Robert Reich brings up whether GE was cutting corners with security controls within the Mark 1 Reactor, but he does not address why and how regulators failed to stop a 90% failure calculation from widespread adoption. Did they accept compensating controls? Liability offset? Low probability of melt?
The New York Times reports that G.E. marketed the Mark 1 boiling water reactors, used in TEPCOâ€™s Fukushima Daiichi plant, as cheaper to build than other reactors because they used a comparatively smaller and less expensive containment structure.
Yet American safety officials have long thought the smaller design more vulnerable to explosion and rupture in emergencies than competing designs. (By the way, the same design is used in 23 American nuclear reactors at 16 plants.)
In the mid-1980s, Harold Denton, then an official with the Nuclear Regulatory Commission, said Mark 1 reactors had a 90 percent probability of bursting should the fuel rods overheat and melt in an accident. A follow-up report from a study group convened by the Commission concluded that â€œMark 1 failure within the first few hours following core melt would appear rather likely.â€