At the Davis-Besse nuclear power plant in Ohio, it was discovered in 2002 that boric acid had almost eaten through a 15 cm thick reactor pressure vessel head. The corrosion exposed the stainless steel liner, which was for years the only barrier preventing a loss-of-coolant accident. A government study estimated that the hole would have widened to the point where the liner ruptured in another 2−11 months of operation. Emergency backup systems were also found to be impaired. (Schneider et al., 2007; Lochbaum, 2004)

Many warning signs had been overlooked since the leak began in 1996. Commercial imperatives were given priority over reactor safety. Regulatory oversight by the US Nuclear Regulatory Commission (NRC) was insufficient.

An NRC report said: “NRC appears to have informally established an unreasonably high burden of requiring absolute proof of a safety problem, versus lack of reasonable assurance of maintaining public health and safety, before it will act to shut down a power plant.” (NRC, 2002)

Above and below: Davis-Besse reactor, Ohio, USA: large hole in the reactor vessel head.

Physicist David Lochbaum (2004) wrote: “The NRC often states that risk insights cut both ways − they can trim regulations having little or no safety merit and they can also impose requirements in previously undervalued areas. But in practice, the NRC’s risk-informed sword is razorsharp on the side that slashes regulations and dull on the side that enforces regulations. [Dozens of example] show that the NRC abides by or abandons its absolute proof standard as necessary to allow nuclear plants to continue operating. The NRC must immediately stop admitting or rejecting circumstantial evidence based on the answer it is seeking. The data must determine the outcome, not vice versa.”

Lochbaum also noted in his 2004 report on nuclear power in the US:

  • the number of significant safety-related events had decreased in recent years but the rate of “near-misses” (elevated risks of reactor meltdown) appeared to have increased: “In other words, while the number of events is decreasing, their severity is increasing, with the near-misses getting nearer and nearer to disaster.”
  • 27 nuclear power reactors were shut down between 1984−2004 for more than a year for extensive repairs to safety equipment: “Years of overlooking problems and applying “band-aid” fixes at these plants resulted in a backlog of safety problems that took a long time to resolve.”