Few have been constructed, including some Soviet nuclear submarine reactors in the 1970s, but a number of proposed new nuclear reactor designs are lead-cooled.

A barge with a submarine reactor was sunk in the Kara Sea 1972.

The radioactivity in submarine reactors, at least those of American design, has several layers of containment, including the reactor vessel and the fuel elements themselves.

They are watching the dilution of uranium that had been enriched for military use, so it is unsuitable for bombs or submarine reactors, but can be turned into fuel for civilian power plants.

New American help included a nuclear submarine reactor and assistance with the Blue Streak missile programme.

Prototype of nuclear submarine reactor to be closed down.

Officials said Russia lacks the technology to safely remove spent uranium fuel from the submarine reactors as well as sites ashore to store waste before processing.

Electric Boat, in Groton, turned out a steady stream of nuclear-powered submarines and the United States Navy ran a landlocked submarine reactor in Windsor Locks, for training.

Paul Blanch, for example, moved to Connecticut in 1966, as an instructor at the submarine reactor in Windsor Locks, and went on to become a nuclear engineer at Northeast Utilities.

Since the 1950s it has been the site of several nuclear research establishments, including a prototype fast breeder reactor and a test for submarine reactors.