SYMPOSIA PAPER Published: 01 June 2023
STP164720220077

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

Source

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).

Author Information

Nanstad, Randy, K.
Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN, US
Almirall, Nathan
Dept. of Mechanical Engineering, University of California, Santa Barbara, CA, US
Wells, Peter
Dept. of Mechanical Engineering, University of California, Santa Barbara, CA, US
Server, William, L.
ATI Consulting, Black Mountain, NC, US
Sokolov, Mikhail, A.
Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, TN, US
Long, Elliot, J.
Electric Power Research Institute, Palo Alto, CA, US
Odette, G., Robert
Dept. of Mechanical Engineering, University of California, Santa Barbara, CA, US
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Pages: 48–64
DOI: 10.1520/STP164720220077
ISBN-EB: 978-0-8031-7742-0
ISBN-13: 978-0-8031-7741-3