Equations are discretized with respect to a space coordinate using the control volume method with approximation of convection terms by an upwind scheme. A staggered grid is applied on the space coordinate where scalar flow variables (pressure, enthalpies and volume fractions of the phases) are determined at centers of computational volumes and vector variables (phase velocities) are determined at boundaries of computational volumes.

A non-iterative semi-implicit scheme with automatic selection of time integration step is used for numerical solution of finite difference equation systems. It is described in detail in [2, 10].

A sweep method is used to numerically solve heat transfer equations for heat conduction structures.

An implicit Euler method is used for the solution of the point kinetics model equations. Dynamic processes in equipment components are calculated by integration of ordinary first-order differential equations separately for each component using the Euler method or the Runge-Kutta-Merson method with explicit connection to the thermal-hydraulic module.