Context: At this point in history, the USA and USSR had aircraft fleets on constant patrol with tanker resupply. The concept was to simultaneously shorten the response time of strategic nuclear forces by having them "idle" nearer the target zones than their home bases and more importantly to reduce the potential losses of such strategic strike forces to a "bolt from the blue" preemptive & disarming attack. In a world where the President and SAC command would have to wait hours for B-36 & predicessor aircraft to make their way to their targets in Russia.

There were three real issues with this project: shielding weight, landing weight and politics. 1. Shot down or crashing, one of these aircraft would be a "dirty bomb" and could generate a nuclear contamination disaster. This alone made the project risky. Remeber, during the heyday of strategic nuclear bombing shootdowns were expected & ariplane to target assignments were made on the basis of the expected (and dismal) survival rate of inbound bombers. Also a single crash on US soil would have been... politically unpopular. 2. The lead, graphite and cement used to shield static nuclear facilities doesn't exactly work when trying to build an airplane, which made crew shielding dubious and reduced the loiter time of such a vehicle to the radiation tolerance of the crew. 3. A mich more minor issue was that of building landing gear that could hold the weight of the reactor on landing let alone a crash.

All that asside, a flying nuke plant is a great idea and I for one would not be surprised to see this idea resurrected for extreme loiter duration robotic aircraft :/