ML120690171
| 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 | |
| Shared Package | |
| ML120690160 | List: |
| References | |
| Download: ML120690171 (9) | |
Text
NRC/EPRI MRP Meeting Rockville, MD February 29, 2012 William Sims Entergy Boric Acid Corrosion Testing Program: Industry Perspective
2
© 2012 Electric Power Research Institute, Inc. All rights reserved.
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
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© 2012 Electric Power Research Institute, Inc. All rights reserved.
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
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© 2012 Electric Power Research Institute, Inc. All rights reserved.
Background (3/3)
- Conclusions from Results:
- Results support current inspection intervals:
structurally significant wastage will not occur between inspections at currently prescribed intervals
- Results support current inspection methods: visual inspection is a reliable technique for detection of leakage, even at low flow rates BMN Test 5: 0.006 GPM leakage 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 /> Low Alloy Steel Alloy 600 Tube
5
© 2012 Electric Power Research Institute, Inc. All rights reserved.
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
- Not structurally significant CRDM Tests at 0.01 GPM; 1500 ppm B Volumetric corrosion rate 0.10 to 2.1 in3/yr 32 day test = 35 lb boric acid
6
© 2012 Electric Power Research Institute, Inc. All rights reserved.
Boric Acid Corrosion Test Program Timeline
- 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 BAC Guidebook Rev 2 Issued 2011 MRP BAC Program Testing Complete 2006 ASME Code Case N-729-1 Issued 2009 ASME Code Case N-722-1 Issued 2004 MRP BAC Test Program Begins 2004 MRP-117 Issued 2003 STP BMN Leakage 2003 EA-03-009 Issued 2002 Davis Besse CRDM Event 1991 Bugey 3 First Reported CRDM Cracking IMT Gap P-AS-01 Closed
7
© 2012 Electric Power Research Institute, Inc. All rights reserved.
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
8
© 2012 Electric Power Research Institute, Inc. All rights reserved.
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
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© 2012 Electric Power Research Institute, Inc. All rights reserved.
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