As part of the FRM II conversion from highly enriched uranium (HEU) to low enriched uranium (LEU), significant progress has been made in the development of advanced reactor core designs. Since the conversion effectively entails the creation of an entirely new reactor core within an existing facility, it requires cutting-edge multiphysics simulations and high-fidelity modeling techniques.

The project’s overarching goal is to develop the best possible reactor core model for FRM II, ensuring that its unmatched scientific performance is fully preserved. To achieve this, new coupling schemes between neutron transport and computational fluid dynamics (CFD) codes have been developed. A key advancement was the implementation of mathematically exact involute geometries in the Monte Carlo neutron code Serpent 2, enabling accurate modeling of the FRM II core without geometric approximations. Additionally, high-performance postprocessing tools were established to support efficient and reliable analysis workflows.

These innovations led to the identification of the first viable low enriched uranium core design for FRM II, published in 2023 - marking a major milestone toward the successful and performance-preserving conversion of the reactor.

For more information please contract Christian Reiter or see Umrüstung - TUM FRMII