Definitive operational limits on TBR and blanket fission power that would constrain fissile-breeding breakout in ARC-class FPPs

Determine definitive operational threshold values for the tritium breeding ratio (TBR) and the blanket fission power in an ARC-class fusion power plant employing a FLiBe liquid immersion blanket that would render a fissile-material breeding breakout scenario infeasible under the plant’s operating conditions and design constraints.

Background

The paper performs a self-consistent time-dependent OpenMC neutronics analysis of an ARC-class fusion power plant with a FLiBe liquid immersion blanket to evaluate the feasibility and timelines of breeding significant quantities of weapons-usable material from U-238 and Th-232 under breakout scenarios. It characterizes how fertile mass and Li-6 enrichment affect key parameters, including time to a significant quantity, TBR, blanket fission power, isotopic purity, self-protection time, and decay heat.

In summarizing two-dimensional parameter sweeps (fertile mass versus Li-6 enrichment) for both breeding pathways, the authors note that while Li-6 enrichment can substantially extend breakout timelines and modestly alter TBR and blanket fission power, their study—based on a simplified blanket model—does not establish definitive limiting thresholds for TBR and fission power that would make a breakout scenario infeasible. They indicate that more detailed reactor design studies are needed to analyze vulnerability and to identify such operational limits.