... that’s a nuclear-POWERED cruise missile.
Ever heard of "Project Pluto"? It was intened to be a supersonic atomic-powered cruise missile with multiple warheads (a bomber, really) that could fly for weeks.
Apparently, it has an open cycle engine with radioactive exhaust. Wikipedia: "It was proposed that after delivering all its warheads, the missile could then spend weeks flying over populated areas at low altitudes, causing secondary damage from radiation."