he more we learn about a case of severe corrosion discovered at a nuclear plant in Ohio last March, the more frightening the incident appears. The corrosion, which ate nearly all the way through the thick lid of a reactor, left the vessel dangerously vulnerable to rupturing. Even more alarming were the slipshod industrial practices and lax regulatory oversight that allowed it to happen. If those practices are not changed, the same pressure to keep reactors operating while ignoring warning signs may threaten the safety of nuclear plants all around the country.

The corrosion was found almost by accident at the Davis-Besse nuclear plant in Oak Harbor, about 25 miles east of Toledo. For several years operators had missed the significance of warning signs that boric acid was leaking and accumulating in potentially dangerous amounts. During inspections last February, a workman stumbled onto hidden corrosion that shocked everybody. Boric acid had eaten through six inches of carbon steel, leaving only a stainless steel liner about a quarter-inch thick to hold in high-pressure cooling water.

When investigators looked into the matter afterward, they found disturbing evidence that both the First Energy Nuclear Operating Company, which runs Davis-Besse, and the Nuclear Regulatory Commission had put production interests ahead of safety. The industry's own oversight group, The Institute of Nuclear Power Operations, concluded in November that the power company had shifted focus from "implementing high standards to justifying minimum standards." It accused the company of excessive focus on production goals and "lack of sensitivity to nuclear safety."

Unfortunately, the regulatory agency that was supposed to ride herd on unsafe plants was equally negligent. A report just released by the N.R.C.'s inspector general concludes that the regulatory staff was slow to order Davis-Besse to shut down for inspection, in large part because it did not want to impose unnecessary costs on the owner and did not want to give the industry a black eye. Although the N.R.C. insists that safety remains its top priority, its timidity in this case cries out for a searching Congressional inquiry into whether the regulators can still be counted on to protect the public from cavalier reactor operators.