SEABROOK — A recent Nuclear Regulatory Commission report detailing the results of an inspection of the concrete degradation at NextEra Energy Seabrook indicates the nuclear power plant’s staff is taking the needed steps to ensure structural integrity and operability, as it continues to delve into the problem.
The report details the findings of a three-week on-site inspection by agency regulators, according to NRC Division 1 spokesman Neil Sheehan, as well as four months of in-office reviews to assess the adequacy of actions taken by NextEra to address the plant’s alkali-silica reaction issues.
Discovered in June 2009 in some of the 2-foot thick walls of the plant’s subterranean tunnels, ASR is a slow chemical reaction that can happen when moisture interacts over a long period of time with the alkaline cement and reactive silica found in some aggregates used to make concrete. ASR forms a gel that expands, causing micro-cracks that affect concrete properties, but which can take five to 15 years to show up.
While repeatedly assuring the public that Seabrook Station is safe, the NRC has stated it will make no final decision on NextEra Energy Seabrook’s request for a 20-year extension of its operating license until the commission is satisfied that all its concerns have been addressed and is assured the plant can continue to operate safely.
The results of the inspection will be the topic of discussion on Tuesday, Dec. 11, when the NRC holds a meeting in Hampton to update the public on the ASR situation at Seabrook Station.
This May, the NRC issued a Confirmation Action Letter listing actions the plant will take in regard to monitoring the current ASR conditions. That includes a lengthy analysis currently being done by the University of Texas to evaluate ASR’s possible future impact on the structure’s physical integrity. That study is expected to continue into mid-2014.
Based on its assessments during the recent inspections, the NRC closed five of 11 items in the Confirmatory Action Letter regarding regulatory commitments it made to address the concrete degradation, Sheehan said. The remaining six items will be reviewed during another inspection planned for early 2013.
“In other words, our reviews of the condition are ongoing,” Sheehan said. “We have said previously that no final NRC decision on the plant’s license renewal application will be made until we fully understand and approve of NextEra’s plans in response to Seabrook (Station’s) concrete degradation.”
The inspection team determined NextEra Energy Seabrook had appropriately demonstrated that the ASR-impacted structures were “operable, but degraded and non-conforming.”
According to the report, “NextEra adequately demonstrated that the structures would maintain structural integrity for design basis loads and load combinations for normal, accident and environmental extreme conditions, including seismic. The degraded and non-conforming ASR-affected structures are being addressed through NextEra’s (Confirmatory Action Plan) and the planned (University of Texas) testing program.”
The team found there is no intention on the part of the plant’s owner to stop its evaluations of the structure until the degree of ASR degradation on the station’s steel-reinforced concrete structures is reconciled with its design and licensing basis, and that the progression of ASR is appropriately monitored to ensure that the physical integrity of the plant and its operabilty is maintained for the duration of its current license.
Further, inspectors determined NextEra’s current position is that no reinforced concrete structure at Seabrook Station will be precluded from monitoring for the effects of ASR until a satisfactory petrographic examination has been completed on that structure to confirm the absence of ASR.
The NRC distributed its report to Seabrook Station watchdog, Newburyport-based C-10. The letter to Debbie Grinnell, delineates answers to a number of questions she posed to the agency specifically concerning ASR at the power plant.
Among her questions, Grinnell asked about the current extent of ASR at Seabrook Station, its likelihood of appearing in other areas, the affect ASR degradation could have on the plant overall and the mitigation strategies possible to remedy the ASR problem.
After addressing Grinnell’s questions one by one, NRC Director of Division Reactor Safety Christopher Miller assured her the agency was taking this matter “very seriously” and had put together a “team of dedicated professionals to thoroughly evaluate this issue.”
“While we have completed the first phase of our review, we recognize that significantly more work is needed both to validate operability assumptions and to establish appropriate future structural monitoring of the ASR affected buildings,” Miller wrote to Grinnell. “We appreciate your organization’s interest in these matters and will continue to keep you and other members of the public informed as we continue to assess this issue.”