License Amendment Request:

Methodology for the Analysis of Concrete 

Seismic Category I Structures with 

Concrete Affected by Alkali Silica 

Reaction 

Seabrook Station

June 15, 2016
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3

The foundation for everything we do are the Values and 

Core Principles of our Nuclear Excellence Model
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Seabrook Attendees

• Ken Browne NEE Seabrook ASR Project Manager

• Mike Ossing NEE Seabrook Licensing Manager

• Brian Brown NEE Seabrook Principal Engineer

• Larry Nicholson NEE Fleet Licensing Director

• John Simons MPR Gen Manager Power Projects

• Dr. Said Bolourchi SG&H Senior Principal Engineer

• Jim Moroney MPR ASR Test Program PM

• Phil Rush MPR Engineering Associate
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Presentation Outline

• Alkali-Silica Reaction

• Overview of License Amendment Request (LAR)

• Structural Capacity Testing of ASR-Affected Specimens

• Evaluation of Structural Deformation

• Monitoring of ASR Expansion and Structure Deformation

• Summary of LAR changes

• Closing Remarks

-Presentation describes Next Era current intent regarding License Amendment Application
6

Alkali-Silica Reaction
7

Alkali-Silica Reaction

• ASR (alkali-silica reaction) is a chemical reaction between silica from 

the aggregate (gravel and/or sand) and alkali constituents in the 

cement

• Reaction produces a gel that expands as it absorbs moisture and 

exerts a tensile stress from within the concrete

forms

alkali cement + 

reactive aggregate

expansive gel

K+

Na+

cracking of the 

aggregate and paste

+ H2O

gel

gel

SiO2

SiO2

SiO2

OHOH-
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Overview of License Amendment Request
9

Overview of License Amendment Request

• Next Era proposes a change in the UFSAR methodology to address 

ASR concrete degradation at Seabrook Station

• ACI 318-71 and the ASME Code do not include provisions for 

addressing ASR and its effects

– Incorporate loads imposed by ASR into the design basis

• Evaluate structures affected by ASR to demonstrate that they satisfy 

the acceptance criteria of the original construction code

– ACI 318-71 for all seismic Category I structures other than containment

– ASME Boiler & Pressure Vessel Code, Section III for containment
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Overview of License Amendment Request

– Applies to Seismic Cat 1 Structures and Containment Structure

– Establish ASR expansion limits from testing:

Shear capacity

Flexural capacity and reinforcement development length

Anchor bolts embedded in concrete with ASR

– 3 Stage Analysis process for Building Deformation Assessment:

Specify how ASR loads are combined with other design basis loads for analyzing structures including 

defining load factors

Include the effects of concrete creep, shrinkage and swelling in structure deformation analyses

Identify ANSYS as the computer code used for ASR building deformation analyses

Permit use of the 100-40-40 procedure from Regulatory Guide 1.92, Revision 3 for detailed evaluations 

(“Stage Three”) analyses of ASR-affected structures.

Use of cracked section properties and redistribution of self-limiting loads for ASR-affected structures

– Attachments:

UFSAR Markup and ‘Clean’ Pages

MPR 4288, Rev 0 Seabrook Station: Impact of ASR on Structural Design Structural Design Evaluations

MPR 4273, Rev 0 Seabrook Station: Implications of Large Scale Test Program Results on Reinforced 

Concrete Affected by ASR

SGH (#TBD) Computation of Load Factors for ASR Demands 

. 
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Structural Capacity Testing of 

ASR-Affected Specimens
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Structural Capacity Testing of 

ASR-Affected Specimens

• MPR conducted large-scale test programs to investigate 

structural impact of ASR on reinforced concrete

– Improve current understanding of ASR and its effects on 

reinforced concrete structures

– Evaluate instruments for monitoring (measuring) the through- thickness (out-of-plane) expansion of concrete from ASR
13

Structural Capacity Testing of 

ASR-Affected Specimens

Anchor Test 

Program

Shear Test 

Program

Reinforcement 

Anchorage 

Test Program

Instrument 

Evaluation 

Program

Beam Test Programs
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Structural Capacity Testing of 

ASR-Affected Specimens

Test Program Results Key Conclusion

Anchor Test 

Program

• Anchor performance

• insensitive to through-thickness expansion

• reduces at high levels of in-plane cracking

• No difference between performance of anchors 

installed before and after ASR expansion

No impact on anchors at 

Seabrook based on expansion 

levels expected

Beam Test 

Programs

• Control specimens showed consistency with 

ACI 318 equations for shear capacity, flexural 

capacity and lap splice length

• ASR-affected specimens showed: 

• No adverse impact of ASR on shear capacity, 

flexural capacity, reinforcement anchorage and lap 

splice performance

• Behavior indicative of pre-stressing due to ASR 

expansion

Original design strength and code 

equations can be used for ASRaffected reinforced concrete 

structures 

• Shear capacity

• Flexural capacity

• Reinforcement development length 

Instrumentation 

Evaluation 

Program

Snap ring borehole extensometers were accurate 

and reliable throughout duration of program

Snap ring borehole 

extensometers selected for use at 

Seabrook Station
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Structural Capacity Testing of 

ASR-Affected Specimens

• Licensing Implications

– Impact on UFSAR

Large-scale testing or reinforced-concrete beams showed

– No adverse impact of ASR on shear capacity, flexural capacity or reinforcement 

development length

– Use of Code equations and design compressive strength to determine capacity is 

conservative

No change to the UFSAR-described methodology is necessary for 

determining capacity provided ASR expansion is within limits from testing

– ASR expansion limits

Expansion limits established based on range of expansion covered in testing

Limits to be controlled within Structural Monitoring Program
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Evaluation of Structural Deformation
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Evaluation of Structural Deformation

• Inspections of Seabrook structures have identified 

deformation due to ASR expansion effects

– ASR-related expansion may impose an additional, internal load on 

reinforced concrete adjacent to ASR-affected areas

– ASR-related expansion of concrete backfill can impose an external 

load on adjacent structures 

– Seismic gap widths and close clearances between structures and 

plant components may be reduced
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Methodology for Analysis of Structural 

Deformation

• LAR describes progressive approach for evaluating structures 

with deformation

– Stage One – Screening Evaluation

– Stage Two – Analytical Evaluation

– Stage Three – Detailed Evaluation

• Structures require an analysis of all load combinations with 

ASR loads included
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Evaluate 

Responses due to 

ASR loads (Sa)

Stage 1:

Screening 

Evaluation

Field 

Observations

Stage 2: 

Analytical 

Evaluation

Original Design 

Demands & 

Capacities

Adequate 

Margin with 

“Sa”

No

Define Threshold 

for Monitoring

Yes

Evaluation of Structural Deformation

“Sa” = Load associated with ASR
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Stage 2: Analytical Evaluation

Finite 

Element 

Modeling

Correlate with Field 

Observations 

“Sa” Inputs Based on 

Field Measurements and

other self straining loads

Define Threshold for 

Monitoring

Yes

Original Design 

Demands & Capacities

Adequate 

Margin with 

“Sa”

Stage 3:

Detailed 

Evaluation

No

Calculate Sa

Evaluation of Structural Deformation
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Stage 3: Detailed Evaluation

Finite 

Element 

Modeling

Refined “Sa” Inputs 

Based on Additional 

Field Measurements

Original 

Design Loads 

Inputs

Define Threshold for 

Monitoring

Evaluate Using Total 

Factored Design Demands 

Including “Sa”

• Cracked section

• Redistribution of Self- limiting load

• 100-40-40 

Combination of 

seismic components

Evaluation of Stage 3 Structural Deformation
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Evaluation of Structural Deformation

• Including ASR loads with other design basis loads requires 

definition of load factors for each loading combination

– ACI 318-71 and 1975 Edition of ASME B&PV Section III Division 2 does 

not include load factors for ASR

– SGH developed load factors consistent with ACI 318-71 and ASME 1975 

Edition load factor development 

– Load factors for ASR will be used in the analysis of Seabrook structures 

and included in Tables 3.8-1 and 3.8-16 of the UFSAR

• Structures evaluated to demonstrate that additional ASR 

expansion is permissible

– Margin is included in the acceptance criteria for each stage to ensure 

that additional deformation does not challenge design limits

– A higher level of deformation is analyzed relative to current 

measurements to set the threshold for monitoring
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Evaluation of Structural Deformation

• Stage 2 or Stage 3 evaluation will use an ANSYS finite element model

– Alternate computer codes were used in the original analyses of Seabrook 

structures

– ANSYS has been used for analyzing safety-related structures in other plant 

designs (e.g., AP1000, ESBWR)

– NRC has previously accepted the use of ANSYS for structural analysis at other 

facilities

• Effects of creep, shrinkage, and swelling of concrete must be 

accounted for in the structure deformation analyses 

– Creep, shrinkage and swelling loads are discussed in the Seabrook UFSAR but 

they were considered negligible in the original design analyses

– ACI 318-71 includes load factors for loads caused by creep, shrinkage and 

swelling
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Review of ASR Expansion and Structure 

Deformation Monitoring
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Review of ASR Expansion and Structure 

Deformation Monitoring

• Continued monitoring of ASR and its effects is necessary

– Expansion caused by ASR must be measured and remain bounded by limits 

established from the large-scale test program

– Periodic measurements of structure deformation are necessary to ensure limits 

from deformation analyses are satisfied

• Separate monitoring requirements will be included in the Structural 

Monitoring Program (SMP) for ASR expansion and structure 

deformation

• SMP uses a three-tiered approach to classify the results of inspections

– ASR expansion levels and structure deformation measurements will be evaluated 

using classification levels

– Increased monitoring and analysis are necessary for progressively higher levels 

of ASR expansion and structure deformation
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Typical methods used to measure ASR expansion at Seabrook

Review of ASR Expansion and Structure 

Deformation Monitoring
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Tiers for classifying ASR cracking

Review of ASR Expansion and 

Structures Monitoring

• Limits established in the large-scale test program will be included in the Structural Monitoring Program

Tier Structural Monitoring 

Program Category

Recommendation for 

Individual Concrete 

Components

CRITERIA

Combined Cracking Index 

(CCI)

3 Unacceptable (requires further 

evaluation) Structural Evaluation 1.0 mm/m or greater

2 Acceptable with Deficiencies

Quantitative Monitoring and 

Trending 0.5 mm/m or greater

Qualitative Monitoring 

Any area with visual presence of 

ASR (as defined in FHWA-HIF12-022) accompanied an 

estimated summation of crack 

widths not supporting a 0.5 

mm/m CI in the vertical or 

horizontal direction.

1 Acceptable

Routine inspection as prescribed 

by the Structural Monitoring 

Program

Area has no indications of pattern 

cracking or water ingress- No 

visual presence of ASR
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Review of ASR Expansion and 

Deformation Monitoring

Stage Deformation Evaluation Stage Monitoring Interval

1D Screening 3 years

2D Analytical 18 months

3D Detailed 6 months

• Inspection requirements for structures with ASR-induced deformation

• Parameters that are measured are specific to each structure 

– Parameters will be defined in the structure deformation evaluation

– Limits established from deformation evaluation
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Summary of LAR Changes

• NextEra will submit the following changes to the Seabrook UFSAR:

– ASR expansion loads are taken into account for seismic Category I 

structures

– Load factors for ASR loads are included in the design load combinations

– Creep, shrinkage and swelling effects are evaluated in the process of 

analyzing structures with ASR-related deformation

– ANSYS is used for deformation evaluations

– Stage Three deformation evaluations may use 100-40-40 method from 

NRC Regulatory Guide 1.92, Revision 3, for combining seismic loads 

instead of the SRSS method in Revision 1 of this regulatory guide.
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Closing Remarks

• License Amendment Request Represents multiple years 

of research and learning about ASR

• Third Party Reviews in progress

• Submit to NRC by July 31st