The overarching goal of the project is the realistic simulation of single-phase natural convection of water in large vessels, as it occurs in passive heat removal systems of innovative reactor concepts (e.g., SMRs). This aims to increase the reliability of safety analyses for such systems.

The project comprises three main objectives:

• Development and validation of a Fine-Grid-CFD model to study the flow and heat transfer by natural convection of water in large vessels under typical conditions of passive heat removal systems.
• Creation and training of ML-based models to describe turbulent parameters based on datasets generated with the FG-CFD model, and consequently the development of a Coarse-Grid-CFD model.
• Implementation of the validated CG-CFD model into the 3D module of the STH-code ATHLET and application of the extended program version for analyzing and evaluating heat removal in passive safety systems of selected SMR concepts.

Through this, the project contributes to the further development of reactor safety analysis methods and strengthens scientific and technical expertise in the field of nuclear safety research.