Whether its you or someone else who fired a nuke, simply fast travel to the blast zone and rush inwards into the middle of the very zone. You will hear a sound of warning while you wait and soon enough you will see the nuke coming down, for atleast few seconds before it detonates, blowing up the whole zone and killing you. Remember, all your junk you carry will drop, and if you want it back, you must enter the now highly radiated zone. If you want to keep your junk before doing this achievement, you will have to head to a stash or junk stash to keep the items. You will have to do this fast before the nuke is launched, as there doesn't go long, either a minute or two, before the nuke hits its target and you lose valuable time running into the middle of the zone. If you die on the outskirts of the zone, from the blastwave, then you won't get the achievement.