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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

COUPLED-NEUTRONIC-THERMALHYDRAULIC STABILITY APPRAISAL OF SUPERCRITICAL FORCED FLOW CHANNELS FOLLOWING LUMPED PARAMETER APPROACH

Get access (open in a dialog) DOI: 10.1615/IHTC16.nee.023961
pages 7907-7914

Resumo

Possible appearance of instabilities is of major concern for the operation of Supercritical Water Reactor (SCWR), owing to the substantial density variation experienced by the fluid during its passage through the cooling channels. Any supercritical fluid suffers drastic variation in all thermophysical properties around the pseudocritical point, which is the primary reason for instigating dynamic instabilities in such channels. Present study aims towards thorough exploration of the same, while coupling the thermalhydraulic characteristics with related fuel rod dynamics and neutronics, through a reduced-order model. A lumped-parameter-based approach is adopted to get a simple, yet robust, mathematical framework. The entire flow region is divided into three zones, namely, a heavy-fluid region, a light-fluid region and an intermediate heavy and light fluid mixture region. The zones are separated by time-dependent boundaries, imposing variable lengths on them. Equations for the conservation of mass, momentum and energy are integrated over each zone, thereby developing a set of ODEs and algebraic equations, with coolant exit enthalpy and length of each zone being the primary variables. A two-node lumped parameter representation is considered for the fuel rod, to incorporate the concerned heat transfer behavior into the calculation. The US reference design of SCWR is selected as the prototype, with an operating pressure of 25 MPa. Increase in heated length and reduction in hydraulic diameter are found to destabilize the system. Inlet orifice coefficient stabilizes the system, whereas the exit orifice coefficient destabilizes. Effect of fuel time constant and enthalpy reactivity coefficient have also been studied.