yes there are two workable defensive systems against nukes...
one is a pre-deployment consignment of the weapons fabrication and possible fuel source facilities to the scrap heap. The israelis have had 100 percent success rate in employing this measure.
the other is the US money for weapons program. for a certain amount of money, the US will buy your old nuclear weapons and turn them into scrap. each weapon bought is 100 percent reduced from your opponents inventory.
other than that, there is no other nuclear defense that is 100 percent reliable. its not the nuke that is dangerous...its the delivery systems.
as long as your opponent chooses to deliver the nuke to you in a well reconized package, you have a chance of getting it. say like on a ballistic missile with a good reconizable thermal bloom at launch, and a reconisable launch container you can hit with a laser, a kinetic kill weapon, or an explosive before it delivers the payload. its when the delivery system changes to a non reconizable or familar form ( a car, a bus, a ship, a plane, or a human being with a backpack are some examples) is when all the sophistication and instrumentation in the world will not stop it.
Maybe with the implacement of good ole neutron detectors will will finally be able to screen for them...but for now its a very difficult task.
sorry to be so pestimistic...but...reality doth bite