ML12356A043

Safety Implications and Status of ASR Condition - Public Meeting on 12/11/2012

ML12356A043
Person / Time
Site:	Seabrook
Issue date:	12/11/2012
From:	Conte R, Cook W, Marilyn Evans, Chris Miller, Raymond W Office of Nuclear Reactor Regulation, NRC Region 1
To:
References
Download: ML12356A043 (24)

Text

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 OH-OH-forms

+ 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

• NextEras 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

• NextEras methods used for assessing operability of ASR-affected reinforced concrete structures - reasonable and generally comprehensive.

• NextEras 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 NextEras monitoring and testing program to address uncertainties in evaluating the current level and progression of ASR - early 2013

INSPECTION RESULTS NextEras 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