 The decision to put the RCPs on the inside of the vessel was a fairly radical innovation.With the existence of eight separate RCPs as opposed to the 2 or 4 of a typical PWR, when one pump goes out, that pump can be shut down and isolated, not be worked on until the next outage.It has in the past been proposed to use higher enrichments for IRIS, allowing a longer cycle life, but the design now calls for 4.95% enriched Uranium, which is the same as what is being used in current plants.