Officials from the Nuclear Regulatory Commission recently spent a week at NextEra Energy Seabrook nuclear power plant in association with the federal agency's review of NextEra's license amendment request that deals with the plant's concrete degradation.
Seven members of the NRC staff spent from June 5-9 at Seabrook Station. During the week, NRC members reviewed numerous documents and inspected the plant, as it gauges NextEra's safety plan to monitor and manage the alkali-silica reaction phenomenon present in concrete throughout the power plant.
Discovered by Seabrook Station employees in 2009 and immediately reported to the NRC, alkali-silica reaction - or ASR - is a slow chemical reaction that can occur when alkaline cement reacts with silica found in some types of concrete aggregates when moisture is present. It manifests itself as a gel in the concrete, that expands and causes micro-cracks that can affect the properties of concrete, as well as cause deformation.
ASR can take as long as 15 years to make itself known. It is commonly found in bridges and dams, but so far Seabrook Station is the only American nuclear power plant to exhibit ASR, although it has been found in the concrete of nuclear plants elsewhere in the world.
According to the NRC, ASR has not affected the safety of Seabrook Station. The concrete walls throughout the complex remain structurally sound, repeated inspections by the federal regulatory agency have determined. The NRC credits the plant's two-foot thick, rebar-reinforced walls for being able to maintain federal standards for load bearing capacity where ASR is present.
Seabrook Station went online in 1990 and has a NRC operating license that extends to 2030. In 2010, however, NextEra applied to the NRC to have its license extended to 2050. Such license extension applications are common in the U.S. nuclear power industry.
The federal agency told NextEra its application is on hold until the company can prove to the commission that it can safely manage the ASR problem as the plant ages and ensure public safety.
NextEra embarked upon a two-year study of the ASR problem, which was conducted by the Ferguson Structural Engineering Laboratory at the University of Texas. It is the results of that study that NextEra used to produce its August 2016 operating license amendment proposal. The amendment addresses how NextEra will manage ASR over decades to come at Seabrook Station to protect public safety.
According to NRC Region I spokesman Neil Sheehan, NRC staff estimate it would take about 22 months to review the 400-page amendment and supplement, committing to finish its review of the license amendment request by the third quarter of 2018.
Since its filing about a year ago, NRC staff members reviewing the amendment have asked for more information from NextEra on specific areas to augment the amendment, according to NRC documentation, and last month's audit resulted in at least six more topics about which the NRC wants NextEra to supply more information.
During the week-long audit, Sheehan said, the NRC team posed numerous questions to NextEra staff and explained they would be issuing six more Requests for Additional Information to NextEra based on the site visit. But, Sheehan added, that's not out of the ordinary in such circumstances.
"We would not consider a half-dozen Requests for Additional Information to be unusual for a license amendment request, particularly one involving complex and novel issues," Sheehan said. "The number does not signify shortcomings on the part of the company as it developed the proposal. The NRC staff is diligently reviewing NextEra's plan and the requests allow for the compilation of details that are important to their evaluations."
The NRC is reviewing the license amendment request in accordance with the Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, according to NRC documentation. The amendment proposal, if approved, would adopt methodology for the managing of ASR, and revise Seabrook Station's Updated Final Safety Analysis Report to include those methods, according to the NRC.