So, we are listenting to an EntityExplodeEvent, then place down TNT and let it blow.

You will notice that event if you set the yield in the event to 0.0, blocks still drop, although a yield multiplicator of 0 should be 0 I mean x*0=0

I made example code below to test this, but this is mainly an issue in Towny, which has a block regeneration feature that needs to be fixed, since currently it allows for duplication, we did find a hotfix which is just setting it to a material that does have any drops (AIR).

An example Listener (I was too lazy to compile a plugin)

@EventHandler(ignoreCancelled = true)
public void onEntityExplode(EntityExplodeEvent event) {
    event.setYield(0.0F);
}