Seabrook Station

Public Meeting

Safety Implications and Status of 

Alkali-Silica Reaction Condition in 

Safety Related Structures

Nuclear Regulatory Commission
NRC Representatives

• Christopher Miller – Director, Division of 

Reactor Safety

• Michele Evans Director – Division of Operating 

Reactor Licensing

• Richard Conte – Senior Project Manager

• William Cook – Team Leader

• William Raymond – Senior Resident Inspector 
NRC Representatives

 Karl Farrar Chris Miller Michele Evans Rich Conte 

Bill Raymond Bill Cook 
Agenda

• What is Alkali-Silica Reaction (ASR)

• Virtual Tour of Plant

• Safety Implications

• Inspection Results, to date

• Future Activities

• Closing Remarks

• Respond to Questions
What is ASR?

Concrete Ingredients
6

What is ASR?

Chemical Reaction

alkali (in cement) 

reacts with silica (in 

aggregate) and 

water

silica gel forms

K+

Na+

cracking occurs 

as gel expands

gel

gel

SiO2

SiO2

SiO2

OHOHforms + H2O
What is ASR?

Indications of ASR

• ASR has been identified in 

localized areas of Seabrook 

concrete structures

• ASR is a chemical reaction in 

concrete, which occurs over time 

in the presence of water, between 

the alkaline cement and reactive 

silica found in some aggregates.

• ASR forms a gel that expands 

causing micro-cracks that effect 

concrete material properties

ASR Gel Ring

Reactive Aggregate

Cracking through Aggregate
TOUR OF PLANT

Confirmed localized areas of ASR

• Effected Structures include:

– “B” Electrical Tunnel

– Containment Enclosure 

Building

– Residual Heat Removal 

Vault

– Emergency Diesel 

Generator Building

– Emergency Feedwater 

Building
Annulus area 

between Primary 

Containment and 

Containment 

Enclosure Building

9

Base Slab

30-inch Thick 

Enclosure Wall 

48-inch Thick 

Containment 

Wall

TOUR OF PLANT
TOUR OF PLANT

Other locations where ASR identified

 Primary Auxiliary 

Building

 Main 

Steam/Feedwater 

Pipe Chase East

 Alternate Cooling 

Tower

 Service Water Pump 

House

 Containment

VISUAL CRITERIA

Pattern cracking

Secondary deposits

Staining and discoloration

Deposits of alkali silica gel 
Pattern Cracking (approx. 3 ft x 3 ft area)

TOUR OF PLANT
ASR Monitoring Method

12

TOUR OF PLANT
SAFETY IMPLICATIONS

• NextEra engineering analysis (independently reviewed by NRC team) 

confirmed adequate design (safety) margin remains for ASR-affected 

reinforced concrete structures

• No significant visible deformations, distortions, or displacement 

identified in affected structures

• No indications of rebar degradation

• ASR limited to localized areas of the effected structures

• ASR degradation progressed slowly
Confirmatory Action Letter 

(CAL) 1-2012-002

Letter dated May 16, 21012, confirming eleven 

commitments made by NextEra, during a meeting with 

the NRC staff on April 23, 2012, associated with 

corrective actions to address ASR-affected reinforced 

concrete structures at Seabrook Station.
CAL Commitments

Revise Prompt Operability Determination (POD) for B 

electrical tunnel

Submit root cause evaluation

Submit Interim Assessment

Submit integrated corrective action plan

Revise POD for buildings identified in extent-of-condition 

review

Complete short term aggregate expansion testing

Complete long term aggregate expansion testing

Submit technical details of testing plan

Update Structures Monitoring Program

Perform six-month crack measurements

Complete anchor testing program
INSPECTION RESULTS

Review of Confirmatory Action Letter (CAL) Items

(6 of 11 Reviewed, 5 Closed)

• Prompt Operability Determination for “B” Electrical Tunnel 

(CAL No. 1) - Closed

• Prompt Operability Determination for Other Effected 

Structures (CAL No. 5) - Closed

• Interim Structural Assessment (CAL No. 3) - Closed

• Complete Mortar Bar Test (CAL No. 6) - Closed

• Initial Six-Month Crack Measurements (CAL No. 10) -

Closed
INSPECTION RESULTS

Other Areas Reviewed

• NextEra’s inspection of structures for evidence of ASR, 

independently reviewed by NRC staff 

• Primary Containment engineering evaluation and 

operability assessment completed for ASR indications on 

three areas of the containment exterior surface

• Two issues closed, related to adequacy of operability 

determinations and engineering analysis calculations 

effected by ASR
INSPECTION RESULTS

Team Conclusions

• NextEra’s methods used for assessing operability of ASRaffected reinforced concrete structures - reasonable and 

generally comprehensive.

• NextEra’s margins assessment provided a reasonable 

operability basis; the degraded and non-conforming condition 

is being addressed via a testing program, expected to be 

completed mid-2014

• NRC staff plans to review NextEra’s monitoring and testing 

program to address uncertainties in evaluating the current 

level and progression of ASR – early 2013
INSPECTION RESULTS

NextEra’s Margins Approach
THE FUTURE

What is to be addressed in Next Report?

• Remaining six CAL items:

• Root cause evaluation

• Integrated action plan

• Research and development plan

• Anchor testing

• Prism testing

• Structures Monitoring Program

• Follow-up of observations from first report
CLOSING REMARKS

Chris Miller

Director Division of Reactor Safety
Questions and Answers
List of Key Documents 

• Confirmatory Action Letter No. 2012-002, issued May 16, 

2012 (ML12125A172)

• Inspection Report No. 05000443/2012009, issued 

December 3, 2012 (ML12338A283)

• NextEra Letter of May 24, 2012, in response to CAL Item 

No. 3, provided the Interim Structural Assessment 

(ML12151A397)
Contacting the NRC

• Report a safety concern

• 1-800-695-7403

• allegation@nrc.gov

• General questions

• www.nrc.gov

• Region I Public Affairs

• Diane Screnci, 610-332-5330 

diane.screnci@nrc.gov

• Neil Sheehan, 610-332-5331 or 

neil.sheehan@nrc.gov