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Nathaniel G. Cofie
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Proceedings Papers

Technical Basis for Inspection Optimization and Deferral of PWR Pressurizer Component Examinations

Nathaniel G. Cofie, Dilip Dedhia, Scott T. Chesworth, Do Jun Shim, Robert Grizzi
Proc. ASME. PVP2024, Volume 1: Codes & Standards; Computer Technology & Bolted Joints, V001T01A076, July 28–August 2, 2024
Publisher: American Society of Mechanical Engineers
Paper No: PVP2024-124330
https://doi.org/10.1115/PVP2024-124330
View Paper titled, Technical Basis for Inspection Optimization and Deferral of PWR Pressurizer Component Examinations
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Topics: Inspection, Optimization, Pressurized water reactors, Welded joints, ASME Standards, Vessels, Fracture mechanics, Nozzles, Pressure, Reactor vessels
Proceedings Papers

Technical Basis for Inspection Optimization and Deferral of PWR Steam Generator Component Examinations

Nathaniel G. Cofie, Dilip Dedhia, Scott T. Chesworth, Do Jun Shim, Robert Grizzi
Proc. ASME. PVP2023, Volume 1: Codes & Standards, V001T01A052, July 16–21, 2023
Publisher: American Society of Mechanical Engineers
Paper No: PVP2023-105958
https://doi.org/10.1115/PVP2023-105958
View Paper titled, Technical Basis for Inspection Optimization and Deferral of PWR Steam Generator Component Examinations
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Topics: Boilers, Inspection, Optimization, Pressurized water reactors, ASME Standards, Pressure, Welded joints, Nozzles, Pressure vessels, Vessels
Proceedings Papers

Technical Basis for Revision to Code Case N-702

Matthew Walter, Kevin Wong, Nathaniel G. Cofie, Mo Uddin, Gary Dominguez
Proc. ASME. PVP2023, Volume 1: Codes & Standards, V001T01A004, July 16–21, 2023
Publisher: American Society of Mechanical Engineers
Paper No: PVP2023-107044
https://doi.org/10.1115/PVP2023-107044
View Paper titled, Technical Basis for Revision to Code Case N-702
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Topics: Acceptance criteria, ASME Standards, Boiling water reactors, Engineering standards, Failure, Feedwater, Fracture mechanics, In-service inspection, Inspection, Nozzles
Proceedings Papers

Application of Leak-Before-Break to Small Diameter Stainless Steel Piping in PWRs

Nathaniel G. Cofie, Dilip Dedhia, Do Jun Shim
Proc. ASME. PVP2021, Volume 4: Materials and Fabrication, V004T06A038, July 13–15, 2021
Publisher: American Society of Mechanical Engineers
Paper No: PVP2021-62368
https://doi.org/10.1115/PVP2021-62368
View Paper titled, Application of Leak-Before-Break to Small Diameter Stainless Steel Piping in PWRs
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Topics: Leakage, Leak-before-break, Pipes, Pressurized water reactors, Stainless steel
Proceedings Papers

Further Validation of the Technical Basis of Code Case N-838 for Flaw Tolerance Evaluation of CASS Piping

Timothy J. Griesbach, Dilip Dedhia, David O. Harris, Nathaniel G. Cofie, Aparna Alleshwaram, Kyle Amberge
Proc. ASME. PVP2015, Volume 1B: Codes and Standards, V01BT01A008, July 19–23, 2015
Publisher: American Society of Mechanical Engineers
Paper No: PVP2015-45191
https://doi.org/10.1115/PVP2015-45191
View Paper titled, Further Validation of the Technical Basis of Code Case N-838 for Flaw Tolerance Evaluation of CASS Piping
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Topics: Pipes, Fracture toughness, Fracture (Materials), Fracture mechanics, ASME Standards, Ferrites (Magnetic materials), Flow (Dynamics), High temperature, Stainless steel, Temperature
Proceedings Papers

Evaluation of a Weld Overlay Design for a Bimetallic Weld Using the Failure Assessment Diagram

Jens Heldt, Christopher Lohse, Nathaniel G. Cofie, Michael Lashley
Proc. ASME. PVP2014, Volume 1: Codes and Standards, V001T01A015, July 20–24, 2014
Publisher: American Society of Mechanical Engineers
Paper No: PVP2014-29111
https://doi.org/10.1115/PVP2014-29111
View Paper titled, Evaluation of a Weld Overlay Design for a Bimetallic Weld Using the Failure Assessment Diagram
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Topics: Design, Failure, Overlays (Materials engineering), Alloys, Stress, ASME Standards, Brittle fracture, Failure mechanisms, Fracture (Materials), Fracture (Process)
Proceedings Papers

The Influence of Flow Strength and Fracture Toughness on the Computed Reliability of Thermally Aged Grade CF-8M Cast Austenitic Stainless Steel Piping

Timothy J. Griesbach, Dilip Dedhia, David O. Harris, Nathaniel G. Cofie, Kyle Amberge, Aparna Alleshwaram
Proc. ASME. PVP2014, Volume 1: Codes and Standards, V001T01A052, July 20–24, 2014
Publisher: American Society of Mechanical Engineers
Paper No: PVP2014-28089
https://doi.org/10.1115/PVP2014-28089
View Paper titled, The Influence of Flow Strength and Fracture Toughness on the Computed Reliability of Thermally Aged Grade CF-8M Cast Austenitic Stainless Steel Piping
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Topics: Flow (Dynamics), Fracture toughness, Pipes, Reliability, Stainless steel, Probability, Fracture (Materials), Failure, Electromagnetic scattering, Fracture mechanics
Proceedings Papers

Basis for ASME Section XI Code Case for Flaw Tolerance Evaluation of CASS Piping

Timothy J. Griesbach, David O. Harris, Nathaniel G. Cofie, Alan Chockie, Dilip Dedhia
Proc. ASME. PVP2013, Volume 1A: Codes and Standards, V01AT01A057, July 14–18, 2013
Publisher: American Society of Mechanical Engineers
Paper No: PVP2013-97712
https://doi.org/10.1115/PVP2013-97712
View Paper titled, Basis for ASME Section XI Code Case for Flaw Tolerance Evaluation of CASS Piping
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Topics: Pipes, Nondestructive evaluation, Inspection, Piping systems, Stainless steel, ASME Standards, Failure, Ferrites (Magnetic materials), Fracture mechanics, Grain size
Journal Articles

Failure Bending Moment for Pipes With an Arbitrary-Shaped Circumferential Flaw

Yinsheng Li, Kunio Hasegawa, Akira Shibuya, Nathaniel G. Cofie
Journal: Journal of Pressure Vessel Technology
Publisher: ASME
Article Type: Research Papers
J. Pressure Vessel Technol. August 2011, 133(4): 041207.
https://doi.org/10.1115/1.4002927
Published Online: May 17, 2011
View Articletitled, Failure Bending Moment for Pipes With an Arbitrary-Shaped Circumferential Flaw
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Topics: Collapse, Failure, Pipes, Stress, Shapes
Journal Articles

Prediction of Collapse Stress for Pipes With Arbitrary Multiple Circumferential Surface Flaws

Yinsheng Li, Kunio Hasegawa, Kunio Onizawa, Nathaniel G. Cofie
Journal: Journal of Pressure Vessel Technology
Publisher: ASME
Article Type: Research Papers
J. Pressure Vessel Technol. December 2010, 132(6): 061204.
https://doi.org/10.1115/1.4001732
Published Online: October 14, 2010
View Articletitled, Prediction of Collapse Stress for Pipes With Arbitrary Multiple Circumferential Surface Flaws
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Topics: Collapse, Failure, Pipes, Stress, Symmetry (Physics)
Proceedings Papers

Post Weld Overlay Residual Stresses in Dissimilar Metal Welds Considering Various Butt Weld and Weld Repair Fabrication Sequences

Francis H. Ku, Christopher S. Lohse, David G. Dijamco, Charles J. Fourcade, Richard L. Bax, Nathaniel G. Cofie
Proc. ASME. PVP2009, Volume 6: Materials and Fabrication, Parts A and B, 569-576, July 26–30, 2009
Publisher: American Society of Mechanical Engineers
Paper No: PVP2009-78091
https://doi.org/10.1115/PVP2009-78091
View Paper titled, Post Weld Overlay Residual Stresses in Dissimilar Metal Welds Considering Various Butt Weld and Weld Repair Fabrication Sequences
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Topics: Maintenance, Manufacturing, Metals, Overlays (Materials engineering), Residual stresses, Welded joints, Simulation, Boiling water reactors, Nozzles, Pipes
Proceedings Papers

Sensitivity of Stress-Strain Parameters in Leak-Before-Break Evaluations

Nathaniel G. Cofie, Robert O. McGill, G. Angah Miessi, Jim Wu
Proc. ASME. PVP2007, Volume 3: Design and Analysis, 125-131, July 22–26, 2007
Publisher: American Society of Mechanical Engineers
Paper No: PVP2007-26425
https://doi.org/10.1115/PVP2007-26425
View Paper titled, Sensitivity of Stress-Strain Parameters in Leak-Before-Break Evaluations
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Topics: Leak-before-break, Stress, Leakage, Stress-strain curves, Fracture mechanics, Mechanical properties, Pipe sizes, Pipes
Proceedings Papers

Effect of Size of Butt Weld Repairs on Weld Overlay Residual Stresses

Carl R. Limpus, David G. Dijamco, Richard Bax, Nathaniel G. Cofie
Proc. ASME. PVP2007, Volume 1: Codes and Standards, 653-659, July 22–26, 2007
Publisher: American Society of Mechanical Engineers
Paper No: PVP2007-26636
https://doi.org/10.1115/PVP2007-26636
View Paper titled, Effect of Size of Butt Weld Repairs on Weld Overlay Residual Stresses
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Topics: Maintenance, Overlays (Materials engineering), Residual stresses, Compressive stress, Manufacturing, Modeling, Welded joints, Finite element analysis, Nuclear power stations, Pipes
Proceedings Papers

Technical Basis for Alternate Successive Inspection Requirements for Vessels and Piping Welds as Prescribed in Code Cases N-526 and N-735

Nathaniel G. Cofie, Peter C. Riccardella, John H. Merkle, Hien Do
Proc. ASME. PVP2008, Volume 1: Codes and Standards, 297-306, July 27–31, 2008
Publisher: American Society of Mechanical Engineers
Paper No: PVP2008-61412
https://doi.org/10.1115/PVP2008-61412
View Paper titled, Technical Basis for Alternate Successive Inspection Requirements for Vessels and Piping Welds as Prescribed in Code Cases N-526 and N-735
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Topics: Inspection, Pipes, Vessels, Welded joints, Acceptance criteria, Stress, ASME Standards, Flow (Dynamics), In-service inspection, Leakage
Proceedings Papers

Effectiveness of Stainless Steel Buffer Layer to Address Hot Cracking During Weld Overlay Repair of Dissimilar Metal Alloy 82/182 Welds With Stainless Steel Piping

Nathaniel G. Cofie, Richard E. Smith, Richard L. Bax, Christopher S. Lohse, Bill Hermanns, Jerry Valsvig, Luis D. Yepez, Dixon Parker
Proc. ASME. PVP2008, Volume 1: Codes and Standards, 43-52, July 27–31, 2008
Publisher: American Society of Mechanical Engineers
Paper No: PVP2008-61411
https://doi.org/10.1115/PVP2008-61411
View Paper titled, Effectiveness of Stainless Steel Buffer Layer to Address Hot Cracking During Weld Overlay Repair of Dissimilar Metal Alloy 82/182 Welds With Stainless Steel Piping
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Topics: Alloys, Cracking (Materials), Fracture (Process), Maintenance, Overlays (Materials engineering), Pipes, Polishing equipment, Stainless steel, Welded joints, Metals
Proceedings Papers

Net Section Plastic Collapse Analysis of Two-Layered Materials and Application to Weld Overlay Design

Arthur F. Deardorff, Nathaniel G. Cofie, David G. Dijamco, Aparna Chintapalli
Proc. ASME. PVP2006-ICPVT-11, Volume 1: Codes and Standards, 67-75, July 23–27, 2006
Publisher: American Society of Mechanical Engineers
Paper No: PVP2006-ICPVT-11-93454
https://doi.org/10.1115/PVP2006-ICPVT-11-93454
View Paper titled, Net Section Plastic Collapse Analysis of Two-Layered Materials and Application to Weld Overlay Design
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Topics: Collapse, Design, Overlays (Materials engineering), Stress, Pipes, Fracture toughness, Maintenance, Boiling water reactors, Pressurized water reactors, Thermal expansion
Proceedings Papers

Residual Stress Analysis of a Bimetallic Weld Subjected to Stress Improvement and Weld Overlay Repair

Nathaniel G. Cofie, David G. Dijamco, Carl R. Limpus, James J. Cirilli, Heather M. Malikowski, Allen T. Roberts
Proc. ASME. PVP2006-ICPVT-11, Volume 3: Design and Analysis, 735-742, July 23–27, 2006
Publisher: American Society of Mechanical Engineers
Paper No: PVP2006-ICPVT-11-93455
https://doi.org/10.1115/PVP2006-ICPVT-11-93455
View Paper titled, Residual Stress Analysis of a Bimetallic Weld Subjected to Stress Improvement and Weld Overlay Repair
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Topics: Maintenance, Overlays (Materials engineering), Stress, Stress analysis (Engineering), Welded joints, Boiling water reactors, Alloys, Compressive stress, Cycles, Inspection
Proceedings Papers

Technical Basis for Proposed Revisions to ASME Code Case N-513 and Some Applications to Moderate Energy Piping

Robert O. McGill, Nathaniel G. Cofie, Russell C. Cipolla, Guy DeBoo
Proc. ASME. PVP2006-ICPVT-11, Volume 1: Codes and Standards, 53-60, July 23–27, 2006
Publisher: American Society of Mechanical Engineers
Paper No: PVP2006-ICPVT-11-93428
https://doi.org/10.1115/PVP2006-ICPVT-11-93428
View Paper titled, Technical Basis for Proposed Revisions to ASME Code Case N-513 and Some Applications to Moderate Energy Piping
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Topics: ASME Standards, Pipes, Safety