Transient Flow Field on Containment Floor Predicted by Two-Dimensional Shallow Equation Solver

Abstract

For the analysis of debris transport on containment floor, a model to predict the flow field should have a fast-running capability and high accuracy. A model is developed to calculate the transient flow field on the containment floor involving a complex geometry in the advanced pressurized water reactor (PWR) such as Advanced Power Reactor (APR)-1400, which does not have a switchover from injection to recirculation following a loss-of-coolant accident (LOCA). Two-dimensional shallow water equation (SWE) is solved using the finite volume method (FVM). Unstructured triangular meshes are used to simulate the complex structures on the containment floor. Harten-Lax-van Leer (HLL) scheme, one of the approximate Riemann solver, is adopted to capture the dry-wet interface and to determine the momentum flux at the interface. An experiment of a sudden dam break having water reservoir and L-shape open channel is simulated and compared with the calculated result, which supports the validity of the present model. The model is also applied to calculation of the flow field of APR-1400. The calculated flow field can be characterized by the propagation of waves generated by surface level difference and by the reflection of waves from solid wall. The transient flow rates entering to the Holdup Volume Tank (HVT) can be predicted within a practical limit of computational resource.