The Nuclear Regulatory Commission is reconsidering deep-seated safety assumptions after a massive earthquake and tsunami crippled a Japanese nuclear plant in March and revealed potential deficiencies in the United States' own safety guidelines.

Martin Virgilio, NRC's deputy executive director for reactor and preparedness programs, said the commission is reanalyzing its safety requirements, both voluntary and mandatory, for combating the loss of electricity to plants and ensuring key safety equipment is operable and accessible during an emergency.

"What we once thought was not necessary for adequate protection, may in fact become necessary for adequate protection as a result of our study," Virgilio on Thursday told the Advisory Committee on Reactor Safeguards, a part-time panel of federal workers that has the authority to question NRC's decisions on licensing and reactor safety.

An NRC task force made up of senior officials and staff is slated to issue a final report on its findings on July 12, with a public release of its recommendations on July 19.

Although the task force has not found any indication U.S. reactors are unsafe, the group has revealed that nuclear plant operators rely on voluntary initiatives to safeguard reactors from catastrophic events like those that befell Japan's Fukushima Daiichi plant and that industry is not always following those guidelines.

For example, inspections earlier this month found operators are not consistently implementing voluntary "severe accident management guidelines," steps to be taken after a reactor's fuel has been damaged during an emergency and the operator is attempting to limit radioactive releases. The guidelines, or SAMGs, were implemented in the 1990s and do not fall under NRC's oversight program.

NRC inspectors found that safety equipment, mainly pumps, were found to be inoperable, missing or inaccessible because of plant modifications. NRC Chairman Gregory Jaczko and Commissioner George Apostolakis earlier this month pointed out the weakness of relying on voluntary safety standards to address rare but extreme threats to nuclear plants (ClimateWire, June 16).

"We've been somewhat inconsistent as a function of time and also issue-specific around whether [some rules are] voluntary or whether [they are] brought into the regulations," Virgilio said. "That's one of our key findings of the task force. Where we go with that, I think it's a little bit too soon to tell."

The task force is also looking into safety assumptions underlying requirements for plants to combat loss of on-site and off-site power. Those rules, Virgilio said, do not consider major events that would wipe out both sources of electricity, like the earthquake and tsunami that struck Japan. The rules also assume that AC power at the plants would be operable within hours, he said.

As NRC faces mounting internal and external pressures to ensure U.S. reactors are safe, Said Abdel-Khalik, chairman of the ACRS, asked Virgilio if the task force is probing the commission's overall ability to regulate the nuclear industry.

"Is the task force asking the bigger question of whether or not the NRC is an effective regulator?" Abdel-Khalik asked.

"In part I think we are," Virgilio said. "If we're not doing it there, we'll be doing it during the longer term."

Rethinking safety

Abdel-Khalik said he was concerned that NRC inspectors this month found some plant operators could not access or operate key safety equipment, and asked Virgilio why planned, triennial inspections had not detected the problems earlier (E&ENews PM, June 6).

Virgilio said inspections may need to be more robust when reviewing compliance with SAMGs and added that cooling systems for spent fuel pools are not covered by the voluntary safeguards.

"I will speculate that the team is going to find that our triennial fire inspections were not as robust as they needed to be," Virgilio said. "Maybe we didn't do a smart enough sample. We need to rethink, and that's clearly what the near-term task force is looking at."

The task force is also re-evaluating mandatory plans that operators must have to show they can continue cooling and operating the plant, even if power is lost. Those requirements, also called the "station blackout rule," ensure operators prevent core damage or damage to the spent fuel pools if electricity is lost during a rare, catastrophic event.

But Virgilio said the rule -- which requires operators to show they can cope with the loss of off-site power for up to four to eight hours -- assumes that power will be restored within two to four hours. The rule does not contemplate the failure of all on-site and off-site alternating current power sources and distribution, a disastrous domino-effect that plagued the Fukushima plant after electricity from the grid was wiped out and diesel generators were washed away by the tsunami.

"[The station blackout rule] really doesn't contemplate the loss of off-site power and the failure of the on-site power supplies as a result of that one event," he said. "We did not, as we promulgated the station blackout rule, think about one external event that would impact both the on-site and the off-site power supplies."

Virgilio said the task force will compare the design requirements for the Fukushima plant to requirements for American reactors, Virgilio said, and will incorporate any "lessons learned" into its recommendations.

The task force is also looking at the commission's safety recommendations that were made in the 1980s to improve safety for hardened vents in boiling water reactor Mark I containment systems, which relieve pressure that builds up around the reactor during a severe accident. Those safety improvements were not included in NRC regulations and were changed on a plant-specific basis, Virgilio said.

"The fact that these are not included in regulation means that these ... are outside your purview," Abdel-Khalik said. He added that if it weren't for the crisis unfolding in Japan and the venting of the Fukushima plant, NRC might not have learned of the various ways in which the vents were changed on American plants.

"Probably not," Virgilio agreed. "We did know there were differences but to the extent that we're starting to see now, I think that's new information to us."

The task force is still learning about hardened vents at the six-reactor Japanese plant and believes that hydrogen gas migrated from Unit 3 through piping into the fourth reactor unit, where an explosion later occurred.

Calling for a moratorium

A handful of anti-nuclear watchdog groups are demanding the commission stop issuing licenses and approving license extensions until the task force gleans lessons from the Japanese crisis (E&ENews PM, April 14).

The coalition of at least 45 anti-nuclear groups including Pilgrim Watch, Beyond Nuclear and Friends of the Earth in April petitioned NRC to halt licensing decisions.

Attorney Diane Curran, speaking on behalf of the groups last week, told the ACRS that it too must not approve any licenses or license extension applications until the task force has completed its review. The ACRS has the responsibility and authority to evaluate hazards of all proposed reactor operations before NRC issues or renews a license, Curran said, but the panel cannot meet its obligations without first incorporating lessons from the Fukushima disaster.

Curran expressed frustration that instead of slowing the process, NRC granted a 20-year license extension to the Vermont Yankee plant in March and granted a similar extension in April to the Palo Verde Nuclear Generation Station outside of Phoenix.

The groups say that NRC and the ACRS should halt license activities, just as it did in the early 1980s after a partial meltdown occurred at the Three Mile Island nuclear plant in Pennsylvania.

"In order for the ACRS to meet its responsibility to provide a well-reasoned and supported analysis about the hazards and the adequacy of safety standards in your reports on each licensing decision, you require significantly more information about the Fukushima disaster and its lessons," the groups said in a June 22 letter to the ACRS.

Rep. Ed Markey of Massachusetts, the ranking Democrat on the House Natural Resources Committee, has joined the groups in urging NRC to halt all licensing activities until lessons are learned from the Japanese disaster (Greenwire, April 15).