Israel has a good case and arguement to use nuclear devices, however, I think they can get away with using them in an engineering function. If you want to cause mass death and destruction, play with the nuke yield simulator at the bottom of my post.
The best way to deal with subterranian engineered structures is with low yield nuclear weapons:
It is actually one of the safest uses of nuclear devices, actually it is engineering, basically a way to destroy underground structures with almost ZERO surface radiation (plus you create a nice, deep, nuclear-engineered ditch).
The United States experimented with using twenty (20) nuclear weapons to build a trench through Nicaragua making a BIGGER Panama Canal. They also wanted to use Peaceful Nuclear Explosions (PNEs) to build an artificial bay on the North slope of, AK. See: Operation Plowshares. But I digress.
Just look at the photos from Nevada. If they were all in a line, it would be a perfect, man made barrier:
The Isreaelis have all that they need:
1) Acceptable use CAUSE for using "special weapons",
2) Nuclear weapons,
3) A 3km buffer to limit civilian casualties,
4) An urgent need to collapse the tunnels,
5) Finally, it sends a message to the rest of the Mud-slime world (especially Iran) that they are NOT afraid to use nuclear weapons (albiet, in a scientific, controlled, engineering sense):
If you want to entertain the thought of using small, tactical nuclear weapons, use THIS LINK TO EXPLODE YOUR OWN NUKE OVER GAZA
Enjoy!