Understanding of thermal-hydraulic instabilities and the mutual interactions at supercritical pressure

Abstract

In the present work, a steady state and a simple transient models are integrated to simulate various thermal-hydraulic (TH) static and dynamic instabilities in a single vertical channel, subjected to time independent power, for supercritical fluid (SCF). The scheme of U.S. supercritical water reactor (SCWR) design is analyzed for different TH instabilities and the mutual interactions of such instabilities. An in-house steady state TH model, which solves a set of nonlinear coupled mass, momentum and energy conservation equations accounting for the pressure and enthalpy dependent thermodynamic equation of state, is implemented to find the solution at the initial equilibrium condition. The steady state model is then validated against the recently available experimental results. Next, the simple transient model is integrated with the steady state model to simulate Ledinegg excursion, pressure drop oscillations (PDOs), density wave oscillations (DWOs), and the mutual interactions of each other in presence as well as in absence of a surge tank at the upstream of the heated section. A number of simulations are carried out considering various typical pump (external) characteristic curves. Results provide the understanding what are the different operational criteria on which the Ledinegg excursion, PDOs and DWOs, or the interactions of the aforementioned TH instabilities will depend.