Not anything new--the US Army had several floating reactors in the 60's and 70's which were under an Army NPP license (just like SL-1). One of them--the Sturgis--powered the Panama Canal off and on for several years.
They were all decommissioned in the late 70's, and the reactors were removed, but the radioactive piping remains. All are still under an Army radioactive materials license. The Sturgis is maintained at a pier in Baltimore, and is scheduled to be towed later this year to Texas and be dismantled.