Text

C-10 Documents for Seabrook ASR May 7, 2025 - Advisory Committee on Reactor Safeguards Full Committee 2025
	ML25121A280
Person / Time
Site:	Seabrook
Issue date:	05/01/2025
From:	Abramson S; C-10 Research & Education Foundation
To:	Lawrence Burkhart; Advisory Committee on Reactor Safeguards
References
	Download: ML25121A280 (1)
	v • d • e

April 30, 2025 via electronic mail To:

U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Attn: Advisory Committee on Reactor Safeguards Lawrence Burkhart, Chief, Technical Support Branch, ACRS

Cc:

Travis Daun, Senior Resident Inspector, Seabrook Station

Nik Floyd, Senior Reactor Inspector Matt R. Young, Chief Projects Branch 2 Division of Operating Reactor Safety Raymond Lorson, Regional Administrator, Region I

Mel Gray, Chief, Engineering Branch 1

Subject:

C-10 Research & Education Foundation requests time to present during the upcoming May 7, 2025 Advisory Committee on Reactor Safeguards (ACRS) Full Committee (FC) meeting regarding Alkali-Silica Reaction (ASR) at Seabrook Station.

We are writing to respectfully request that time be made available for C-10 to present during the upcoming May 7, 2025 ACRS Full Committee meeting within the 1:00 pm -

6:00 pm agenda block which is dedicated to the Alkali-Silica Reaction issue at Seabrook Station.

Enclosed please find a white paper entitled Assessment of NIST Shear Wall Tests and Their Relevances, by Prof. Victor E. Saouma (Emer.), which sets forth Dr. Saoumas technical evaluation of tests conducted for the NRC at a substantial cost by the National Institute of Standards and Technology (NIST) on ASR-affected squat shear walls (Weigand, Sadek, Thonstad, et al., 2021). As you will see, Dr. Saouma has identified significant and highly concerning implications of the NIST study for the integrity of ASR-impacted safety structures at the Seabrook Station nuclear power plant.

We understand that the Advisory Committee on Reactor Safeguards is an independent body authorized by Atomic Energy Act of 1954, as amended, chartered for the following purposes:

to review and report on safety studies and reactor facility license and license renewal applications; to advise the Commission on the hazards of proposed and existing production and utilization facilities and the adequacy of proposed safety standards; to initiate reviews of specific generic matters or nuclear facility safety-related items; and to provide advice in the areas of health physics and radiation protection.

C-10 Research & Education Foundation l 11 Chestnut St., Amesbury, MA 01913

1

C-10 respectfully submits that in order to satisfy these weighty responsibilities, the ACRS should obtain the best and most up-to-date information and technical analysis.

Dr. Saouma is one of the worlds foremost experts on ASR, whose views had a significant and positive effect on the terms of the ASR monitoring and assessment program approved by the NRCs Atomic Safety and Licensing Board in 2019. At that time, Dr. Saouma was not aware of the NIST study and it was not addressed in testimony by NextEra or the NRC Staff. And yet, its implications for the safety of the Seabrook reactor are profound. Therefore, we urge you to consider Dr. Saoumas significant concerns regarding the implications of the NIST study for the Seabrook reactor. This is especially important in light of the facts that (a) monitoring data has shown that ASR is progressing more quickly than estimated by NextEras NRC-approved LSTP, (b) we understand a new testing program would be eventually required to address the observed rate of ASR expansion at Seabrook, and (c) the NIST study shows that repeating the original LSTP tests would not produce any useful result.

In addition to considering Dr. Saoumas White Paper, we respectfully request you to provide him with at least 15 minutes during the upcoming May 7, 2025 ACRS full committee meeting to provide a succinct presentation of his analysis and take questions from committee members.

Thank you for your consideration of our request and for your service on the Advisory Committee of Reactor Safeguards. We look forward to your response, and will be in attendance at the May 7, 2025 ACRS full committee meeting.

Kindly, Sarah Abramson Executive Director C-10 Research & Education Foundation, Inc.

Office: 978-465-6646 Mobile: 603-793-0600 sarah@c-10.org Web: c-10.org C-10 Research & Education Foundation l 11 Chestnut St., Amesbury, MA 01913

2

Assessment of NIST Shear Wall Tests and Their Relevances for Seabrook Station Safety Presentation to the Advisory Committee on Reactor Safeguards May 7, 2025 Emeritus Prof. Victor E. Saouma (CEAE)

Department of Civil Engineering University of Colorado C-10 Consultant 1/5

Key Findings NIST study, (Weigand, Sadek, Thonstad, et al., 2021), independently raises two major concerns regarding Seabrook Stations structural safety:

1 While NextEra reported an increase in shear strength due to ASR, NIST observed a decrease.

2 NextEra relied on the empirical equation E = 57,000 p

f c to relate compressive strength to elastic modulus. NIST found the experimental data to be widely scattered, not clustering around the proposed relation, thus rendering the equation unreliable for determining past expansion.

2/5

Related to the above:

NextEra failed to recognize that the Containment Enclosure Building (CEB),

being circular, is governed by membrane shell theory (with negligible bending) and should not be modeled as a flexural member. The dominant response involves in-plane shear, requiring testing of squat shear walls.

Instead, NextEras test specimens generated out-of-plane shear.

The outcomes of the Large-Scale Testing Program (LSTP) were foreseeable and should have been anticipated based on prior studies, notably (Ahmed, Burley, and Rigden, 1998). The cause is the ASR induced chemical prestressing, which increases internal friction and thereby enhances shear capacity.

The findings reported by NIST are broadly consistent with the testimony I presented to the NRCs Atomic Safety and Licensing Board in 2019.

3/5

Accordingly, I continue to hold the expert opinion that Seabrook Stations safety has not been adequately demonstrated, given the presence of ASR in containment and other critical structures, and in light of the serious deficiencies in how ASR has been addressed.

I therefore join C-10 in urging the Advisory Committee on Reactor Safeguards (ACRS) to undertake a thorough, independent, and expedited technical review of the contradictions between the NIST report and NextEras LSTP.

Should NextEra propose further ASR testing, the program must incorporate the findings of the NIST study, the conclusions of this assessment, and the results of your own independent evaluation.

4/5

Ahmed, T., E. Burley, and S. Rigden (1998). The state and fatigue strength of reinforced concrete beams affected by alkali-silica reaction. In: Materials Journal 95.4, pp. 376-388.

Weigand, J., F. Sadek, T. Thonstad, S. Marcu, R. Villegas, and L. Phan (2021). Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 3: Assessing Cyclic Performance of ASR-Affected Concrete Shear Walls. Tech. rep.

NIST TN 2180. National Institute of Standards.

5/5

White Paper Assessment of NIST Shear Wall Tests and Their Relevances for Seabrook Safety Prof. Victor E. Saouma (Emer.)

University of Colorado, Boulder C-10 Research and Education Foundation Consultant Submitted to Advisory Committee on Reactor Safeguards April 30, 2025

Contents About the Author ii Executive Summary iii

Background

iv Notice to Readers iv 1

NIST Findings Challenge the LSTP Test Configuration 1

2 Relevance of NIST tests on shear strength 6

3 Relevance of NIST tests on past expansion 7

4 Summary of Conclusions 10 A Glossary 13 B NIST Findings Challenge the LSTP Test Configuration 14 B.1 Proof of validity of membrane action......................

14 B.2 Use squat shear walls...............................

16 C II Relevance of NIST tests on shear strength; Further details 16 C.1 Highlights of LSTP and NIST Shear Wall Test Results............

20 C.2 What is Chemical prestressing 21 C.3 What are Squat Shear Walls...........................

22 D Relevance of NIST tests on past expansion; Further details 24

ii About the Author Victor E. Saouma, with over 40 years of research experience, including nearly 15 years devoted to Alkali Silica Reaction (ASR), has made significant contributions to the field.

His ASR research encompasses 11 major funded projects, two books (Saouma and Hariri-Ardebili, 2021), (Saouma, V.E., 2013), 9 major reports, 9 short courses, and 13 peer-reviewed papers.

He chaired an international committee through RILEM (International Meeting of Lab-oratories and Experts of Materials, Construction Systems, and Structures), focusing on the diagnosis and prognosis of structures affected by ASR. He served as the editor of a RILEM report comprising over 450 pages and contributions from 30 leading researchers, underscoring his expertise.

He is a past President and Fellow of the International Association of Fracture Mechanics for Concrete and Concrete Structures and is, accordingly, well-versed in concrete cracking issues.

He has advised the Tokyo Electric Power Company (TEPCO) on the nonlinear dynamic analysis of large arch dams and on ASR-related problems affecting massive rein-forced concrete structures. He conducted shear tests for TEPCO and for the Electric Power Research Institute (EPRI).

He was a key contributor to EPRIs report Structural Modeling of Nuclear Containment Structures.

Saoumas research on ASR has been funded by various organizations, including the Nuclear Regulatory Committee, Oak Ridge National Laboratory, and the Bureau of Recla-mation. His technical reports are available online.

His research interests extend to theoretical, numerical, and experimental fracture me-chanics, chloride diffusion in concrete, real-time hybrid simulation, and centrifuge testing of dams.

His international collaborations include France, Spain, Switzerland, Italy, and Japan.

In addition to his scientific expertise, Saouma is a trained civil engineer. He has taught linear and nonlinear structural analyses as well as reinforced and advanced reinforced con-crete design, providing him with a broad perspective on engineering challenges.

In studying ASR over fifteen years, he has observed that ASR is an extraordinarily complex and nefarious reaction.

Although it has been recognized since the 1940s, the emergence of structures suffering from this phenomenon has become more evident only recently (as it may take many years to manifest itself). Consequently, ASR has attracted the attention of researchers from many disciplines: chemists, mineralogists, geologists, material scientists, mechanicians, experimentalists, and, notably, structural engineers.

No single discipline can independently provide a definitive answer to the questions posed by ASR.

However, those who adopt a comprehensive perspective are best positioned to offer informed opinions.

In 2019, on behalf of the C-10 Research and Information Foundation (C-10), he served as an expert witness in a license amendment proceeding before the U.S. Nuclear Regula-tory Commission (NRC), (NRC-ML19312B609, 2019), concerning the state of ASR at the Seabrook nuclear power plant. His testimony resulted in the implementation of stronger measures for monitoring the state of ASR over a 20-year license renewal term.

Given his diverse research background, encompassing theoretical, experimental, numer-ical, and field work, as well as his leadership role in addressing ASR globally, he is well-positioned to evaluate the adequacy of the work conducted at Seabrook Nuclear Power Plant.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

iii Executive Summary This White Paper provides an expert technical assessment of tests conducted by the National Institute of Standards and Technology (NIST) on alkali-silica reaction (ASR)-affected squat shear walls (Weigand, Sadek, Thonstad, et al., 2021) and evaluates their implications for the structural integrity and safety of Seabrook Station.

The NIST study raises three major concerns regarding Seabrooks structural safety:

1. NextEra predicted an increase in shear strength in ASR-affected structures based on beam tests from the Large-Scale Testing Program (LSTP). Although this increase was not explicitly exploited, it influenced the license amendment request. In con-trast, NISTs squat wall testsa more appropriate configurationshowed a decrease in strength, demonstrating the inapplicability of LSTP results and raising serious concerns about the adequacy of NextEras assessment and monitoring program.

2. This disparity between the NIST and LSTP results was foreseeable. The selection of beam flexure tests to predict Containment Enclosure Building (CEB) behavior reflected a fundamental misunderstanding: cylindrical shells resist lateral loads pri-marily through membrane action (in-plane shear) with minimal bendingnot beam flexure, which captures out-of-plane shear.

Tests should have been performed on specimens which capture in-plane shear fail-ure, as consistently done by other researchers studying cylindrical shells. Given its prior research on CEB shear behavior (e.g., Cornell/MIT projects), the NRC had the knowledge and responsibility to recognize that the proposed NextEra beam test was fundamentally non-representative.

Moreover, it appears NextEra did not conduct an adequate literature review; chemical prestressing effects, long documented (e.g., (Ahmed, Burley, and Rigden, 1998)), show that reinforced concrete beams will gain shear strength in the presence of ASR.

3. NextEra relied on the empirical equation E = 57, 000 p

fc (MPR-ML16279A050, 2017) to relate compressive strength to elastic modulus. However, NIST found the experi-mental data widely scattered, not clustering around the equation. This scatter high-lights the need to explicitly account for uncertainties. NISTs findings thus invalidate the procedure developed in (NRC-ML18226A205, 2018) for inferring past expansion.

I continue to hold the expert opinion that Seabrooks safety has not been adequately demonstrated, given the presence of ASR in critical structures and the serious deficiencies in how ASR has been addressed.

I therefore join C-10 in urging the Advisory Committee on Reactor Safeguards (ACRS) to undertake a thorough, independent, and expedited technical review of the contradictions between the NIST report and NextEra LSTP. Should NextEra propose further ASR test-ing, the program must incorporate the findings of the NIST study, the conclusions of this assessment, and the results of an independent evaluation.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

iv

Background

An excellent scoping study by Snyder and Lew (2013) laid the groundwork for a compre-hensive investigation into the effects of alkali-silica reaction (ASR) on concrete structures.

Building on this initial effort, a 2014 Interagency Agreement between the NRC and NIST (NRC-NIST Interagency Agreement, 2014) was established to develop a technical basis and regulatory guidance for NRC staff to evaluate ASR-affected concrete structures [and to] assess the structural performance of ASR-affected concrete structures for design basis static and dynamic loading and load combinations through its service life, including the period of extended operation for the 20-year license renewal period. The $5.6 million con-tract was principally motivated by the discovery of ASR at Seabrook around 2010 and led to the publication of several detailed technical reports:

1. Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 3: Assessing Cyclic Performance of ASR-Affected Concrete Shear Walls Weigand, Sadek, Thonstad, et al., 2021

2. Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 1: Assessing In-Situ Mechanical Properties of ASR-Affected Concrete Sadek, Thonstad, Marcu, et al., 2021

3. Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 2: Assessing Bond and Anchorage of Reinforcing Bars in ASR-Affected Concrete Thonstad, Weigand, Sadek, et al., 2021

4. Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 3: Assessing Cyclic Performance of ASR-Affected Concrete Shear Walls Weigand, Sadek, Thonstad, et al., 2021

5. Material Research Support for the Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction Feldman, Eason, Bajcsy, and Snyder, 2022 A significant component of the NIST study was the conduct of shear capacity testing in shear walls containing ASR. In contrast, the LSTP tests were conducted on concrete beams containing ASR.

As discussed in more detail below, the results of the NIST study, issued in 2021, demon-strated that ASR weakens shear walls. This is a significant finding for Seabrook Station, given that the LSTP tests used to assess ASR at Seabrook showed that concrete beams were strengthened by ASR. The test data from the NIST Study were also inconsistent with the LSTPs application of ACI 318-71 to calculate capacity, thereby demonstrating that the equation is not suitable for ASR in shear walls.

Notice to Readers This report has been prepared solely using data and information that are publicly available at the time of writing. No proprietary, confidential, or otherwise restricted sources have been accessed or utilized in the preparation of this document.

Furthermore, any figures or illustrations presented herein that do not include explicit units of measurement are not derived from actual empirical data.

Such figures are in-tended exclusively for qualitative representation and conceptual illustration and shall not be construed as suitable for quantitative interpretation or application.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

1 NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 1

1 NIST Findings Challenge the LSTP Test Configuration NIST conducted a series of carefully controlled tests under an Interagency Agreement (NRC-NIST Interagency Agreement, 2014).

Representativeness of Structural Testing In structural safety evaluations, the prototype refers to the actual structure of concernsuch as the Containment Enclosure Building (CEB)while the model de-notes the test specimen used to simulate its behavior. For ASR-affected concrete, reproducing only the concrete mix in the test specimen is scientifically inadequate.

To generate meaningful (and regulatory-relevant) data, the test must be explicitly designed to replicate the same failure mechanism that governs the structural be-havior of the prototype. Absent this, the test results cannot be extrapolated with confidence, and any safety conclusions drawn from them risk being fundamentally flawed.

Membrane Behavior in thin walled structures Membrane action refers to the internal force distribution in thin-walled structures where loads are resisted primarily through in-plane stresses (axial, hoop, and shear) without sig-nificant bending or transverse shear. It is characteristic of shells and plates subjected to smooth, distributed loading, Fig. 1.

In-Plane Out of Plane Crack Figure 1: In-plane and out-of-plane shear This assumption of membrane action is discussed in (Timoshenko, Woinowsky-Krieger, et al., 1959, Sec. 91) (and expanded in §B.1.

More specifically ASME III (2015) specifies procedures for calculating membrane stress resultants in cylindrical shell structures subjected to internal pressure and other loads (see Articles CC-3200 and CC-3300).

While membrane forces dominate the global behavior, the Code requires supplemen-tary evaluation of bending moments and out-of-plane shear stresses at regions of struc-tural discontinuityincluding penetrations, changes in thickness, supports, and attach-mentswhere flexural behavior may become significant.

Thus, the ASME Code reflects the well-established engineering principle that membrane forces govern the overall load-carrying response of cylindrical containment structures, while Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

1 NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 2

localized bending effects must be explicitly assessed where discontinuities introduce non-membrane actions.

In other words, the tests by NextEra are only applicable in discontinuity locations.

Characteristics of Beam and Squat Shear Wall Tests Let us look closely at the fundamental differences of the two models.

Beam tests Squat shear wall tests 1

Out-of-plane shear In-plane shear 2

Shear/flexure failure mode Shear failure mode 3

Not representative of failure mode in CEB Representative of failure mode in CEB 4

Chemical prestressing enhances the shear strength Chemical prestressing does not significantly impact the shear strength 5

Flexure dominates Shear dominates 6

Chemical prestressing (§C.2) will always in-crease shear strength Insensitive to chemical prestressing 6

Shear strength predictably higher with ASR Shear strength unlikely to be higher 8

Does not account for biaxial state of stress Accounts for biaxial state of stress 9

Used only by NextEra Used by all other researchers investigating CEB behavior 10 Applicable for localized concentrated lads Applicable to entire CEB 11 NextEra found increased in shear strength NIST found lower shear strength NextEras Argument and C-10 counterargument for beam test LSTP argument in (NRC-ML19261A762, 2019)

...the LSTP did not test for the in-plane shear mode. This was because the out-of-plane shear failure mode was judged to be more critical than in-plane shear mode (note: nominal permissible out-of-plane shear stress in concrete per the ACI 318-71 code is 2 p

fc versus allowable total shear stress of 10 p

fc for in-plane shear.)

C-10 Counterargument This justification confuses code-prescribed permissible stress levels with the actual stress states induced by seismic loading. As discussed earlier (see page 1), seismic loads acting on cylindrical containment structures such as the CEB generate predominantly in-plane membrane stresses, with negligible out-of-plane shear.

Confusing Code Imposed Stress Limits with Structural Response Argument Interestingly the LSTP makes the distinction between in-plane and out of plane.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

1 NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 3

...the LSTP did not test for the in-plane shear mode. This was because the out-of-plane shear failure mode was judged to be more critical than in-plane shear mode (note: nominal permissible out-of-plane shear stress in concrete per the ACI 318-71 code is 2 p

f c versus allowable total shear stress of 10 p

f c for in-plane shear.)

NRC-ML19261A762 (2019)

The LSTP justified the omission of in-plane shear testing by citing the lower allowable out-of-plane shear stress specified in ACI 318-71 (2 p

fc versus 10 p

fc for in-plane shear).

Why it is erroneous This justification confuses code-prescribed permissible stress levels with the actual stress states induced by seismic loading. As discussed earlier (see page 1), seismic loads acting on cylindrical containment structures such as the CEB gen-erate predominantly in-plane membrane stresses, with negligible out-of-plane shear.

Thus, focusing on out-of-plane shear, regardless of its lower code limit, fundamentally misrepresents the critical response mechanisms governing the CEBs seismic behavior.

Why The question of why Texas selected the beam configuration has not been explained.

1. I conjecture that a few years earlier, Deschenes, Bayrak, and Folliard (2009) conducted tests for the Texas Department of Transportation using the setup shown in Fig. 2.

Hence, by the time the LSTP started, those tests were completed. Remarkably, the dimensions of these girders are identical to those later selected for NextEra.

For Texas DOT first For Nextera next 332" Figure 2: Identical test geometries used by Texas for TxDOT (Deschenes, Bayrak, and Folliard, 2009) and for NRC-sponsored testing (Bayrak, 2012). Both specimens are 332 inches long.

2. It is further speculated that NextEra was fully aware, based on well-established find-ings (Ahmed, Burley, and Rigden, 1998), that ASR increases the shear strength of reinforced concrete beams (§C.2). Nevertheless, it acted as if this outcome had not yet been determined. If they had conveniently selecting a beam configurationrather Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

1 NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 4

than a more representative squat shear wall test, then tests would have been struc-tured in a way that would predictably confirm an increase in shear strength.

It is noteworthy that among all researchers investigating ASR, only LSTP employed a beam specimen, rather than adopting a geometry that more directly captures shear degra-dation and failure mechanism of cylindrical containers.

It is therefore strongly suspected that the test configuration was selected not based on its relevance to containment structures, but rather out of mere convenience replicating a setup with which the laboratory was already familiar.

Illustrative examples of Other shear tests Researchers investigating the response of a CEB have all used a test which captures the in-plane shear failure mechanism, either through squat shear walls (Fig. 3(b), 3(c), 3(d))

or shear blocks (Fig. 3(a)), or in plane tests (Fig. 3(e)).

Interestingly, the NRC had funded a research study on shear in CEB. Indeed shear panels were also used, (White, Perdikaris, and Gergely, 1980), Fig. 3(e).

21" 10" 4"

MTSHead MTSHead 30" (a) Colorado 23rd Conference on Structural Mechanics in Reactor Technology Manchester, United Kingdom - August 10-14, 2015 Division I Seven LVDTs were used to measure the horizontal displacement along the height of the specimen from bottom beam to the top beam on both sides of the specimen. The Force - Displacement plot was obtained using the summation of the forces from both actuators against displacement of top of the shear wall (bottom of the top beam) with respect to the top of the lower beam.

Figure 3: Schematic drawing showing the test setup for shear walls Figure 4: Test setup of a shear wall showing the top frame and loading beam The specimens were loaded using the two actuators working simultaneously. The rate of loading began with 0.005 mm/sec and was increased to a maximum of 0.15 mm/sec as cycles progressed. The first two cycles applied 0.2 mm lateral displacement in the plane of the wall in each direction and the subsequent cycles were at maximum displacements of 0.4, 0.6, 0.8, 1, 1.4, 1.8, 2, 2.5, 3, 4, 4.5, 5.5, 6, and 7 mm. For each displacement two complete cycles were applied. For the Regular shear wall, after completing 2 cycles at 7 mm, the load was increased monotonically until the wall could not maintain the axial load of 800 kN which happened at a displacement of 8.2 mm. In the case of the ASR wall, the specimen was pushed in one direction by 7 mm in the first cycle and then in the opposite direction. During this part of the cycle, the axial load started to drop as the lateral displacement increased and needed constant increase in load. At 7 mm displacement, it was decided to continue load monotonically and at 7.1 mm, the wall failed to maintain the axial load. The test was terminated at that point.

RESULTS AND OBSERVATIONS (b) Toronto Experimental Program 30 2.5 TEST SETUP AND LOADING PROTOCOL This section describes the experimental setup for testing of ASR-affected concrete shear walls. The setup was designed to allow for application of 200 kip (890 kN) of constant vertical loading and lateral reversed cyclic loading based on a prescribed protocol to the shear wall specimens up to failure, while preventing out-of-plane displacements and maintaining safe operation throughout testing. The experimental setup included the NIST PERFORM Laboratorys structural reaction (strong) floor, hydraulic actuators, a primary reaction frame made up of a foundation frame and loading beam, a lateral bracing frame (LBF), and a Concrete Structural Reaction Block (CSRB) Wall (Figure 2.17). The strong floor consists of a 6.0 ft (1.83 m) thick heavily reinforced concrete slab. Both the foundation frame and the CSRB block wall were anchored to the strong floor using 1-1/2 in (38.1 mm) diameter UNF high-strength threaded rods connected into the sockets embedded in the strong floor. Each high-strength threaded rod was post-tensioned to its working capacity, or a load of approximately 100 kip (445 kN).

Figure 2.17. Experimental setup for testing ASR-affected concrete shear wall specimens (1.000 kip = 4.448 kN)

The foundation frame (see Figure 2.17) was erected as an assembly of structural steel reaction frame components. Two parallel W27x235 foundation beams, which were anchored to the strong floor near their ends where vertically-spanning actuators framed into them, provided a platform to mount the footing of the shear wall specimen. Six outriggers extended perpendicularly as cantilevers from the foundation beams to provide both stability to the overall foundation frame and additional tie-down (c) NIST S. Sawada, Y. Takaine, T. Okayasu, A. Nimura, R. Shimamoto / Journal of Advanced Concrete Technology Vol. 19, 477-500, 2021 482 In addition, cylindrical specimens of ASR concrete with 100 mm diameter and 200 mm height that were prepared at the same time as web concrete casting were exposed wrapped in wet cloth under the same condition as the web wall (outside ambient temperature). Com-pressive strength, static elastic modulus and tensile strength were periodically obtained according to JIS A1107, JIS A1149 and JIS A113, respectively. Poisson's ratio was also obtained as the ratio of the transverse strain to the longitudinal strain at 1/3 of the maximum strength in the stress-strain curve. Strains for the static modulus and Poisson's ratio were measured using strain gauges (PL-60 and PL-90, Tokyo Measuring Instruments Laboratory Co., Ltd.). Surface length change was meas-ured as change in 100 mm gauge length of contact points on rings wrapped around the surface of cylindrical specimen. Elastic wave velocity was also measured in the similar manner to the web wall.

2.4 Lateral loading tests After one-year exposure, the No. 1 and No. 2 specimens were subjected to lateral loading tests. The lower slab of the specimen was tightly fixed to the reaction floor using 20 PC steel rods. The lateral force was cyclically applied to the upper slab of specimen by four 1000 kN hydraulic jacks while applying a constant vertical force. The ver-tical force was applied through the steel frame by pulling the four PC steel rods using 500 kN center hole type hydraulic jacks in order to apply constant stress of 2 MPa evenly over the entire cross-sectional area of the web wall. The set-up of the loading apparatus is shown in Fig.

6. The loading history was controlled by the shear de-formation angle (see Appendix for calculation method) of the web wall according to Fig. 7.

During the lateral loading tests, applied force, hori-zontal and vertical displacement, and rebar strain were measured. The surface cracks were also recorded at the peak and at the time of unloading of each loading cycle.

The arrangements of strain gauges and contact type dis-placement meters are shown in Figs. 5 and 8, respec-tively.

3. Experimental results 3.1 Monitoring The property changes of cylindrical specimens using same ASR concrete of the No. 3 and No. 4 specimens are shown in Figs. 9 to 12. As shown in Fig. 9, expansion reached approx. 2780x10-6 until 18 months of exposure.

The compressive strength of the cylindrical specimens 250 1500 250 1000 500 2800 1000kN Jacksx2 500kN Jacksx4 3000kN Reacktion jacksx2 1000kN Jacksx2 500kN Load cellx4 spherical bearingx4 1250 650 325 PL PL 3000kN Reaction jacksx2 4000 Reaction bed Upper slab Lower slab Reaction wall Fig. 6 Set-up of loading apparatus.

(d) Kajima R.N. White et al. /Strength and stiffness oj'reinJbrced concrete contain,nent HQUAKE N v l

CRACKED ELEMENT element v

i Nh --II------

Nv Nh ear containment vessel under combined internal n and seismic forces.

ental program men description cimen shown in fig. 2 is a 48-inch square inches thick, with ttfickened corner regions tion of the shearing forces. The slab is rein-h one layer of no. 6 reinforcing bars in one nd two layers of no. 6 bars in the other All reinforcement is Grade 60 and is cen-thickness of the specimen. Sections e central uniform thickness portion of en have a shearing area of 288 in 2.

mental setup and measurements Ty 4--

~ "'-~..

-k,

~

÷6" SPACING

-?-+ 7 ' L~--TWO #6 "r 6" °P^'ING THICKENED

,an" lY

~

"~ """

CORNER REGIONS ~

-~

6" i

o DETAILS OF BIAXIAL SPECIMEN TENSILE CORNER

~\LOAD COMPRESSIVE CORNER LOAD

~f. COMPRESSIVE CORNER LOAD

.DIAGONAL D2

~

)

DIAGONAL DI TENSILE CORNER LOAD

b. LOADING METHOD C SHEAR STRESSES ALONG X = O Fig. 2. Specimen geometry and loading.

in the reinforcing bars was applied by ams acting against steel pipe reaction t around the specimen in both orthogonal Extensive measurements were made in the central 2-ft square region of the specimen. Dial gages and dis-86 R.N. White et al. /Strength and stiffness oj'reinJbrced concrete contain,nent VESSEL

//

(

1 EARTHQUAKE N v l

CRACKED ELEMENT element v

i Nh --II------

Nv Nh Fig. 1. Nuclear containment vessel under combined internal pressurization and seismic forces.

2. Experimental program 2.1. Specimen description The specimen shown in fig. 2 is a 48-inch square flat slab, 6 inches thick, with ttfickened corner regions for application of the shearing forces. The slab is rein-forced with one layer of no. 6 reinforcing bars in one direction and two layers of no. 6 bars in the other direction. All reinforcement is Grade 60 and is cen-tered in the thickness of the specimen. Sections through the central uniform thickness portion of the specimen have a shearing area of 288 in 2.

2.2. Experimental setup and measurements Ty 4--

~ "'-~..

-k,

~

÷6" SPACING

-?-+ 7 ' L~--TWO #6 "r 6" °P^'ING THICKENED

,an" lY

~

"~ """

CORNER REGIONS ~

-~

6" i

o DETAILS OF BIAXIAL SPECIMEN TENSILE CORNER

~\LOAD COMPRESSIVE CORNER LOAD

~f. COMPRESSIVE CORNER LOAD

.DIAGONAL D2

~

)

DIAGONAL DI TENSILE CORNER LOAD

b. LOADING METHOD C SHEAR STRESSES ALONG X = O Fig. 2. Specimen geometry and loading.

Tension in the reinforcing bars was applied by hydraulic rams acting against steel pipe reaction frames built around the specimen in both orthogonal directions (fig. 3). The frames are independent of each other and of the shear loading equipment, and float freely with the slab as it undergoes distortions.

The sets of rams in each direction are connected to a common hydraulic pressure pump to ensure equal loads on each of the two sets of orthogonal steel.

Shear loads were applied by alternately pulling and pushing on the thickened corners of the speci-men. The corner forces were generated by large hydraulic rams fastened to a massive prestressed con-crete test frame (fig. 3). Some secondary reinforcing steel (no. 4 bars) was placed in the corner regions to Extensive measurements were made in the central 2-ft square region of the specimen. Dial gages and dis-placement transducers measured deformations. Other quantities measured included local values of crack width changes and crack slip along orthogonal cracks in both directions, and extensional stiffness of the specimen in both directions. Reinforcing bar strains were measured at locations outside the specimen, using wire electrical resistance strain gates.

The key deformation pattern the shear distortion of the central part of the specimen - was calculated by taking the average of the tensile and compressive diagonal deformations. An effective shear modulus was then calculated from this average shearing distor-(e) In-Plane shear tests funded by the NRC in the Early 80s, (White, Perdikaris, and Gergely, 1980); Cornell/MIT program Figure 3: Various test setups used for concrete in-plane shear tests Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

1 NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 5

Figure 4: Configuration of (Proestos, Bentz, and Collins, 2019)

Finally, Proestos, Bentz, and Collins (2019) conducted an in-plane and out of plane test in containment walls. He used a configuration shown in Fig. 4.

Note that all of these tests accounted for the uniaxial or biaxial confinement present in structural panels subjected to in-plane shear loading.

Conclusion Wrong test

1. NextEra explicitly acknowledges that it did not test for in-plane, rather opted for out-of-plane, configuration, thereby selecting beams instead of squat shear walls (used by all other researchers), §C.3.

2. NextEra confused code-imposed allowable stress limits with the actual stress states that govern the structural response under given loading conditions.

3. NextEras test is not aligned with (ASME III, 2015).

4. NextEra failed to recognize that in this case, one must use membrane theory

5. Biaxial confinement not present in LSTP.

6. Rather than selecting a test configuration specifically tailored to con-tainment structures, it is reasonable to conjecture that Texas LSTP investigation simply recycled the geometry of previously tested beams, prioritizing convenience over representativeness.

The supporting material is provided in Appendix B Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

2 RELEVANCE OF NIST TESTS ON SHEAR STRENGTH 6

2 Relevance of NIST tests on shear strength When confronted with two sets of experimental results that yield conflicting conclu-sions, the validity of each must be assessed not solely on the basis of outcome but on the fidelity of the test setup in replicating the failure mechanism of the proto-type. The results derived from the test configuration that most accurately captures the governing structural behavior of the prototype should be given precedence. This principle is especially critical in safety assessments, where the representativeness of the test model directly impacts the reliability of the conclusions drawn. Disregarding this criterion risks favoring results that may be experimentally sound yet structurally irrelevant.

As mentioned above, other researchers have investigated the impact of ASR on shear strength. Some of them are described in Appendix C, and results tabulated in Table 2.

However of paramount importance for Seabrook are the contrasting results of the LSTP and NIST, shown in Table 1.

Table 1: Comparison of LSTP and NIST tests Texas MPR-ML18141A785 (2016)

NIST

1. There is no reduction of shear capacity in ASR-affected con-crete with through-thickness expansion levels up to XXX%

or volumetric expansion levels XX.

2. The XXX ASR-affected test were all capable of reaching their calculated shear strength per ACI 318-71.

1. The presence of ASR caused a 26 % reduction in the mean normalized yield moment capacity (My/Mn).

2. ASR brought the normalized yield moment capacity ratios My/Mn to less than 1.0(i.e. unsafe).

3. The yield moment capacity My being less than Mn means that ACI 318 capacity calculation procedure is unconservative and not applicable for walls affected by ASR.

Conclusion Wrong test

1. Contrary to NextEras findings, all other tests, Table 2 (with excep-tion to the Toronto tests) conducted by various researchers have con-sistently shown a decrease, not an increase, in shear strength.

2. This outcome was essentially a forgone conclusion, as it was already well established that ASR increases the shear strength of reinforced concrete (Ahmed, Burley, and Rigden, 1998).

3. In simple terms, the results of the beam test lack credibility because the test itself was fundamentally flawed.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

3 RELEVANCE OF NIST TESTS ON PAST EXPANSION 7

The supporting material is provided in Appendix C 3

Relevance of NIST tests on past expansion An empirical equation is only valid to the extent that it reliably represents the under-lying experimental data. When the observed data points exhibit significant scatter or systematically deviate from the proposed equation, the validity of that equation is fundamentally compromised. In such cases, relying on the equation for predictive or design purposes is unjustified, as it may lead to erroneous conclusions. Any use of empirical relationships must therefore be accompanied by a clear assessment of their uncertainty and applicability range, particularly when the stakes involve structural safety or regulatory compliance.

Reliable determination of past expansion is critical to assessing structural safety. The methodology used to estimate this expansion is discussed in detail in Appendix D.

This procedure is well established and codified in ASTM C469 (2016). A concise sum-mary is presented below:

1. Measure the Current Elastic Modulus Ecurrent using ASTM C469:

2. Estimate the Original Elastic Modulus from compressive strength at 28 days (in psi) using ACI 318:

E28-day = 57,000 p

fc (1)

3. Compute the Normalized Modulus:

En = Epresent E28-day (2)

4. Estimate ASR Expansion from a pre-established empirical calibration curve:

ASR = f(En) where E28days is the elastic modulus determined 28 days after casting, Epresent is the elastic modulus determined presently, f c is the concrete compressive strength, En is the normalized elastic modulus, ASR the total volumetric expansion since casting, and f(*) a function determined through curve fitting of discrete experimental points.

Whereas Eq. 1 is indeed included in the ACI code, it is always presented as an empirical approximation rather than a universally valid relationship.

The NIST report clearly demonstrated the limitations of this equation, showing that it does not hold for ASR-affected concrete, as illustrated in Fig. 5.

Interestingly, the only other extensive investigation relating E to fc was conducted by Dolen (2005), specifically for ASR-affected concrete, as shown in Fig. 5(b) (blue markers represent ASR specimens).

Once again, the level of uncertainty is comparable to that observed in the NIST results, reinforcing the conclusion that the relationship between com-pressive strength and elastic modulus cannot be reliably captured by a single equation (Eq.

1).

This is particularly relevant when applied to a task as critical as determining past Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

3 RELEVANCE OF NIST TESTS ON PAST EXPANSION 8

1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 50 60 70 80 Modulus of Elasticity (ksi)

Sqrt of Compressive Strength (psi^0.5)

Walls 1&2 up to 90 d Walls 1&2 after 90 d Wall 3 up to 90 d Wall 3 after 90 d Wall 4 up to 90 d Wall 4 after 90 d ACI 318-14 +20%

ACI 318-14 Section 19.2.2.1 ACI 318-14 -20%

Used by NextEra (no error bars)

(a) NIST, (Weigand, Sadek, Thonstad, et al.,

2021)

(b) Reclamation, (Dolen, 2005)

Figure 5: Experimental evidence of the variability of E(f c) for Concrete with ASR; NIST and Bureau of Reclamation expansion at Seabrook, the uncertainties should be explicitly accounted forsuch as by including margins of error (Fig. 7).

Since the compressive strength data used for comparison correspond to specimens tested at 28 days (i.e., less than 90 days), we concludebased on these findingsthat the elastic modulus E is systematically overestimated by Eq. 1.

Relevance NIST found that ENIST 28 is larger than ENextEra 28 This directly implies that the normalized modulus valuesdefined by Eq. 2, where E28 appears in the denominatorare also larger for NextEra:

ENextEra n

> ENIST n

Based on the calibration curve (developed under the LSTP) that relates normalized elastic modulus to ASR expansion, this discrepancy leads to an underestimation of the actual expansion.

Does not account for Uncertainties The procedure to determine past expansion critically hinges on two key components:

1. The estimation of the elastic modulus based on compressive strength.

2. The calibration curve that relates the drop in normalized elastic modulus to ASR-induced expansion.

Both of these components are subject to significant uncertainty1, which must be explicitly acknowledged and incorporated into the evaluation.

The magnitude and implications of these uncertainties are illustrated in Fig. 7.

1During the administrative hearing (NRC-ML19312B609, 2019, pg 522) C-10 asked the judges to include Uncertainty bands. This was refused.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

3 RELEVANCE OF NIST TESTS ON PAST EXPANSION 9

80 60 AAR Expansion 1.0 NextEra NIST Example:

E28 NextEra = 60; E28 NIST =80; Epresent =20 En NextEra =20/ 60= 0.33; En NIST = 20/80 = 0.25 With time accompanying AAR expansion we have a decrease in the present elastic modulus Epresent; En=Epresent/E28 Knowing En we can estimate expansion En=1, no expansion, as En expansion Expansion is underestimated!

Before 90 days (per NIST)

Based on ACI Eq (E=57fc) 80 En NIST =0.25 En NextEra =0.33 0

0 Figure 6: Why is the current monitoring procedure unconservative and dangerous according to the NIST report Throughthicknessexpansion 0.0%

0 1.

NormalizedElasticModulus MarginofError Qualitativecurve; MarginofError Figure 7: Impact of uncertainties associated with the determination of past expansion Conclusion Wrong test

1. NIST tests have demonstrated the inapplicability of the ACI Code equation relating compressive strength to elastic modulus, as the as-sociated variabilities and uncertainties are unacceptably large.

2. Hence the procedure employed by NextEra to estimate past expansion systematically underestimates the true extent of expansion.

3. As a result, the current structural monitoring program is fundamen-tally flawed and presents a significant safety risk, as it fails to account for the full magnitude of ASR-induced expansion.

The supporting material is provided in Appendix D Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

4

SUMMARY

OF CONCLUSIONS 10 4

Summary of Conclusions The principal conclusions drawn throughout this white paper are summarized below for ease of reference.

LSTP erroneous test configuration

1. NextEra explicitly acknowledges that it did not test for in-plane, rather opted for out-of-plane, configuration, thereby selecting beams instead of squat shear walls (used by all other researchers), §C.3.

2. NextEra confused code-imposed allowable stress limits with the actual stress states that govern the structural response under given loading conditions.

3. NextEras test is not aligned with (ASME III, 2015).

4. NextEra failed to recognize that in this case, one must use membrane theory

5. Biaxial confinement not present in LSTP.

6. Rather than selecting a test configuration specifically tailored to containment struc-tures, it is reasonable to conjecture that Texas LSTP investigation simply recycled the geometry of previously tested beams, prioritizing convenience over representativeness.

Relevance of NIST report on shear strength

1. Contrary to NextEras findings, all other tests, Table 2 (with exception to the Toronto tests) conducted by various researchers have consistently shown a decrease, not an increase, in shear strength.

2. This outcome was essentially a forgone conclusion, as it was already well established that ASR increases the shear strength of reinforced concrete (Ahmed, Burley, and Rigden, 1998).

3. In simple terms, the results of the beam test lack credibility because the test itself was fundamentally flawed.

Relevance of NIST tests on past expansion

1. NIST tests have demonstrated the inapplicability of the ACI Code equation relating compressive strength to elastic modulus, as the associated variabilities and uncertain-ties are unacceptably large.

2. Hence the procedure employed by NextEra to estimate past expansion systematically underestimates the true extent of expansion.

3. As a result, the current structural monitoring program is fundamentally flawed and presents a significant safety risk, as it fails to account for the full magnitude of ASR-induced expansion.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

REFERENCES 11 References ACI 318 (2019). Building code requirements for structural concrete (ACI 318-19) and com-mentary. American Concrete Institute.

Ahmed, T., E. Burley, and S. Rigden (1998). The state and fatigue strength of reinforced concrete beams affected by alkali-silica reaction. In: Materials Journal 95.4, pp. 376-388.

ASME III, B. (2015). BPVC Section III-Rules for Construction of Nuclear Facility Components-Division 2-Code for Concrete Containments. Tech. rep. American Society of Mechanical Engineering.

ASTM C469 (2016). 469, Standard test method for static modulus of elasticity and Pois-sons ratio of concrete in compression. In: Annual book of ASTM standards 04.02.

Bayrak, O. (2012). Structural Assessment of Seabrook Station; Findings and Structural Test-ing Plan. Tech. rep. Online; accessed 2018-07-11. University of Texas, Austin.

Deschenes, D., O. Bayrak, and K. Folliard (2009). ASR/DEF-damaged bent caps: shear tests and field implications. Tech. rep. Austin, TX: Ferguson Structural Engineering Laboratory, The University of Texas.

Dolen, T. (2005). Materials Properties Model of Aging Concrete. Tech. rep. Report DSO-05-05. U.S. Department of the Interior, Bureau of Reclamation, Materials Engineering and Research Laboratory, 86-68180.

Feldman, S., R. Eason, P. Bajcsy, and K. Snyder (2022). Material Research Support for the Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction. Tech. rep. NISTIR 8415. National Institute of Standards.

Gulec, K. and A. Whittaker (2009). Performance-Based Assessment and Design of Squat Reinforced Concrete Shear Walls. Tech. rep. State University of New York at Buffalo.

Habibi, F., S. Sheikh, N. Orbovic, D. Panesar, and F. Vecchio (2015). Alkali Aggregate Reaction In Nuclear Concrete Structures: Part 3: Structural Shear Wall Elements.

In: Proceedings of the 23rd Conference on Structural Mechanics in Reactor Technology (SMiRT23).

Hariri-Ardebili, M. and V. Saouma (2018). Sensitivity and Uncertainty Analysis of AAR Affected Shear Walls. In: Engineering Structures 172, pp. 334-435.

Institution of Structural Engineers (1992). Structural effects of alkali-silica reaction. Tech-nical guidance on the appraisal of existing structures. Tech. rep. Report of an ISE task group.

MPR-ML16216A242 (2016). MPR-4273, Revision 0, Seabrook Station - Implications of Large-Scale Test Program Results on Reinforced Concrete Affected by Alkali-Silica Re-action. July 2016 (ML16216A242) ). Online; accessed 2018-10-15.

MPR-ML16279A050 (2017). Seabrook Station - Approach for Determining Through-Thickness Expansion from Alkali-Silica Reaction. Redacted Document.

MPR-ML18141A785 (2016). Seabrook Station - Approach for Determining Through-Thickness Expansion from Alkali-Silica Reaction. Redacted Document.

NRC-ML18226A205 (2018). Non-Proprietary Draft Safety Evaluation Nextera Energy Seabrook, LLC Seabrook Station, Unit No. 1;Docket No. 50-443; (ML18226A205, 2018.

NRC-ML19261A762 (2019). NRC Staff Testimony of Angela Buford, Bryce Lehmanm and George Thomas.

NRC-ML19312B609 (2019). Official Transcript of Proceedings; NextEra Energy Seabrook, LLC Seabrook Station, Unit 1; Docket Number: 50-443-LA-2;ASLBP Number:17-953-02-LA-BD01. Newburyport, Massachusetts.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

REFERENCES 12 NRC-NIST Interagency Agreement (2014). Structural Performance of Nuclear Power Plant (NPP) Concrete Structures Affected by Alkali-Silica Reaction (ASR). Tech. rep. Intera-gency Agreement No. NRC-HQ-60-14-I-0004.

Proestos, G. T., E. C. Bentz, and M. P. Collins (2019). Reinforced Concrete Containment Walls Subjected to Combined In-Plane and Out-of-Plane Shear Stresses: Experimental Investigation and Sectional Analysis. In: Transactions, SMiRT-25 Charlotte, Division V, North Carolina, USA, pp. 4-9.

Sadek, F., T. Thonstad, S. Marcu, J. Weigand, T. Barrett, H. Lew, L. Phan, and A. Pintar (2021). Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 1: Assessing In-Situ Mechanical Properties of ASR-Affected Concrete. Tech. rep. NIST TN 2121. National Institute of Standards.

Saouma, V. (2025). The Four Books of Structural Analysis. Manuscript in Preparation,

p. 1250.

Saouma, V. (2017). Effect of AAR on Shear Strength Panels. Tech. rep. Final Report to NRC, Grant No. NRC-HQ-60-14-G-0010, Task 1-C. University of Colorado, Boulder.

Saouma, V. E. and M. A. Hariri-Ardebili (2021). Case Study: Seabrook Station Unit 1 ASR Problem. In: Aging, Shaking, and Cracking of Infrastructures: From Mechanics to Concrete Dams and Nuclear Structures. Springer International Publishing, pp. 969-1030. isbn: 978-3-030-57434-5. doi: 10.1007/978-3-030-57434-5_36.

Saouma, V.E. (2013). Numerical Modeling of Alkali Aggregate Reaction. 320 pages. CRC Press.

Sawada, S., Y. Takaine, T. Okayasu, A. Nimura, and R. Shimamoto (2021). Structural performance evaluation and monitoring of reinforced concrete shear walls affected by alkali-silica reactions. In: Journal of Advanced Concrete Technology 19.5, pp. 477-500.

Snyder, K. and H. Lew (2013). Alkali-Silica Reaction Degradation of Nuclear Power Plant Concrete Structures: A Scoping Study. In: NIST Interagency/Internal Report (NISTIR)-

7937.

Thomas, M., B. Fournier, and K. Folliard (2013). Alkali-aggregate reactivity (AAR) facts book. Tech. rep. United States. Federal Highway Administration. Office of Pavement Technology.

Thonstad, T., J. Weigand, F. Sadek, S. Marcu, T. Barrett, H. Lew, L. Phan, and A. Pintar (2021). Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR); Task 2: Assessing Bond and Anchorage of Reinforc-ing Bars in ASR-Affected Concrete. Tech. rep. NIST TN 2127. National Institute of Standards.

Timoshenko, S., S. Woinowsky-Krieger, et al. (1959). Theory of plates and shells. Vol. 2.

McGraw-hill New York.

Wald, D., G. Martinez, and O. Bayrak (2017). Expansion behavior of a biaxially reinforced concrete member affected by alkali-silica reaction. In: Structural Concrete.

Weigand, J., F. Sadek, T. Thonstad, S. Marcu, R. Villegas, and L. Phan (2021). Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Re-action (ASR); Task 3: Assessing Cyclic Performance of ASR-Affected Concrete Shear Walls. Tech. rep. NIST TN 2180. National Institute of Standards.

White, R. N., P. C. Perdikaris, and P. Gergely (1980). Strength and stiffness of reinforced concrete containments subjected to seismic loading: research results and needs. In:

Nuclear Engineering and Design 59.1, pp. 85-98.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

A GLOSSARY 13 APPENDICES A

Glossary AAR/ASR: Alkali aggregate reaction2(or aggregate silica reaction).

ASLB: Atomic Safety Licensing Board.

BDAM: Building Deformation Aging Management (how NextEra monitors ASR expan-sion).

Compressive Strength f c is the maximum stress under compression that the concrete can sustain before failure.

Drift d: is the gradual irreversible movement or displacement over time due to external forces. In a seismic analysis, we want to structure to be resilient and accommodate as large of a drift before failure.

Ductility: is the ability of the structure to undergo large deformation (drift) before failure.

Ductility enables energy absorption during seismic excitation, which is beneficial.

Free body diagram (FBD) is a simplified graphical representation of a body isolated from its surroundings, showing all external forces and moments acting upon it. It is a fundamental tool used to analyze equilibrium and internal force distributions in structures.

Elastic Modulus: slope of the stress strain curve for concrete. Analogous to spring stiffness of the specimen.

FSEL: Ferguson Structural Engineering Laboratory in Texas (where tests were performed).

Flexural Resistance: the maximum moment that can be resisted before failure.

Hysteretic Energy: is the energy absorbed during one cycle of push and pull. The larger the value, the more energy is absorbed during a seismic excitation.

LAR: License Amendment Request.

LSTP: Large Scale Testing Program. This encompasses all tests performed at the Univer-sity of Texas through NextEras funding.

Moment M: is the result of a force applied with an eccentricity thus inducing rotation about an axis.

Nominal Moment Mn: is the moment computed by the ACI-318 design code correspond-ing to operating load. It should always be smaller than the yield moment (as we do not want the structure to yield under normal service load).

2Alkali-Silica Reaction (ASR) is often used interchangeably with Alkali-Aggregate Reaction (AAR), al-though strictly speaking, AAR includes reactions with both silica and other reactive aggregate types. In most contexts, including this document, ASR and AAR are treated as equivalent.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

B NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 14 Normalized Elastic Modulus, En is the present value of the elastic modulus divided by the one at time of construction (estimated from the compressive strength) typically at 28 days.

Shear wall test: involves pushing/pulling a wall from a top beam connecting to it. This causes positive (push) or negative moment (pull).

Stiffness: is the slope of the force displacement (or moment drift diagram).

Yield Moment My: is the moment at which we start having plastic or irreversible defor-mation. It should always be larger than the nominal moment.

Onset Yielding Elastic Range Inelastic Range Drift Drift at onset yielding Drift Positive Moment Negative Moment Peak Resistance (Peak Moment Capacity)

Peak Negative Moment Resistance (Capacity)

Moment M Yield Moment My Peak Positive Moment Resistance (Capacity)

We want to maximize energy dissipation We want to maximize drift Mn is the nominal moment based on the ACI-318 code My/Mn should not be less than 1.

Figure 8: Graphical Illustration of Key Terms B

NIST Findings Challenge the LSTP Test Configuration B.1 Proof of validity of membrane action To prove that membrane theory holds, we follow the classical derivations established by Timoshenko, Woinowsky-Krieger, et al. (1959, Art. 112, p. 457).

Assumptions of Membrane Theory Membrane theory of shells relies on the following assumptions:

The shell is thin, meaning that its thickness is much smaller than its other dimensions.

Stresses normal to the middle surface (transverse shear stresses and normal stresses) are absent (except at discontinuities).

Deformations involve stretching of the middle surface without significant bending.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

B NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 15 k

k d

h dx L

r CL CL y

x z

k r

(a) Shell x

y z

dx rd p

px pz x

x

' +

dx N

N x

N

' x N

x' N

x x

N N

d

+

x x

N' N'

+

dx x

N' N'

d

+

(b) Membrane forces Figure 9: Free body diagram of an infinitesimal circular shell element, membrane theory (Saouma, 2025)

External loads are sufficiently smooth and distributed so that bending effects are secondary.

For the CEB:

The structure is a thin-walled, axisymmetric cylinder.

The primary loads of interest are lateral inertial forces induced by seismic events.

No significant concentrated loads or local effects are present that would induce large bending or transverse shear.

Membrane Equilibrium Equations To further reinforce the notion that membrane theory should be adopted, we consider an infinitesimal element of the shell bounded by x (longitudinal) and (circumferential) coordinates. Following Timoshenko, Woinowsky-Krieger, et al. (1959, Art. 112, p. 457), summing forces in each direction yields:

Force Equilibrium in the Longitudinal (x) Direction N

x x + 1 r

N x

= 0 (3) where:

N x is the membrane force per unit length in the x-direction (longitudinal force),

N x is the membrane shear force per unit length acting between x and directions, r is the radius of the cylinder.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

B NIST FINDINGS CHALLENGE THE LSTP TEST CONFIGURATION 16 Force Equilibrium in the Circumferential: () Direction N

x x

+ 1 r

N

+ N r

r = p (4) where:

N is the circumferential membrane force per unit length (hoop force),

N r is the radial membrane force per unit length, p is the lateral pressure (equivalent seismic load).

Force Equilibrium in the Radial Direction:

N r

r + 1 r(N r + N) = 0 (5)

However, for thin shells subjected to lateral loading, N r is usually small compared to N x

and N

, and thus often neglected in first-order membrane analysis. In the derivation of the membrane equilibrium equations (Timoshenko, Woinowsky-Krieger, et al., 1959, Art. 112),

no body force term appears in the x-direction equilibrium because:

Gravity acts vertically (radially inward), not horizontally.

Seismic loading is modeled through an equivalent lateral force (p), not as a body force in x.

Therefore, there are no distributed body forces acting in the x-direction to be included in the membrane equilibrium equations.

In summary, based on the classical derivations provided by Timoshenko, Woinowsky-Krieger, et al. (1959, Art. 112, p. 457), and the physical characteristics of the CEB, it is fully appropriate and technically correct to use membrane theory to model the seismic response of the containment enclosure building. The dominant stress resultants are the in-plane membrane forces (Nx, N, and Nx), and out-of-plane bending and shear effects are negligible for the distributed seismic loads considered.

B.2 Use squat shear walls This leads to the key question: which shear mode is more critical for the CEB? Given the substantial longitudinal and hoop reinforcement, the CEB is well-equipped to handle flexure and its associated shear demands. However, the absence of adequate shear-specific reinforcement raises serious concerns. In-plane shear, therefore, is the more critical failure modeunderscored by early NRC-funded studies that exclusively addressed it.

Even among in-plane tests, important distinctions must be made. Conventional shear walls, due to horizontal load eccentricities, tend to develop significant flexural effects. To minimize these influences and better isolate pure shear behavior, panels with small height-to-length ratios, commonly referred to as squat shear walls, are used (§C.3). In such con-figurations, flexural effects are minimized, making them more suitable for studying shear-dominated response.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

C II RELEVANCE OF NIST TESTS ON SHEAR STRENGTH; FURTHER DETAILS17 C

II Relevance of NIST tests on shear strength; Further details Searching the literature we found the following (in-plane) shear tests, Table 2 for context.

Some observations:

Texas Not only was the LSTP (Large Scale Test Program) conducted by the University of Texas, Fig. 10, upon which the NRC (Nuclear Regulatory Commission) heavily relied for issuing the license to operate Seabrook, the least relevant, but it was also flawed due to the presence of a large unintended pre-test crack. This factor should cast many doubts on the reliability of its results. The report concludes that shear Figure 10: Texas shear tests (Wald, Martinez, and Bayrak, 2017), (note splitting crack, explained in C.2) strength increasedwithout disclosing the quantitative data supporting this claim.

--Non-Proprietary Version--

basis of affected struct:ui-es at Seabrook Station and provides guidance for evaluations of those structm*es_

6.2.1 Anchors and Embedments Results from the Anchor Test Program indicate that there is no reduction of anchor capacity in ASR-affected concrete with in-plane expansion level of less than l mm!m. Tue cmTent maximum in-plane expansion observed at Seabrook Station is considerably less than this expansion level. Because the two-dimensional reinforcement mats at Seabrook Station should cause in-plane expansion to plateau at relatively low levels it is unlikely that ASR will cause expansion ofl rmn!m.

In-plane expansion due to ASR creates microcracks parallel to the axis of an anchor, which are most pronom1ced in the concrete cover. These microcracks that open perpendicular to the concrete surface have the potential to provide a preferential failure path within a potential breakout cone leading to degraded anchor perfonnance. Conversely, through-thickness expansion has the potential to create microcracks perpendicular to the axis of an anchor. These potential microcracks that open parallel to the concrete smface do not provide a preferential failure path to result in degraded anchor performance. Test results confumed that anchor pe1fo11113nce was insensitive to through-thickness expansion of up to aboul

%- Accordingly

.MPR recommends in-plane expansion (e.g. via CCI) as the monitored parameter for assessing anchor pe1formance.

6.2.2 Shear Performance Results from the Shear Test Program indicate that there is no reduction of shear capacity in ASR-affected concrete with through-thickness expansion levels ~%, which is the maximum expansion level exhibited by the test specimens. TuellllASR-affected test specimens (total o~

tests) were all capable of reaching their calculated shear strength per ACT 318-71. The test results indicated a repeatable trend that higher levels of ASR resulted in higher shear capacity due to ASR-induced prestress_ For conservatism MPR does not recommend taking credit for this prestressing as palt of structural evaluations.

While ASR-related expansion is a volmnetric effect, the Shear Test Program used through-thickness expansion as the monitored parameter representing ASR degradation because in-plane expansion plateaued at relatively low levels (approximately JI%).

6.2.3 Reinforcement Anchorage Results from the Reinforcement Anchorage Test Program indicate that there is no reduction in the performance of reinforcement lap splices in ASR-affected concrete with through-thickness expansion levels up to *

% which is the maximmn expansion level exhibited by the test specimens_ Tue eight.As'R-affected test specimens were all capable of reaching their calculated flexural strength per ACI 318-71, and the yield and bending moments were relatively insensitive to the level of ASR-induced expansion.

MPR-4273 Revision 0 6-4 Toronto Following the completion of the tests by Habibi, Sheikh, Orbovic, Panesar, and Vecchio (2015), shown in Fig. 11, a workshop was organized under the auspices of the Organisation for Economic Cooperation and Development (OECD), specifically through the Assessment of Structures subject to Concrete Pathologies (ASCET) initia-tive. One of the workshops key objectives was to launch a blind simulation benchmark aimed at predicting the behavior of structural elements affected by ASR.

The University of Colorado was among the participants.3 To the best of the authors knowledge, the University of Colorado was the only participant to subsequently pub-lish a peer-reviewed analysis of this benchmark exercise (Hariri-Ardebili and Saouma, 3Interestingly, the NRCrepresented by Jacob Philipwas a co-organizer, and NIST (through Fahim Sadek) was nominally present but did not submit an analysis.

Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

C II RELEVANCE OF NIST TESTS ON SHEAR STRENGTH; FURTHER DETAILS18 2018), thereby contributing to the academic rigor and technical transparency of the program.

23 Conference on Structural Mechanics in Reactor Technology Manchester, United Kingdom - August 10-14, 2015 Division I Seven LVDTs were used to measure the horizontal displacement along the height of the specimen from bottom beam to the top beam on both sides of the specimen. The Force - Displacement plot was obtained using the summation of the forces from both actuators against displacement of top of the shear wall (bottom of the top beam) with respect to the top of the lower beam.

Figure 3: Schematic drawing showing the test setup for shear walls Figure 4: Test setup of a shear wall showing the top frame and loading beam The specimens were loaded using the two actuators working simultaneously. The rate of loading began with 0.005 mm/sec and was increased to a maximum of 0.15 mm/sec as cycles progressed. The first two cycles applied 0.2 mm lateral displacement in the plane of the wall in each direction and the subsequent cycles were at maximum displacements of 0.4, 0.6, 0.8, 1, 1.4, 1.8, 2, 2.5, 3, 4, 4.5, 5.5, 6, and 7 mm. For each displacement two complete cycles were applied. For the Regular shear wall, after completing 2 cycles at 7 mm, the load was increased monotonically until the wall could not maintain the axial load of 800 kN which happened at a displacement of 8.2 mm. In the case of the ASR wall, the specimen was pushed in one direction by 7 mm in the first cycle and then in the opposite direction. During this part of the cycle, the axial load started to drop as the lateral displacement increased and needed constant increase in load. At 7 mm displacement, it was decided to continue load monotonically and at 7.1 mm, the wall failed to maintain the axial load. The test was terminated at that point.

RESULTS AND OBSERVATIONS Manchester, United Kingdom August 10 14, 2015 Division I Seven LVDTs were used to measure the horizontal displacement along the height of the specimen from bottom beam to the top beam on both sides of the specimen. The Force - Displacement plot was obtained using the summation of the forces from both actuators against displacement of top of the shear wall (bottom of the top beam) with respect to the top of the lower beam.

Figure 3: Schematic drawing showing the test setup for shear walls Figure 4: Test setup of a shear wall showing the top frame and loading beam The specimens were loaded using the two actuators working simultaneously. The rate of loading began with 0.005 mm/sec and was increased to a maximum of 0.15 mm/sec as cycles progressed. The first two cycles applied 0.2 mm lateral displacement in the plane of the wall in each direction and the subsequent cycles were at maximum displacements of 0.4, 0.6, 0.8, 1, 1.4, 1.8, 2, 2.5, 3, 4, 4.5, 5.5, 6, and 7 mm. For each displacement two complete cycles were applied. For the Regular shear wall, after completing 2 cycles at 7 mm, the load was increased monotonically until the wall could not maintain the axial load of 800 kN which happened at a displacement of 8.2 mm. In the case of the ASR wall, the specimen was pushed in one direction by 7 mm in the first cycle and then in the opposite direction. During this part of the cycle, the axial load started to drop as the lateral displacement increased and needed constant increase in load. At 7 mm displacement, it was decided to continue load monotonically and at 7.1 mm, the wall failed to maintain the axial load. The test was terminated at that point.

RESULTS AND OBSERVATIONS Figure 11: Toronto shear test (Habibi, Sheikh, Orbovic, Panesar, and Vecchio, 2015)

Colorado has conducted an original test which was as close as pure shear as possible, Fig.

12. The Report submitted to the NRC can be found here.

4" MTSHead MTSHead 30" Figure 12: Colorado shear tests (Saouma, 2017)

NIST These tests, Fig. 13, will be discussed below in relation to each other, including the one listed above, and most importantly, in relation to the issued license by the NRC.

Final comments, quoting from the NIST report Weigand, Sadek, Thonstad, et al.

(2021) write:

The study by Habibi et al. (2018) was performed at the University of Toronto under the sponsorship of the Canadian Nuclear Safety Commission and is, to the authors Victor Saouma/C-10 NIST Shear Wall Tests and Seabrook Safety

C II RELEVANCE OF NIST TESTS ON SHEAR STRENGTH; FURTHER DETAILS19 30 included the NIST PERFORM Laboratorys structural reaction (strong) floor, hydraulic actuators, a primary reaction frame made up of a foundation frame and loading beam, a lateral bracing frame (LBF), and a Concrete Structural Reaction Block (CSRB) Wall (Figure 2.17). The strong floor consists of a 6.0 ft (1.83 m) thick heavily reinforced concrete slab. Both the foundation frame and the CSRB block wall were anchored to the strong floor using 1-1/2 in (38.1 mm) diameter UNF high-strength threaded rods connected into the sockets embedded in the strong floor. Each high-strength threaded rod was post-tensioned to its working capacity, or a load of approximately 100 kip (445 kN).

Figure 2.17. Experimental setup for testing ASR-affected concrete shear wall specimens (1.000 kip = 4.448 kN)

The foundation frame (see Figure 2.17) was erected as an assembly of structural steel reaction frame components. Two parallel W27x235 foundation beams, which were anchored to the strong floor near their ends where vertically-spanning actuators framed into them, provided a platform to mount the footing of the shear wall specimen. Six outriggers extended perpendicularly as cantilevers from the foundation beams to provide both stability to the overall foundation frame and additional tie-down Figure 13: NIST shear tests knowledge, the only test data available in the literature on seismic performance of structural walls affected by ASR.

Kajima The most comprehensive test involving shear walls with AAR (Alkali-Aggregate Reaction) was conducted in Japan by the Kajima Corporation (Sawada, Takaine, Okayasu, Nimura, and Shimamoto, 2021). The funding sources of this research un-derscores the seriousness and depth of investigation involved.

S. Sawada, Y. Takaine, T. Okayasu, A. Nimura, R. Shimamoto / Journal of Advanced Concrete Technology Vol. 19, 477-500, 2021 482 In addition, cylindrical specimens of ASR concrete with 100 mm diameter and 200 mm height that were prepared at the same time as web concrete casting were exposed wrapped in wet cloth under the same condition as the web wall (outside ambient temperature). Com-pressive strength, static elastic modulus and tensile strength were periodically obtained according to JIS A1107, JIS A1149 and JIS A113, respectively. Poisson's ratio was also obtained as the ratio of the transverse strain to the longitudinal strain at 1/3 of the maximum strength in the stress-strain curve. Strains for the static modulus and Poisson's ratio were measured using strain gauges (PL-60 and PL-90, Tokyo Measuring Instruments Laboratory Co., Ltd.). Surface length change was meas-ured as change in 100 mm gauge length of contact points on rings wrapped around the surface of cylindrical specimen. Elastic wave velocity was also measured in the similar manner to the web wall.