"Ahem, astronauts being exposed to radio-active elements in order to avoid solar radiation....unlikely."

You wouldn't want your astronauts standing near the location for the hole when you nuke it.

"Impactors on the Moon make holes but not very deep compared to their diameter and that's not want we want.
We need deep and narrow holes."

I thought you wanted an easy way to get a few meters of regolith over a living area. Another way is find big crater, have a fairly strong structure, put lstructure against the rim wall, then collapse [say with explosives] the rim wall so it buries the structure.