Quote Originally Posted by Dawnseeker View Post
The idea behind an explosive demolition is that the force of the explosion above the well would cause the casing and base of the well to essentially implode, forming a plug in the well. The belief by the experts I've interviewed is that any form of undersea detonation would demolish the casing entirely, and probably widen the hole in the seabed, exacerbating the problem, instead of solving it.
That's a description of a conventional explosion...

As far as they have said, a nuclear blast would have roughly the same deleterious effect. Fallout is not a concern because the explosion would be done far enough beneath the surface that nuclear material would not rise into the atmosphere. It is also not likely that there would be a significant danger to coastal environments from the explosion because the nuclear material would have plenty of time to dissipate in the ocean. There have been dozens of nuclear blasts underwater and above ground, beginning in New Mexico in 1945 without any detectable human effects, other than the two detonated in Japan.
...but with a nuclear explosion, you'd generate magma for a brief period of time. If the cavity is made small enough and deep enough, there would be a seal when the molten rock cools.

While it is true, as some have mentioned, that the Russians have successfully plugged 4 natural gas wells using nuclear explosions, these were all in land-based wells, not a mile beneath the ocean.
...and given that the oil is being expelled at the volume / velocity that it is, given that amount of water pressure, it indicates that the well is extremely pressurized, thus the relief wells may also have problems in getting the drilling mud to stay in place due to high pressure.

The relief well(s) is the appropriate current step, but if it doesn't work, then what?