A nuke (of any size) will be detonated above ground in a test orchestrated by humans.
A nuclear missile is decommissioned in order for its fissile material to be used to power a nuclear power plant that provides power to an AI datacenter.
A nuke (of any size) will be detonated in a conflict or as an act of terror by humans.
An AI accident or malevolent act causes a nuke to detonate.