A Very Well Thought Out Theory
I just realized something. Nuclear power doesn’t exist in the Christopher Nolan Batman ‘verse. Bane proves, time and again, to be the master of the cunning plan, with almost limitless resources at his disposal. When he decides he wants to hold Gotham hostage, instead of simply breaking into a US or Russian military base and hijacking a nuclear warhead–which, given some of the other stunts he pulls of we can reasonably assume he would be capable of; hell John Travolta did it, and he’s an idiot–he goes through an incredibly torturous process of obtaining an experimental fusion reactor and weaponizing it.
Earlier, Bruce Wayne shuts down work on that same reactor because of its potential for destruction, instead of simply insisting that it be designed in such a manner as to be extremely difficult to turn into a bomb. There is never any mention of how the world has already be living and surviving with the threat of everything from backpack-sized atomic demolitions charges to missiles tipped with multi-megaton hydrogen bombs, and thus could probably deal with the threat of a improvised nuke so large it requires a heavy cargo hauler to transport.
Bruce’s atavistic fear of the potential destruction of the fusion reactor, and his unwillingness to let it go forward in a safer configuration seems to indicate that the science of nuclear fusion is poorly understood; perhaps they had not yet developed the technology to the point where they could be sure a reactor *would* be safe. It seems strange to shut down work on clean energy if one (very minor, and highly unlikely) side effect could be that it was turned into a bomb; his concerns become much more reasonable if he is a resident of a world that has no sense of context for nuclear blasts, and has thus not developed any methods of preventing them from happening, or have any firm idea of what scale the damage would be in other than a vague notion that it could destroy a whole city.
This theory is further supported by the fact that they never attempt to find the bomb using radiological sensors, which are installed in all real-world American port cities to attempt to prevent just this kind of scenario from happening.
This raises an interesting question. How did the United States and her allies force the capitulation of Imperial Japan at the conclusion of World War Two? The atomic bombings of Hiroshima and Nagasaki were what gave the Emperor the political excuse he needed to force his government to surrender, and even they weren’t enough to prevent an attempted 11th hour coup d’etat against him.
My theory? The timely advent of Superman, who must have traveled back in time to ensure that the stage was set properly for his peaceful upbringing in the heartland of a victorious post-War America. I expect the post-trailer JLA tease in Man of Steel to back me up, perhaps with an appearance by Clock King.