Novel hybrid Monte Carlo/deterministic technique for shutdown dose rate analyses of fusion energy systems

•Develop the novel Multi-Step CADIS (MS-CADIS) hybrid Monte Carlo/deterministic method for multi-step shielding analyses.•Accurately calculate shutdown dose rates using full-scale Monte Carlo models of fusion energy systems.•Demonstrate the dramatic efficiency improvement of the MS-CADIS method for the rigorous two step calculations of the shutdown dose rate in fusion reactors.