My father worked on the nuclear plane. When you asked him, it was cut off because of crazy hippies. Jane Fonda was at fault. What would happen when it crashed? Just be careful that it doesn't crash.
Crazy, indeed.
Obviously strong radiation will necessarily do damage. But the mechanism by which low-level radiation causes increased mortality over decades is quite complex, and could possibly be disrupted. There's no fundamental reason why medicine couldn't prevent all cancers. In that case radiation will become like most other hazards: OK as long as you limit exposure.
If so, it'll be awesome to ride around in hypersonic nuclear jets.
It is the same thing with transmutations caused by neutron radiation. If the proton count of the atom changes, the moecule that it is part of has to change as well. Again, there is no way to counter all the possible results of this process.
And finally, even if we countered the effect in humans, the wildlife would be similarly exposed, but without any treatment to counter the effects.
Directly fission powered airplanes are simply a pipe dream.