An advanced new fully implicit numerical method for two-phase flow subchannel analysis based on the Drift Flux Model

In this paper, a new and efficient fully implicit numerical model is introduced using the Drift Flux Model (DFM) for simulation of the reactor core thermal-hydraulics using subchannel analysis. Although several fully implicit models have been developed to simulate two-phase flow in a single channel, but development of an efficient model for more realistic conditions, i.e. reactor core, would be useful. Based on the benefits of the Newton method, a procedure for the accurate approximation of the inverse of the Jacobian matrix and a fully implicit numerical scheme is developed. To benchmark the present model, a well scaled 8 x 8 rod bundle was simulated and fifteen steady-state test series and two transient cases were selected to analyses the subchannel grade void distributions in NUPEC (Nuclear Power Engineering Corporation) 8 x 8 rod bundle test facility. The steady-state void distributions predicted by the model are in agreement with the measured data for a wide range of thermal-hydraulic parameters investigated. Transient calculations were also performed with different time scales and it is concluded that the model is not subject to any time step restrictions. (C) 2017 Elsevier Ltd. All rights reserved.