ML120690171

Slides and View Graphs - Boric Acid Corrosion Testing Program: Industry Perspective

ML120690171
Person / Time
Site:	Davis Besse
Issue date:	02/29/2012
From:	Sims W Electric Power Research Institute, Entergy Corp
To:	Office of Nuclear Regulatory Research
Carpenter C E 301-251-7632/RES
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ML120690160	List: ML120690165 ML120690171
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Boric Acid Corrosion Testing Program: Industry Perspective NRC/EPRI MRP Meeting Rockville, MD February 29, 2012 William Sims Entergy

Background (1/3)

• Boric Acid Corrosion of Low Alloy Steel at Alloy 600 CRDM Penetrations is a Long-Standing Issue

- Leakage at CRDM penetrations first observed at Bugey 3 in 1991

- Leakage and/or minor wastage observed at other plants

• Significant Wastage Observed at Davis Besse in 2002 Prompted Revision to Inspection Guidance/Regulations

- NRC Order EA-03-009

- MRP 117

- ASME Code Case N-729 (now codified in 10CFR50.55a)

No leakage has been observed in Reactor Vessel Penetrations since inspections have been instituted

© 2012 Electric Power Research Institute, Inc. All rights reserved. 2

Background (2/3)

• Lack of Directly Relevant Data Available to Support Development of Inspection Guidance in 2002 Industry Began a Comprehensive BAC Test Program in 2004 to:

- Improve understanding of fundamental factors controlling BAC though bench-scale testing

- Improve mechanistic understanding of BAC

- Mockup testing under prototypical conditions to provide directly relevant data

• Typical geometry, temperatures, flow rates and coolant chemistry

- Include Bottom Mounted Instrument Nozzle penetrations in program

© 2012 Electric Power Research Institute, Inc. All rights reserved. 3

Background (3/3)

• Conclusions from Results: Low Alloy Steel

- Results support current inspection intervals:

structurally significant wastage will not occur between inspections at Alloy 600 Tube currently prescribed intervals

- Results support current inspection methods: visual inspection is a reliable technique for detection of BMN Test 5: 0.006 GPM leakage leakage, even at low flow Boric Acid Deposits Visible after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> rates

© 2012 Electric Power Research Institute, Inc. All rights reserved. 4

Boric Acid Deposits versus Wastage

• At 1500 ppm boron, leakage of 0.01 GPM equates to 600 pounds of boric acid in 18 months

- 6.9 cubic feet at full density

• 11,900 in3

- 0.5 in3 readily detected by visual inspection (MRP-167)

- Corresponding wastage 3 in3 or less CRDM Tests at 0.01 GPM; 1500 ppm B

• Not structurally significant Volumetric corrosion rate 0.10 to 2.1 in3/yr 32 day test = 35 lb boric acid

© 2012 Electric Power Research Institute, Inc. All rights reserved. 5

Boric Acid Corrosion Test Program Timeline 1991 Bugey 3 2002 Davis 2003 EA- 2003 STP 2004 2004 MRP 2006 ASME 2009 ASME 2011 MRP BAC 2012 BAC IMT Gap First Reported BAC Test Guidebook CRDM Cracking Besse CRDM 03-009 Issued BMN Leakage MRP-117 Issued Program Begins Code Case N-729-1 Code Case N-722-1 Program Testing Rev 2 Issued P-AS-01 Event Issued Issued Complete Closed

• IMT Gap: P-AS-01 Boric Acid Corrosion of Carbon and Low Alloy Steels (High Priority)

- Gap will be closed with completion of activities this year

© 2012 Electric Power Research Institute, Inc. All rights reserved. 6

Use of Results

• Support Current Damage Predictions

• Enhance Technical Basis for Current Inspection Requirements

- Supports use of visual inspections to ensure safety significant damage does not occur between inspections

- Supports extended volumetric inspection intervals for mitigated CRDM penetrations

• Update Boric Acid Corrosion Guidebook (MRP-58)

- Last revision 2001

- Revise Guidebook to update operational experience and incorporate test results

© 2012 Electric Power Research Institute, Inc. All rights reserved. 7

Overall Conclusion

• Current Inspection Programs and Industry Practices are Effective in Ensuring Conditions Leading to Structurally Significant Boric Acid Corrosion Do Not Occur

- Volumetric inspections to provide detection of flaws before leakage occurs

- Visual inspections to provide early detection of leakage

- Maintaining cleanliness of potentially affected areas

- Coolant system leakage monitoring

• Conclusion Supported By Operating Experience Over the Last 10 Years

© 2012 Electric Power Research Institute, Inc. All rights reserved. 8

TogetherShaping the Future of Electricity

© 2012 Electric Power Research Institute, Inc. All rights reserved. 9