Title: On the use of charged particles to characterize precipitation in irradiated reactor pressure vessel steels with a wide range of compositions

Abstract

Nuclear reactor lifetimes may be limited by nano-scale Cu-Mn-Ni-Si precipitates (CRPs and MNSPs) that form under neutron irradiation (NI) of pressure vessel (RPV) steels, resulting in hardening and ductile to brittle transition temperature increases (embrittlement). Physical models of embrittlement must be based on characterization of precipitation as a function of the combination of metallurgical and irradiation variables. Here we focus on rapid and convenient charged particle irradiations (CPI) to both: a) compare to precipitates formed in NI; and, b) use CPI to efficiently explore precipitation in steels with a very wide range of compositions. Atom probe tomography (APT) comparisons show NI and CPI for similar bulk steel solute contents yield nearly the same precipitate compositions, albeit with some differences in their number density, size and volume fraction (f) dose (dpa) dependence. Yet, the overall precipitate evolutions are very similar. Advanced high Ni (>3 wt%) RPV steels, with superior unirradiated properties, were also investigated at high CPI dpa. For typical Mn contents, MNSPs have Ni₁₆Mn₆Si₇ or Ni₃Mn₂Si phase type compositions, with f values that are close to the equilibrium phase separated values. In contrast, in steels with very low Mn and high Ni, Ni_2-3Si silicide phase type precipitate compositions are observed;more » and when Ni is low, the precipitate compositions are close to the MnSi phase field. Low Mn significantly reduces, but does not eliminate, precipitation in high Ni steels. A comparison of dispersed barrier model predictions with measured hardening data suggests that the Ni-Si dominated precipitates are weaker dislocation obstacles than the G phase type MNSPs.« less

Authors:

Almirall, Nathan ^[1]; Wells, Peter ^[1]; Yamamoto, Takuya ^[1]; Yabuuchi, Kiyohiro ^[2]; Kimura, Akihiko ^[2]; Odette, GR ^[1]

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+ Show Author Affiliations

1. Univ. of California, Santa Barbara, CA (United States)
2. Kyoto Univ. (Japan)

Publication Date:

Fri May 01 00:00:00 EDT 2020

Research Org.:

Idaho National Laboratory (INL), Idaho Falls, ID (United States); Univ. of California, Santa Barbara, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Nuclear Energy (NE)

OSTI Identifier:

1618333

Alternate Identifier(s):

OSTI ID: 1618349

Grant/Contract Number:  

AC07-05ID14517; AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Nuclear Materials

Additional Journal Information:

Journal Volume: 536; Journal Issue: 1; Journal ID: ISSN 0022-3115

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; 42 ENGINEERING; 22 GENERAL STUDIES OF NUCLEAR REACTORS; Reactor pressure vessel steels; Charged particle irradiation; Atom probe tomography; Irradiation embrittlement; Nano-scale precipitates; Thermodynamic models