The reactor I used doesn't use any cooling rod/capsules at all since they in fact HOLD heat for hours. My reactor just keeps throwing like 8 buckets of water into the reactor every second and removes 8 empty buckets in a continuous cycle. should it ever lag up or bug, it will explode. It's run stable for hours though np. I surrounded it with double wall of reinforced materials incase it does go up since it's directly under the center of town :) It won't be making any craters anytime soon.