From back in the days when the atom was your friend and Americans took a whole different view on the topic of radioactive Japanese, in 1961 General Electric started pushing their concept of a compact refractory-metal reactor at the heart of a closed “pod” for marine propulsion. The powerplant was based on work then ongoing for nuclear powered aircraft… a nuclear reactor taking the place of the combustors in the middle of a turbojet. In the case of the 601 power package, the complete system was encased in a submerged watertight pod. It obviously could not use outside air, so instead it simply recycled neon. The pod was ringed with heat exchangers to cool the neon before ducting it back to the inlet. The turbojet was transformed into a turbohaft engine; the back of the pod was filled with gears to step down the RPMs of the shaft into something that could be used by a conventional marine propeller.
Two versions were described, a large (60 inch diameter) and a small (45 inch diameter) version. The illustration of the 601B probably shows the smaller version, based on the L/D. General Electric claimed that these units would make dandy propulsion systems for cargo vessels… basically, since all of the propulsion system was in outboard pods, the ship could be nothing but a big empty cargo hold. Also, they could be used to make hydrofoils and smaller submarines, down to four-man units. Entertainingly, nuclear powered torpedoes were also suggested.