Review of reactor containment building corrosion events ... · –Corrosion rates in concrete 5 to...

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1

Andrew Ruminski

Westinghouse Electric Company

Materials Center of Excellence

Churchill

Review of reactor containment building

corrosion events and prediction corrosion rates

2


Operating Experience

• Non-uniform, through-wall, corrosion at interface between

containment liner steel & concrete

• Several incidents worldwide1-3

– Brunswick Unit 2 - 1999

– Anna Unit 2 - 1999

– D.C. Cook Unit 2 - 1999

– Beaver Valley Unit 1 - 2009 and 2013

– Ringhals Unit 2 - 2006

– Various French plants

1) Sandia National Laboratory Report SAND2010-8718, “Nuclear Containment

Steel Liner Corrosion Workshop: Final Summary and Recommendations

Report,” July 2011.

2) V. Shah and C. Hookman, “Long-term aging of light water reactor concrete

containments,” Nuclear Engineering & Design, Vol. 185 (1998), pp. 51-81

3) P. Effsing, “Containment Leakages – Ringhals Unit 2,” PWROG-MSC

Hollywood, Florida, April 2015.

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Through-Wall Corrosion Incidents

• Incidents associated with organic foreign material

– Embedded gloves, brushes, and / or lumber

– Source of chlorides, sulfates & organic acids

• Ringhals Unit 2 attributed to pitting corrosion & MIC

Average Penetration Rates (mmpy)

North Anna 2 0.41

D. C. Cook 2 0.38

Beaver Valley Unit 1 0.25

Passivity perturbed

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Conditions of Through-wall Corrosion

• Measurable sulfates, fluorides, & chlorides at interface

• Black corrosion deposits (magnetite) at concrete interface

• Formation of magnetite due to low oxygen & chlorides3-6

• Sulfur bearing specimens & yellow deposits on plant side– Possible evidence of MIC

• pH from swipe ~ 6 – Non-passivating

– Conducive to SRB-MIC 7

3) R. Javaherdashti, Microbiologically Influenced Corrosion: An Engineering

Insight, Springer-Verlag, London (2008).

4) F. R. Pérez et al.,“Effect of Chloride Concentration, Immersion Time and Steel

Composition on the Spinel Phase Formation”, Materials Chemistry and Physics,

117, 214-223, (2009).

5) C. T. Lee et al., “An In Situ Raman-Electrochemical Investigation of Carbon

Steel Corrosion in Na2CO3 / NaHCO3, Na2SO4 and NaCl Solutions”, Journal of

the Electrochemical Society, 153 (2), B33-B41, (2006).

6) C. A. Barrero et al., “On Magnetite Formation as a Corrosion Product of Steel”,

Proceedings of the International Conference on the Applications of the

Mössbauer Effect, September 2-7 2001, Oxford.

7) R. Javaherdashti, Microbiologically Influenced Corrosion: An Engineering

Insight, Springer-Verlag, London (2008).

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Liner / Concrete Interface

EDS Data from Thick Black Oxide (Magnetite)

Spectrum

C

(w %)

O

(w %)

Si

(w %)

Ca

(w %)

Mn

(w %)

Fe

(w %)

1 2.6 30.6 0.1 0.1 1.2 65.4

Black

Oxide

Swipe:

pH ~6

SO4-2 0.8 µg / cm2

F- 0.2 µg / cm2

Cl- 0.1 µg / cm2

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Plant Side, Leaking from Hole

Yellow

Deposit

EDS Data from Yellow Deposit

Spectra

C

(w %)

O

(w %)

Cr

(w %)

Si

(w %)

S

(w %)

Ti

(w %)

Mn

(w %)

Fe

(w %)

Cu

(w %)

Zn

(w %)

1 13.3 37.0 0.2 0.2 1.6 0.1 0.2 46.7 - 0.7

2 2.5 5.3 - 0.2 1.3 0.8 0.5 88.3 - 1.2

3 12.4 38.1 - 0.1 0.4 - - 48.2 - 0.7

4 14.5 42.7 1.1 1.0 1.6 0.2 0.6 37.0 0.9 0.4

5 18.4 29.6 - 0.3 0.9 0.6 0.2 48.9 - 1.1

6 77.2 22.8 - - - - - - - -

Sulfur bearing

Possible MIC byproduct

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Published Data

• General corrosion rates of steels near ambient 6-9

– Less severe than liner plate rates observed in NPP

• Atmospheric conditions ~ 0.025 mm per year (mpy)

• Passivating high pH environment (~ 12.5) in concrete 1-2

– Corrosion rates in concrete 5 to 10 lower

6) ASM Handbook of Corrosion Data, edited by B. D. Craig, First Edition, p. 160.

7) M. Raphael and R. Shalon, “Influence of Climate on Corrosion of Reinforcement,” Proceedings International RILEM Symposium, Vol. 1, 1971, pp.

177-196.

8) E. Escalante and S. Ito, “Measuring the Rate of Corrosion of Steel in Concrete,” Corrosion Rates of Steel in Concrete, ASTM STP 1065, N. Berke

et al. editors, pp. 86-102.

9) C. Locke and A. Siman, “Electrochemistry of Reinforcing Steel in Salt Contaminated Concrete,” Corrosion of Reinforcing Steel in Concrete, ASTM

STP 713, D. Tonini and J. Gaidis editors, pp. 3-16.

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Summary of Published Ambient Corrosion Rates

Corrosion Rates for Structural Carbon SteelExposure Conditions mmpy Ref

Atmospheric, 1st Several Years 0.025 6

Atmospheric, Past Several Years 0.013 6

Encased in concrete, no salt 0.003 7

Encased in concrete, exposed salt 0.013 8

Encased in concrete,1.0% NaCl 0.14 9

Observed NPP Liner Corrosion ~3x greater

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Thermal Effects

• Corrosion data assumed to be 25oC (77oF)

• Operating temperature of NPP liner <49oC (<120oF)

• Activation energy of 36 800 J / mole 10

• Rate approximately 3 times greater than “ambient”

10) Jäggi et al., Corrosion of Reinforcement in Concrete, Chapter 7, “Macrocell Corrosion of Steel in Concrete – Experiments and Numerical

Modelling,” 2007, pp. 75-88.

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Breakdown of Corrosion Immunity – Acid

• Reduction in pH

– Carbon dioxide from the atmosphere

• Eventually Reduce the pH to approximately 8.3

– Organic debris embedded in the concrete

– Acids from MIC (pH as low as 4)

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Breakdown of Corrosion Immunity – Chlorides

• Cl- ion to OH- ratio greater than 0.3

• Passivating film on steel is penetrated

– Corrosion initiated

• Iron ion precipitation/hydrolysis reaction reduces pH

– Chloride and acidic attacks synergistic

• Corrosion rate with chlorides 50 times greater passivated

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Effect of Moisture

• Oxygen & electrical conductivity of concrete impact

corrosion

• Both low oxygen solubility & diffusivity low in water

saturated concrete

– Worst case corrosion with intermittent wetting

– Intermittent wetting also intensifies contamination

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Predicted Corrosion Rate

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Time to Penetrate Containment Liner

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Summary

• Steel in Containment Concrete – Passivated with corrosion rate (~0.01 mmpy)– Active corrosion rate with carbonation (~0.08 mmpy)– Corrosion rate with contamination (~0.44 mmpy)

• 10 mm liner penetration– >1000 years with passivation– >100 years with active corrosion (non contamination)

• Penetration incidents associated with contamination – Chlorides, organic acids, MIC – Up to 0.4 mmpy– >25 year to penetrate liners

Review of reactor containment building corrosion events ... · –Corrosion rates in concrete 5 to...

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