CODES

Lee, Jaejin, Alberto Facchini, and Han Gyu Joo. "Development of a drift-flux model based core thermal-hydraulics code for efficient high-fidelity multiphysics calculation." Nuclear Engineering and Technology 51.6 (2019): 1487-1503, DOI: https://doi.org/10.1016/j.net.2019.04.002.

The Efficient Simulator of Core Thermal-hydraulics is a pin-level core thermal-hydraulics (T/H) code which aims at providing an accurate yet fast solution of the T/H distributions to high-fidelity multiphysics core analysis systems targeting massively parallel computing platforms.

ESCOT adopts a four-equation drift-flux model, SIMPLE Consistent (SIMPLEC) algorithm, and fuel conduction model which uses the FRAPCON code empirical models for the equations of state of solid materials. The balances are integrated using the Finite Volume Method in a staggered grid discretization structure. The code is highly parallelized with MPI employing both axial and radial domain decomposition and the PETSc library for the solution of the linear systems.

ESCOT can use ASME or IAPWS steam tables, Zuber & Findlay or Chexal-Lellouche drift-flux correlations to calculate Vgj and C0, employs the Armand’s two-phase flow multiplier and the Equal Volume exchange turbulent mixing and Void Drift (EVVD) to catch the mixing phenomena due to the presence of eddies inside the subchannel. The flow regime map coincides with the one of the RELAP5 code.

ESCOT has been validated using the most known validation experiments such as PNNL 2x6, CNEN 4x4, GE 3x3, PSBT. The code is able to reproduce the various key flow phenomena such as pressure drop by spacer grids, cross flow, flow reversal, void formation and mixing. Moreover, the solutions agree not only with the experiments within the error bands but they are comparable to other subchannel-scale codes such as CTF, MATRA, and CUPID. In particular, the results of two-phase flow validations demonstrated that DFM could predict solutions as well as the two fluid model for the pre-CHF conditions.

The code has been used for standalone application to full core of PWRs and the solution can be provided in less than a minute. The code has also been coupled to the nTRACER code through an external wrapper code.