If a dirty nuclear bomb is planted in a city, even if it can be found, it could be very hard to defuse.
Today’s invention is a way to move any such device to safety with maximum speed.
The bomb would be placed (perhaps by a mobile robot) in a spring-mounted box atop a tunnelling machine with its axis vertical. This would also contain a small, remotely controlled explosive device.
The drill would be fired up, creating a path, perhaps through many floors within a building, towards the ground.
A cable attached to the box would allow the whole system not to crash downwards at any time.
Eventually, when ground level was reached, the drill would rapidly create a vertical shaft around the bomb in the box, channelling the spoils behind as backfill (and perhaps also pumping in concrete, if the situation allowed this).
With a deep enough shaft, the added, trigger explosive could be detonated, allowing any radiation from the nuclear blast to be absorbed by the surrounding earth.