HELIOS with an ENDF/B-VI based nuclear-data library is the ideal tool for lattice physics calculations. Because of its full geometric flexibility the constraints of most of today's lattice codes are eliminated. HELIOS is applicable to BWR and PWR, as well as Magnox, RBMK, CANDU, AGR and VVER fuel assemblies.

Multi-assembly geometries, up to full reactor cores for research reactors can be calculated. HELIOS has been extensively validated and enjoys a world-wide reputation among power plant operators, fuel vendors, research institutes and universities alike.