I got to S5G in Nov '87, while it was in the middle of refueling. It added 6 months to my time at prototype.@NukeET: I do remember in NPS, talking about the one-off boats that were early experiments in which is the best plant. The S1G, liquid sodium, the S3G, horizontal SG, the S5G natural circ and ginormous main turbine, and of course the S1C, electric 72 pole DC main motor. Fun fact. Not long before I attended NPTU S1C, they had refueled the core, which was only 9 modules; they left the old center one in just to see what happened.