Development of a three-field model for two-phase annular-mist flow

The widely used safety analysis codes such as RELAP5 and TRAC use two-phase, two-field representation to describe the thermal-hydraulic phenomena of nuclear power plant. But the averaged description of liquid phase is significantly different from actual phenomena especially when droplet entrainment exists. On the other hand, COBRA-TF, which describes the entrainment field as a separate one from continuous liquid film, is showing the advanced features for the thermal-hydraulics codes but its applicability is highly restricted to the reactor core. Recently, USNRC is developing a thermal-hydraulic analysis code that consolidates the capabilities of various codes and TRAC-M is the base of the efforts. With this situation, the implementation of three-field modeling into TRAC-M/F90 is necessary and as for the first application, the implementation into one-dimensional component is presented