I am sure you have moved on but for anyone else having this problem it's not bugged. You have to build the control actuator at your workbench then go the reactor that needs the part. Click the reactor and there should be a Control Actuator button on the bottom that is darker than other buttons. Click it and a green arrow will appear on the button. The part will be installed by a pawn now.

I'm having the same problem, even though I've already installed an actuator in my other reactor. I have an actuator already built and waiting, click the button on the turned-off reactor, and it acts like it's being pressed but nothing happens. No icon change, nada.