ML062270077
| ML062270077 | |
| Person / Time | |
|---|---|
| Site: | Palisades, Palo Verde, Waterford, San Onofre  |
| Issue date: | 05/23/2006 |
| From: | Naujock D NRC/NRR/ADES/DCI/CNPB |
| To: | Chan T NRC/NRR/ADES/DCI/CNPB |
| Naujock D, DCI/CPNB, 415-2767 | |
| References | |
| TAC MD0571 | |
| Download: ML062270077 (12) | |
Text
Weld Overlay of Cast Material Carl Latiolais Program Manager PDI Performance Demonstration
2
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Objectives
- Issue
- Identify cast locations associated with dissimilar metal butt welds
- Describe limitations
- Describe actions being taken
- Summarize
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© 2006 Electric Power Research Institute, Inc. All rights reserved.
Issue
- Several dissimilar metal weld butt welds are joined to cast components
- If these welds are overlaid the design will require that the overlay cover cast base material
- There has been one application of this type of overlay already
- Review of configuration drawings from several plants indicate this type of overlay may be required for several configurations that present in the fleet
- Presently, there are no PDI qualified procedures available to examine the cast base material covered by these weld overlays
- Appendix VIII, Supplement 11 does not address overlay over cast materials
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© 2006 Electric Power Research Institute, Inc. All rights reserved.
Locations
- Westinghouse Plants
- All butt welds connecting the cold legs to both the steam generator and RPV
- Some butt welds connecting the cold legs to both steam generator and RPV
- Large diameter 29.00 to 31.00
- Quite thick 2.5 to 3.0
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© 2006 Electric Power Research Institute, Inc. All rights reserved.
Locations
- Combustion Engineering (CE) Plants
- Majority of welds greater than 6.0 in diameter in most CE units have cast CF8M safe-ends
- Safety Relief (2 Units)
- Waterford
- San Onofre
- Surge Lines at the Hot Leg and Pressurizer
- All units with the exception of Palo Verde and Palisades
- Shut Down Cooling
- All units with the exception of Palo Verde and Palisades
- Safety Injection
- All units with the exception of Palo Verde and Palisades
- Reactor Coolant Pump (RCP) Suction and Discharge
- All units with the exception of Palo Verde and Palisades
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© 2006 Electric Power Research Institute, Inc. All rights reserved.
Locations
- Babcock & Wilcocks (B&W)
- Reactor Coolant Pump (RCP) Suction and Discharge
- Only one unit in the fleet has been identified to date
7
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Limitations
- The only area that is not examined with qualified techniques is the cast base material adjacent to the original butt weld under the overlay
- Volume is dependant on the thickness of the base material
- Upper 25%
- Presently the qualified techniques are capable of;
- Examining 100% of the weld overlay material
- Examining 100% of the weld overlay to base material and weld to assure bonding
- Examining 100% of the susceptible inconel material contained in the examination volume
- Determining if any flaws had propagated into the overlay from the cast base material
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© 2006 Electric Power Research Institute, Inc. All rights reserved.
Limitations SA 351 CF8M Cast SS Safe End SA 508 Cl 2 Nozzle 45 Degree Inputs used for coverage calculations:
Weld length - 28.11" OD Overlay thickness -.5" Original weld thickness - 1.40" Original weld width - 1.60"
= Area of no coverage due to Cast SS material limitation
= Area of coverage in Circumferential scan direction Volume required for complete examination = 248.48 cubic inches Volume obtained in Circumferential scan direction= 56.78 cubic inches Total volume obtained: 56.78 cubic inches or 91.40%
9
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Work Underway
- A limited amount of funding has been provided to evaluate the capabilities of examining the cast material on the thinner wall thicknesses
- Safety Relief
- Pressurizer Surge
- Hot Leg Surge
- Safety Injection
- Shut Down Cooling
- Additional proposals have been presented that will expand the project if acceptable results are obtained to the larger component with increased wall thickness
10
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Work Underway
- Micrograph information has been requested
- Calibration blocks with cast safe-ends made of same material as what is installed in the plants
- Scrap material of the same vintage
- This information will be used to;
- Order similar material for mock-ups
- Evaluate the effects on the ultrasound
- Detection capability before weld overlay will also be evaluated
11
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Long Term Plan
- If we are successful on thinner material work will be expanded to thicker components such as the RCP
- Code work will start to address qualification
- Complexity of code changes will be based on the changes in techniques required to do successful examination
- If current qualified techniques are capable of achieving acceptable results very few changes are needed
- If techniques are not successful a technical basis can be made that shows examination of this area is not critical to the design and function of the overlay
- No flaw mechanism
- In most cases greater than 90% of the volume can be examined without taking credit for this area
- No structural credit taken in the design of the overlay for the area not examined
12
© 2006 Electric Power Research Institute, Inc. All rights reserved.
Summary
- No qualified procedures are available for the examination of weld overlays over cast components
- Work is underway to evaluate current techniques to determine if the examination is possible
- If successful a code case will be drafted to address examination and qualification