ML16216A241

MPR-4288, Revision 0, Seabrook Station: Impact of Alkali-Silica Reaction on Structural Design Evaluations, July 2016

ML16216A241
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Site:	Seabrook
Issue date:	07/31/2016
From:	NextEra Energy Seabrook
To:	Document Control Desk, Office of Nuclear Reactor Regulation
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SBK-L-16071
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SBK-L-16071 ENCLOSURE 2 MPR-4288, Revision 0, "Seabrook Station: Impact of Alkali-Silica Reaction on Structural Design Evaluations." July 2016. (Non-Proprietary)

--Non-Proprietary Version--rtl MPR MPR-4288 Re visio n 0 (Seabrook FP# 101020) July 2016 Seabrook Station: Impact of Alkali-Silica Reaction on Structural Design Evaluations QUALITY ASSURANCE DOCUMENT This document has been prepared , reviewed , and approved in accordance with the Quality Assurance requirements of 1 OCFR50 Appendix Band/or ASME NQA-1, as specified in the MPR Nuclear Quality Assurance Program. Prepared for NextEra Energy Seabrook P. 0. Bo x 300; Lafayette Rd. Seabrook, NH 03874

--Non-Proprieta r y Ve r sion--Seabrook Station: Impact of Silica Reaction on Structural Design Evaluations MPR-4288 Revis i on 0 (Seabrook FP# 101020) Jul y 2016 QUALITY ASSURANCE DOCUMENT This document has been prepared , rev i e w ed , and approved in accordance with t he Qual i ty Assu r ance requ i rements of 1 OCFR50 Appendi x Band/o r ASME NQA-1 , as spec i fied in the MPR Nuclea r Qual i ty Assurance Program. Prepared by: -7 Ja es Moroney/ Prepared by: R ,/,at t/ Robert J. V yda , P.E. Rev i ewed by: &,,.....4 Roberts. Keatil1Q , £. App r oved by' J n W. Simons Addit i onal Contributors C. B ag l ey R. As h wo rth Prepared for NextEra Energy Seabrook P. 0. Box 300; Lafayette Rd. Seabrook , NH 03874 320 K I NG S TREET A LE XANDRIA , V A 22314-3230 703-519-0200 F AX: 703-519-0224 www.mpr.com Revision 0 MPR-4288 Revi s ion 0 Affected Pages A ll --Non-Proprietary Version--RECORD OF REVISIONS Description Initi al I ss u e 111

--Non-Proprietary Version--Contents 1 Introduction

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1-1 1.1 Purpose ............................

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................ 1-1 1.2 Background

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........................................................................ 1-1 2 Summary .....................

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2-1 2.1 Structural Lim it States ..........................................................

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2-1 2.2 Other Design Considerations

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............................................ 2-2 3 Key Elements of Structural Design Basis .......................................................

3-1 3.1 Codes of Record ...................................................

.................................................... 3-1 3.2 Key Elements of Design ................................................

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........................... 3-2 4 Overview of MPR Evaluations

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4-1 4.1 Summary of Literature R eview ...............................

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............... 4-1 4.2 Importance of Confinement

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4-1 4.3 MPR Structural Test Programs ..................

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...... 4-2 4.4 Scope of Eva luati ons ................................................................................

................ 4-3 5 Structural Limit States ......................................................................................

5-1 5.1 Flexure ................................................................

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5-1 5.2 Shear ....................

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...... 5-3 5.3 Compression

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........................................................... 5-5 5 .4 Structural Attachments

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5-7 6 Design Considerations

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6-1 6.1 Reinforcement Steel Strain ..............

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................................. 6-1 6.2 Reinforcement Fracture ..................

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.......... 6-2 6.3 Seismic Response ....................................

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...... 6-4 6.4 Applicability of Design Basis Material Properties

................................................... 6-9 6.5 Effect of Structural Deformation

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................... 6-10 7 References

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7-1 MPR-4288 Revision 0 I V

--Non-Proprietary Version--Tables Ta bl e 4-1. Sco p e of Eva lu at i o n s .........................................................

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.......................... 4-3 MPR-4288 Revision 0 v

--Non-Propr i etary Vers i on--Figures F i gu r e 1-1. ASR Expansion Mec h an i sm .................................................................................... 1-2 Figure 6-1. Design Basis Seismic Ground Response Spectrum , 5% Damp i ng (Reference

1) ... 6-6 F i gure 6-2. Illustrat i on of Peak-Broadened Spectrum about Structura l Frequenc i es (fn) ........... 6-8 MPR-4288 R ev i s i o n 0 v i

--Non-Proprietary Version--1 Introduction

1.1 PURPOSE

T hi s report describes the effect of alkal i-s ili ca reaction (ASR) o n th e struct u ra l design b asis of affected concrete structures at Seabrook Stat i on and provides g uid ance for performing eva luati o n s for struct u ra l adequacy. T h e impact of ASR on structura l limit states (flexure, s h ear, and compression capacities a n d that of the attachments to concrete structures) as we ll as severa l additiona l design considerat i ons (strain in reinforc in g bars , fracture of reinforcing stee l , se i smic response, co n c r ete m ater i a l properties , and building deformation r e lat ed issues) are di sc u ssed. The content of this r eport is based on the results of MPR-sponsored l arge-scale test programs performed for NextEra as well as information available in the published li terature, as it re l ates to the topics li sted above. This report h as been prepared as a compan i on to MPR-4273 , Seabrook Station -Implications of Large-Sca l e Test Program Results on Reinforced Concrete Affected by A lk ali-Silica Reaction.

T h e l arge-sca l e test programs discussed in MPR-4273 provided representative test d ata that support assessing the effect of ASR on specific portions of the structural design basis. Key conc lu sions from MPR-4273 are used in the overa ll evaluat i on h erein.

1.2 BACKGROUND

1.2.1 Alkali-Silica Reaction (ASR) ASR occurs in concrete when reactive si li ca in the aggregate reacts w ith h ydroxyl i ons (Off) and a lkali ion s (Na+, K+) in the pore solut i o n. T h e reaction produces an a lk a li-s ili ca te ge l that expa nd s as i t absorbs m o i sture, exerting tensile stress on the s urroundin g co n cre te a nd r esu ltin g in cracking.

Typica l cracking caused by ASR is described as " pattern" or " map" cracking and is usually accompan i ed by dark staining adjacent to the cracks. F i gure 1-1 provides an illu stration of this process. MPR-42 88 R ev i s i o n 0 1-1 alkali cement+ reactive aggregate --Non-Proprietary Version--

expansive gel cracking of the aggregate and paste Figure 1-1. ASR Expansion Mechanism The cracking degrades the mechanical properties of unconfined concrete, necessitating an assessment of the adequacy of the affected structures and supports anchored to the structures.

1.2.2 ASR at Seabrook Station NextEra has identified ASR in multiple safety-related, reinforced concrete structures at Seabrook Station (Reference 7). After an extent of condition determination that identified affected structures at the site, MPR performed an interim structural assessment (Reference 2]) of selected ASR-affected structures to evaluate their adequacy given the presence of ASR. Based on the low level of observed cracking and the apparent slow rate of change , MPR concluded that the evaluated structures were suitable for continued service for at least an interim period (i.e., at least several years). The interim structural assessment supports continued operability of plant structures affected by ASR. The interim structural assessment (Reference

21) utilized a conservative treatment of data from existing literature, supplemented by limited testing of anchor bolts , to produce conclusions suitable for a short-term structural assessment.

In support of Jong-term evaluations , MPR conducted large-scale test programs at Ferguson Structural Engineering Laboratory (FSEL) using specimens that were designed and fabricated to represent reinforced concrete at Seabrook Station to the maximum extent practical.

The methodology for the long-term evaluation will rely on a combination of published literature data and results from the large-scale test programs to determine the potential effects of ASR on adequacy of structures at Seabrook Station. MPR-42 88 R ev i s ion 0 1-2

--Non-Proprietary Version--2 Summary The presence of ASR in reinforced concrete structures at Seabrook Station impacts the structural design basis of the affected structures and requires evaluation.

This section summarizes the impact of ASR on applicable structural limit states and other design considerations necessary for evaluation of Seabrook Station structures.

The effects of ASR expansion on the structural behavior of reinforced concrete structures can be explained with basic structural mechanics.

These effects can be evaluated using the provisions of the structural design codes applicable to Seabrook Station (ACI 318-71 and ASME B&PV ,Section III , Division 2, 1975 edition).

Guidance on performing the evaluations is summarized in Sections 2.1 and 2.2. 2.1 STRUCTURAL LIMIT STATES The applicable design codes provide methodologies to calculate structural capacities for the various limit states and loading conditions applicable to Seabrook Station. MPR evaluated each relevant limit state using published literature and the results of the MPR/FSEL large-scale test programs that used specimens designed and fabricated to represent reinforced concrete at Seabrook Station. The following guidance applies for structural evaluations of ASR-affected concrete structures at Seabrook Station:

• Flexure/Reinforcement Anchorage

-Based on the MPR/FSEL large-scale test program results , structural evaluations should consider that there has been no adverse impact on flexural capacity and reinforcement anchorage (development length) performance , provided that through-thickness expansion is at or below.% and expansion behavior is comparable to the test specimens ,

• Shear -Based on the MPR/FSEL large-scale test program results , structural evaluations should consider that there has been no adverse impact on shear capacity , provided that through-thickness expansion is at or below.% and expansion behavior is comparable to the test specimens.

• Compression

-ASR expansion in reinforced concrete results in compressive load in directions where expansion is restrained by reinforcing steel. The ASR-induced compressive load is additive to compressive stresses due to other loads and should be included in design calculations performed in accordance with the original design code (including determination of an appropriate load factor). Our evaluation concludes that ASR expansion does not reduce the compressive strength of confined concrete, in its structural context. However , inclu s ion of the chemical prestressing effect due to ASR w ill have an impact on total loading of compression elements.

This effect can be calculated in MPR-428 8 R ev i s ion 0 2-1

--Non-Proprietary Version--accordance with the appropriate design code, b y treating ASR as a chemical prestressing mechanism that results in a self-equilibrating state of stress in reinforced concrete.

• Anchors and Embedments

-Based on the MPR/FSEL large-scale test program results, structural evaluations should consider that there is no adverse effect to post-installed or cast in-ace anchor/embedment capacity , provided that in-plane expansions remain at or below %. Through-thickness expansion is not relevant for anchor/embedment capacity.

2.2 OTHER

DESIGN CONSIDERATIONS In addition to the impact on structural limit states, MPR reviewed other design considerations that are potentially affected by ASR. Key conclusions from these evaluations are as follows:

• Reinforcement Strain Safety-Related Structures (other than Containment)

-Reinforcement strain beyond yield is permitted for ultimate strength calculations by ACI 318-71 , the design code for Seabrook Station. Furthermore, reinforcement yielding is a design feature required by ACI 318-71 for flexural elements in ultimate capacity calculations to prevent a brittle failure mechanism.

Therefore, evaluation of reinforcing steel in ASR-affected structures at Seabrook Station should be performed in accordance with the provisions of the original design code, taking into account chemical prestressing and any deformation effects. This approach ensures that reinforced concrete elements meet the ductility requirements that are implicit in flexural design criteria stipulated in ACI 318-71. Containment

-Seabrook Station has identified local regions in the Containment structure where ASR development could result in the local yielding of the reinforcement steel. The effect of this ASR development (taking into account chemical prestress and deformation effects) on the Containment structure should be evaluated using provisions in the ASME Code for reinforcement yielding due to secondary stresses as well as those for local yielding.

Evaluation using the original design code ensures that both the ductilit y and concrete serviceability requirements implicit in the original design basis of the Containment are maintained.

• Reinforcement Fracture -The reinforcement steel at Seabrook Station is not susceptible to brittle fracture due to ASR-induced expansion, which has been observed in Japanese structures.

Seabrook Station was designed and constructed in accordance with codes that do not permit rebar bending to the extent (i.e., small diameter) that would be required for susceptibility to rebar fracture.

Additionally, quality control requirements in effect during original construction at Seabrook Station were sufficient to ensure that design and construction practices were consistent with code requirements.

• Seismic Analysis -The MPR/FSEL large-scale test program results indicated that ASR development affected the flexural stiffness of the specimens, but MPR concludes that the effect on structures at Seabrook Station is not significant and is bounded by the current se ismic analysis.

In general, flexural stiffness increased with severity of ASR. An MPR-4288 Rev i s ion 0 2-2

--Non-Proprietary Version--increase in flexural stiffness can be viewed as an improvement to the seismic response , in the context of Seabrook Station's design basis , although it is not enough to be significant.

At low loading prior to flexural cracking , specimens exhibited a slight decrease in flexural stiffness that corresponds to cl% change in seismic response, as explained in Section 6.3. This difference is small compared to other uncertainties in the seismic analysis and is covered by peak broadening of the seismic spectrum in the UFSAR.

• Design Concrete Material Properties

-Published literature identified that ASR reduces unconfined material properties of concrete (compressive strength , elastic modulus, tensile strength), which is consistent with the results obtained in the MPR/FSEL large-scale test programs.

However , the test program results also showed that the reduction in concrete material properties does not have an adverse effect on structural performance of affected structures when through-thickness expansion is less than.%. These results confirm that structural performance of reinforced concrete structures cannot be reasonably re-evaluated for ASR simply by adjusting the ASR-affected properties of unconfined concrete and neglecting the self-equilibrating state of stress due to ASR-induced prestress.

Based on thi s observation , structural evaluations of ASR-affected structures at Seabrook Station should conservatively use the material properties specified in the original design specifications.

• Effect of Building Deformations

-Operating experience at Seabrook Station has shown that ASR expansion can result in building deformations , the structural effects of which mu st be taken into account in a comprehensive structural evaluation.

That is , supplementary loads can be generated when ASR-induced expansions in a structural element are restrained by (I) interference with another structure, or a component thereof , or (2) connection to a non A SR-affected region (e.g., expansion of an ASR affected wall restrained at the foundation mat connection or adjacent ASR-affected and non affected wall segments). The calculation of supplementary loads due to restraint of expansion can be significant and must be addressed on a on a case-by-case basis , by taking boundary conditions into account. The approach for performing this assessment is outside the scope of this report and is being addressed by NextEra in a separate effort. MPR-42 88 R ev i s ion 0 2-3

--Non-Proprietary Version--3 Key Elements of Structural Design Basis Th i s section summarizes key elements of the structural design basis for reinforced concrete structures at Seabrook Station. The discussion focuses on e l ements of the design basis that are potentially impacted by ASR. T he comp l ete design basis in fo rm at i on is provided in the Seabrook Station Updated Final Safety Ana l ys i s Report (UFSAR; Reference l) and Seabrook Struct ural D esign Cr iteri a (Refere nc e 9). 3.1 CODES OF RECORD 3.1.1 Safety-Related Structures except Containment Safety-r e l ated structures other than Containment were designed and constructed to comply with the 1971 edition of ACI 318 , Building C od e R e quir e m e nt s for R e infor ce d C oncr e t e (Reference

3) per the Seabrook Station UFSAR Sect i on 3.8.4. The app li cab l e l oads are determined in accordance wit h AC! 318-71. These l oads in c lud e normal l oads (startup , operation and shutdown), environmental loads (severe and extreme), abnormal loads , and s it e-specific loads. The app li cable load combinations define the required strength at various l ocations from normal and unusual l oad conditions. The l oad combinations are li sted in UFSAR Table 3.8-16 and determined in accorda n ce w ith AC I 3 18-71. While ACI 3 18-71 contai n s provisions for Working Stre ngth Design (WSD) and Ultimate Strength Design (USO), the Seabrook design methodology for safety-r e l ated structures other than Containment i s USO. 3.1.2 Containment The Containment structure was designed and constructed to the 1975 edition of the ASME Boiler & Pressure Vessel Code Section III , Division 2 , Subsection CC (Reference 2), as described in the Seabrook Stat i o n UFSAR Section 3.8.1. The applicable l oads are determined per Reference 2 , Article CC-3000. These lo ads in c lud e test pressure l oads , normal l oads (startup, operation and s hutd own), environme nt al l oads (severe and extreme), and abnormal l oad s 1* The applicable l oad combinat i ons define the r equ ir ed strength of Containment at var i ous locations.

The l oad combinat i ons are li sted in UFSAR Tab l e 3.8-1 and determined per Reference 2 , Art i c l e CC-3000 an d reflect a comb in at i on of WSD and USO methodologies.

Using WSD , stresses are computed based on the assumption of an e l astic strain profile. In USO , a non-linear strain profile can be used , wh i ch models the behavior of concrete much more accurately at its limit state. 1 Sev eral s it e-r e l a t e d (sit e-s p ec ifi c) l oa d s we r e c o n si d e r e d , but n o n e h a d a s ignifi ca nt effe ct on con ta inm e nt d es i g n. M PR-4 288 R ev i s ion 0 3-1

--Non-Proprietary Version--The Containment structure must behave elastically to these external loads and satisfy the structural acceptance criteria listed in UFSAR Table 3.8-2 and described in UFSAR Section 3.8.1.5 which complies with Reference 2 , Article CC-3000. A secondary stress is defined as a normal or shear stress developed by the constraint of adjacent material or by self-constraint of the structure.

Secondary stresses are self-limiting; additional strain reduces the internal forces required to maintain local equilibrium , thus reducing the stress; primary stresses are not self-limiting. For the Containment structure , the applicable code limits may be exceeded for peak , localized or secondary stresses.

Local yielding , minor distortions, and concrete cracking are permitted for these self-limiting conditions , Article CC-3136.4 of the ASME Code (Reference 2). However, it is important to note that the treatment of type stresses can vary in Reference 2, depending on the specific situation.

Therefore, the appropriate class ifi cation of ASR-indu ced stresses should be made in accordance with the original design code when performing design evaluations of ASR-affected structures.

3.2 KEY ELEMENTS OF DESIGN 3.2.1 Reinforcement The steel reinforcing bars used in safety-related structures at Seabrook Station conform to ASTM Specificat i on A615-75 (Reference

12) per Reference

11. Typ i cal reinforcement i s Grade 60 and ranges in size from #8 to #11 (for structures other than Conta inm ent; References 13 and 14) or # 14and#18 (Containment structure; Reference 31 ). Reinforcing bars were typically placed in two-dir ectional mats with one mat near each concrete face of a structural member. The spacing between individual bars typically ranges from 6 to 12 inches. Clear concrete cover for rebar is typically 2 inches for internal faces and 3 inches for external faces. Transverse reinforcement (i.e., reinforcement provided through the wall thickness) is only provided in some areas (e.g., Containment and Containment Enclosure Building (CEB)). 3.2.2 Seismic Design The se i smic design of safety-related structures is described in UFSAR Section 3.7(B). All safety-related structures are supported on competent bedrock or concrete fill over bedrock which fixes the structure bases against translation and rotation.

The design basis seismic analyses for reinforced concrete structures are elastic models with suitable linearized material properties.

The seismic response is a function of the natural frequency and damping characteristics of the structure and the seismic demands acting upon the structure.

The seismic demand on related structures is the ground motion response spectra provided in UFSAR Section 2.5. 3.2.3 Concrete Material Properties The se l ection of material properties for design of concrete structures at Seabrook Station is based on the standard concrete mix specification (including Containment and other safety-related structures) from original plant construction (Reference 10). ACI 318-71 recognizes the concrete mix specification as the primary location to specify the design concrete compressive strength.

MPR-42 8 8 R ev i s ion 0 3-2

--Non-Proprietary Version--Other material properties for concrete design (e.g., elastic modulus) are calculated based on the specified concrete compres s ive strength. 3.2.4 Anchorage to Concrete A variety of designs and configurations for anchorage to concrete are used in safety-related applications at Seabrook Station. These designs can be divided into two broad categories:

cast-in-place anchorages and post-installed anchors. Cast-In-Place Anchorages Cast-in-place anchorages (including anchors and embedments) are suspended in the supporting structure's formwork and concrete is then cast around it. Load is transferred through bearing from the anchorage directly to the concrete.

Cast-in place anchorages in use at Seabrook Station include embedded plates (with Nelson studs), embedded Unistrut type channels (with embedment studs), Richmond Studs , and anchor bolts. The design of safety related concrete structures at Seabrook Station is governed by ACI 318-71 , which requires that cast-in-place anchorages must be capable of developing adequate strength without damage to the concrete and that their adequacy be demonstrated with testing. This means cast-in-place anchors (e.g., Nelson studs or embedded Unistrut-type channels) are designed with embedment depths such that the limiting failure mode is ductile failure of the anchor steel. Post-Installed Anchors Post-installed anchors are installed by drilling a hole in the existing concrete and inserting an anchor bolt. The anchor transfers load to the concrete through friction and/or bearing at the anchor/hole interface.

Post-installed anchors in use at Seabrook Station include both expansion anchors (e.g., Hilti Kwik Bolts) and undercut anchors (e.g., Drillco Maxi-Bolts).

Seabrook Station is committed to the requirements ofNRC IE Bulletin 79-02 (Reference

15) for post-installed anchor design. ln accordance with this commitment , a safety factor of 4 on mean failure load is used for the design of post-installed anchors for pipe supports.

This safety factor is applied to all safety-related post-installed anchors at Seabrook Station. Review of relevant design documentation (Reference

21) indicates that design practices at Seabrook Station are consistent with these requirements.

Post-installed anchor allowable loads are based on the following:

• Expansion Anchors: The allowable loads for all expansion anchors (e.g., Hilti Kwik Bolts) specified for use at Seabrook Station are based on qualification testing performed by Hilti or a third party (Abbot Hanks) (References 16, 17 , & 19)2. The tensile load capacities 2 For H i lti K w ik B o lt 2 a n c h o r s, th e d es i g n lo a d s p rov id e d in Re fe r e nc e 17 a r e c o n s i s t e nt w ith th ose s p ec ifi e d in th e Hilti Kwik Bolt 2 Technic a l Guid e (R efe renc e 18), w ith a Safet y Fac tor of 4 a pplied. MPR-4 288 R evis i o n 0 3-3

--Non-Proprietary Version--were determined by unconfined tensile testing in unreinforced test specimens 3. A ll owable loads are based on the tested mean failure load with an app li ed safety factor of four.

• Undercut Anchors: The Stat i on Pipe Support Design Guide lin es (Reference

20) indicate that undercut anchors (e.g., Drillco Maxi-Bolts) must be embedded to sufficient depth such that tensile failure of the anc hor steel i s the limiting fai lure mode. Review of anchor dimensions and the material specification (Reference

21) shows that the design allowable loads are based on tensile fai lur e of the anchor bolt shank with a safety factor of 4 app li ed. Wh il e the basis for specified minimum embedment depths is not provided, scop in g calculations indi cate that the minimum embedme nt depths pro v ide 40% margin between shank tensile fai lur e and theoretical concrete breakout failure , based on the 45° shear cone method , a commonly used approach during the or i g in a l construction period of Seabrook Station. 3 B as ed on a r ev i ew o f qu a lifi ca ti on t est r e p o rts (R efere n ces 16 , 17 , & 1 9), w hich did n ot n o t e th e p rese n ce of r e inforcin g st ee l. MPR-4 288 R ev i s i o n 0 3-4

--Non-Proprietary Version--4 Overview of MPR Evaluations Determining the effect of ASR development on the structural design basis of safety-related structures at Seabrook Station is based on a detailed review of data provided in publicly available literature supplemented with data from a series of large-scale test programs that MPR conducted at FSEL. MPR-4273 , S e abrook Station -Implications of Larg e-Scal e T e st Program Results on R e infor ce d Concrete Aff e ct e d by Alkali-Silica Reaction (Reference

8) contains a more detailed discussion of the test programs and the literature review that supported development of the test approach.

4.1

SUMMARY

OF LITERATURE REVIEW MPR conducted a comprehensive review of published research on the structural implications of ASR and industry guidance for evaluating ASR-affected structures.

A focused review of published research on the structural implications of ASR (Reference

5) identified dozens of technical references on testing of ASR-affected concrete.

The most relevant references were used to support the interim structural assessment for Seabrook Station by providing a conservatively bounding capacity reduction factor for structural limit states (e.g., shear and reinforcing bar anchorage) accounting for the presence of ASR to evaluate the continued operability of ASR-affected plant structures.

While most research on ASR has focused on the science and kinetics of ASR, there is a substantial body of knowledge that exists in the literature on structural testing of ASR-affected concrete specimens.

However , the application of the conclusions from the literature to structures at Seabrook Station can be challenged by lack of representativeness.

As a result, for selected structural limit states, NextEra commissioned MPR to perform large-scale structural testing using specimens that were designed and fabricated to be representative of structures at Seabrook Station. Consequently , results from the large-scale test programs provide information that can be used in lieu of less representative data from published literature for the limit states that were within the scope of the test programs.

4.2 IMPORTANCE

OF CONFINEMENT The presence of confinement is a central factor for the effect of ASR on structural performance.

Reinforcing steel, loads on the concrete structure (e.g., self-weight), and the configuration of the structure (i.e., restraint offered by the structural layout) may provide confinement that restrains in-situ expansions due to , ASR and limits the resulting cracking in concrete.

Confinement limits ASR expansion of the in-situ structure , which reduces the extent of deleterious cracking and the MPR-4 288 R ev i s i o n 0 4-1

--Non-Proprietary Version--resultant decrea se in structural performance

4. Accordingly , evaluation of the effect of ASR at Seabrook Station mu st consider the confinement conditions that exist at the plant (i.e., m ost l y two-dimensional reinforcement mats for safety-related structures).

When reinforcement is present to restrain the tensile force exerted by ASR expansion, an equivalent compressive force develops in the concrete that is comparable to prestressing.

If loads applied on the structure result in tensile stresses (direct , diagonal , or otherwise), the compressive stresses in the concrete mu s t be completely overcome before additional tensile load is reacted by the reinforcement.

Cracking in confined concrete would not occur until the tensile stress imposed by external loads exceeds the compressive stress in the concrete from the prestressing effect plus the tensile strength of concrete which can be conservatively taken as zero. The prestressing effect does not reduce the ultimate tensile capacity of the reinforcement.

In some cases, literature indicates that the prestressing effect of ASR creates a stiffer structural component with a higher ultimate strength than an unaffected member -the mechanics of which can be explained by using the first principles of prestressed concrete behavior and design. Test data show that this prestressing effect applies even when ASR expansion has yielded the reinforcing bars (Reference 5). Once again , this behavior i s consistent with the behavior of presetressed elements behavior under external loads. 4.3 MPR STRUCTURAL TEST PROGRAMS MPR directed three structural test programs at FSEL to support NextEra's efforts to resolve the ASR issue identified at Seabrook Station. In each test program , ASR developed in the fabricated test specimens and was routinely monitored so that load testing could be performed at particular levels of ASR distress.

The magnitude of ASR-distress was isolated as the primary test variable and structural response for the wide range of ASR distress was studied. This approach enabled systematic development of trends for structural performance with the progression of ASR. The resulting data sets were a significant improvement upon the collection of published literature so urces , because test data across the range of ASR level s were obtained using a common methodology and identical test specimens. A brief overview of each structural test programs is provided below.

• Anchor Test Program -This test program evaluated the impact of ASR on performance of expansion anchors and undercut anchors installed in concrete.

Test specimens included seven large-sca l e blocks that were designed and fabricated to represent the reinfor ce d concrete structures at Seabrook Station and two sections of reinforced concrete bridge girders that were avai I able at FSEL. The test program consisted of a total of.anchor tests.

• Shear Test Program -This test program evaluated the impact of ASR on shear capacity of reinforced concrete specimens.

Three-point load tests were performed on large-scale beams that were designed and fabricated to represent the reinforced concrete structural 4 The restraint offered by some part s of a structure on other parts of i t , need s to be expl i citly t aken int o account , as di sc u ssed in ot h er sectio n s of this r eport. MPR-4288 R ev i s ion 0 4-2

--Non-Proprietary Version--components at Seabrook Station. FSEL fabricate.shear test specimens and conducted a total of.tests (two tests performed on most specimens).

• Reinforcement Anchorage Test Program -This program evaluated the impact of ASR on reinforcement anchorage of rebar l ap splices embedded in concrete and also provided in s i ghts on flexural strength and stiffness.

Four-point bending tests were performed on l arge-sca l e beams that were designed and fabricated to represent the reinforced concrete structures at Seabrook Station. FSEL fabricated lr einforcement anchorage test specimens and conducted a total of ltest s (one test per specimen).

The test specimens fabricated for the MPR/FSEL test program were designed to be representative of the structura l characteristics of safety-r e l ated structures of Seabrook Station. The specimen dimensions and reinforcement configurat i ons were similar to a reference l ocation at Seabrook Station , with minor modifications made to ensure the spec im en's fai lur e mode was consistent w i th test objectives.

Additionally, cement, coarse and fine aggregates were chosen to ensure that the specimen was representative of the mechanical behavior of the concrete mix used at Seabrook Station. Refer to MPR-4273 (Reference 8), Sections 2 and 3 for a more detailed discussion of the test program and test specimen design. 4.4 SCOPE OF EVALUATIONS The comprehensive lite rature review id e ntifi ed a number of areas w h ere the structura l design basis cou ld be affected by development of ASR. This r eport divides the potentially imp acted areas int o two groups: structural limit states and design cons id erations.

Th i s report evaluates the potential impact of ASR for each of these areas an d provides gu idelin es for structura l eva lu ations of ASR-affected structures at Seabrook Station. Table 4-1. Scope of Evaluations Structural Limit States (Section 5) Design Considerations (Section 6)

• Flexure & reinforcement anchorage/

• Reinforcement steel strain reinforcing steel development

• Reinforcing bar fracture

• Shear strength

• Seismic response

• Compression

• Applicability of design basis mate ria l

• Anchor bolts and structural properties attachments to concrete

• Effect of structural deformations Ax i al tension i s not included in the scope of evaluations.

The impact of ASR on gross axial tension in concrete is n ot cons id e red sign ifi cant as tensile strengt h of concrete is commonly neglected in reinforced concrete d es i gns comp li a nt w ith , for examp l e , ACI 318. The methodology of the Seabrook Stat i on design codes for reinforced concrete structures (ASME B&PV , Section IJl , Division 2, 1975 Edit i on and ACI 318-71) requires that the contribution of the gross concrete section in tension is neglected in axial (and flexural) limit states. MPR-42 8 8 R ev i s ion 0 4-3

--Non-Proprietary Version--5 Structural Limit States T hi s section eva luat es the potential impacts of the ASR aging mechanism on structural limit states that are applicable for ASR-affected r e in forced concrete st ru ct ur es at Sea bro ok Station. The applicable limit states in c lud e fle x ur e (including reinforcement anchorage), s h ea r , and co mpr ession. 5.1 FLEXURE Eva luati on of t h e effect of ASR o n the flexure limit state co n si der ed b ot h flexural capac it y and reinforcement anchorage development.

5.1.1 MPRIFSEL

Large-Scale Test Program Results T h e MPR/FSEL l arge-sca l e test program eva lu ated the effect of ASR o n reinforcement a n c horag e d eve l o pm e nt (Reference 8). These tests can a l so b e u s ed t o investigate the effect on flexural capacity and flexural stiff n ess. Reinforcement anc h orage and flexural capac it y are eva luat ed in this section; flexural st i ffness i s eva lu ated in Sectio n 6.3. R esu lt s from the l arge-sca l e test demonstrated that AS R-aff ected spec im ens wit h through-thickness expans i o n of up tcmo/o were ab l e to fully develop the minimum reinforcement l ap sp li ce specified b y AC I 3 18-7 1 and exh ibit e d no reduction in the flexural ca paci ty. The test spec im ens had two-dim ensional r einforcement mats without transverse reinforcement simi l ar to structures at Seabrook Station (sim il ar r einforcement s i ze , spacing and material).

Through-thickness expansion of.% was the hi g h est AS R l eve l exhibited b y the t est spec im e n s. The l ack of an adverse effect on reinforcement anc h orage and flexural capacity may exte nd t o hi g h er expa n sion levels. For in-pl a n e ex p ansion , a ll test p rogram spec im ens l eveledoff at.% t.%. Expans i o n s occurred predominately in the through-thickness direction , making th rough-thickness expansion the be s t indicator of ASR development.

Add iti ona ll y , flexural stiffness tracked wit h through-thi ckness expansion l eve l , indi cat in g that throu gthickness expans i on i s an appropr i ate parameter for monitoring AS R progression. 5.1.2 Comparison to Literature Flexural Performance T h e results of the most app li cab l e publically avai l ab l e test data regarding the effect of ASR on flexural performance are based on l arge-sca l e spec i mens (20 inch b y 20 in ch), as reported in Reference s 5 and 28. MPR-42 88 R ev i sio n 0 5-1

--Non-Propr i etary Version--* For specimens without transverse reinforcement , the test results of ASR-affected test specimens showed a range that was predominately better than control test specimens.

Specifically , the flexural capacity of the A SR-affected test specimens ranged from a 43% increase to 7% decrease relative to the control specimens.

• For specimens w ith transverse reinforcement, the test results showed the ASR-affected specimens performed better than the control specimens by approximately 5% (Reference 5). The increase in flexural capacity is due to ASR-indu ced prestressing.

Overall, testing performed on relatively l arge-sca le spec im ens shows no significant loss of strength or stiffness in ASR affected specimens (Reference 5). Considering the effects of chemica l prestressing due to ASR , and putting that int o context with axial load-bending moment interaction diagrams avai l ab l e in prestressed concrete design textbooks , the improvement in flexural capacity due to ASR can be explained.

That is , axial load l eve l s that are l ess than the balanced flexural l oad tend to in crease the flexural capacity of the concrete e l ements. In a broad sense , the chemical pressing effect imp oses ax i a l loads on concrete sections resulting in an increase in flexural capacity. However , no credit will be taken for an increase in flexural capacity.

Reinforcement Anchorage The most app li cab le publically ava il ab l e test data for reinforcement anchorage are based on a bar pullout test in ASR-affected concrete (Reference 5). The bar pullout test method i s the l east desirable method of reinforcing bar anchorage testing as boundary conditions present in a typical pullout test do not represent actua l boundary conditions present in a typical structural component (Reference 27). While suc h tests were common in the ear l y days of structura l testing , and inform ed reinforcing bar development design , the engineer in g comm unit y moved away from this type of testing on the basis of a wide range of representativeness is sues assoc i ated with them. Wit h that context , the results still provide an insight into the sign ifi cant performance benefit provided by transverse reinforcement in ASR-affected structures , regardless of the testing methodology and problems associated with that methodology.

For specimens without transverse reinforcement , the test results showed a 40% l oss in capac it y. The l arge observed loss is a result of the test method generating stress fields that are different and significant l y more severe than those found in actua l structural e l ements subjected to flexure. In brief , such a drop in capac i ty i s attr ibut ed to free expansion experienced in the relatively sma ll co ncret e blocks tested. The same study produced test results for specime n s with transverse reinforcement that were indicative of a 10% strength l oss. 5.1.3 Evaluation Flexural Capacity Results from l arge-scale tests are available regarding the imp act of ASR on flexural performance with and without transverse reinforcement.

Published results from l arge-scale testing of more representative specimens with transverse reinforcement (Reference

5) indi cate no loss in flexural capacity due to the presence of ASR. The MPR/FSEL test programs of specimens without transverse reinforcement also indicate no l oss of flexural capacity. According l y , flexural MPR-4 2 88 R ev i s ion 0 5-2

--Non-Proprietary Version--performance will not be adversely affected by ASR at the expansion levels exhibited in the scale test programs.

Reinforcement Anchorage The MPR/FSEL test program used a more representative test method (e.g., flexural test of a large-scale beam containing a rebar splice, as compared to a rebar pullout test of a small specimen), which provides several advantages:

• the test method is viewed as being among the best methods that produces " more realistic measures of bond strength in actual structures" according to the technical report produced by ACI Technical Committee 408 (Reference

27) and reapproved by the committee in 2012.

• specimens were more representative of structures at Seabrook Station with respect to

• mechanical properties of concrete, reinforcing bar size, and clear cover.

• the test results were highly repeatable.

As a result , structural evaluations for Seabrook Station can use the MPR/FSEL test programs conclusions (i.e., no loss ofreinforcement anchorage or flexural capacity for through-thickness expansion up t.%) in lieu of the resu l ts from the published literature.

A SR-affected structures with transverse reinforcement are expected to maintain the i r performance at higher levels of ASR expansion than those without transverse reinforcement , so the large-scale test results are conservative with respect to structures with transverse reinforcement.

For structural evaluations at Seabrook Station, the additional compressive stress due to the effect of ASR chemical prestressing on the overall stress state in flexural elements must be checked in the appropriate structural calculations.

While flexural elements at Seabrook Station were designed to be tension controlled (Reference 21 ), ASR-affected elements should be evaluated to verify that tension-controlled design criteria are still satisfied with the additional ASR-induced compressive stress. 5.1.4 Co nc l usi o n The calculated flexural strength per the Seabrook Station design codes (ACI 318-71 or ASME B&PV Section III , Division 2, l 975 Edition) is appropriate because testing showed no decrease in flexural capacity.

Note that these tests were performed in a context where all flexural capacity ca l culat i ons were performed according to ACI 318-71. A l i mitation of.% throughthickness expansion is applied consistent with the level of ASR expansion exhibited by i ecimens i n the MPR/FSEL large-scale test programs.

Structural behavior at l evels greater than % expansion may be acceptable.

A lim i t on in-plane expansion is not necessary, as expansion is predominate l y i n the through-thickness direction.

5.2 SHE AR Evaluation of the effect of ASR on the shear limit state focused on one-way shear (beam shear), but also included two-way (punching) shear. MPR-42 8 8 R e vi s ion 0 5-3

--Non-Proprietary Version--5.2.1 MPRIFSEL Large-Scale Test Program T h e MPR/FS EL large-scale test program eva lu ated the effect of ASR on shear demonstrated that ASR-affected spec im ens w ith through-thickness expans i on of up to.% did not exhibit a l oss of shear capac it y (Reference 8). Through-thi ckness expansion of.% was the highest ASR level exhibited by the shear test spec im ens. The l ack of an adverse effect on s hear capacity may extend to higher expansion levels. The calculated shear strength per the Seabrook Station design codes (ACI 318-71 and ASME B&PV Section III , Division 2) i s appropriate to u se for evaluation of ASR-a ffected struct ur es for expansion l eve l s up to this limit. Expa n sion behavior of the s h ear test spec im ens was co n s i ste nt with the reinforcement anchorage (Reference 8). Because in-plane expans i on of a ll test specimens le ve l-off at.% to.%, through-thickness expa n sion was u sed to character i ze ASR development.

The test results showed that shear capacity incr eased with incr easing through-thickness expansion.

However , no cred it wi ll be taken the in crease in shear strengt h due to ASR. 5.2.2 Comparison to Literature Published lit erature on struct ural testing of ASR-affected reinforced concrete includes a range of results that genera lly refle cts the degre e of reinforc eme nt. Previous stud i es note that triaxially reinforced concrete wi ll on l y be slightly affected, even by fairly severe ASR expans i ons (Reference 7). The result s from larg e-sca l e spec im ens (i.e., specimens with a cross-section of 42" x 21 ")w i th transverse reinforcement showed a 16% gain in shear strength due to the presence of ASR (Re ference 5). These test specimens were tested at in-plane expansion l eve l s vary in g from 0.7% to 1.2% measured in the direction of shear reinforcement.

Test dat a ava il ab l e in published lit erat ur e show that ASR-affected test specimens w ith o ut shear reinforcement displa ye d shear capacit i es ranging from a slight increase to a l oss of 25% (Reference 29). Test spec im ens for result s at the l ow e nd of thi s range h ad a relativel y sma ll cross section (5" x 3 "). lt s hould be noted that the study that generated the results suggesting a 25% reduction spec ifi ca ll y noted that the sma ll test spec im ens likel y exaggerated th e deleterious effect of ASR , because the depth of ASR cracks is relatively greater in sma ll er specime n s. 5.2.3 Evaluation As discu ssed above , the MPR/FSEL larg e-sca l e test spec im ens without transverse reinforcement s h owed no l oss in shear capac it y due to ASR expans i on. This beha vior is s imilar to triaxially reinforced concrete.

Because the MPR/FSEL t est program spec imen s we r e much more representativ e of Seabrook Station than published literatur e (e.g., I" x I" specimen cross-section , as compared to 5" x 3") and the MPR/FSEL test results we r e hi g hly repeatable , structura l eva lu ations for Seabrook Station s h ou ld consider that there is no impact to shear capacity.

MPR-4288 R evisio n 0 5-4

--Non-Proprietary Version--5.2.4 Other Limit States Considered Two-Way (Punching)

Shear R es ult s from the one-way shear eva lu at i on described above are applicable to punching shear (two-way shear). Punching shear involves a truncated pyramid (as opposed to a diagonal shear plane see n in a beam test) and this difference in geometry does not affect the overa ll conc lu sion of the MPR/FSEL testing that there i s no adverse impact for through-thickness expansion up to .%. T h e lit erat ur e review performed in Reference 5 identified a st ud y of punching s h ear in reinforced concrete plates. Spec im ens w ith a thickness of 8 cm (-3 in) and ASR-i ndu ced expansions up to 0.7% were studied. T hi s study co n c lud ed that ASR had littl e effect, provided that delamination had not occurred.

T h e study (Refere n ce 6) states that the beneficial effects of ASR-induced prestress appear to counteract the detrimental effects of ASR on material properties such that there i s not a genera l reduction in punching shear performance.

As discussed in the previous sect i on, the u se of sma ll sca l e testing to represent shear performance of l arge e l ements i s conservat i ve, as it exacerbates the detrimental effects of ASR. Because the test specimens from Reference 6 were s ignificantl y thinner (-3 in) than structural members at Seabrook Station (2 to 4 ft), the results of that study conservatively bound the behavior of structural wal l s at Seabrook Station. Co n s id er in g th e results reported in R eference 6 and the performance of the s h ear specimens tested at FSEL, punching shear strength of structural wa ll s and s l abs at Seabrook Station i s not affected by ASR. 5.3 COMPRESSION ASR expans i on resisted by stee l reinforcement results in a compressive stress in the concrete.

In the case of structura l e l ements in w hi c h the concrete i s l oaded in tension (e.g., s h ear or flexure), the ASR-indu ced expansion acts as a chemical prestress , in which the reinforcement tensile l oad due to the expans i on i s opposed by concrete compression to produce a state of int erna l force balan ce. The l oa d associated with overcoming the pre-compression du e to ASR i s lik e l y greater than that wh i ch would cause crack in g of concrete in a case w h ere ASR-induced prestre ss does not ex i st. However , the compressive stress caused by AS R i s add it ive to the app l ied compressive stress in a ll e l ements , and must be in c lud ed in design ca l culat i ons. 5.3.1 Mechanics of ASR-lnduced Concrete Compression In the absence of external l oads , the tensile force developed in reinforcing bars due to ASR-indu ced expans i ons must be equal to the compressive resultant forced developed in concrete.

If the in-pl ane expans i o n s are known , or can b e conservatively est im ated, the tensile force in the reinforcing bars can b e calcu l ated from first principles.

Once the te n s il e force i s known , the area of concrete that serves to counteract that force (i.e. the cross-sect i ona l area) can be used to ca l culate the compressive stress in concrete. The application of design basis l oads s hould be considered in conjunct i on with the se lf-equilibratin g stresses generated b y ASR. That i s, the impact of ASR on structural performance can be modeled on the basis of first principles. MPR-4288 R ev i s ion 0 5-5

--Non-Prop rietary Version--The concept of accounting for i nternal prestress due to reinforcement strain is typical in prestressed concrete design (Reference 30 , Section 19.2). 5.3.2 Literature Review Initial review of the potential implications of ASR on structures at Seabrook Stat i on (Reference

5) identified one test program in the literature with results relevant to the eva lu ation of axial compression (Reference 23). This test program used medium-scale specimens (9 inch square cross-section), and showed an 18% loss of performance at 0.7% longitudinal (in-p l ane) expansion.

5.3.3 Evaluation

Understanding the impli cations of the compression testing discussed in Reference 23 requires determining i f the reason for decreased compression capacity observed in the testing was the addition of ASR-induced compressive stress prior to l oadi n g or a c h ange in the unconfined compressive strength of the concrete.

The limiting test result in Reference 23 showed an 18% reduction in compressive capacity.

Based on the test spec im en parameters provided in Reference 23 and using the approach discussed in Section 5.3.1, a scoping ca l culation determined that the ASR-indu ced compressive stress in the limiting test spec imen wou ld reduce the axia l compress i ve capacity by approx im ate l y 9%. The difference in ax i a l compressive capac it y between the first-prin ciples scoping calculation (9% reduction) and the test result (18% reduction) from Reference 23 is negligible when examined in the context of the normal st r ength variat i on tolerated within reinforced concrete construction, espec i a lly w ith reduced-scale specimens. For reference, the acce pt ab l e variation b etween two concrete cy lind er compression tests is 8-10% per ASTM C39 (Reference 24). According l y, MPR concludes that the decrease in compression capacity from the testing documented in Reference 23 was due to the addition of ASR-induced compress i ve stress rather than a change in compress i ve strengt h of confined concrete.

Results of the MPR/FSEL l arge-scal e flexural testing support this conclusion.

Spec ifi ca ll y, this testing demonstrated that the theoretical flexural capac it y determined using ACI Code ca lcul at i ons was realized. A decrease in compress ion capac i ty due to a c h ange in unconfined concrete compressive strength wou ld lik e l y h ave resulted in compress i o n zone failure of the flexural specimen prior to yie ldin g of flexural reinforcement and reaching full flexural capacity. 5.3.4 Conclusion Increased compressive stress due to ASR expansion is additive to compressive stresses due to ot h er l oads. The additional compress i on l oad due to ASR expans ion must be in c lud ed in the eva lu ation of A SR-a ffected struct ur es at Seabrook Station. T h e magnitude of the add iti o n a l compress i ve stress can be ca l c ul ated using basic struct ural mechanics based on the measured in-plane expansion.

This effect s h ould a l so be considered in the eva lu at i on of flexural elements , as the additional compression will affect the development of tensile re in forcement strain. Additionally , our evaluation concludes that structural evaluation of ASR-affected structures should be performed using the nominal (spec ifi ed) compressive strength, consistent with current practices.

MPR-428 8 R e vi s ion 0 5-6

--Non-Proprietary Version--5.3.5 Bearing Performance Our lit erat u re rev i ew and eva lu at i on did not identify any plausible means through which ASR cou ld directl y impact bearing capacity , wh i ch is a function of the in-situ (e.g., confined) compressive strength. T h at said , in creased l oading on a bearing surface due to constrained ASR expansion , (e.g., loading due to contact betwe e n structures) sho uld be considered in structura l calculat i ons using the approach for ca l culatin g ASR-induced compressive stress discussed above. 5.4 STRUCTURAL ATTACHMENTS L i terature providing test data on anchor capacity of ASR-affected concrete was not publicly ava il ab l e. Therefore, MPR and FSEL performed a l arge-sca l e test program to determine the tensile capacity of sha ll ow embedment anchor s i n ASR-affected concrete , the conclusions of which are provided below. Refer to Reference 8 for a more detailed discussion of the test program. 5.4.1 MPRIFSEL Large-Scale Test Program The large-scale te s ting program in cluded unc o nfined t e nsion tests 5 of p o st-insta ll ed w edge-st y l e anchors (Hi lti Kwik Bolt 3) and undercut anchors (Dri ll co Max i Bolts). The undercut a n c h ors a l so r eprese nt cast-in-pl ace e mb e dm e nt s. The testing program did not in c lud e anchor s h ear tests , because tension tests wou ld be more sens i tive to ASR expans i on than shear tests. The test results show no l oss of tensile performance up to.% in-p l ane expansion.

The test program a l so concluded that anchor performance is not sens i tive to through-t hi ckness expansion or time of anchor i nsta ll at i on relative to the AS R expansion.

T h rough-thickness expansion has the potential to create microcracks perpendicular to the axis of an ancho r. An anc h or l oaded in te n s i on wou l d compress the through-thickness expansion and c l ose any potential microcracks with in the area of influ ence of that anchor. Without a " short-c ir c uit" of the breakout cone, through-thickness expansion d oes not affect anchor performance.

Degradation of performance ex i sts at hi g h er l eve l s of in-pl ane expa n s i on b eca u se in c r eased crack in g due to ASR int erfere s with shear cone development during anc h or loading. 5.4.2 Evaluation The structura l capac i ty of anchors and other concrete attachme n ts identified in Seabrook's responses t o IE Bulletin 79-02 (Reference

15) are n ot adversely affected b y AS R for in-pl ane e x pansion of up to.%. As di sc u ssed in Sect i on 3.3 , Seabrook S t at i on h as a ser i es of Hi I ti expa n sio n a n cho r designs in serv i ce. Our r ev i ew of the avai l ab l e design information (e.g., anc h or co nfi g u ration and d es i gn 5 T h e MP R/FSE L fu ll-sca l e t es tin g p rogra m did n o t in c l u d e di rec t s h ear t es ts o n a n c h o r s in s t a ll e d in t es t sa mpl es. Te n s i on t ests a r e m ore se n s iti ve t o AS R ex p a n s i o n th a n s h ear t ests. Th erefo r e, di rect s h ear tes ts on t es t sa mpl es we r e n ot n ecessa r y. M P R-4288 R ev i s i o n 0 5-7

--Non-Proprietary Version--capacities) concluded that the test results using Hilti Kwik Bolt 3 anchors are applicable to the other K wik Bolt designs in service at Seabrook Station. Based on this, we conclude that the current design basis capacities anchors and other concrete attachments are acceptable for use in design calcu l ations when in-plane expansion is less than .%. MPR-42 88 R ev i s ion 0 5-8

--Non-Prop ri etary Version--6 Design Considerations This section evaluates the potential impacts of the ASR aging mechanism on design considerations that are applicable for ASR-affected reinforced concrete structures at Seabrook Station. Spec ifi cally, this section addresses reinforcement steel strain , reinforcement fracture , seismic response , applicabi lit y of design basis material properties , and the effect of structural deformation.

6.1 REINFORCEMENT

STEEL STRAIN ASR expansion results in tensile strain of the embedded stee l reinforcement , whi l e placing the concrete in compress i on. This section discusses provisions from the applicable design codes that pertain to reinforcing steel strain due to ASR expa n sio n. 6.1.1 Reinforcement Strain in AC/ 318-71 AC! 318-71 recommends that flexural elements be designed suc h that they are contro ll ed , which ensures sufficient ductility prior to failure. A tension-controlled element i s designed such that the reinforcing steel on the tension side wi ll yie ld prior to co mpr ess iv e failure of the concrete on the compression side of the ele ment , with s uffici ent margin. contro ll ed sections are advantageous because they provide v i s u a l evidence of structural distress (e.g., lar ge deflections and substant i a l flexural cracki n g) prior to failure. The design of flexural elements limit s the amount of tensile reinforcement to l ess than 75% of the amount necessary to produce balanced condit ion s under flexure (ACI 3 18-71 , 10.3.2). A balanced co nditi o n in a flexural cross sect i on is defined as a sect ion where the tensile reinforcement re aches y i e ld (for examp l e at a strain of 0.00207 for, ASTM A6 15 , Gr. 60 reinforcing bars) just as the concrete on the compress i o n side reaches its assumed fai lur e strain of 0.003 (ACI 318-71, 10.3.3). De sign of a flexural eleme nt w ith 75% of the balanced-section reinforcement r esults in tension reinforcement stee l with 0.376% tensile stra in (for Gr. 60 reinforcement) at nominal capacity, wh i ch is a va lu e we ll beyond the y i e ld point (0.207%), and as such accommodation for ductility is made in flexural d esig ns. The 75% limit is furth er r educed to permit addit i onal l oad redistribution of negative moments resulting in yie ldin g in continuous flexural members (ACI 3 18-71 , 8.6). T h e di scussio n a b ove d emonstrates that reinforcement strain beyond y i e ld i s permitted b y the design code for Seabrook Station (A Cl 318-71 ), for the purposes of flexural capac it y calculation.

Furthermore , reinforcement strains that correspond to l eve l s of stra inin g that are well above yield in g is a USD design fe a ture , to ensure ductile performance , and is required by ACI 318-71 for flexural elements. MPR-4 2 88 R ev i s ion 0 6-1

--Non-Proprietary Version--6.1.2 Reinforcement Strain in ASME B&PV Code, Section 3, Division 2 Code Design Approach The Containment structure at Seabrook Station was designed in accordance with the ASME B&PV Code , Section 3, Division 2, 1975 Edition (Reference 2). The design intent of this code is to ensure that the overall Containment structure behaves elastically under design and service external loading. To accomplish this , the code limits the average tensile stress ofreinforcement to the following:

• Service Loads (Normal):

50% of yield stress (WSD)

• Factored Loads (Severe/ Abnormal):

90% of yield stress (USD) These code limits on the design stress of reinforcement are applied on an average stress basis and are not applicable to peak or localized stresses.

Specifically , local yielding , minor distortions , and concrete cracking are permitted in self-limiting conditions (i.e., secondary stresses such as expansion due to ASR), per Reference 2 , Article CC-3136.4.

The allowance of reinforcement yielding is limited such that increased concrete cracking does not cause deterioration of the Containment (Reference 2 , CC-31 I O(d)(2)).

While it should be noted that the treatment of expansion stresses under the B&PV code varies depending on the configuration and loading it is clear that the code permits reinforcement yielding due to secondary stresses (e.g., thermal stresses or bending at gross discontinuities) as well as local yielding due to primary loads , provided the structure remains in structural equilibrium and general yielding does not occur. Additionally , the code provides specific guidance for the evaluation ofregions with local yielding (Reference 2 , CC-3511.1 (c)). Effect of ASR on Reinforcement Design ASR expansion ofreinforced concrete produces a displacement-limited chemical prestress.

Additional stresses may be imposed due to the restraint of ASR-affected elements by unaffected elements.

As described above , the ASME B&PV Code provides guidance for evaluating primary and secondary stresses from ASR-induced expansion, including reinforcement yielding due to local effects. As such , the evaluation of the effect of ASR expansion on the Containment structure should be performed in accordance with the original design code. 6.2 REINFORCEMENT FRACTURE Operating experience from ASR-affected structures in Japan , particularly within the Japanese transportation industry , has raised the possibility of ASR expansion contributing to the fracture of reinforcing steel. Examples of such failures have been documented in a number of structures in Japan , such as bridge piers and protective walls (Reference 25). This section discusses relevant research determining the cause of these failures and evaluates the susceptibility of ASR-affected structures at Seabrook Station to similar failures.

6.2.1 Literature

Review The Japanese Society of Civil Engineers created a task force to investigate the causes and structural implications of the reinforcement fractures discussed in Reference

25. This effort MPR-42 88 R ev i s io n 0 6-2

--Non-Proprietary Version--produced a s i g nifi cant amou nt of in formation avai l ab l e in the public lit erature. In 2011, researcher s at FSEL performed a study of stee l reinforcement brittle fracture 6. Th i s study included a detailed li terature review and a ser i es of tests to better understand the factors contr ibutin g to steel r e in force m e nt embr i tt l ement and crack initi ation (Reference 26). The FSEL review of Japanese field st udi es and l aboratory testing ava il ab l e in the public literature id e ntifi ed the following:

• Reinforcing stee l brittle fractures were observed in bent reinforcement on l y (e.g. st irrup s or hooks).

• T h e fractures largely occurred in rebar bent to diameters sma ll er than wou ld be permitted by current American design codes or ACI 318-71.

• The fai lur es were a ll brittle in nature , indi cat ing a change in mechanical properties in the normally ductile l ow ca rb o n steel r e in forceme nt.

• Laboratory testing concluded that the fract ur es initiated at the s i tes of compress i on cracks in the intrados (in side surface at the bend) of the bent steel. As part of their study, FSEL performed a se ries of reinforcement b end test s to investigate the corre lati on between bend diameter and deformation p attern o n the initi ation of compress i o n cracks on the bend int rados. App licabl e results of the FSEL testing are in c lud ed in the fo ll ow in g discussion.

6.2.2 Crack

Initiation Mechanics T h e m ec h a ni cs of the crack initi at ion and materia l e mbrittl eme nt r es ultin g in reinforcement fracture are descr i bed in R eference 26. Bending a steel r e in force ment bar results in elongation of the b ar along the bend extrados (outside) and co mpr ess i o n at th e int rados (inside).

A dditi ona ll y, contact with the bending pin flattens the bar deformations (r id ges on the bar surface to aid concrete bonding), resulting in l arge stress co n ce ntrati ons. Compression stresses at the intrad os increase as the r e bar i s bent to a s mall er diameter, pot e nti a ll y resulting in com pres s i on cracks at the stress concentration l ocat i ons. Subsequent to b e ndin g the bar , the appl i cation of a tensile force has two effects. First , tensile force produces l oca l tensile stra inin g at the crack l ocat i o n s potentially resulting in crack propagation. Second, the t e n si l e l oa d causes a c han ge in the m ec hani ca l properties of the lo w carbon stee l bar , referred to as s train aging. This has th e effect of incr eas in g th e ten s ile stre n gt h (stra in hardening) and decreasing th e ductilit y (strain em brittl ement) suc h that brittle fai lur e can occur. 6.2.3 Susceptibility of Reinforcement to Fracture at Seabrook Station As discussed above, the potential for reinforcing steel brittle fracture requires the stee l bar to be bent to a very tight diameter.

The FSEL st ud y (Reference

26) noted that observed fai l ures were 6 This effort was n ot part of the MPR/FSEL test programs performed for NextEra. MPR-4288 R ev i s ion 0 6-3

--Non-Proprietary Version--in reinforcing bars bent to diameters smaller than permitt ed by current US design codes , which are equivalent to those provided in ACI 318-71 and ASME B&PV Code Section Ill , Divi s ion 2 , 1975 Edition. Note that the bend tests performed in the FSEL study included bend diameters consistent with the Seabrook design codes. Additionally , b e nd tests performed by FSEL using deformed reinforcement bent in accordance with ACI requirements did not show evidence of compression cracking at the intrados (only one specimen tested showed evidence of smal I compression crack formation). The issue of brittle reinforcement fracture i s largely limited to older structures in Japan. MPR is not aware of any operating experience in the United States indicating that the brittle fracture of s teel reinforcement designed in accordance with ACI 318 had occurred. Finally , it is imp ortant to note that steel reinforcement brittle fracture is a function of excessively small bend diameters and is not directl y related to the development of ASR. The addition of any expansive or tensile force on the crack site could r es ult in brittle fracture of cracked and strain em brittled bars. Based on the discussion above , the reinforcement steel at Seabrook Station is not suscept ibl e to brittle fracture.

Seabrook Station was de s i g ned and constructed in accordance with codes that do not permit rebar bending to the extent that would be required for susceptibility to rebar fracture. Additionally , quality control requirements in effect during orig in al construction of Seabrook Station would have prevented th e poor construction pra ct ic es that resulted in the observed rebar fractures in Japan. 6.3 SEISMIC RESPONSE This section discusses the potential effects of ASR-indu ced cracking on the structural rigidity (i.e., stiffness) of the seismic Category I reinforced concrete structures at Seabrook Station. Cracked concrete sections have reduced st i ffness properties in comparison to un-cracked concrete sections.

In general , a change in the stiffness of the structural member would modify:

• the d eflec tion s of st ructure s for a given static load (e.g., dead load s), and

• the dynamic response of the structure when subjected to vibratory loads (e.g., rotating equipment loads and seismic loads). The change to deflections from static loads i s addressed as part of the plant's normal structural monitoring pro gra m and corrective action process. Likewise , changes t o the dynamic response for non-seismic vibratory l oads (e.g., modal separation for rotating equipment) also wou ld be addressed as part of the plant's normal monitoring programs. The consequences of changes to the dynamic re s ponse of st ructures for seismic loads are of particular intere st because thi s could affect the seismic design and qualification of al l safety-related structures , systems , and components (SSCs). A change in the dynamic response of the overal l structure would change the seismic loads , seismic deflections , and also the in-structure amplified response spectra at the mounting location SSCs l ocated in the structures.

The sub se ction s b e lo w summarize results from the MPR J FSEL tests and provide ju s tification that the struct ural dynamic response do es not change for the ASR affected members at Seabrook Station. MPR-4288 R evisio n 0 6-4

--Non-Proprietary Version--In general , the re spo nse of a st ructure to a seismic event is affected by the stiffness of structural m e mbers in flexure and shear, and their stiffness in response to axial loads. Flexural st iffness is the most sensitive to cracking and would be most affected by ASR-induced cracking.

Modern design codes such ACI 318-11 al low the flexural stiffness of cracked beams and wal Is to be represented as a fraction of the nominal flexural rigidity in a linear analysis.

By comparison, this version of ACI 318 does not specify any reduction factor for axial rigidity or any reduction factor for shear rigidity if the shear loads are less than the shear capacity.

Therefore , the effects of ASR on the seismic performance of Category I structures were evaluated based on the effects of ASR on fle x ural stiffness.

6.3.1 ASR Test Results on Stiffness The MPR/FSEL large-scale testing (Reference

8) produced the following key observations re gar ding stiffness in ASR-affected reinforced concrete members.

• The initial flexural stiffness of ASR-affected test specimens (i.e., prior to flexural cracking) was le ss than the control specimen.

The reduction is attributed to the presence of numerou s A SR-induced cracks in the test specimen prior to the application of load during the structural test. There was no discernible relationship between the severity of ASR versus the fle x ural stiffness prior to flexural crackin.i.i, On average , the initial flexural stiffness of ASR-affected test specimens was about.% less than what would be the calculated flexural stiffness (Reference 8).

• The service level flexural stiffness (i.e., from 0% to 60% of yield moment) of ASR-affected test specimens was greater than the control specimen.

The increased stiffness i s attributable to the ASR-induced the test specimens. The flexural stiffness of ASR-affected test specimens was I% to.% larger than the control specimen , with stiffness generally increasing with through-thickness expansion.

6.3.2 Plant

Seismic Design Basis The Seabrook Station UFSAR (Reference 1), Section 3.7(B) describes the seismic design of safe ty-related structures.

All safety-related structures , with the exception of some electrical manholes and ductbanks , are supported on competent bedrock or concrete fill over bedrock , which fixes the structure bases against translation and rotation.

The design basis seismic analyses for reinforced concrete structures are elastic models with suitable linearized material properties. Two methods of seismic analysis are used: (1) response-spectrum and (2) history. Seismic response-spectrum analyses are used to obtain the structural displacements and seismic loads. Time-history analyses are used to obtain the in-structure response spectrum used for design and qualification of other SS Cs. In either analysis method , mathematical models for the overall reinforced concrete structures are constructed with lumped masses connected by simplified linear elastic springs , commonly referred to as a " stick model." The stick model is u se d to obtain the seismic response of the overall structure.

As necessary , separate analyses are performed with individual models to obtain the amplified seismic response spectrum or seismic loads at specific location s such as floor slabs or walls. MPR-4288 R evis i o n 0 6-5

--Non-Proprietary Version--The se i smic response is a function of the natural frequency of th e structure , structura l damping , and the seismic demands acting upon the structure. The se i smic demand on safety-related structures is th e grou nd motion re sponse spectra provided in UFSAR Section 2.5. Fig ure 6-1 illustrates the h or i zonta l and vertical design basis gro und response spectra for Seabrook Stat i on using data from UFSAR Figures 2.5-43 a nd 2.5-44. T h e design ba s i s ground response spectra are also known as the safe s hutd own eart hqu ake (SSE) spectra. The operat in g basis eart hqu ake (OBE) i s defined as o n e half of the SSE. :§ c 0 Ill ... Q) a:; u 0.1 u < iii ... ..... u -Horizontal Q) c.. Vl -vertical -* -4Hz 0.01 0.1 1 10 100 Frequency (Hz) Figure 6-1. Design Basis Seismic Ground Response Spectrum , 5% Damping (Reference

1) 6.3.3 ASR Effect on Structural Damping In genera l , seism i c ana l yses in clude damping to account for energy dissipation during structura l vibrat i on. The se i smic response of a structure i s inversely proportional to the magnitude of damping. Cracked concrete has l arger effective damping rat i o than un-cracked concrete , reducing the se i s mic r esponse w ith respect to co ncret e un affected b y ASR. Therefore, it i s conservative to neglect the addit i onal damping due to ASR-induced crack in g. 6.3.4 ASR Effect on Natural Frequency T h e tables in UFSAR Sect i on 3.7(B) summarize the n at u ra l frequenc i es of the Category I str uctur es at Seabrook Stat i on. Based on review of t h e tables , the sma ll est n atura l frequency of any Category I structure at Seabrook Station i s about 4 Hz. The natural frequency of the structure is proportional to the square root of the structural stiffness (k) divided by the mass (m). ASR does not change the mass of the structure. According l y, the natural frequency of the MPR-42 88 R ev i s ion 0 6-6

--Non-Proprietary Version--structure would change proportionally to the square root of the c han ge in the stiffness.

In general , there are three type s of member stiffnesses cons id ered in a structural seismic analysis.

• Flexural St i ffness -governs deflections of s l abs , columns , beams , and beam-like members subject to bending l oads. The flexural stiffness is directly proportional to the product of a member's modulus of e l ast icit y (E) and area moment of inertia (I) of the cross sect i on that resists the bending l oad.

• Shear Stiffness-governs deflections of members l oaded in-pl ane , in cases where shear stress related distortions contr ibut e sign ifi cant l y to overa ll defl ected shape of a m e mb er. The shear st iffn ess i s directly proportional to a member's shear modulus of e l ast icity (G) and the cross-section area (A) parallel to the direction ofloading.

• Axial St i ffness -governs deflections of members subject to l ongitudinal loads. The axial stiffness is directly proportional to a member's modulus of elasticity (E) and cross-section area (A) perpendicular to the direction of l oad in g. Of a ll the three st i ffness types listed above , the flexural stiffness is the most significant l y affected by cracks overall. Modern design codes a ll ow the flexural st iffne ss of cracked beams a nd wa ll s to be represented as a fraction of the nominal flexural rigidity (El) in a lin ear ana l ysis. Such reductions are not common practice for ax ial o r s h ear rigidity.

For examp l e , the importanc e of flexural stiffness with re spect to cracks is illu strated in ASCE 43-05 (Reference 22). Table 3-1 of ASCE 43-05 provides reduction factors for flexural rigidity that range from 0.50 to 0.70 to account for crack effects. Similarly , modern versio n s of ACI 3 18 (e.g., the 201 1 Edition) allow the flexural stiffness of cracked beams and walls due to serv i ce load s to be taken as 0.35 times the n o minal elastic st iffn ess (El). By compar i son , ACJ 3 18-11 and ASCE 43-05 do n ot spec if y any reduction factor for axia l rigidity or any reduction factor for s hear rigidity if the s h ear l oads are les s than the shear capacity.

Furthermore , the lin ear mat er ial prop ert i es for shear m odu lu s (G) and cross sect i ona l areas (A) can be written in terms of the e l astic modulus (E) and m oment of inerti a (I), respectively.

Based on the above, the effects of ASR on th e se i smic performance of Catego r y I st ructures are therefore eva lu ated ba sed on the effects of ASR on flexural st iffne ss a l one. 6.3.5 ASR Effects on Flexural Stiffness For heavil y lo aded reinforced concrete members in flexure, the Seabrook design analyses wou ld co nsider so m e reduction factor t o account for flexural cracking.

Re su lt s from the te sts of ASR-aff ected specime n s demonstrated that the flexural rigidity increases with the severity of ASR. The increa se d ri g idit y cou ld be v i ewed as an improv ement for the se i sm i c response.

As s hown in Figure 6-1, th e se i s mi c demand s decrease for frequencies lar ger than about 3 Hz. The s mallest natural frequency i s about 4 Hz. According l y , there i s no adverse effect on th e se i sm i c displacements and seism ic l oads for h eavi l y l oaded concrete member s l oaded in flexure. For lightl y loaded flexural members , design analyses may be based on uncracked section properties using the nominal fle x ural rigidit y (E l). Results from the tests of ASR-affected spec imen s indi cate some decrease in the fle x ural rigidity shou ld be expected prior to the onset of MPR-4 288 R ev i si on 0 6-7

--Non-Proprietary Vers i on--flexural cracking.

There was n o corre l at i on in the decrease in flexural ri g idit y with the severity of ASR , but the mea s ur e d flexural stiffuess in ASR-affected specimens was about I% smaller than the calculated flexural stiffness.

As described in the previous section, relative changes to the st i ffuess change the natural frequencies by a square root relationship.

Accord in g l y, al% reduction in the nominal flexural rigidity cou ld reduce the calcu l ated natural freq uen c i es by about I%. Reducing the natural frequency of Category I st ructure s does not significantly affect the se i smic response (loads or deflections) itself. Figure 6-1 shows the seismic demands in the high frequency range(> 10 Hzl have an approximately lin ear relationship when plotted on a l og-l og scale. T hi s means that al% reduction in the n atura l frequency could only in crease the seismic response byl% for hi gh frequency modes. The se i smic demands have even l ess sensitivity in the 4 Hz to 9 Hz range , which i s the range of the dominant structural modes. Furthermore , the I% frequency s hift due to ASR effects is we ll w ithin the normal var i ation in concrete properties overall. ACI 318-95 states that the modulus of elasticity can typically vary as much as +/-2 0% about the specified values. Such large uncertainties in material properties are factored into the Seabrook seismic design. UFSAR Section 3.7 (B).2.9 indicates that the peaks of the ca l cu l ated in-structure response spectra are broadened by at least+/- 10% to acco unt for uncertaintie s in material properties and modeling techniques.

Figure 6-2 illu strates the effect of peak bro adening. The dashed lin es illu strate the ca l cu l ated response with discrete peaks at the struct ural natural frequencies (fn). The solid dark lin e illustrates the broadened spectra that are +/- 10% of the structura l natural frequency (f n). Based on the above , MPR concludes ASR does not significant l y affect the flexural stiffness and there is no adverse effect on the seismic analyses . .. ----*COMPUTED .1 -FOR OESIOl'f USE .. .1 .2 .) A Q_!H.1+-+1_1-f., ,, ,, ,, '1

• 1 I I I I I I I I I I I I I I I I I I I I I l I ' I ' I / I f' Figure 6-2. Illustration of Peak-Broadened Spectrum about Structural Frequencies (fn) MPR-4288 R ev i s ion 0 6-8

--Non-Proprietary Version--6.4 APPLICABILITY OF DESIGN BASIS MATERIAL PROPERTIES 6.4. 1 Literature Review The observed expansion on the surface of unconfined concrete can be corre l ated to degraded properties such as uniaxial compression , modulus of elasticity , and tensile strengt h. R eference 4 provides l ower-b ound degraded properties based on measured free expansion in unconfined concrete. The l ower bound properties tabulated in Reference 4 show that compressive strength is a weak function of the observed expansion , wh il e tensile strength and elastic modulus are much stronger functions of the extent of ASR degradation.

However, ASR affects confined (i.e., reinforced) concrete structures differently than unconfined structures.

The effect of confinement must be taken into account when eva lu at in g reinforced concrete structures affected by ASR. 6.4.2 MPRIFSEL Large-Scale Test Programs The MPR/FSEL l arge-scale test programs (Reference

8) in cluded extensive cylinder and core testing corresponding to the var i ous beam test specimens. Testing and eva lu at i on of material properties of extracted cores show significant reduction in elastic modulus and moderate reductions in compressive and splitting tensile strengt h , whic h is similar to Reference

4. As part of l oad testing , FSEL determined the theoretical capac it y based on design eq u atio n s from AC I 318-71 a nd th e 28-day cy linder test results , which did not ex hibit deleterious expans i on due to ASR. The l oad test results of ASR-affected specimens exceeded the theoret i ca l capacit i es calcu l ated using nominal material properties , indicating that the use of material properties obta in ed from extracted cores to calculate the structura l capacity of an ASR-affected e l ement i s not appropr i ate. 6.4.3 Conclusion Given the interplay between ASR-indu ced crack in g and structural restraint , it is imperative that eva luation of the st ru ctural imp acts due to ASR focus on struct ural testing rather than simp l y material prop e rt y testing of co n c rete cores r e moved from the st ructur e and n eg l ect in g the effects of confinement in struct ur al eval u a ti on . The ASR-indu ced prestressing effect is on l y present w h en the expansion is confined.

If the concrete is removed from it s native stress field (i.e. it s structural context), the prestressing effect i s l ost. A core sample from an ASR-affected , reinforced concrete structure wil l not be confined by the stresses imparted by the reinforcement and surrounding concrete after it i s removed from the structure. Therefore, such a core i s n ot directly representative of the concrete w ithin it s struct ural context. Measured mechanical properties from a core taken from a confined ASR-affected structure have limit ed app li cability to in-s itu performance; suc h results o nl y represent the performance of an unconfined or unreinforced concrete.

The use of th ese properties by themselves w ith out recognizing and explicit l y modeling the effects of confi n eme nt wou ld result in an analysis which does not represent actua l structural behavior a nd could h ave adverse consequences (i.e., in accurate determination of structure dynamic response).

Evaluations of ASR-affected structures at Seabrook Station could conservatively use the material properties specified in the origina l design spec ifi cations. As shown in MPR/FSEL large-scale MPR-4 2 88 R ev i s i o n 0 6-9

--Non-Proprietary Version--test programs , the experimental evidence suggests that effects of confinement more than compensate the mechanical property degradation of unconfined concrete.

The reduction in concrete material properties does not have an adverse effect on structural performance of ASR-affected structures at Seabrook Station when through-thickness expansion is l ess than .%. 6.5 EFFECT OF STRUCTURAL DEFORMATION Unrestrained expans i on of ASR-affected concrete in a struct ur e d oes not produce any str u ctura l l oa d s. In th e case of ASR expans i on in reinforced concrete, expans i on restrained b y reinforcing stee l results in a balanced set of int erna l forces wh i ch do not impact the overa ll structura l equilibrium of the structure (i.e., the state of balance between externally app li ed forces and moments and react i on forces and moments). In addition to these stra in-limit ed int ernal l oads, supp l ementary load s can be generated when ASR-induced expansions in a structura l e l ement are restrained by:

• interference with another s tructure , or a component thereof, or

• connection to a non A SR-affected region (e.g., expansion of an ASR affected wa ll restrained at the foundation mat connection , or adjacent ASR-affected and non ASR-affected wa ll segments).

These supp l ementary l oads are most significant when ASR-indu ced expansion occurs over a large area , the effect s of which have been observed at Seabrook Station in the form of building deformation.

The l oads c r eated by the restraint of expa n sion in ASR-affected co ncr ete by adjacent structura l e l eme nt s must be cons id ered in design eva lu ations of ASR-affected structures.

The effect of ASR-indu ced building deformation on structural l oad in g is a function not on l y of the amount of ASR expans i on but o n the struct ur e geometry and restraint cond iti ons. These l oads may be sign ifi cant and must be eva l uated on a case-b y-case basis. NextEra h as initiated a program at Seabrook Stat i on for the monitoring and eva lu ation of ASR-affected structures wh i ch includ es assess ing the effect of st ru ct ural de format i on on the abi lit y of the structure to m eet it s design r eq uir ements. T h e details of thi s effort are outs id e the scope of this report. MPR-4288 R ev i sion 0 6-10 7 I. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. MPR-42 88 R ev i sion 0 --Non-Proprietary Version--References Seabrook Updated Final Safety Analy s is Report (UFSAR), Revision 12. ASME Boiler and Pressure Vessel Code 1975 Edition ,Section III , Division 2. ACI 318-71 , " Building Code Requirements for Reinforced Concrete ," American Concrete Institute , 1971. Institution of Structural Engineers , " Structural Effects of Alkali-Silica Reaction:

Technical Guidance on the Appraisal of Existing Structures

," London , UK , 1992. Bayrak , 0., " Structural Implications of ASR: State of the Art ," July 2014 (Seabrook FP# 100697). Ng , K.E. and Clark , L.A., "Punching Tests on Slabs with Alkali-Silica Reaction ," The Structural Engineer Vol. 70, No. 14 (1992), pp. 245-252. United States Nuclear Regulatory Commission, NRC Information Notice 2011-20, "Concrete Degradation by Alkali-Silica Reaction," November I 8 , 2011. (ADAMS Accession No. MLl 12241029)

MPR-4273 , " Seabrook Station -Lmplications of Large-Scale Test Program Results on Reinforced Concrete Affected by Alkali-Silica Reaction ," Revision 0 , July 2016. (Seabrook FP# 10 I 050) Seabrook System Description No. SD-66 , " System Description for Structural Design Criteria for Public Service Company of New Hampshire Seabrook Station Unit Nos. 1 & 2 ," Revision 2 with Addenda 1 , 2 , and 3. Seabrook Station Standard No: 9763-006-69-7 , "Specification for Standard Concrete Mixes ," Revision 2. Seabrook Station Standard No: 9763-006-14-1 , " Specification for Furnishing , Detailing , Fabricating , and Delivering Reinforcing Bars ," Revision 10. ASTM A6 l 5-75 , " Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement

," American Society for Testing and Materials , 1975. Seabrook Station Standard No: 9763-006-14-2 , " Specification for Installation of Reinforcing Bars in Containment Structure ," Revision 8. Seabrook Station Standard No: 9763-006-14-3 , "Specification for Installation of Rebars in Category I Structures (Other Than Containment)," Revision 7. IE Bulletin 79-02 , " Pipe Support Base Plate Designs Using Concrete Expansion Anchors ," Revi s ion 2. Foreign Print 44412 , " Hilti Anchor and Fastener Design Manual ," Revision 0. 7-1

--Non-Proprietary Version--17. DRR 92-64 , Hilti Kwik-Bolt II , Rev. 0. 18. H-437C , " Hilti Fa s tening Technical Guide , April 1991. 19. Foreign Print 100174 , " Hi I ti Kwik Bolt 3 Product Technical Guide ," Revision 0. 20. Foreign Print 18559 , " UE&C Additional Information for Pipe Support Design Guidelines

," Revision 1 plus changes. 21. MPR-3727 , " Seabrook Station: Impact of Alkali-Silica Reaction on Concrete Structures and Attachments

," Revision 1. (Seabrook FP# 100716) 22. American Society of Civil Engineers (ASCE) Standard 43-05 , " Seism i c Design Criteria for Structures , Systems , and Components in Nuclear Facilities." 23. Chana , P.S and Korbokis , G.A., " Structura l Performance of Reinforced Concrete Affected by Alkali-Silica Reaction:

Phase l ," Tran s port and Road Research Laboratory , Department of Transport , Contractor Report 267 , I 991. 24. ASTM C39-03 , " Standard Test Method for Compre ss ive Strength of Cylindrical Concrete Specimens.

25. "M i yagawa , T., Seto , K., Sasaki , K., M i kata , Y., Kuzume , K., and Minami , T., " Fracture of Reinforcing Stee l s in Concrete Str u cutres Damaged by A lk a li-S ili ca Reaction -F i e ld S ur vey , Mechanism , and Maintenance

," Journa l of Advanced Concrete Technology, Vol. 4 No. 3 (199 1): 339-355. 26. Webb , Z.D., " Experimental Investigation of ASR/DEF-Indu ced Reinforcing Bar Fracture," MS Thesis , The University of Texas at Austin , 2011. 27. ACI Committee 408 , " Bond and Development of Straight Reinforcing Bars in Tension ," (AC! 408R-03), Farmington Hills: Amer i can Concrete Institute , 2003. 28. C l ark , L., " Cr iti ca l Review of the Structura l Implications of the A l ka li-Si li ca Reaction in Concrete," Transport and Road Research Laboratory Contractor Report 169 , l 989. 29. Ahmed , T., Burley , E., and Ridgen , S., " The Static and Fatigue Strength of Reinforced Concrete Beams Affected by Alkali-Silica Reaction , " ACI Materials Journal Vol. 95 No. 4 (1998): 356-368. 30. A.H., Darwin , D., and Dolan , C.W., " Design of Concrete Structures," Thirteenth Edition. 31. Seabrook Station Drawing 9763-F-10 1 435 , " Containment Concrete Typ i cal Reinforcement

," Revision 7. MPR-4288 7-2 R evision 0 J