Can you refill a nuclear silo with a trigger?

Give it to a computer, make sure they can afford to build it, and run the 'Brood Wars Terran 2 - Town B' AI script for them.

To expand on the above:
You have to give the attached CC to the computer player, then run the script. Apparently it tries to create ghosts too, so you might get placement errors or some-such. I haven't always seen that myself, though.

Then give the CC back to the human player. The nuke unit inside the depot will still belong to the original computer player it was created for, however, so units killed by it will be counted for the CPU (luckily it will kill all units, ignoring alliance status). If this is an issue, you can place a small location that is Air only above the nuclear silo. Have a trigger that is "CPU player brings 1 nuclear missile to [location], give 1 nuclear missile from CPU to [human player] at [location]". With this trigger, you'll see the colour of the missile is briefly that of the original CPU player, but it'll change to the human player once it's been run.

That's the 'Brood Wars Terran 2 - Town A' script. I don't recommend it.

Right, I recall there are 2. I believe there might be some differences between them though, like they take different approaches for the nukes. One of them causes the AI to build the nuke, while the other actually places the nuke unit directly into the building. One is more prone to failure than the other.

'Town A' creates the nukes instead of building them, and tries to create Ghosts in an unalterable location.

'Town B' just builds the nukes using resources like normal, and does nothing else. It always works as expected.

Thanks guys. What about detecting and moving nukes placed in the editor?

The only nuke units that will behave remotely like regular nukes are those that are created in silos, either by human players manually or using the method outlined above.

Any nuclear missile units you place in the editor won't behave as you want them to.

You can move around preplaced nukes using AI scripts such as Junk Yard Dog or Set Generic Command Target + Make These Units Patrol.

You had a similar question here which describes how to use Set Generic Command Target and Make These Units Patrol in detail.

Thx roy! Thats perfect. Thanks much!