Pebble Bed Reactor - sswelm/KSP-Interstellar-Extended GitHub Wiki
"Akula" Pebble Bed Reactor ( wikipedia ) provides tremendous power output, which operates up to potentially higher temperatures than Molten Salt designs but has a power output that is inversely related to temperature. This reactor is considerably lighter and have a higher core temperature than molten salt design, Despite these advantages, it hold a relatively small amount of fuel which is used at a considerably higher rate.
Unlike the other fission reactor, the design enables the lifetime of the reactor (at full power) to be nearly the same despite the size of the reactor. When the reactor is running at 25%, there is a slight difference in terms of fuel consumption between reactor sizes. This difference is not terribly helpful as none of the reactors are capable of running for more than a year without refueling.
While additional fuel can be processed using the ISRU Refinery, the weight of these modules/resources reduces the effectiveness of a reactor being used as a continuous source of power. This reactor is likely to be used on manned missions where it can be turned on and off as needed for bursts of energy. A kerbal is required to start and stop reactor.
