Neutron and thermal embrittlement of RPV steels: An overview

Randy K. Nanstad, Mikhail A. Sokolov, Susan R. Ortner, Paul D. Styman

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

8 Scopus citations

Abstract

Because the reactor pressure vessel (RPV) represents the first structural line of defense against the release of radiation to the public, the design and fabrication of the RPV for any nuclear reactor facility is performed at very high standards in accordance with consensus codes that are based on mechanical and physical properties of the steels used to construct the vessel. Nuclear RPVs may weigh up to 800 tons with wall thicknesses up to approximately 330 mm and are clad on the inside with stainless-steel weld metal and given a final post-weld heat treatment. The RPV is a unique structural component in that it operates under high pressures and temperatures and is exposed to relatively high neutron radiation. Although typical RPV steels and welds have excellent fracture toughness at room temperature and above when put into service, the degrading effects of high-energy neutron irradiation can cause levels of irradiation-induced embrittlement in radiation-sensitive materials of concern for the structural integrity of the RPV. In recent decades, remarkable progress has been made in developing a mechanistic understanding of irradiation embrittlement. This progress includes developing physically based and statistically calibrated models of Charpy V-notch-indexed transition temperature shifts based on results from RPV surveillance programs complemented by significant results from comprehensive research experiments performed in test reactors. In addition, advances in elastic-plastic fracture mechanics allow for a relatively small number of relatively small specimens to characterize the fracture toughness of RPV steels with statistical confidence. This paper presents a review of the primary mechanical properties, test procedures, examples of applicable codes and standards, and specimen types used to characterize RPV steels and welds, the effects of neutron irradiation on those most relevant mechanical properties, and a brief review of the effects of thermal aging on RPV materials. The paper closes with a summary.

Original languageEnglish
Title of host publicationInternational Review of Nuclear Reactor Pressure Vessel Surveillance Programs
EditorsMilan Brumovsky, William L. Server
PublisherASTM International
Pages68-106
Number of pages39
ISBN (Electronic)9780803176515
DOIs
StatePublished - 2018
EventWorkshop on Nuclear Reactor Pressure Vessel Surveillance Programs - Chicago, United States
Duration: Jun 29 2016 → …

Publication series

NameASTM Special Technical Publication
VolumeSTP 1603
ISSN (Print)0066-0558

Conference

ConferenceWorkshop on Nuclear Reactor Pressure Vessel Surveillance Programs
Country/TerritoryUnited States
CityChicago
Period06/29/16 → …

Funding

This manuscript was authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). The authors wish to express their appreciation for the financial support provided by the U.S. Department of Energy Light-Water Reactor Sustainability (LWRS) Program (to RKN and MAS) and the U.K. Office of Nuclear Regulation (to SRO and PDS). We also appreciate management support from Keith Leonard and Stephen Druce.

FundersFunder number
U.S. Department of EnergyDE-AC05-00OR22725

    Keywords

    • Charpy impact
    • Embrittlement
    • Fracture toughness
    • Irradiation
    • Master Curve
    • Mechanical properties
    • NDT
    • Neutron
    • Tensile strength
    • Thermal aging

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