Development and assessment of a three-field subchannel code for thermo-hydraulic transient analysis under reflood conditions

Abstract

A three-field twelve-equation subchannel code was developed that contains separate energy equations for the continuous liquid and droplet phases. Several physical models were modified and optimized to accommodate the code and improve predictions of reflooding. Eight RBHT tests were used to assess the code. Comparisons show that the predictions of the code are in good agreement with experimental data on the quench front propagation, peak cladding temperature, and temperatures of the cladding, vapor and spacer grid. Moreover, the code can capture trends in droplet size and velocity and obtain the continuous liquid-droplet temperature difference. The impact of new interfacial heat transfer model, droplet impingement heat transfer model and energy equations on the reflooding calculation are analyzed. Overall, the code is applicable to the simulation of the reflooding phenomenon, and the results can provide guidance for model modification. Meanwhile, the pre-assessment of droplet temperature provides new perspectives for the code development.