NRC wants more information about concrete condition at Seabrook Station

Mar 31 - McClatchy-Tribune Regional News - Jim Haddadin Foster's Daily Democrat, Dover, N.H.

Federal inspectors have confirmed a concrete condition found in an underground tunnel at Seabrook Station poses no immediate safety threat, but the Nuclear Regulatory Commission is calling for more information about how the issue will be managed in the future.

The plant operator has applied to have its operating license extended from 2030 to 2050, but the application has been delayed while the NRC reviews the concrete condition.

Tests showed groundwater has deteriorated some of the concrete in the underground tunnel by more than 20 percent. The discovery of prompted the NRC to delay a safety report connected with the plant's request for a 20-year license extension.

NextEra representatives have said the issue has been dealt with, the area in question is now dry and the structural integrity of the concrete continues to meet standards.

The NRC this week issued the findings of the latest inspection at Seabrook Station, which focused on NextEra's analysis of the concrete issue.

Six inspectors visited the power plant during two separate trips in September and November 2011 to evaluate the concrete issue. An inspector also visited the Illinois laboratory where NextEra's concrete testing is conducted to verify its procedures are sound.

In a letter dated Monday, March 26, the director of NRC's reactor safety division wrote the concrete condition poses no immediate safety threat, but he instructed NextEra to be prepared to discuss plans for future management at an April 23 meeting with the NRC.

"The inspectors concluded that these structures can currently perform their safety related functions despite the observed degradation due to (the condition)," Miller wrote. "However the NRC still has concerns associated with long term operability, therefore additional information is needed."

The NRC has requested more information about the effects groundwater leakage might have on other parts of the tunnel, such as the steel rebar that reinforces the concrete, as well how fast ASR progresses and how aspects of the concrete will be affected by the condition.

NextEra was also notified of two low-level violations, which must be addressed in a pending action plan.

The NRC is requesting the corrective plan includes information about the overall progression of the concrete issue, its effects and its causes, as well as a list of actions to correct or mitigate the issue and a timeline for key actions.

The degradation was caused by an alkali-silica chemical reaction in concrete. Such a reaction occurs over time when concrete is in contact with water. The alkaline cement paste and reactive, non-crystalline silica found in some common coarse aggregates can form a gel in the presence of water. The gel expands and causes tiny cracks in the concrete, changing its physical properties.

NRC representatives believe the decay is the first confirmed instance of such deterioration in a safety-related concrete structure at a nuclear plant in the United States.

Asked to comment on the inspection report, NextEra spokesperson Al Griffith responded via email this week that the operators are pleased the NRC has made clear there are no immediate safety concerns at Seabrook Station. The plant has a comprehensive strategy in place to effectively manage ASR, Griffith wrote, which includes augmented monitoring, improved analysis techniques and efforts aimed at mitigation.

"We share with the NRC the desire to complete ASR analysis and testing so that we fully understand any potential long-term impact ASR may have on our safety-related systems and structures," he wrote.

One of the two low-level violations noted during the recent inspections resulted from failure to fully evaluate the potential "structural and seismic impacts" of the concrete degradation, according to the inspection report. The second minor violation stemmed from failure to re-evaluate a "use-as-is" determination for certain safety-related structures impacted by the concrete condition before implementing a design change.

Sheehan said in addition to the two issues that were noted in the inspection report, the NRC has previously documented three other minor violations between May and August 2011. NextEra will need to address all inspection findings in its corrective plan.

Asked if the company has met its obligations to the NRC to assemble a long-term plan, Sheehan said the commission is "not fully satisfied with the responses we've received back."

"We still need more information on their analysis on why the buildings would be able, in the long term, to perform their safety functions, and what kind of comprehensive plan the company is developing to address that," he said.

The company was also scheduled to present an engineering evaluation by the end of March.