Investigating the distribution characteristics of boiling flow and released nuclide in the steam generator secondary side using CFD methodology

The steam generator (SG) plays an important role for the pressurized water reactor (PWR) not only in the primary-to-secondary heat transfer but also in the pressure boundary as the fission product barrier. Therefore, the leak or rupture of SG tubes results in the decrease of heat exchange capability as well as the release of radioactive nuclide to the environment. Therefore, a multi-dimensional flow boiling model is proposed in this paper to simulate the thermal–hydraulic characteristics and released nuclide distribution in the SG secondary side. This model can provide the local velocity, temperature, enthalpy, void fraction and released nuclide distributions, etc. The three-dimensional distribution characteristics of released nuclide can be reasonably captured, which includes dilution, dispersion and swirling phenomena, etc. The simulation results can provide the operator the distribution characteristics of two-phase field and released nuclide. They can also help the operator confirm the assumption for the homogeneity of released nuclide concentration for chemical sampling in the blowdown system, judge the possible leak location, and carry out the diagnostic and appropriate actions.