Reactor Coolant (quest)

Reactor Coolant is a Brotherhood of Steel repeatable quest $$

Detailed walkthrough
This quest becomes available once the main questline of the Brotherhood of Steel has been completed. Proctor Ingram will ask the Sole Survivor to create some reactor coolant. Once the reactor coolant has been crafted, it can be returned to Proctor Ingram for a reward of 100 caps per unit.

Once the quest starts, reactor coolant becomes available as a craftable item: