Warnings about the Mark 1 nuclear reactor design were being sounded as far back as 1972, focused on what would happen to the primary containment vessel surrounding the reactor if cooling systems failed, as has happened in Japan's ongoing earthquake-tsunami disaster, The New York Times reported Tuesday.
The containment vessel, typically made of steel and concrete, is designed to prevent melting fuel rods from spewing radiation into the environment if cooling efforts completely fail.
Most installations around the world use a type of system, known as a pressurized water reactor, which is sealed inside a thick, steel-and-cement tomb.
But the type of containment vessel and pressure suppression system used in the failing reactors at Japan's Fukushima Daiichi plant are physically less robust, and have long been considered more susceptible to failure in an emergency than other, newer designs.
The Mark 1 boiling water reactors were developed by General Electric and marketed as less expensive and easier to build, based partly on their comparatively smaller and less costly containment structures, the Times reported.
In 1972, an Atomic Energy Commission safety official said the sort of "pressure-suppression" system used in G.E.'s Mark 1 plants presented unacceptable safety risks and it should be discontinued.
Among concerns raised by Stephen Hanauer in his 1972 memo was that the smaller containment design was more susceptible to explosion and rupture from a buildup in hydrogen, a situation that may have led to the recent blasts at the Fukushima Daiichi plant.