SYMPOSIA PAPER Published: 01 June 2023

History and Development of U.S. NRC Regulatory Guide 1.99


An overview is provided detailing the basis and evolution of U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.99 from initial publication to the current second revision. This regulatory guide concerns the prediction of reactor vessel aging effects due to neutron irradiation, including effects on RTNDT and upper-shelf energy. The core of this regulatory guide is an embrittlement trend curve supporting the prediction of material properties in relation to the material chemistry and neutron fluence received. The results of the 2019 U.S. NRC assessment of the regulatory guide are then presented. Finally, we discuss preliminary work supporting potential alternatives to the embrittlement trend curve present in the current revision of the regulatory guide.

Author Information

Widrevitz, Daniel, S.
Office of Nuclear Reactor Regulation, Washington, DC, US
Poehler, Jeffrey, C.
Office of Nuclear Regulatory Research, Washington, DC, US
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Pages: 398–416
DOI: 10.1520/STP164720220041
ISBN-EB: 978-0-8031-7742-0
ISBN-13: 978-0-8031-7741-3