Same as closed issue #4014.
I think it still has the bug or something...
I made water-cooled reactor on my server, but can't extract steam from reactor in any way.
So I tried to build in creative for debug, but no steam extraction. It has steam in reactor's GUI.

No steam extraction

I'm using the modpack called All the Mods V1.50

Not a bug, it's user error. Configure the port from INPUT to OUTPUT. Also, the reactor pushes steam out. No need to pull. Tested and works fine as seen with attached screenshot.

Thank you for the response.
I couldn't find the documentation about it. I'll try soon and close this issue.