System-Level Tritium Transport Modeling for the Outer Fuel Cycle of the SCYLLA Breeding Blanket and Relevance for UNITY-2

The accurate prediction of tritium behavior in fusion reactor systems is critical for developing advanced breeding blankets and meeting future regulatory requirements for tritium safety. Kyoto Fusioneering introduces a system-level tritium transport model built in EcosimPro for a self-cooled lithium-lead breeding blanket. This study focuses on the self-cooled yuryo lithium-lead advanced (SCYLLA) design, which employs a silicon carbide fiber composite (SiCf/SiC) as the structural material and LiPb (15.7 at. % Li) as both the coolant and breeder.The model accounts for the recombination/dissociation at interfaces, tritium trapping, dynamic pulsed generation rates, charge exchange neutrals, and gas permeation, ensuring high fidelity under operational conditions. The framework captures the interactions across the SCYLLA subsystems, including the lithium-lead loop, tritium removal, activation product removal, helium removal, and corrosion control, enabling the robust evaluation of transport and extraction efficiency.SCYLLA underpins the development of enabling technologies such as vacuum sieve trays and permeation sensors, validated at UNITY-1 (Kyoto, Japan) with deuterium before tritium qualification at UNITY-2. The model also feeds the fusion fuel cycle simulator for UNITY-2, improving the predictions of hydrogen isotopologue concentrations and facilitating the integration of complex fuel cycle models.This work, which combines subsystem modeling, safety considerations, and phased validation, marks a significant step toward tritium management technologies for commercial fusion energy, positioning SCYLLA as a cornerstone for self-sufficient, regulatory-compliant next-generation reactors.