Spotlight
Special NRC Oversight at Seabrook Nuclear Power Plant: Concrete Degradation
In 2009, NextEra Energy Seabrook, LLC (NextEra) realized that the intrusion of moisture into sections of walls in certain below-grade structures at the Seabrook nuclear power plant, in Seabrook, N.H., could cause the degradation of some of the concrete as evidenced by pattern cracking. It was confirmed in 2010 that what is occurring at Seabrook is alkali silica reaction, or ASR. The result of the reaction is a gel, which can expand and may cause micro-cracks in the concrete. Graphics detailing the chemical reaction and the expansive gel can be viewed on slide 9 of the May 10, 2012 presentation titled, "Seabrook Station Safety in Light of the Alkali-Silica Reaction Occurring in Plant Structures."
More recently, NextEra has identified that some of the ASR-affected structures at Seabrook have evidence of ASR bulk expansion (macro-cracking and some reinforced concrete wall displacements) due to the aggregate effect of ASR-induced micro-cracking.
The structures identified to be affected by ASR remain "operable but degraded," meaning that NextEra has determined the structures can continue to perform their safety functions. The basis for continued operability include confirmatory engineering design reviews using computer-based finite element analysis and detailed reviews of structural design calculations that demonstrate that sufficient safety margins remain based upon field measurements and/or bounding (worst-case) ASR degradation values. Reinforced concrete structural design margins for Seabrook were established in accordance with American Concrete Institute (ACI) Code 318-1971 and ensure that the as-built (design) structural capacity exceed any assumed load or specified load combinations. NRC inspectors have reviewed these analyses, design reviews and design calculations during onsite inspections and have concluded that NextEra has adequately demonstrated that the concrete structures as Seabrook affected by ASR remain "operable but degraded" while the NRC staff conducts ongoing licensing reviews. For more information on the event and the status of NRC follow-up and planned activities, see the following topics on this page:
- Summary of Event and Plant Conditions
- Confirmatory Action Letter
- Enhanced Oversight
- Developments Since Confirmatory Action Letter Closure
- Licensing
- Next Steps
- Publicly Available Documents
- Public Meetings
Summary of Event and Plant Conditions
In 2009 during the Seabrook License Renewal process, it was identified that the aggressiveness of the groundwater chemistry on concrete structures in contact with groundwater/soil needed to be determined. Testing was performed and in August 2010, Seabrook confirmed the presence of ASR degradation of concrete in below-grade walls of several Category 1 structures. Seabrook is the first plant in the U.S. nuclear industry to exhibit ASR in concrete structures on site. In response, NRC issued Information Notice (IN) 2011-20, "Concrete Degradation by Alkali Silica Reaction," on November 18, 2011, to provide the industry with information related to the ASR identified at Seabrook.
The NRC staff’s review of this issue to date has determined that there are no immediate safety concerns due, in part, to existing safety margins, the localized nature of the ASR, and ongoing crack monitoring.
Concrete issues, other than ASR, have also been experienced at other nuclear power plants. Crystal River 3 was shut down due to cracking (e.g., delamination) of the concrete walls in the plant's containment building. The issue occurred during work on an opening in the containment in preparation for a steam generator replacement project. Duke Energy, the plant's owner, announced on Feb. 5, 2013 that it planned to permanently cease operations at the Florida facility. In 2011, the Davis-Besse nuclear power plant discovered cracking in the Ohio plant's Shield Building wall, a concrete enclosure around containment, while contractors were creating an opening for replacement of the reactor vessel head. Information related to this issue can be found in NRC Inspection Report IR 05000346/2012007. It should be noted that the concrete degradation mechanisms in these plants are different than that identified at Seabrook.
Confirmatory Action Letter
On May 16, 2012, the NRC staff issued a Confirmatory Action Letter (CAL) to the plant's owner, NextEra, confirming regulatory commitments made by the company to address ASR at the plant as a result of a management meeting with NRC staff on April 23, 2012.
On May 24, 2012, NextEra sent NRC a response to the CAL which included the root cause for the organizational causes associated with the occurrence of ASR at Seabrook and an evaluation entitled, "Impact of ASR on Concrete Structures and Attachments."
On May 1, 2013, NextEra sent NRC a second submittal addressing the remaining CAL items, which included the details of their large specimen testing program and revised integrated corrective action plan.
The NRC conducted inspections to independently review NextEra's actions to complete their commitments. NRC documented the results in NRC Inspection Reports (IR) 05000443/2012009 and 05000443/2012010. Based on our reviews, NRC issued a closure letter on October 9, 2013, which closed CAL 1-2012-002.
Enhanced Oversight
On July 9, 2012, a "Working Group Charter" was developed to ensure that all aspects of the ASR issue were coordinated with the staff.
Further, on Sept. 14, 2012, a "Deviation Memorandum" that allows the agency to continue to devote additional review resources to the Seabrook ASR issues was approved by the NRC's Executive Director for Operations. The NRC's Reactor Oversight Process does not prescribe increased oversight for the plant based on its overall performance. However, the NRC staff determined that additional inspections and assessments were needed to support the review of licensee commitments and planned large-scale concrete specimen testing by the licensee, the development of staff technical guidance, and stakeholder communications and outreach activities.
Following the completion of the second CAL follow-up inspection report (NRC IR 05000443/2012010) and mid-cycle performance assessment per IMC 0305, NRC closed the Deviation Memorandum as documented in NRC letter, "Mid-Cycle Performance Review," dated September 3, 2013. The NRC continues to conduct inspections approximately every six months as part of the Reactor Oversight Process baseline inspection program and document the results in publically available inspection reports. The NRC also maintains oversight by the Seabrook ASR Issue Technical Team (SAITT). Accordingly, a revision to the SAITT Charter was issued on February 19, 2014 to reflect completion of activities associated with the CAL and to update the NRC ongoing review objectives.
Developments Since Confirmatory Action Letter Closure
Following closure of the Confirmatory Action Letter on Oct. 9, 2013, the NRC held a public meeting in Hampton, N.H., to discuss the ASR issue in detail, as well as the agency's monitoring efforts going forward. In 2014 and 2015, the NRC conducted periodic inspections and audits at the Seabrook facility and at the University of Texas focused solely on the ASR issue.
NextEra's testing of large-scale ASR-affected test specimens at the Ferguson Structural Engineering Laboratory (FSEL) at the University of Texas – Austin commenced in late 2013 and was completed under NextEra's direction in February 2016. Based on testing program developments in 2015, NextEra revised its structures-monitoring/ASR-monitoring aging-management program to include through-wall expansion monitoring. This expansion will be monitored by devices installed in the first half of 2016 in over 40 representative locations.
In 2014, the NRC documented findings involving discrete, horizontal cracking in an internal wall of the Residual Heat Removal (RHR) vault and displacements and cracking associated with the Fuel Storage Building. In 2015, the NRC documented findings that identified global bulk expansion of the containment enclosure building. The staff concluded these findings were of very low safety significance because the safety function of these structures was not affected. Additionally, as part of the license renewal process, the NRC requested additional information from NextEra to assess whether the effects of aging involving building deformation and discrete cracks will be adequately managed so that intended functions are maintained consistent with the current licensing basis during the period of extended operation. NextEra's response was received by the NRC on Aug. 9, 2016, and is currently under review.
In 2016, the NRC documented an unresolved item when it was identified that further inspection was warranted to review an issue of concern regarding implementation of the Seabrook Structures Monitoring Program and structural evaluations of the CEB and RHR/CS Vault. The inspection that reviewed this unresolved item identified a violation for two examples where NextEra did not perform initial and prompt operability determinations for ASR-affected structures until prompted by NRC inspectors. NextEra responded to this violation in early June 2016. A future inspection will review NextEra's corrective actions. Also in 2016, NextEra has had three meetings with NRC staff, on March 29, April 28 and June 15 to discuss ASR-related issues at Seabrook. As described further in the Licensing section, on Aug. 1, 2016, NextEra submitted License Amendment Request (LAR) 16-03 to revise the Seabrook Updated Final Safety Analysis Report (UFSAR) to include methods for analyzing seismic Category I structures with concrete affected by ASR.
Licensing
The NRC has two licensing actions under review that are directly associated with ASR: a license renewal application (LRA) and a license amendment request (LAR) to update the current licensing basis to recognize the effects of ASR.
In May 2010, NextEra, submitted an LRA to renew the Seabrook facility operating license for up to an additional 20 years. An item was left open in the Seabrook license renewal Safety Evaluation Report (SER) due to NRC staff concerns that NextEra had not enhanced the Structures Monitoring Program to manage the effects of ASR. For the NRC staff to complete its LRA review and close this SER open item, NextEra needs to update the licensing renewal application to include a sufficient aging management program for concrete structures impacted by ASR to ensure safe operation for extended operation (2030–2050). The project schedule and application information can be found on the NRC webpage devoted to the Seabrook Station, Unit 1 – License Renewal Application. On Aug. 9, 2016, the NRC received NextEra's updated LRA submittal and it is currently under NRC staff review.
On June 15, 2016, a public meeting was held with NextEra to provide an opportunity to present to the NRC staff its plan for an LAR regarding revising the licensing basis for the Alkali-Silica Reaction at the Seabrook facility. On Aug. 1, 2016, NextEra submitted the LAR to revise the licensing basis of the current operating license. NextEra has requested approval of a methodology to analyze seismic Category I concrete structures affected by ASR. This application is currently under NRC staff review.
Next Steps
The NRC will continue evaluation of ASR at Seabrook through:
- Continued review of NextEra's structures monitoring program implementation and results, which will be documented in subsequent inspection reports approximately every six months.
- Review licensing documents and evaluations submitted to the NRC in support of aging management of concrete structures impacted by ASR.
Publicly Available Documents
The following table lists the publicly available documents that the NRC has issued in connection with the special oversight of Seabrook.
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| Date | Title/Description |
|---|---|
| 12/21/2016 | Alkali Silica Reaction Monitoring Aging Management Program Audit Report Regarding The Seabrook Station, Unit 1, License Renewal (CAC No. ME4028) |
| 12/12/2016 | Requests For Additional Information For The Review Of The Seabrook Station License Renewal Application (CAC No. ME4028) |
| 10/13/2016 | Regulatory Audit Plan – Alkali Silica Reaction Aging Management Program, Regarding Seabrook Station, Unit 1, License Renewal Application Review (CAC No. ME4028) |
| 10/12/2016 | Seabrook Station, Unit No. 1 -Acceptance of Requested Licensing Amendment Action Re: Alkali-Silica Reaction |
| 09/30/2016 | Supplement to License Amendment Request 16-03 Revise Current Licensing Basis to Adopt a Methodology for the Analysis of Seismic Category I Structures with Concrete Affected by Alkali-Silica Reaction. |
| 09/19/2016 | Seabrook Station, Unit No. 1 -Supplemental Information Needed For Acceptance Of Requested Licensing Action Re: Alkali-Silica Reaction |
| 08/09/2016 | Seabrook Station, License Renewal Application (LRA) Relating to the Alkali-Silica Reaction Monitoring Program |
| 08/05/2016 | ASR Operability Determinations and Functionality Assessments Sample – NRC Inspection Report 05000443/2016002, Section 1R15 |
| 08/01/2016 | License Amendment Request (LAR) 16-03, "Revise Current Licensing Basis to Adopt a Methodology for the Analysis of Seismic Category I Structures with Concrete Affected by Alkali-Silica Reaction" |
| 06/29/2016 | Seabrook Station, Unit No. 1 – Acknowledgement of Reply to Notice of Violation – NRC Inspection Report 0500443/2016008 |
| 06/06/2016 | Seabrook Station - Reply to a Notice of Violation EA-16-101 - Seabrook Station, Inspection Report 05000443/2016008 Related to Alkali-Silica Reaction Effects on Safety-Related Concrete Structures and Notice of Violation |
| 05/06/2016 | NRC Inspection Report 05000443/2016008 - Alkali-Silica Reaction (ASR) Effects on Safety-Related Concrete Structures and Notice of Violation (NOV) |
| 03/29/2016 | NextEra Drop-In with Division of License Renewal (DLR), Division of Operating Reactor Licensing (DORL), and Division of Engineering (DE) |
| 02/12/2016 | ASR Problem Identification and Resolution Sample – NRC Inspection Report 05000443/2015004, Section 4OA2 |
| 12/23/2015 | Summary of Telephone Conference Call Held on December 22, 2015, Between the NRC and NextEra Concerning a RAI Pertaining To Seabrook Station Operability Determinations for ASR-Affected Structures |
| 12/17/2015 | ASR Monitoring Aging Management Program Audit Report Regarding the Seabrook Station |
| 12/03/2015 | NextEra response to RAI for the Review of the Seabrook License Renewal Application– Set 25 |
| 11/19/2015 | Schedule Revision and Change of Project Manager for the Review of the Seabrook Station License Renewal Application |
| 10/02/2015 | RAI for the Review of the Seabrook License Renewal Application – Set 25 |
| 08/05/2015 | ASR Problem Identification and Resolution Sample – NRC Inspection Report 05000443/2015002, Section 4OA2 |
| 06/30/2015 | MPR-4153, Approach for Determining Through-Thickness Expansion from ASR (Enclosure 3 to the letter titled "NextEra second response to RAI – Set 23") |
| 06/30/2015 | NextEra second response to RAI for the Review of the Seabrook License Renewal Application – Set 23 |
| 05/04/2015 | Schedule Revision for the Safety and Environmental Reviews of the Seabrook Station License Renewal Application |
| 02/23/2015 | NextEra response to RAI for the Review of the Seabrook License Renewal Application – Set 23 |
| 02/06/2015 | ASR Problem Identification and Resolution Sample – NRC Inspection Report 05000443/2014005, Section 4OA2 |
| 11/25/2014 | RAI for the review of the Seabrook License Renewal Application – Set 23 |
| 11/21/2014 | NextEra Revised response to RAI for the review of the Seabrook License Renewal Application – Set 20 |
| 08/05/2014 | ASR Maintenance Effectiveness Sample – NRC Inspection Report 05000443/2014003, Section 1R12 |
| 05/15/2014 | NextEra response to RAI for the Review of the Seabrook License Renewal Application – Set 20 |
| 05/06/2014 | ASR Problem Identification and Resolution Sample – NRC Inspection Report 05000443/2014002, Section 4OA2 |
| 02/19/2014 | Revision to NRC Seabrook Alkali-Silica Reaction Issue Technical Team Charter |
| 01/30/2014 | ASR Problem Identification and Resolution Sample – NRC Inspection Report 05000443/2013005, Section 4OA2 |
| 01/15/2014 | Request for Additional Information (RAI) for the Review of the Seabrook License Renewal Application – Set 20 |
| 12/23/2013 | Aging Management Program Audit Report Regarding Seabrook Station License Renewal Application |
| 12/06/2013 | NRC response to UCS letter regarding ASR concrete degradation |
| 11/04/2013 | Union of Concerned Scientists (UCS) letter regarding ASR concrete degradation at Seabrook Station, dated 11/4/2013 |
| 10/09/2013 | Seabrook Station, Unit No. 1 – Closure of Confirmatory Action Letter 1-2012-002 |
| 09/13/2013 | Supplemental license renewal application information submitted to the NRC on September 13, 2013 regarding the Seabrook ASR monitoring program |
| 08/09/2013 | Seabrook Station, Unit No. 1 – Confirmatory Action Letter Follow-Up Inspection – NRC Inspection Report 05000443/2012010 |
| 05/01/2013 | NextEra response to Confirmatory Action Letter Items 2, 4, 8, dated May 1, 2013 |
| 02/28/2013 | NextEra response to Confirmatory Action Letter Item 11, dated February 28, 2013 |
| 01/14/2013 | Revision to Confirmatory Action Letter, Seabrook Station, Unit 1 – Information Related to Concrete Degradation Issues |
| 12/13/2012 | NextEra response to Confirmatory Action Letter, dated December 13, 2012 |
| 12/03/2012 | Seabrook Station, Unit No. 1 – Confirmatory Action Letter Follow-Up Inspection – NRC Inspection Report 05000443/2012009 |
| 09/05/2012 | NRC staff request for deviation from Reactor Oversight Process to provide increased oversight of ASR issues at Seabrook |
| 07/09/2012 | Charter for NRC technical team assigned to look at ASR issues at Seabrook |
| 06/28/2012 | NexrEra response to CAL: Large scale testing |
| 06/21/2012 | NexrEra response to CAL: Large scale testing (enclosure) |
| 06/08/2012 | NexrEra response to CAL: Corrective Action Plan |
| 05/24/2012 | NextEra response to CAL: Impact of ASR on Concrete Structures and Attachments (Foreign Print 100716) |
| 05/24/2012 | NextEra response to NRC CAL on Seabrook ASR |
| 05/16/2012 | Supplemental license renewal application information submitted to the NRC on May 16, 2012 regarding ASR monitoring at Seabrook |
| 05/16/2012 | NRC Confirmatory Action Letter (CAL) issued to NextEra on May 16, 2012 regarding information required on ASR issues at Seabrook |
| 05/10/2012 | NextEra Letter Committing to Supplemental to Actions for Resolution of ASR issues |
| 05/03/2012 | NextEra Letter Committing to Actions for Resolution of ASR Issues |
| 03/26/2012 | NRC Inspection Report 05000443/2011010, issued March 26, 2012 on ASR at Seabrook |
| 08/12/2011 | ASR – 1R15 Operability Samples – NRC Inspection Report 05000443/2011003 |
| 05/23/2011 | NextEra Energy Seabrook - NRC License Renewal Inspection Report 05000443/2011007 |
| 05/12/2011 | ASR – 1R12 Maintenance Effectiveness Sample – NRC Inspection Report 05000443/2011002 |
Public Meetings
The following table lists the public meetings in connection with the special oversight of Seabrook.
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| Date | Title/Description |
|---|---|
| 06/21/2016 | The NRC will host an open house with the public to discuss the NRC's assessment of safety performance at Seabrook for 2015. Following the open house, the NRC will then give an update and respond to questions regarding the NRC's evaluation of the effect of the ASR in concrete structures at Seabrook |
| 06/15/2016 | The purpose of this meeting is for NextEra Energy to present to the NRC staff its plan for a license amendment request regarding revising the licensing basis for Alkali-Silica Reaction at the Seabrook Station, Unit No. 1.
|
| 06/06/2016 | The purpose of this public meeting is for C-10 to address the NRC PRB regarding the 2.206 Petition submitted by C-10 on December 22, 2015, regarding Seabrook. Related Documents
|
| 04/28/2016 | The purpose of this public meeting is for NextEra Energy Seabrook, LLC (NextEra) to discuss with U.S. Nuclear Regulatory Commission (NRC) staff about (a) the staff request for information (RAI) and (b) NextEra's plan for response to the RAI and the completion of the licensing action for Seabrook Station (Seabrook) license renewal. |
| 12/18/2013 | The NRC conducted an open house and a public meeting with NextEra to discuss NextEra's testing program regarding concrete degradation caused by the Alkali-Silica Reaction (ASR) at Seabrook Station. |
| 02/21/2013 | The NRC conducted a public meeting with NextEra to discuss aging effects and management associated with alkali-silica reaction regarding the license renewal application for Seabrook Station. |
| 12/11/2012 | The NRC conducted an open house and public meeting to discuss the safety implications and status of its review of NextEra's commitment actions related to the ASR conditions in safety-related structures at Seabrook Station. |
| 04/23/2012 | The NRC conducted a public meeting with representatives from NextEra to discuss NextEra's plans and schedule regarding concrete degradation caused by ASR at Seabrook as referenced in the NRC inspection report.
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