STGEN COMPUTER-PROGRAM METHODOLOGY AND APPLICATION TO THE STEAM LINE BREAK TESTS IN THE RD-12 STEAM-GENERATOR

A computer model for calculating a U-tube stream generator response to a main stream line break accident is presented. The stream generator is nodalized into three regions: riser, steam drum, and downcomer. Mass and pressure (temperature) are the main state variables representing each region. Models for steam drum swelling, tube bundle heat transfer, liquid subcooling, void fraction distribution and two-phase flow in the various flow connections are all formulated based on the state variables of the regions. The model was tested in a series of experiments carried out with the steam generator RD-12. Comparison between the experimental data and code predictions are discussed for small and large breaks. The model correctly predicts the major quantitative trends and many of the quantitative features. This includes global system variables such as the pressure variations as well as local variables such as quality, void fractions, liquid levels, and dryout level.