Numerical study of external inertia and compressible volume on nuclear coupled density wave oscillations in a supercritical pressure channel

Abstract

In this study, the effect of external inertia and compressible volume on density wave oscillations (DWOs) is analyzed, for a virtual supercritical water reactor (SCWR), including the effect of neutron coupling on the thermal–hydraulic field variables. An existing mathematical model is extended for the intended purpose. The model developed is validated against the available experimental and numerical results. Next, the model is applied for the analysis of a pressure vessel SCWR which is similar to the design and operating conditions of the U.S. SCWR. Extensive numerical simulations are carried out to obtain marginal stability boundaries (MSBs) at different operating conditions. The simulation results indicate that the stability of the system decreases if any one of the external outlet inertia or the inlet compressible volume increases; whereas the increase in any one of the external inlet inertia or the outlet compressible volume, increases the stability of the system. Finally, a case study is undertaken to demonstrate how to stabilize a SCWR system with a large upstream compressible volume by increasing the inlet external inertia which, otherwise, would have been unstable.