non-proliferation 
noun [mass noun]
The prevention of an increase or spread of something, especially the number of countries possessing nuclear weapons: this will be the most important conference in our lifetime on disarmament and non-proliferation...
- This would seem to undermine the whole idea of nuclear non-proliferation.
- We agree with Holdstock and Waterston that all efforts must be made for non-proliferation of nuclear weapons.
- A new nuclear non-proliferation policy begins with the principle that we can no longer keep the nuclear genie in the bottle.