures and temperatures (25–30 MPa, 500–520 oC exit temperature). Such a high coolant temperature at turbine inlet provides high thermal efficiency (~42%) which is substantially greater than any other LWR (~30%). Consequently, it also experiences significant density difference throughout the coolant channel, from the inlet to the outlet (720 kg/m3 to 90 kg/m3), which raises grave concerns about flow instabilities in the SCWR. To ensure a proper design of SCWR without any safety issues, detailed stability analysis over wide parameter ranges is needed.
