SYMPOSIA PAPER Published: 01 June 2023

Improved Upper-Shelf Energy Prediction Model and Implications for the U.S. PWR Fleet


U.S. 10 CFR Part 50, Appendix G, “Fracture Toughness Requirements,” specifies that vessel materials must maintain a Charpy upper-shelf energy (USE) of no less than 68 J (50 ft-lb) throughout the life of the vessel. If the USE is projected to fall below 68 J, a fracture-mechanics equivalent-margin analysis (EMA) must be performed according to ASME Section XI, Appendix K to demonstrate the margins of safety against fracture that are equivalent to those required by ASME Section XI, Appendix G. Irradiated USE is typically calculated using Regulatory Guide 1.99, Revision 2 methodology, which has been the subject of an adequacy review by the U.S. Nuclear Regulatory Commission. Modern improved USE prediction models have been developed and published. This paper considers improved USE predictions, high-fluence fracture-toughness data, and completed EMAs and draws implications for the U.S. pressurized water reactor fleet considering extended operation.

Author Information

Hall, J., Brian
Westinghouse Electric Company, LLC, Pittsburgh, PA, US
Hall, Gordon, Z.
Westinghouse Electric Company, LLC, Pittsburgh, PA, US
Long, Elliot, J.
Electric Power Research Institute, Inc., Palo Alto, CA, US
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Pages: 159–173
DOI: 10.1520/STP164720220066
ISBN-EB: 978-0-8031-7742-0
ISBN-13: 978-0-8031-7741-3