He's no fun any more
It may be possible for a nuclear aircraft to crash without harming the environment any more than the impact of any 2,000-tonne or heavier aircraft, without fuel, would do.
2,000-tonne? Maybe it could be as light as 1,500 tonnes if it's three or four reactors, with three or four no-fooling radiation shields, and hardly anything else. These shields would be like solid 12-foot balls of iron, except about twice heavier, because they'd be made of tungsten, with a cramped reactor compartment in the middle. They would bury themselves deeply in anything they were dropped on. That's not necessarily helpful, nor a hindrance, to their preventing radiation leakage; it's just the way it is.
Some high-temperature coolant, maybe lead or maybe heavy B2O3, would penetrate the thick heavy metal walls and come out again and have its heat transferred to air. The post-shutdown heat could be taken up in boiling the coolant that was inside at the time of a crash. It could work.
--- G.R.L. Cowan, H2 energy fan 'til ~1996