Parametric Analysis of Coupled Thermal Hydraulic Instabilities in Forced Flow Channel Using Reduced-Order Three-Zone Model

One of the significant issues of supercritical water reactor (SCWR) is the variation of coolant density along its axial direction of flow, which further creates a stability issue in the reactor. This causes the dynamic instability in the coolant channel. Present work is focused to study the parametric effects on the stability of the system using a simplified three-zone lumped parameter model by considering the neutronics coupled with thermal hydraulics. The coolant channel is divided into three zones, namely heavy fluid region, light fluid region, and intermediate heavy and light mixture fluid region. The interface of these hypothetical regions is separated by time dependence boundaries. A set of governing equations are solved for the individual zones that provide another set of algebraic and ODEs, which has coolant enthalpy and the length of each boundary as a primary variable. The US reference design of SCWR has been considered at 25 MPa as the operating pressure. Increasing the length of the coolant channel and hydraulic diameter can destabilize the system. Increasing inlet orifice and decreasing in the exit orifice coefficient have a stabilizing effect on the system.