After reading this thread, I wonder if anyone had ever read or looked at the DA Pamplet, Effects of Nuclear Weapons. I have a couple of copies, including one with the blast effects circular slide rule in the back. Against that, calculators and spread sheet programs make calculating damage effects using the formulas given in the book a lot easier to do.
The idea of using nuclear weapons to create tsunamis is really the stuff of science fiction. The energy required to generate a tsunami makes even a 20 megaton nuke look like a .22 Long Rifle round. As for scrubbing the island with one, given the mountains in the middle, dream on.
The radiation from a couple of 20 kiloton air bursts in not going to be any form of a long term problem. The bomb at Hiroshima was somewhere between 12.5 to 15 kilotons, while the Nagasaki bomb was about 22 kilotons, using plutonium, which is a much longer headache than the U-235 in the Hiroshima bomb. As for usiing nuclear explosions to drive the radiation plume from the land burst further into the island, no winner there. You do not get any form of sustained wind from a nuclear burst, as the fireball and heated air in the plume with suck air in, not blow it out. The shock wave propagates outward, but the following wind flow is in the opposite direction. The result is opposite pressure patterns on damaged buildings and structures which can increase the damage within the initial burst radius to a degree, depending on building construction. Earthquake-proof structures will survive much better than standard construction.
With respect ot half-life of isotopes, ten half lives reduce the radiation by 1000, 20 half lives reduce it by 1,000,000. So a 5 year half life isotope would have decayed to 1/1,000,000th of activity after 100 years. The most likely source of long-term radiation from a nuclear burst is Cesium-137 and Strontium-90. For anything else, you would have to manufacture that in a nuclear facility. To contaminate the entire large island adequately is going to take a lot of material, and then you still have to deal with your contaminant in the environment. it is not going to stay in one spot, but is going to keep moving. If highly radioactive, then there is likely going to be a fairly short half life. Remember the 10-20 rule, after ten, activity drops 1000, after twenty, activity drops 1,000,000.
One other factor that no one seems to have considered is how reliable are the nuclear weapons used? How long have they been in the stockpile?
