UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

REGION I 

2100 RENAISSANCE BOULEVARD, SUITE 100 

KING OF PRUSSIA, PENNSYLVANIA 19406-2713 

 December 6, 2013 

David Wright, PhD 

Co-Director and Senior Scientist 

 Global Security Program 

Union of Concerned Scientists 

Cambridge, Massachusetts 02138 

Dear Dr. Wright: 

Thank you for your letter dated November 4, 2013, highlighting Dr. Paul Brown’s commentary 

on NRC Inspection Report 0500443/2012010 and outlining his recommendations for addressing 

the alkali-silica reaction (ASR) impacting the reinforced concrete structures at Seabrook Station. 

We appreciate your interest and Dr. Brown’s independent assessment of the impact of ASR on 

reinforced concrete structures at Seabrook nuclear power plant. We welcome Dr. Brown’s 

feedback and hope that we may continue our dialogue with him and other interested members 

of the public as NextEra and the NRC gain a better understanding of the effects of ASR on 

Seabrook safety-related structures. The NRC staff is holding a public meeting near Seabrook 

on December 18, 2013, at which the staff will discuss the ASR issue with NextEra managers 

and then respond to questions from the public. We would welcome further discussion with you 

there. 

We have provided a response to Dr. Brown’s specific comments in an enclosure to this letter. 

Our enclosure also addresses similar comments provided in the summary document prepared 

by the Union of Concerned Scientists and the C-10 Foundation. 

The NRC continues its efforts to better understand the impact of ASR on reinforced safetyrelated structures at the Seabrook Station. Our inspections and assessments to date have 

determined the ASR-affected structures at Seabrook Station remain capable of performing their 

intended safety functions with margin from initial design and construction. Long-term resolution 

of this issue will require a thorough understanding of the effects of ASR and additional testing, 

monitoring and potential compensatory actions by NextEra. The NRC will continue to carefully 

assess NextEra’s actions to resolve this issue and conduct inspections at Seabrook Station to 

ensure corrective actions are effective. 

 
D. Wright 2 

Please feel free to contact Mr. Melvin Gray (610-337-5209) or Mr. William Cook (610-337-5074) 

of my staff should you have any further questions or comments to share with us. 

Sincerely, 

 /RA/ 

 William M. Dean 

 Regional Administrator 

Enclosure: 

NRC Response to Dr. Paul Brown’s Commentary 

cc w/encl: Distribution via ListServ 
D. Wright 2 

Please feel free to contact Mr. Melvin Gray (610-337-5209) or Mr. William Cook (610-337-5074) 

of my staff should you have any further questions or comments to share with us. 

Sincerely, 

 /RA/

 William M. Dean 

 Regional Administrator 

Enclosure: 

NRC Response to Dr. Paul Brown’s Commentary 

cc w/encl: Distribution via ListServ 

Distribution: (LTR-13-0871 G20130777 EDATS: RegionI-2013-0330) 

RIDSEDOMailCenter Resource G. Dentel, DRP 

RIDSNRRDLR Resource R. Barkley, DRP 

W. Dean, RA (R1ORAMAIL Resource) M. Draxton, DRP 

D. Lew, DRA (R1ORAMAIL Resource) P. Cataldo, DRP, SRI 

D. Roberts, DRP (R1DRPMAIL Resource) C. Newport, DRP, RI 

M. Scott, DRP (R1DRPMail Resource) A. Cass, DRP, Resident AA 

R. Lorson, DRS (R1DRSMail Resource) N. McNamara, RI, SLO 

J. Trapp, DRS (R1DRSMail Resource) D. Tift, RI, SLO 

RidsNrrPMSeabrook Resource D. Screnci, RI, PAO 

RidsNrrDorlLpl1-2 Resource N. Sheehan, RI, PAO 

B. Rini, RI, OEDO 

SUNSI Review Complete: __WAC_____ (Reviewer=s Initials) 

ADAMS Package No. ML13309B607 ADAMS Incoming Letter No. ML13309B606 ADAMS Response Ltr: ML13340A405 

DOCUMENT NAME: G:G:\DRS\Seabrook Concrete\Media-Pub\Response Letters\UCS - C10 Seabrook ASR Response 

Letter Rev4 .docx 

After declaring this document AAn Official Agency Record@ it will be released to the Public. ADAMS ML 

To receive a copy of this document, indicate in the box: "C" = Copy without attachment/enclosure "E" = Copy with 

attachment/enclosure "N" = No copy 

OFFICE/kah RI/DRS RI/DRS RI/DRS NRR/DLR NRR/DE 

NAME NFloyd/NF WCook/WC MGray/MG MMarshall/MM * AMcMurtray/AM *

DATE 12/02/2013 12/02/2013 12/01/2013 12/02/2013 12/03/2013 

OFFICE RI/DRS RI/RA 

NAME RLorson/JMT for WDean/WMD 

DATE 12/04/2013 12/06/2013 

* via email OFFICIAL RECORD COPY
Enclosure 

Enclosure 

NRC Response to Dr. Paul Brown’s Commentary 

Background

NRC closure of our Confirmatory Action Letter (CAL) 1-2012-002 (ADAMS Accession No. 

ML13274A670) represents the agency’s assessment by in-office review and direct inspection of 

the specific commitments (eleven numbered CAL items) made by NextEra pertaining to their 

actions to address ASR-affected reinforced concrete structures at Seabrook Station. Closure of 

the CAL represents NextEra having: 1) successfully established a reasonable assurance of 

current operability for ASR-affected, safety-related structures; and, 2) implemented an 

appropriate corrective action plan to monitor and resolve this non-conforming condition, 

consistent with the current state of knowledge of ASR and 10CFR50, Appendix B, Criterion XVI, 

“Corrective Action Program.” 

As documented in NRC Inspection Reports 05000443/2012009 (hereafter referred to as 

Report 1 - ML12338A283) and 05000443/2012010 (hereafter referred to as Report 2 - 

ML13221A172), the NRC summarized extensive reviews and hundreds of hours of detailed 

inspections, meetings and internal deliberations to understand and ensure a clear engineering 

and safety basis had been established by NextEra for the current structures’ operability 

determination. These prompt operability determinations were based upon detailed structural 

evaluations that are independent of the large-scale specimen testing being conducted by 

NextEra per the ASR Project Corrective Action Plan. As documented in our cover letter for 

NRC Report 1, the NRC determined that NextEra's methods for assessing operability of ASRaffected reinforced concrete structures were reasonable and generally comprehensive. NextEra 

conducted a margins analysis, using bounding ASR-affected concrete properties derived from 

research data, to demonstrate that Seabrook structures remained operable. As documented in 

Report 2, Section 9.6, the NRC understands that the resolution of the ASR non-conforming 

condition currently awaits NextEra’s completion of the large scale testing at the University of 

Texas – Austin, Ferguson Structural Engineering Laboratory (FSEL). Upon completion of the 

testing, NextEra may submit a license amendment request pursuant to 10CFR50.59 and 50.90. 

It is understood that should the testing program be unsuccessful, any revisions to NextEra’s 

ASR Project Corrective Action Plan would be appropriately communicated to the NRC. The 

NRC plans to periodically inspect NextEra’s ASR monitoring program and testing activities at 

FSEL. NextEra is required, consistent with their Part 50 license, to maintain reasonable 

assurance of operability of Seabrook Station ASR-affected structures, as ASR insights are 

developed from the ongoing FSEL testing and the Seabrook Structures Monitoring Program 

(SMP). 

The NRC acknowledges that the ASR issue is a complex and challenging phenomena because 

the onset, progression and impact of ASR on nuclear power plant structures is not fully 

understood or directly measureable nor are there established methodologies for assessing and 

monitoring ASR-affected reinforced concrete structures from either a materials property or 

structural performance standpoint (or a combination of these approaches). Accordingly, the 

NRC plans to carefully and deliberately review and assess the ongoing efforts of NextEra to 

address the Seabrook Station ASR issue. 
2 

Enclosure 

Commentary Review

The specific commentaries numbered below are quoted or paraphrased from Attachment 1, 

“Commentary on NRC Inspection Report 05000443/2012010.” We have structured our 

response to parallel Dr. Brown’s commentary and have included, where appropriate, any 

additional considerations addressed in Attachment 2, “Continuing Problems with Monitoring 

Concrete Damage at Seabrook.” 

Commentary 1) (pg.1): The first area of concern is that CCI is not a well-established basis for 

reliably measuring ASR damage in highly reinforced concrete. Our response also addresses 

Attachment 2, Section (1) “Continuing Use of an Unjustified Measure of ASR,” that reiterates 

this concern. 

NRC Response: The NRC agrees with Dr. Brown’s comment that the use of combined crack 

indexing (CCI) is not a well-established basis for monitoring the progression of ASR or 

measuring ASR impact on reinforced concrete. For this reason, NextEra’s ASR-affected safetyrelated reinforced concrete structures’ operability determinations are currently independent of 

this monitoring method. NextEra has provided reasonable assurance of operability for the 

Seabrook ASR-affected structures using appropriate engineering-based structural evaluations 

(reference ADAMS Accession No. ML12151A396 and ML12151A397 for Enclosure 2). The 

evaluations assessed structural design attributes using bounding values for assumed ASR 

degradation derived from concrete industry test data. These evaluations were informed using 

the material property testing results from core samples (47) taken from various Seabrook ASRaffected and non-affected structures. In addition, the structural evaluations assumed the 

structural members of interest were uniformly and entirely impacted by ASR, whereas the 

comprehensive walkdown of Seabrook structures has identified only localized areas of ASR 

degradation on the surface of the structures. The limited number of six-month CCI 

measurements recorded, to date, (18 months of data) has not yielded any noteworthy data 

trends. Likewise, no significant change in any individual CCI values has been observed. 

As documented in Section 7.0 of Report 2 - “The crack growth monitoring provides a visual 

indication of the progression of ASR within a reinforced concrete structure. The relative width 

and number of visible cracks may be correlated to the overall progression of ASR and may be 

used to evaluate ASR impact on structural performance. However, ASR cracking and crack 

propagation is closely associated with the specific reinforcement design and structural loading. 

Accordingly, the adequacy of CCI measurement as a long-term structures monitoring 

methodology for Seabrook structures is being further evaluated by NextEra as part of the UTAustin FSEL testing program.“ In addition, as documented in Section 9.5 of Report 2, the 

inspectors summarized the “reasonable assurance” rationale for CCI interim use in the 

Structures Monitoring Program (SMP) and stated that longer term use may warrant further NRC 

review. 

 
3 

Enclosure 

Commentary 2) (pg. 1): A second area of concern is the lack of predictive capability of CCI. 

Attachment 2, Section (1) “Continuing Use of an Unjustified Measure of ASR,” reiterates this 

concern. 

NRC Response: The NRC agrees with Dr. Brown’s comment on the lack of predictive 

capability of CCI. As discussed in Section 9.5 of Report 2, NextEra acknowledges the need to 

correlate CCI values to ASR progression in the large test specimens, and eventually to the 

station structures. Accordingly, NextEra has initiated efforts to install deep pins, or some 

comparable through-wall monitoring device(s), to measure ASR expansion in the out-of-plane 

direction. Measurement in the through-wall (Z-direction) is intended to complement the X-Ydirection monitoring obtained by CCI. The NRC understands that the testing program is 

intended to determine the adequacy of the CCI monitoring method, and to enhance or develop 

additional methods, as appropriate. 

Commentary 3) (pg. 1): The third area of concern is that there is presently no generally 

accepted technology to mitigate the effects of ASR within an existing concrete structure. 

NRC Response: The NRC agrees with Dr. Brown’s statement that there “is presently no 

generally accepted technology to mitigate the effects of ASR within an existing concrete 

structure.” As outlined in NextEra’s large specimen testing program (ML13151A328), should 

structural remediation of the ASR-affected buildings be necessary, additional large specimens 

may be used to research, develop, and test remediation methods. 

Commentary Section 1.0 (pg. 2): NextEra document, FP100716, discusses the use of lower 

bound values for structural capacity. It is not clear in the report how these values were applied. 

This lower bound would have a significant impact on the integrity of lap splices and anchorage 

capacity in particular. 

NRC Response: Section 1.0 of Report 2 is an abbreviated background summary of the efforts 

undertaken by NextEra to address ASR, including the initial operability determination bases. 

The NRC documented the review of the operability determinations (ODs) in Section 3.0 of 

Report 1. Lower bound values used in the ODs were obtained from research test data gathered 

over several decades by numerous research facilities and testing laboratories, based upon 

small scale test specimens. These lower bound values were applied to existing design basis 

structural calculations to ensure, assuming worst case ASR degradation of the most sensitive 

limit states (out-of-plane shear capacity, lap splice length, and anchorage capacities) the 

available margin between design structural capacity and assumed loading conditions was not 

compromised. These calculations demonstrated that the affected structures were still 

operational assuming reasonable, worst-case ASR degradation. 

Commentary 3.0 (pg. 2): No systematic analysis of the corrosion of rebar due to potentially 

aggressive water migration through the concrete. Attachment 2, Section (5) “Lack of 

Information on Corrosion of Steel Reinforcing Bars at Seabrook,” reiterates this concern. 

 
4 

Enclosure 

NRC Response: Dr. Brown is correct that no detailed or exhaustive analysis was conducted to 

assess the impact of ground water infiltration on rebar. However, the NRC has reasonable 

assurance that corrosion of the rebar is not occurring because generally, the alkali environment 

within the concrete inhibits corrosion and no surface indications of corrosion have been 

observed. In addition, the rebar samples taken by NextEra and examined, to date, do not show 

any evidence of corrosion. However, should the two to three-inch cover concrete start to 

severely degrade, further analysis and examination of the rebar would be prudent due to the 

increased vulnerability of the embedded rebar to oxidation mechanisms. Further, if rebar 

corrosion is or were to occur, additional visual indications such as staining and spalling would 

be evident. Reference Section 9.4 of Report 2 for additional inspection detail concerning this 

issue.

Commentary 4.0 (pg. 3): Closure of CAL Item 4 does not appear consistent with the corrective 

action plan being a “living document.” 

NRC Response: The term “living document” implies that the corrective actions being taken by 

NextEra to address ASR may change as more information from either the SMP or the FSEL 

testing program is learned about Seabrook structural response to ASR. Because ASR remains 

a non-conforming condition, NextEra’s corrective action plan remains in effect until, and 

potentially after, this condition is resolved in accordance with the plant’s current operating 

license. The closure of CAL Item 4 was based upon NextEra having met their commitment to 

submit the ASR Project Corrective Action Plan to the NRC. NRC inspections will be conducted 

to determine the adequacy of NextEra’s corrective actions in the long-term resolution of this 

issue. 

Commentary 5.0 and 6.0 (pg.3): Statements of fact, no concerns or recommendations 

expressed. 

Commentary 7.0 (pg. 3): “There is no existing standard that correlates crack displacement in a 

reinforced structure to the extent of ongoing ASR within that structure.” Attachment 2, Section 

(1) “Continuing Use of an Unjustified Measure of ASR,” reiterates this concern. 

NRC Response: The NRC agrees with Dr. Brown. The combined crack indexing (CCI) 

thresholds established in the Seabrook SMP were developed by NextEra using input from 

ACI 349.3R-96, “Evaluation of Existing Nuclear Safety-Related Structures;” Federal Highway 

Administration FHWA-HIF-09-004, dated January 2010, “Report on the Diagnosis, Prognosis, 

and Mitigation of Alkali-Silica Reaction in Transportation Systems;” Institution of Structural 

Engineers, July 1992, “Structural Effects of Alkali-Silica Reaction: Technical Guidance on the 

Appraisal of Existing Structures;” and ONL/NRC/LRT-95/14, “In-Service Inspection Guidelines 

for Concrete Structures in Nuclear Power Plants, December 1995. These CCI thresholds were 

incorporated into the SMP, consistent with available industry guidance, to prompt additional 

engineering evaluations upon identification of structural anomalies consistent with ASR 

progression. The use of CCI as a long-term surrogate for monitoring ASR progression is being 

evaluated by NextEra through their FSEL testing program. 

 
5 

Enclosure 

Commentary 7.0 (pg. 4): “The report does not provide any detail as to this program (ground 

water chemistry monitoring).” 

NRC Response: Other than committing to ACI 349.3R in the Seabrook SMP and the 

associated recommendation for environmental sampling of ground water on a periodic basis, 

outlined therein, NextEra does not have a detailed ground water chemistry analysis program 

specific to the ASR monitoring program. At the conclusion of the Report 2 inspection, NextEra 

was evaluating a new initiative and available methods to chemically analyze and compare 

ground water to collected infiltrated water. Ground water sampling for environmental monitoring 

purposes has been implemented to meet other regulatory commitments. NextEra actions to 

address this issue will be assessed during future NRC inspections. 

Commentary 8.0 (pg. 4): There are no details in the inspection report pertaining to the anchor 

bolt and large specimen shear and lap splice testing programs. Attachment 2, Section (3) 

“Problems with Applying Results of “Replica Testing” to Seabrook,” reiterates this concern. 

NRC Response: The details of these two testing programs were provided to the NRC by 

NextEra with a proprietary and non-proprietary version (Anchor - ML13088A218 and Shear/Lap 

splice - ML13151A328). The NRC reviewed these testing programs to gain an understanding of 

the methodology, expected results and proposed application of the same. These testing 

programs can be likened to confirmatory or research-related testing initiatives, not currently 

subject to NRC review or approval. 

The NRC will conduct inspections of NextEra’s corrective actions to resolve the non-conforming 

condition related to ASR-affected structures documented in their corrective action program. 

This includes inspections of NextEra’s planned corrective actions involving anchor bolt and 

large-scale specimen testing. The results of our inspections will be documented in publically 

available reports. If NextEra staff determines these test results provide a technical basis to 

resolve the non-conforming conditions related to ASR, then the NRC will complete inspections 

to ensure NextEra staff properly implements the regulatory processes described in 10CFR50.59 

and 50.90. Should preliminary testing results indicate a potential problem with Seabrook ASRaffected structures, the NRC would expect NextEra to evaluate that information in accordance 

with their corrective action program similar to other operating experience and assess the impact 

on Seabrook Station. 

Commentary 9.1 (pg.4): “The present report does not provide the criteria for defining what 

constitutes an excessive crack, nor does it provide any detail as to this program.” 

NRC Response: The CCI threshold (1.0 mm/m or greater) and individual crack width (1.0 mm 

or greater) documented in the Seabrook Station Structures Monitoring Program (SMP) are used 

for determining the need for a structural evaluation. These thresholds were developed by 

NextEra using available industry guidance. See Commentary 7.0 (pg. 3) and the NRC 

Response above for additional details regarding the industry reports and guidance used by 

NextEra. 
6 

Enclosure 

Section 3.2.1 of Report 1 identified a minor performance deficiency associated with an SMP 

program requirement. Section 9.1 of Report 2 documents the inspection team’s follow-up to this 

performance deficiency. A clarifying excerpt from Section 3.2.1 is provided below and identifies 

the genesis of this inspection issue. 

“The team observed that 26 locations (including containment) had been identified via NextEra's 

ASR Structures Walkdown as having patterned cracking with a combined crack index (CCl) of 

greater than 1.0 mm/m. CCI is an ASR expansion monitoring method that sums the crack 

widths measured along a fixed rectangular grid line. The sum of the crack widths is then divided 

by the length (perimeter) of the grid to obtain the index value. Per the Structures Monitoring 

Program (EDS 36180, Revision 2), Attachment 3, revised in July 2012, a CCI of >1.0 mm/m 

requires a structural evaluation....” 

Commentary 9.2 (pg. 5): “It is well understood that drilled cores are extracted from an existing 

structure and have been subjected to the service environment associated with the structure. 

This in no way invalidates the results of the testing. The NextEra preposition misuses the 

cautionary language of ASTM C42 and appears to be an attempt to avoid accumulating data 

which might be regarded as problematic.” Also, the report does not provide any details 

regarding any future drilled cores. Attachment 2, Section (2) “Failure to Adequately Use Core 

Testing” and Section (3) “Problems with Applying Results of ‘Replica Testing’ to Seabrook” 

reiterate these concerns. 

NRC Response: The use of drilled cores to assess ASR impact on the concrete is not being 

challenged by either NextEra or the NRC staff. The use of that core test data alone, to assess 

structural performance, is being challenged by NextEra. The misuse of the cautionary language 

of ASTM C42 is improperly attributed to NextEra. That restatement of the ASTM C42 caution in 

the inspection report was added by the inspection team to highlight the introduction of 

uncertainties associated with extracting a drilled core and directly applying the test results, 

which may be adversely impacted for the stated reasons. No additional information pertaining 

to future drilling of cores was documented in the report because the number and location of 

future cores is dependent upon the FSEL testing program and unspecified future correlation 

needs, as determined by NextEra staff. 

The NRC recognizes the merits of the testing and associated research that is being done in 

order to better understand the structural impact of ASR on non-triaxial reinforced concrete 

structures and to develop better methods to monitor ASR-affected concrete degradation. As 

stated in the background section above (and NRC response to Commentary 8.0), the NRC has 

reviewed and gained an understanding of the FSEL testing program and anticipated results, but 

not provided regulatory approval of the same. The “problems” or concerns expressed by Dr. 

Brown with applying test results to Seabrook Station have been identified and discussed 

between the NRC inspectors and NextEra staff. NextEra has outlined the methods to be used 

to correlate specimen test data to Seabrook structures in the test specifications submitted to the 

NRC per the CAL. The adequacy of that methodology has not yet been confirmed, but may be 

subject to NRC review, if used by NextEra pursuant to the 10 CFR 50.59 and 50.90 processes. 

 
7 

Enclosure 

Commentary 9.3 (pg. 5): This section states that ASR causes chemical prestressing. Such a 

statement indicates a misunderstanding of prestressing. 

NRC Response: The report documents “chemical” pre-stressing in quotes to acknowledge that 

this term is being used to characterize the impact of the expansion of the ASR gel on the 

surrounding concrete matrix and rebar. The use of this term was to communicate a condition of 

the ASR-affected reinforced structures and not to imply actual pre-stressing similar to fabrication 

of pre-stressed concrete members. 

Commentary 9.4 (pg. 5): Statement of fact, no concern or recommendation expressed. 

Commentary 9.5 (pg. 5): “An assessment of the probability of mid-wall cracking should also be 

carried out on the actual in-place concrete. Attachment 2, Section (4) “Misunderstanding of the 

Structural Role of Concrete in Layered Construction,” also addresses this concern. 

NRC Response: The NRC agrees with Dr. Brown’s statement and this issue is being 

considered by NextEra staff. See Commentary 9.2 (pg. 5) and the associated NRC Response 

above for additional detail. The NRC is not aware of any core samples taken at Seabrook that 

were found to have evidence of mid-wall cracking. 

Commentary 9.6 (pg. 5): This section indicates that NRC staff finds the use of the CCI as an 

acceptable method of conditional assessment. This is unfortunate because it does not 

encourage NextEra to apply NDE techniques or other (assessment) techniques to quantify 

conditional analyses.” Attachment 2, Section (1) “Continuing Use of an Unjustified Measure of 

ASR,” reiterates this concern. 

NRC Response: The NRC does not discourage the use of additional NDE assessment 

methods. Visual examination is recognized in the concrete industry as an effective means to 

detect ASR. However, petrographic examination is used to confirm the presence of this 

concrete degradation mechanism. Monitoring ASR progression through measurement of 

surface crack growth (at specified time intervals) may be effective, but remains to be validated. 

The NRC continues to follow industry research activities to improve NDE techniques related to 

ASR. Also see Commentary 1) and 2) and the associated NRC Response documented above. 

Commentary 9.6 (pg. 6): The inconsistencies between pin expansion data and the CCI data 

show the complexity of interpreting the results of the analyses being conducted. 

NRC Response: The NRC agrees with this statement. See our responses to Commentaries 1, 

2, 7.0 and 9.6, above. 

Commentary 12 (pg. 6): “The assumption that aircraft impact will not transfer stresses to ASR 

compromised concrete is unfounded.” 

 
8 

Enclosure 

NRC Response: As stated in the Report 2, ASR has not been identified in the containment 

areas presumed to be impacted by the postulated aircraft impact. Secondly, areas of the 

containment identified as having ASR are: 1) localized; 2) below grade; and 3) in heavily 

reinforced sections. As such, there is reasonable assurance that the containment structure’s 

aircraft impact analysis is unaffected. However, as stated in Report 2, if upon closer visual 

examination of the containment dome areas during the 2014 ASME IWL exam, evidence of 

ASR is identified, a re-evaluation of the structural design analysis may be warranted.