That was the USSR. Apparently, this remedy was used four times. It worked three of them.
But that was on the earth's surface, not a mile deep in the ocean, and then a further several thousand feet into the ocean floor:
Crooks & Liars has been discussing this proposal this morning. The strongest argument against nuking the leaks seems to be this:
I have been involved in sub-surface and tunnel shot testing at the Nevada Test Site (NTS) - timing and firing engineer - I have explained why this won't work, and yes, take a look at Baneberry Event - December 1969 - that was an estimated 50 barrels of water that flashed to superheated steam - it fissured through solid granite strata!!! Further, drilling to 18,000 feet is absurd. Our shot holes were between 3,000 and 5,000 feet) And as you drill (a shot emplacement hole is not going to be less than a three foot diameter hole - You need very specialized equipment to drill that diameter hole - the time to drill that would be months - AND you would be drilling a very large hole - IN THE SEA FLOOR! You could NOT keep it dry and the water WILL flash to superheated steam! Opening up more leaks.
Anyone who has been around these things, particularly at the NTS will tell you how absurd this idea is. And the folks at DOE, Los Alamos, Sandia, and Livermore know that this is not practical or possible in any way, in a sub-sea environment. I wish people who have not been around these devices, nor involved in testing them, would PLEASE STFU!