TY - JOUR
T1 - Effects of neutron flux on irradiation-induced hardening and defects in RPV steels studied by positron annihilation spectroscopy
AU - Toyama, T.
AU - Yamamoto, T.
AU - Ebisawa, N.
AU - Inoue, K.
AU - Nagai, Y.
AU - Odette, G. R.
N1 - Funding Information:
This work was partially supported by Grant-in-Aids for Scientific Research of MEXT (Nos. 26709073 and 17H03517 ). The authors thank M. Yamazaki and K. Suzuki for their support with hot laboratory work. Work at UCSB was funded by DOE NEUP grant, DE-AC07-05ID14517 .
Funding Information:
TY and GRO were funded by DOE NEUP grant, DE-AC07-05ID14517 .
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/4/15
Y1 - 2020/4/15
N2 - Neutron-flux effects on irradiation-induced hardening and microstructures in a reactor pressure vessel steel were studied. An A533B-type steel containing no Cu was neutron-irradiated with fluxes of 1 × 1014 n/cm2/s (high-flux) or 1 × 1012 n/cm2/s (low-flux) to the same fluence of approximately 3 × 1019 n/cm2, and the same temperature of approximately 290 °C. The recovery behavior of irradiation-induced defects and irradiation-hardening, ΔHv, was investigated by post-irradiation isochronal annealing from 275 to 450 °C. In both the high- and low-flux cases, the recovery behavior of ΔHv and the average positron lifetime, τave, corresponded well to the annealing, suggesting that defects in which positrons are trapped are the origin of irradiation-hardening. The values of ΔHv and τave in the high-flux sample started to recover at around 350 °C, while those in the low-flux sample started to recover at around 400 °C. Thus, in the high-flux sample, unstable defects transiently existing at low temperature but annealed out at around 350 °C, are indicated. Such defects are suggested to be defect-(Mn, Ni, Si) complexes, where the nature of the defect is that of a mono-vacancy and/or dislocation loops.
AB - Neutron-flux effects on irradiation-induced hardening and microstructures in a reactor pressure vessel steel were studied. An A533B-type steel containing no Cu was neutron-irradiated with fluxes of 1 × 1014 n/cm2/s (high-flux) or 1 × 1012 n/cm2/s (low-flux) to the same fluence of approximately 3 × 1019 n/cm2, and the same temperature of approximately 290 °C. The recovery behavior of irradiation-induced defects and irradiation-hardening, ΔHv, was investigated by post-irradiation isochronal annealing from 275 to 450 °C. In both the high- and low-flux cases, the recovery behavior of ΔHv and the average positron lifetime, τave, corresponded well to the annealing, suggesting that defects in which positrons are trapped are the origin of irradiation-hardening. The values of ΔHv and τave in the high-flux sample started to recover at around 350 °C, while those in the low-flux sample started to recover at around 400 °C. Thus, in the high-flux sample, unstable defects transiently existing at low temperature but annealed out at around 350 °C, are indicated. Such defects are suggested to be defect-(Mn, Ni, Si) complexes, where the nature of the defect is that of a mono-vacancy and/or dislocation loops.
KW - Embrittlement
KW - Neutron flux effects
KW - Positron annihilation
KW - Reactor pressure vessel steels
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U2 - 10.1016/j.jnucmat.2020.152041
DO - 10.1016/j.jnucmat.2020.152041
M3 - Article
AN - SCOPUS:85079056844
SN - 0022-3115
VL - 532
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
M1 - 152041
ER -