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Industry Seeks Greater Clarity on Seismic Hazard Re-Evaluations

The following news article originally appeared in NEI’s Nuclear Energy Overview.

Last week’s meeting of industry and NRC post-Fukushima steering groups indicates that work is proceeding smoothly on the top priority, or Tier 1, recommendations from the agency task force that studied the accident. However, industry executives identified issues related to the flooding and seismic hazard re-evaluations that could affect schedules depending on how they are resolved.

It was the fourth such meeting of the industry and NRC leadership teams. “We certainly value the opportunity to provide input,” said James Scarola, senior vice president and chief nuclear officer of Progress Energy. The industry also was represented by Maria Korsnick, chief nuclear officer and chief operating officer, Constellation Energy Nuclear Group; David Heacock, president and chief nuclear officer, Dominion Nuclear; and Tony Pietrangelo, senior vice president and chief nuclear officer at NEI.

Industry executives expressed concern about the agency’s plan to require licensees to evaluate the potential for flooding to affect downstream dams that impound water that a nuclear energy facility relies on for its ultimate heat sink, or backup supply of long-term cooling.

Scarola said that, based on previous discussions with the staff, the industry believed that the potential impact of flooding on a plant’s ultimate heat sink would be addressed later. “If it is necessary to bring this forward into phase one, we’ll have to look at the schedule for the 20 plants with downstream dams.” Requiring these evaluations in phase one “stands to postpone some of the safety benefits” of the Tier 1 work, he said. “We need to assess whether we really believe this is important enough to bring it forward.”

Pietrangelo pointed out that the flood-induced failure of downstream dams is but one of numerous potential hazards to a nuclear facility’s ultimate heat sink, all of which have to be evaluated. “Do we really want to look at one failure mode in isolation? We’d rather do it holistically, looking at it with other external events.”

The NRC staff said it always intended to have this type of failure mechanism addressed as part of Tier 1. However, “I think we’ve hit on an issue that we really need to continue to discuss,” said Michael Johnson, deputy executive director for reactor and preparedness programs at the NRC.

Another issue is how the NRC plans to handle the results of the re-evaluations of seismic hazards. In a March letter requesting detailed information from licensees, the NRC asked them to re-evaluate the seismic hazard for their sites. Scarola said the industry would like to implement any safety-beneficial changes as soon as possible. “It’s what we do with the analysis that provides benefits,” he said, not the analysis itself.

Heacock echoed his concerns. By the time the analyses are completed, he said, licensees will have a significant amount of information but won’t have actually done anything. “What can we do to get the safety benefits earlier than [waiting until] the end of the analysis?” he said. “This path doesn’t lead anywhere yet.”

Pietrangelo said the industry needs greater clarity about the objective of the seismic hazard re-evaluations. “We are concerned about where this is leading. We don’t have a defined process to disposition the results,” he said.

The discussion briefly turned to containment vents and questions about filtration to prevent or minimize land contamination in the event of a severe accident. The NRC expects to issue final guidance by Aug. 31 on implementing reliable hardened vents for boiling water reactors with Mark I and Mark II containments, said Eric Leeds, director of the office of nuclear reactor regulation at the NRC. The staff’s recommendations concerning filtration for containments will be forwarded to the commission in November.

Leeds said the staff is looking broadly at measures to prevent or minimize land contamination in the event of a severe accident. The industry has urged the NRC to consider options besides external vent filters, arguing it may not be the most effective way to prevent the release of radioactive material. However, the industry agrees that filtration is appropriate, Korsnick said. “We’re very aligned that a filtering strategy is a solid approach.”

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