Actually nukes can be maintained without access to uranium, I doubt the half-life of uranium should be the issue of the maintenance, not just the technology but procedures would have to be taught for saftey and procedures to maintain them as well.
As far as firing back, that's what treaties are for. And we haven't seen any of these treaties in CN or CNRP, as they are different in nature. A Nuclear Retaliation Treaty is a treaty that states that any nuclear attack on the nation will be retaliated immediately by nukes from the allied nation. I would love to give more details, but its still classified above Top Secret so I cannot point out much more than just the idea of it.
I am quite amazed that I haven't seen any of these treaties in CN yet...This way, there is no need to give a nation a nuke when they might change government and you could lose the ally and them still have the nuke. This treaty allows the nuclear capable nation to retain control and support their ally all in one step. Also, we need to consider distance. If a nation poses a threat to me, I want to have a NRT (Nuclear Retaliation Treaty) with a nation that is very close to my adversary, that way, I can be content that by the time their nukes are in orbit enroute to my nation, the shorter range nukes from my ally have already hit my adversary.
IC: Peace be with you