On High-Fluence Irradiation Hardening of Nine RPV Surveillance Steels in the UCSB ATR-2 Experiment: Implications for Extended-Life Embrittlement Predictions

Randy K. Nanstad, Nathan Almirall, Peter Wells, William L. Server, Mikhail A. Sokolov, Elliot J. Long, G. Robert Odette

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

1 Scopus citations

Abstract

Nine archival reactor pressure vessel (RPV) surveillance steels from commercial nuclear power plants were irradiated in the University of California, Santa Barbara Advanced Test Reactor 2 (ATR-2) experiment to evaluate irradiation embrittlement under low-flux surveillance capsule versus higher flux test reactor (ATR-2) conditions. The postirradiation measurements of irradiation hardening, measured as increases in yield stress (Δσy), and corresponding conversions of Δσy to Charpy V-notch 41-J transition temperature shifts (ΔTc) are compared with various embrittlement trend curve (ETC) model predictions for the nine steels. Tensile and converted shear punch and microhardness measurements of Δσy generally show a continuing increase between intermediate and high ATR-2 fluences. The Eason-Odette-Nanstad-Yamamoto and ASTM E900 ETC models underpredict embrittlement at the ATR-2 irradiation condition: irradiation temperature (Ti) of 292°C, neutron fluence (ϕt) of 1.4 × 1020 n/cm2 (E > 1 MeV), and neutron flux (ϕ) of 3.68 × 1012 n/cm2-s. On average, the French FIS and Japanese JAEC ETCs slightly overpredict the ATR-2 data. The increase in Δσy with higher fluence is primarily due to Ni-Mn-Si precipitates, which slowly evolve in both nearly copper-free and copper-bearing steels. Finally, a new Odette-Wells-Almirall-Yamamoto embrittlement model is shown that yields good predictions for the nine steels at high fluences (ϕt > 5.5 × 1019 n/cm2).

Original languageEnglish
Title of host publicationRadiation Embrittlement Trend Curves and Equations and Their Use for RPV Integrity Evaluations
EditorsWilliam L. Server, Milan Brumovsky, Mark Kirk
PublisherASTM International
Pages48-64
Number of pages17
ISBN (Electronic)9780803177413
DOIs
StatePublished - 2023
Event2022 Symposium on Radiation Embrittlement Trend Curves and Equations and Their Use for RPV Integrity Evaluations - Prague, Czech Republic
Duration: Apr 19 2022Apr 22 2022

Publication series

NameASTM Special Technical Publication
VolumeSTP 1647
ISSN (Print)0066-0558

Conference

Conference2022 Symposium on Radiation Embrittlement Trend Curves and Equations and Their Use for RPV Integrity Evaluations
Country/TerritoryCzech Republic
CityPrague
Period04/19/2204/22/22

Funding

The co-authors wish to acknowledge and thank our recently departed lead author, Dr. Randy K. Nanstad, for his enumerable seminal contributions to nuclear reactor pressure vessel research. The large body of knowledge he created has supported the safe, long-term operation of nuclear power plants on an international basis. More generally, Randy’s research also led to major improvements in our understanding of irradiation effects, fracture mechanics, and structural materials. Bill Server acquired the nine surveillance steels studied in this paper under EPRI funding, and Randy authored a report on the technical findings under EPRI sponsorship. EPRI also partially supported the postirradiation examinations of the nine steels. The UCSB ATR-2 irradiation was sponsored by the U.S. Department of Energy (DOE) National Scientific Users Program and was carried out as an UCSB-INL collaboration; we are very grateful for the outstanding ATR-2 INL team led by Dr. Mitch Meyer. Under the sponsorship of the U.S. DOE Light Water Reactor Sustainability Program, postirradiation characterization studies were mainly carried at UCSB by Drs. Peter Wells and Nathan Almirall, with outstanding technical support from David Gragg. A wide variety of ORNL contributions led to the success of this research. This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. DOE.

Keywords

  • flux effects
  • high-fluence data
  • microhardness
  • radiation embrittlement
  • shear punch
  • transition temperature shift correlations

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