Modernization of the SC-INT subchannel thermal-hydraulic code

The article presents the main results of the work cycle on modernizing the source code of the SC-INT computer program designed for subchannel thermal-hydraulic calculations of the water-cooled nuclear reactors cores. The mathematical description of the program is briefly provided, including the method of allocation of control volumes in space, the discrete analog of the basic conservation laws forming the system of nonlinear equations, as well as the method of its solution. The path passed on the internal modernization of the program is described in detail: ejection of outdated Fortran programming language constructions, transition to structure-oriented approach of writing source code, development of modular architecture, as well as implementation of the alternative numerical algorithm for solving the main system of nonlinear equations using the PETSc library. As an example of the SC-INT program capabilities, which appeared after the above described modernizations, the results of thermal-hydraulic calculation in fine-mesh subchannel approximation of a full-scale VVER-1000 reactor core are presented. The core under consideration is assembled from fuel assemblies of different designs: with and without installed «Vikhr» and «Progonka» type intensifier grids. It is demonstrated that the residuals on the main coolant parameters achieved in the simulation of the full-scale core match in order with the corresponding values characteristic for calculations of small-scale experimental fuel assembly models. Thermal-hydraulic calculations of full-scale cores in the subchannel approximation opens the possibility for development of coupled program complexes designed for improved estimation of the parameters of multiphysics processes in the cores of water-cooled nuclear reactors.