SpecificExotic designs of atomic devices have directionality because of interaction with the material surrounding the core. This was revealeddocumented by George Dyson in his book PROJECT ORION, when he revealed the 'pusher capsule' bombs would have had a filler which turned into plasma and 'pushed' on the plate on the bottom of the spacecraft.
However, as seen in the Operation Starfish exoatmospheric explosions, detonations in space are spherical unless the device is specially designed for directionality, and most devices (as per my reading of Chuck Hansen) are not designed for directionality.