Previously shown but not understood HERE, in 1961 GE proposed modifying a B-52G to serve as a testbed for a single XNJ140E-1 nuclear turbojet. The very large engine would be contained in a nacelle attached to the port rear fuselage. With eight conventional J57 chemical turbojets, the testbed aircraft would be capable of putting the engine through the altitude and airspeed paces that would be expected of it in the NX-2 nuclear powered bomber demonstrator (35,000 feet and Mach 0.8). This configuration would be capable of sustained nuclear flight.
Another configuration would have a second XNJ140E-1 nuclear turbojet on the other side of the fuselage, and only four J57’s. This aircraft would be capable of pure nuclear flight from takeoff to landing, with the J57’s as emergency backup.
Approximate isodose lines around the nuclear B-52G in powered flight