Development and implementation of an external neutronic–thermal-hydraulic coupling framework for natural circulation SMR analysis

This work presents an external neutronic–thermal-hydraulic coupling methodology for the analysis of a natural circulation small modular reactor (SMR). The approach is based on an iterative scheme that enables information exchange between independently developed codes (AZTRAN and TLANESY) operating on heterogeneous platforms. The framework was applied to a NuScale-like reactor under steady-state and transient conditions. Convergence was achieved within a limited number of iterations, satisfying criteria of Δ k eff < 1 × 10 −4 and relative deviations below 1 × 10 −2 . Steady-state deviations remained below 1.7% for key parameters related to the thermal-hydraulic. Transient analyses induced by variations in steam generator boundary conditions showed consistent responses governed by neutronic and thermal-hydraulic feedback, with quantified variations in power and circulation under imposed boundary perturbations. The main contribution lies in a flexible and computationally efficient multiphysics framework, including a multichannel natural circulation model, suitable for coupled reactor simulations. • External neutronic–thermal-hydraulic coupling framework for SMR analysis. • Stable convergence achieved under strong nonlinear feedback conditions. • Multichannel natural circulation model incorporated in the coupling scheme. • Quantitative agreement within 1.7% for steady-state key parameters. • Flexible methodology for integrating independently developed simulation tools.