Is there a way to automate refueling the cores for the nuclear locomotive? Because inserters don't seem to want to load cores from a chest hopper and it's a bit frustrating when conventionally fueled locomotives are seemingly easier to keep operating autonomously. Am I missing something simple here?

I have seen no problems with that.. I have made a requester chest asking for cores on the logistic net.
When cores are in the chest, the inserter does hop them without problems in the nuclear locomotive..
Is this exactly what you want?

It is, so I'm confused why it isn't working for me - because that's pretty much exactly what I tried to do. I have a requester chest asking for a core and an inserter where the locomotive idles during that stop, but the inserter won't transfer the core - even when the locomotive is sitting there requesting fuel. Hmm.

I tried fondeling around with the settings of my train..
It doesn't make difference as far as I see if my train is in auto or manual mode.
Train onlu accepts uranium fuel cell. are you having the right request in the requester chest?
is your inserter close enough to the train, has it power and is it in the right direction? (just guessing for you)
Is your inserters hand currently holding another item ? (break down the inserter and replace it, it will clear it's hand)

Tearing it down and setting it back up again has it working now - not quite sure what was up with the inserters before, but it looks good now. Thanks!

The most possible reason looks like your inserter was holding something else in it's hand.. Maybe you did first bring coal to the inserter and then found out nuclear train only accepts nuclear fuel?

have you tried manually putting some fuel in, driving off then sending it back to a waiting inserter (with the inserter only having cores to pull from the chest). I find that sometimes I have to give it a kick start, but after that, they refuel just fine and my trains are all a mix and all being refuelled at the same refuel stop.

I've just got two chests one for advanced fuel, one for nuclear cores