This was one of three sodium cooled reactors (the core was moderated) ordered for the Seawolf program at the same time as three PWR units were ordered to support the USS Nautilus (SSN-571) program; In each case, one reactor was land-based for training and research, one intended for installation on a submarine, and one spare.
This involved ordering three sodium-cooled reactors (with moderated cores) for the Seawolf program at the same time as three PWR units were ordered to support the USS Nautilus (SSN-571) program; each reactor was designated for training/research on land, submarine installation, and a spare.