For me the idea is great however, you did not execute it on the level that you have proven you can reach.
To me it gives an end-of-the world feeling, but not the one that would be caused by the explosion but by the mountains in the back that are just not pleasing behind the nuclear explosion. I would try to make them a bit more visible.
To get rid of the strange feeling, I would aswell add some more buildings in circle around the nuclear explosion...Right now, especially on the left side there is not much you can see about them. Also adding a few (mainly) planks that are really flying towards the camere would be a nice touchup. I personally do believe that a nuclear bomb explosion would cause more dark and grey dust, but maybe that's just me...
However overall the idea is pretty awesome.
But you can definetally improve the execution.
Also the foreground could use some more work. the blank tiles do not fit the rocks the best yet.