Speaker
Description
Interest in stellarator-based fusion power plants has grown considerably within the fusion community, positioning stellarators as a promising alternative to tokamaks and motivating efforts toward their technological maturity and reactor readiness. Within this expanding stellarator ecosystem, the EUROfusion programme provides a coordinated, reactor-oriented, and physics-based framework for advancing stellarator design. In this context, stellarator neutronics has become a key discipline for evaluating radiation transport, shielding performance, nuclear heating, and material damage in complex three-dimensional reactor environments, where strong spatial non-uniformities and intricate magnetic and structural geometries play a dominant role.
Neutronic studies and design efforts must address the inherent complexity of stellarator configurations, including fully three-dimensional geometries, highly irregular spatial constraints such as periodic sector variations, concave–convex transitions, rotated ports, and tightly integrated coil systems. These aspects are critical not only for overall reactor performance assessment but also for supporting the development of subsystems such as breeding blanket (BB) technologies which depend critically on accurate neutron transport predictions.
Extensive work has focused on the Dual Coolant Lithium-Lead (DCLL) BB concept for the Helical-Axis Advanced Stellarator (HELIAS 5-B). Dedicated modelling frameworks such as HeliasGeom (UNED, Python) and SHANE (CIEMAT, Python + VBA CATIA) have enabled increasingly realistic reactor representations, evolving from simplified parametric models to variable radial build configurations to balance Tritium (T) breeding performance and coil shielding. Using these models, further optimization campaigns have been carried out to improve the T Breeding Ratio (TBR) while reducing radiation damage (dpa) under different FW design assumptions to facilitate remote maintenance. In addition, the integration of coil systems into simplified models has enabled detailed shielding analyses focused on radiation damage, neutron fluence, and nuclear heating, identifying vulnerable coil regions requiring enhanced protection against quenching.
More recently, a new generation of optimized quasi-isodynamic (QI) stellarator configurations, demonstrating reactor-relevant plasma performance have been computationally designed. Among the most advanced ones is the CIEMAT-QI4X configuration, for which new BB development activities have started, building on methodologies and experience from HELIAS 5-B studies. In parallel, a mesh-based workflow for rapidly converting CAD stellarator geometries into unstructured MCNP6 models (at KIT) is being successfully validated and benchmarked against CSG-based approaches using SHANE and HeliasGeom for CIEMAT-QI4X.