The Mk VI "Cartridge" Architecture: A Host-Integrated Microreactor Module for Transportable Energy Autonomy

Current microreactor designs often suffer from the "monolith problem": once bulk shielding and heat rejection are integrated, the unit becomes too heavy and logistically rigid for diverse deployments. This paper proposes the Mk VI "Cartridge" Architecture, a split-mass concept that separates a transportable, sealed Power Cartridge (reactor heat source plus sealed thermoacoustic power conversion) from a Host Slot (stationary or mobile infrastructure) that provides qualified biological shielding and thermal management. The architectural objective is to treat the host as the dominant mass carrier (shielding, heat sink, security), while the cartridge concentrates the high-value elements. A notional 1.0 MWth design point targets 300 kWe electrical output and approximately 650 kWth of host-usable thermal export. The concept reframes "portable reactors" as standardized energy inserts compatible with multiple industrial ecosystems, subject to host qualification and a defensible safety case.