PUBLICATIONS

High-fidelity and multi-physics simulation of neutronics and thermal-hydraulics (T/H) coupled capabilities for light water reactor cores has become a critical issue when performing thorough core design analyses. The drift-flux based sub-channel code, ESCOT, has been developed at SNU Reactor Physics Laboratory in order to provide pin-wise T/H solutions for multiphysics analyses targeting both PWRs and BWRs. In a previous research, the basic structure of ESCOT was presented and the code was validated towards single-phase flow problems. The two-phase analysis capability of ESCOT is enhanced by implementing the vapor mass generation model, the interface mass and heat transfer models, the flow regime maps, the wall friction model with two-phase multiplier and the equal volume exchange and void drift (EVVD) model. These models are verified by one unheated two-phase test, the RPI air-water test, and two heated two-phase tests, GE 3x3 and PSBT: Phase I – Exercise 2. The results of ESCOT are compared not only with measured data but also with other sub-channel level T/H codes, CTF and CUPID. It turns out that the EVVD model can yield significant error reduction by better predicting the turbulent mixing and void drift for RPI air-water test case. GE 3x3 and PSBT results show the validity of the EVVD model and vapor generation model of ESCOT in heated conditions. In particular, GE 3x3 is used to assess the local predictions of enthalpy and mass flux distribution of ESCOT, while PSBT is more focused on the bundle average of void fraction. With these validation tests that contain comparable agreements with references in producing the preCHF two-phase flow characteristics, it is demonstrated that ESCOT has the capability of predicting the key phenomena of two-phase flow at a whole core sub-channel level.