From the article: The idea of small reactors is as old as nuclear power itself. In July 1951, five months before a reactor in Idaho became the first in the wor

From the article: The idea of small reactors is as old as nuclear power itself. In July 1951, five months before a reactor in Idaho became the first in the world to produce usable electricity through fission, America began building USS Nautilus, a nuclear-powered submarine. In the 1960s and 1970s small reactors powered bases in Alaska and Greenland, a radar facility in Wyoming, a research station in Antarctica and—from a cargo ship—the Panama Canal Zone. America still uses nuclear-powered submarines and aircraft-carriers. But land-based mini-reactors proved unreliable and expensive and have fallen out of favour. I was thinking the same thing you suggested, that maybe the basically unlimited supply of water for cooling made the ocean-going reactors feasible. Other than that, I'd think a mostly stationary reactor would be simpler to deal with than a ship-based one.