TNT Minecart should not destroy rails its on.

http://minecraft.gamepedia.com/TNT_minecart

What it does: it destroys them

Steps:
1. Create new World
2. Place down some Tracks at the end a activation rail and a solid block
3. Power the activation rail
4. Move a TNT Minecart to the activation rail and it will explode and destroy
the rails in the explosion radius