Depending on how your work tab is split up, hauling to things like fires and engines is the 'Refuel' job.

Good to know! I am not sure what changed or what was different (fuel level was right, not forbidden and I did own it, didn't need to "claim") but I just destroyed the reactor and rebuilt it and for now it seems to be working properly like it did when I first started.

I guess I meet to pay close attention to see if the problem happens again so I can try to discern what is going on at that moment.

Not sure, but it might be a home area issue but only if people don't refuel things unless they're in home area (like putting out fires, or cleaning). Rebuilding it might have automatically set it as a part of the home area for you, which would fix that (if that was the problem).

Not sure about any of that though. Just a thought.

A good thought. I will have to check that if it happens again.

i got a fission reactor on my first ever ship, with nuclear engines. so i filled them all with uranium fuel pods. but the ship tells me it needs 3k chemfuel to start. so i transported chemfuel on board, but i dont know where to put it? or is it a bug?

I think sometimes it will say that you need chemfuel but you actually need uranium fuel pods loaded into your engines. If I had to guess, you need more engines to launch the total weight of your craft. The launch report calculates the fuel you need based upon the size of your ship.

For example if you need 4000 fuel to launch and you have engines that can hold 3000, you need to build another engine.

The question isn't about the launch report. It's about individual engines not being refuelled by colonists.

But yes, that's an odd issue as well. I assume it's because the base game only really recognises chemfuel for ship launch reports?

Yeah. It says chemfuel but if you have nuclear engines it means uranium.

Also an update. My reactor "broke" again without any obvious reason. However. It seems that if the fuel level gets low enough, my colonists will actually still refuel it even though I have the target set to 2500. Around 200 units of fuel from the looks of it.

I identified the "refuel" work type in fluffys work tab and tried assigning them to only that and they still wander. I am going to try moving mods around on my mind list to see if anything helps.

I should note as well. I can always right click the reactor and force them to refuel it. But they only haul to it once. So basically I have to baby sit it and right click it over and over again to fill it up completely.

It's not a mod. I see the same behavior. Colonists only fill the reactors up about 1/3 of the way. The only mod I run besides SOS2 and it's supporting mods is wall lights, and I saw this behavior before installing wall lights.
I just live with it. The nuclear reactors don't run out anyway, their run time is ridiculously long. I'm not even sure it's really a bug.

Thank you very much Bootbottom! That is more or less what I was curious about. Indeed, they only seem to keep it about 1/3 full regardless of the target fuel level.

On a whim, I toggled the power of the reactor off to see if maybe my pawns would be more interested in refueling it when it isn't in operation, but no joy.

I just got a refueling machine from Project Rim Factory and connected it to my stockpile of Uranium Fuel Pods and now my reactor is full all of the time! Not sure what the difference is though.

Glad to help!