ML062270077

Weld Overlay of Cast Material

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

Objectives

• Issue

• Identify cast locations associated with dissimilar metal butt welds

• Describe limitations

• Describe actions being taken

• Summarize

© 2006 Electric Power Research Institute, Inc. All rights reserved. 2

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 3

Locations

• Westinghouse Plants

- Reactor Coolant System

• 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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 4

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 5

Locations

• Babcock & Wilcocks (B&W)

- Reactor Coolant Pump (RCP) Suction and Discharge

• Only one unit in the fleet has been identified to date

© 2006 Electric Power Research Institute, Inc. All rights reserved. 6

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 7

Limitations 45 Degree SA 508 Cl 2 Nozzle SA 351 CF8M Cast SS Safe End

= Area of no coverage due to Cast SS material limitation Inputs used for coverage calculations:

Weld length - 28.11" OD Overlay thickness - .5" Original weld thickness - 1.40"

= Area of coverage in Circumferential scan direction Original weld width - 1.60" 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%

© 2006 Electric Power Research Institute, Inc. All rights reserved. 8

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

- RCP inlet and outlet welds

© 2006 Electric Power Research Institute, Inc. All rights reserved. 9

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 10

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 11

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

© 2006 Electric Power Research Institute, Inc. All rights reserved. 12