The resulting leak caused a 12-day shutdown of the two reactors for repairs.

The plant’s owner, the Exelon Corporation, had long known that corrosion was thinning most of these pipes. But rather than fix them, it repeatedly lowered the minimum thickness it deemed safe. By the time the pipe broke, Exelon had declared that pipe walls just three-hundredths of an inch thick — less than one-tenth the original minimum thickness — would be good enough.

Though no radioactive material was released, safety experts say that if enough pipes had ruptured during a reactor accident, the result could easily have been a nuclear catastrophe at a plant just 100 miles west of Chicago.

Exelon’s risky decisions occurred under the noses of on-site inspectors from the federal Nuclear Regulatory Commission. No documented inspection of the pipes was made by anyone from the N.R.C. for at least the eight years preceding the leak, and the agency also failed to notice that Exelon kept lowering the acceptable standard, according to a subsequent investigation by the commission’s inspector general.

Exelon’s penalty? A reprimand for two low-level violations — a tepid response all too common at the N.R.C., said George A. Mulley Jr., a former investigator with the inspector general’s office who led the Byron inquiry. “They always say, ‘Oh, but nothing happened,’ ” Mr. Mulley said. “Well, sooner or later, our luck — you know, we’re going to end up rolling craps.”

Critics have long painted the commission as well-intentioned but weak and compliant, and incapable of keeping close tabs on an industry to which it remains closely tied. The concerns have greater urgency because of the crisis at the Fukushima Daiichi plant in Japan, which many experts say they believe was caused as much by lax government oversight as by a natural disaster.

The Byron pipe leak is just one recent example of the agency’s shortcomings, critics say. It has also taken nearly 30 years for the commission to get effective fireproofing installed in plants after an accident in Alabama. The N.R.C.’s decision to back down in a standoff with the operator of an Ohio plant a decade ago meant that a potentially dangerous hole went undetected for months. And the number of civil penalties paid by licensees has plummeted nearly 80 percent since the late 1990s — a reflection, critics say, of the commission’s inclination to avoid ruffling the feathers of the nuclear industry and its Washington lobbyists.

Although the agency says plants are operating more safely today than they were at the dawn of the nuclear industry, when shutdowns were common, safety experts, Congressional critics and even the agency’s own internal monitors say the N.R.C. is prone to dither when companies complain that its proposed actions would cost time or money. The promise of lucrative industry work after officials leave the commission probably doesn’t help, critics say, pointing to dozens over the years who have taken jobs with nuclear power companies and lobbying firms.

Now, as most of the country’s 104 aging reactors are applying for, and receiving, 20-year extensions from the N.R.C on their original 40-year licenses, reform advocates say a thorough review of the system is urgently needed.

The agency’s shortcomings are especially vexing because Congress created it in the mid-1970s to separate the government’s roles as safety regulator and promoter of nuclear energy — an inherent conflict that dogged its predecessor, the Atomic Energy Commission.

“It wasn’t much of a change,” said Peter A. Bradford, a former N.R.C. commissioner who now teaches at Vermont Law School. “The N.R.C. inherited the regulatory staff and adopted the rules and regulations of the A.E.C. intact.”

Mr. Bradford said the nuclear industry had implicitly or explicitly supported every nomination to the commission until Gregory B. Jaczko’s in 2005. Mr. Jaczko, who was elevated to chairman by President Obama in 2009, had previously worked for both Representative Edward J. Markey, the Massachusetts Democrat and longtime critic of the nuclear industry, and Senator Harry Reid, the Nevada Democrat and current Senate majority leader who sought to block a nuclear waste repository in his state.

Article source: http://www.nytimes.com/2011/05/08/business/energy-environment/08nrc.html?partner=rss&emc=rss