Which aren't working. Did you know that India now has a fleet of SBN's?

https://en.wikipedia.org/wiki/Arihant-class_submarine

There have been some efforts to make it less likely. Nothing that would outright stop it.

Nonproliferation efforts aren’t even about making it less likely. They’re only about not making it more likely.

The expansion of global trade has done more to stop nuclear war than anything else. You don't want to nuke the guy who gives you all your soybeans.