Study on sodium-water reaction jet evaluation model based on engineering approaches with particle method

If pressurized water/water-vapor leaks from a heat transfer tube in a steam generator (SG) in a sodium-cooled fast reactor, the leakage forms high-velocity, high-temperature, and corrosive jet due to the pressure difference and sodium-water reaction. It would damage the other tubes and might propagate the tube failure in a SG. Thus, it is important to evaluate the effect of the tube failure propagation for safety assessment of a sodium-cooled fast reactor. The computational code LEAP-III can evaluate water leak rate during the tube failure propagation with short calculation time, since it consists of empirical formulae and one-dimensional equations of conservation. One of its models, the temperature distribution evaluation model, evaluates the temperature distribution in SG as circular arc isolines determined by experiments and preliminary analyses instead of complicated real distribution. Although this model has advantages of short calculation time and good agreement about maximum temperature, it provides broader high temperature region than the real one in some case. In order to improve this model to get more realistic temperature distribution, we have developed the Lagrangian particle method based on engineering approaches. In this study, we have focused on evaluating gas flow in a tube bundle system and constructed new models for the gas-particles behavior around a tube to evaluate void fraction distribution near the tube. Through the test analysis simulating vapor discharge in one target tube system and comparison with an existing computational fluid dynamics code, SERAPHIM, it was confirmed that basic behaviors of these models, which is the particles spread out around the target tube without significant inflow into the tube inside, and finally these went along the buoyancy force direction.