The Nuclear Regulatory Commission is routinely waiving fire rule violations at nearly half of the nation’s 104 commercial reactors, even though fire presents one of the chief hazards at nuclear plants.

The policy, the result of a series of little-noticed decisions in recent years, is meant to encourage nuclear companies to remedy long-standing fire safety problems. But critics say it is leaving decades-old fire hazards in place as the NRC fails to enforce its rules.

Fires present a special risk to nuclear plants because they can knock out cables that control-room operators need to safely cool down a reactor. The explosions and fires at Japan’s Fukushima Daiichi plant have shown what can happen when operators cannot activate pumps, valves and other equipment needed to prevent damage to a radioactive core.

The Browns Ferry plant in Alabama, where a devastating cable fire 36 years ago prompted the NRC to adopt tough new fire rules, still doesn’t comply with the requirements to protect cables. Hazards at other plants include unprotected equipment, inadequate fire doors, and missing alarms and sprinklers. To compensate for being out of compliance, plants rely on temporary measures such as stationing workers on a fire watch.

No member of the public has ever been injured from a fire at a U.S. nuclear plant, and the NRC says reactors are safe. But longtime observers of NRC’s fire enforcement say the agency is pressing its luck.

“The agency takes full credit for the grace of God,” said George Mulley, who wrote several scathing reports about lax fire enforcement while chief investigator at the NRC’s Office of Inspector General.

Mulley said the commission has procrastinated for a simple reason: “They don’t want to cost the industry money.”

Fires are common at U.S. plants. There have been at least 153 since 1995, or an average of about 10 a year, according to NRC records.

Small fires, brief fires and fires in areas not considered critical to reactor safety have damaged essential equipment and forced emergency shutdowns, reports reviewed by ProPublica show.

An explosion in an electrical panel at Arizona’s Palo Verde plant in March 2010 and an electrical fire at the Columbia Generating Station in Washington state in August 2009 each knocked out reactor cooling pumps.

On May 3, a truck delivering flammable hydrogen to the Duane Arnold plant in Iowa burst into flames near a building holding machines that control the reactor. Plant operators declared an emergency while firefighters poured water over nearby hydrogen tanks.

Nine years ago, the NRC tried to confront the fire compliance issue, saying nuclear companies had to address problems such as unprotected cables and missing fire barriers, detectors and sprinklers. The industry argued that the plants already were safe enough.

So the agency offered an alternative: Companies could sign up for a new program requiring them to exhaustively study their plants and write new, customized fire plans. As plants worked toward repairs, inspectors would issue violations for only the most dangerous hazards.

Nuclear companies owning 50 reactors initially enlisted. While two test plants have completed their plans and overhauled their plants, the rest continue to operate with a patchwork of interim procedures and fire watches.

“They are not effective measures,” said David Lochbaum, a nuclear engineer with the Union of Concerned Scientists who has worked at Browns Ferry and as a trainer for the NRC. “You can limp by, but you can’t rely on them.”

Addressing deficiencies

NRC chairman Gregory B. Jaczko said in an interview that the agency’s enforcement approach has not diminished safety.

Before waiving a violation, inspectors make sure that the safety risk is low and that companies plan to fix the problem or put in place interim protection.

“We do require them to address the deficiencies,” Jaczko said. “It doesn’t give them a blanket pass on being in compliance [or] meeting the safety standard.”

But when ProPublica asked the NRC for a list of all the fire safety gaps at plants enrolled in the new program, the agency said it did not have one. Instead, companies are required to maintain a list at each plant so inspectors can review them, NRC spokesman Eliot Brenner said.

Those lists are not publicly available, so there is no way to assess what deficiencies exist, how serious they are and how they are addressed.

Until there is a fire.

At South Carolina’s H.B. Robinson plant last year, a high-voltage cable blew up, setting in motion a chain of events that disabled a cooling pump, damaged equipment and shut down a large part of the plant’s power grid after an improperly maintained circuit breaker failed. Errors by operators caused a second fire, and more damages and outages, when they tried to reset the system.

Robinson is one of several plants where the NRC recently has waived fire violations under its new program.

Inspectors had visited Robinson in 2007 and said it did not have enough fire detectors and suppression in the area where the cable later blew. They did not write a violation, and the detectors and suppression were never installed.

Control room operators learned about last year’s fire from co-workers who had seen it. Despite that, Robinson officials said the lack of detection did not affect the response to the fire, and an NRC investigation concluded that the fire protection performed properly during the blaze.

How long plants such as Robinson will have to address deficiencies is unclear. The NRC originally gave nuclear companies two years to transition into the new program. That would have required the first enrollees to submit proposed fire plans by 2007.

But just a few weeks ago, the commission voted unanimously to extend the deadlines for at least the third time, pushing final approvals to 2016 or later.

‘Enforcement discretion’

ProPublica reviewed recent NRC fire inspection records for plants enrolled in the new fire program and found more than three dozen instances in which inspectors had identified deficiencies but did not write violations. The agency calls the policy “enforcement discretion.”

At the Calvert Cliffs plant near Lusby, Md., a 2007 inspection found that if control room workers evacuated because of a fire, plans did not allow enough time for a manual procedure to protect reactor cooling pumps.

Inspectors did not cite the plant. Returning in 2010, they found three different violations that could impede a safe reactor shutdown during a fire, but they also did not write violations.

Last year, inspectors found that cables used to control reactor valves at the Turkey Point plant outside Miami were unprotected from fire. The protection had been missing since at least 2001 and was initially noted in 2004. Citing enforcement discretion, inspectors waived a violation.

The NRC said both plants had taken interim steps to protect reactors while they worked on new fire plans.

The NRC conducts special fire inspections at each plant once every three years. Notice is provided in advance, and inspectors single out three to five areas for scrutiny, review records and test safety procedures.

Plants that are not in the new fire program can also avoid strict adherence to the rules by obtaining a formal NRC exemption. Companies must have an alternate method of fire protection that is no less safe.

Fire exemptions are common. In 2008, the Government Accountability Office found that the NRC had issued more than 900. ProPublica examined the agency’s current exemption list and counted nearly 700 at 56 reactors, most dating to the 1980s. Three plants with six operating reactors also have pending exemption requests or are planning to submit one.

Among the most controversial exemptions is at the Indian Point plant north of New York City.

In 2007, the NRC granted an exemption to Indian Point, saying it was safe for certain cables to be protected with a fire barrier rated to last 24 minutes rather than the one hour required under fire rules.

Opponents sued the next year. Federal district and appeals courts concluded that the NRC had reviewed the exemption properly and dismissed the suit, although the courts did not review the underlying safety technical issues.

“There is an incredible depth of fire protection at this site,” said Jerri Nappi, a spokesman for the plant’s owner, Entergy. “If the NRC believes the plant was not safe, they would shut it down.”

Jaczko conceded that the agency has not moved to address fire safety issues as quickly as he would have liked, but he said the plants in the new fire program will be far safer because of the depth of required analysis.

Lochbaum, however, said the NRC is allowing nuclear companies to “drag their feet.”

“These plants are not a house of cards. It takes a lot of wrong things lined up to lead to a very bad outcome,” Lochbaum said, referring to the many backup systems all nuclear plants have to prevent a serious accident. “But when you start with a bunch of bad things already lined up, like fire protection violations, that shortens the list that is needed to complete the path from challenge to disaster.”

John Sullivan is a contributor to ProPublica, an independent, nonprofit news organization that produces investigative journalism in the public interest. A longer version of this article appears on the organization’s Web site.

ProPublica interns Nick Kusnetz and Sergio Hernandez and news researcher Liz Day contributed to this report.