ML12054A641

Concrete Degradation - Alkali Silica Reaction, W/Handwritten Notes

ML12054A641
Person / Time
Site:	Seabrook
Issue date:	05/24/2011
From:	Office of Nuclear Reactor Regulation
To:
References
FOIA/PA-2012-0119
Download: ML12054A641 (15)

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Seabrook Concrete Degradation -

Alkali Silica Reaction May 24, 2011 Lead: Ed 1

Alkali-Silica Reaction (ASR)

" Occurs over time in concrete between alkaline cement paste and reactive non-crystalline silica found in common coarse aggregates

" Requires susceptible aggregate and adequate moisture Forms a gel that expands and causes microcrack network

" Changes strength of reinforced concrete; reduces stiffness 2

Lead: Bryce/Abd.ul Provide Pictures Of ASR Examples v'

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Background===

" June 2009 - Licensee begins walkdowns as part of license renewal application preparation; groundwater leakage and extensive cracking of concrete in different plant areas

" April to June 2010 - Licensee tests concrete including penetration resistance testing and 12 concrete cores from affected areas in 'B' Electric Tunnel which showed significant reduction in compressive strength and modulus of elasticity

" August 2010 - Petrographic examination of concrete cores confirms presence of ASR

" September 2010 - Licensee completes prompt operability determination concluding structures are operable 3

Lead: Ed Provide Remaining Pictures 3

Background (Cont.)

" September 2010 - Licensee issues a design change package to reflect the reduction in strength and modulus of elasticity in the plant licensing basis

" October 2010 - During license renewal audit, NRC staff identified 6 feet of water in containment annulus region When water removed, patterned cracking indicative of ASR identified on both primary containment and containment enclosure building

" May 2011 - Licensee takes concrete cores from 5 additional areas Results of core testing are pending 4

Lead: Ed 4

Problem Summary

" Below-grade concrete structures experiencing groundwater infiltration.

" Aging management review found degraded conditions in below-grade areas for several structures

" Degradation mechanism identified as or suspected to be ASR

• First nuclear plant in U.S. to experience ASR Lead: Ed 5

Current Status Licensee continuing to develop final operability determination NRC overseeing licensee actions and engaging in development of the final operability determination Quarterly resident report issued May 12, 2011 NCV green) on failure to adequately monitor the control building for the recent Clegra aion NOV (green) on failure to include transition buildings as in-scope structures in Maintenance Rule monitoring program Design basis not exceeded based on licensee operability determination License Renewal Inspection report issued May 23, 2011 Report noted that the aging management review for the ASR issue is incomplete DE, DLR, DORL and Region I are working together to successfully resolve this issue with respect to Parts 50 and 54 6

Lead: Meena A-1 U

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Licensee's Prompt Operability Determination

" Structural integrity of the Control Building was intact

• All systems and components housed within the building were operable and capable of performing their design function

" ASR has resulted in reduction of elastic modulus of concrete and compressive strength in portions of below grade walls

" Developing a comprehensive test and evaluation plan to manage ASR 7

Lead: Meena 7

Licensee Ongoing Actions Extent of Condition and Root Cause Review Operability determination on buildings associated with extent of condition review Apparent root cause review for the 10 CFR 50.65 violations Continuing root cause evaluation related to ASR issue Periodic operability assessments as information is developed for the aging management review will be completed Lead: Meena 8

NRC Staff Ongoing Actions (Seabrook Specific)

Region I preparing a Task Interface Agreement (TIA) to request support from NRR Design change Final Operability determination DE, DLR, DORL and Region I continue to work together to address this issue with respect to both Parts 50 and 54 This issue is currently tracked as an Open Item in the upcoming license renewal SER Lead: Ed While we don't disagree with the supporting information provided by the licensee

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NRC Staff Ongoing Actions (Generic)

Preparing generic communication (IN) to inform other licensees about the ASR potential in plants with groundwater leakage; expected issuance next quarter Operating Experience group has issued an internal communication and continues to follow the issue for generic applicability 10 Lead: Ed 10

ASR on One of the Walls 7;11

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Microscopic Example of ASR 2

Seabrook Station Plan CONCRETE CORE LOCATIONS DIESELCOTL GENERATOR BUILDING BUILDING RCAWALKWAY Ln1I L

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~~STRUCTUREml 4-FT THICK44, WAT TANK PRIMARY WAPTE FARM AUX BLDfhmG CONCRETE BUILDING ARAENCLOSUIRE BUILDING 30-IN THICK 3

Seabrook.Containment and Enclosure Building -Cracking 4

Seabrook Electrical Tunnel 5