Multiphysics coupled calculations using OpenFOAM, Serpent, and external heat conduction solver in high-temperature engineering test reactor HTTR

Abstract

Adequate safety analysis is needed for generation IV Gas Cooled Reactors (GCRs), as nuclear reactor safety is challenged by the complexity of the different physical phenomena. High-fidelity modeling is achieved by comprehensive coupling of these phenomena. This master's thesis provides a neutronics/thermal-hydraulics coupling approach to model GCRs using Serpent, OpenFOAM, and an external heat conduction solver. The approach provides a way to model GCRs without explicitly simulating the TRISO fuel particles, instead a homogeneous fuel region is simulated in OpenFOAM, and then the homogeneous fuel temperature is used as a boundary condition in the heat conduction solver to analytically resolve the layers and kernel temperatures.

The data exchange between the solvers is conducted through a type 8 Serpent coupling interface and a modified chtMultiRegionSimpleFOAM solver to retrieve the volumetric power produced in Serpent. Convergence in the coupling process is determined by assessing the volumetric power values from Serpent. The coupling approach is applied to a single fuel rod and a fuel block in High-Temperature Engineering Test Reactor (HTTR). Given both simulations have similar volumetric power, it is observed that there is a notable discrepancy in solid region temperatures, in contrast to a pronounced agreement in the fluid region properties.