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Title: Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation

The tungsten plasma-facing components of fusion reactors will experience an extreme environment including high temperature, intense particle fluxes of gas atoms, high-energy neutron irradiation, and significant cyclic stress loading. Irradiation-induced defect accumulation resulting in severe thermo-mechanical property degradation is expected. For this reason, and because of the lack of relevant fusion neutron sources, the fundamentals of tungsten radiation damage must be understood through coordinated mixed-spectrum fission reactor irradiation experiments and modeling. In this study, high-purity (110) single-crystal tungsten was examined by positron annihilation spectroscopy and transmission electron microscopy following low-temperature (~90 °C) and low-dose (0.006 and 0.03 dpa) mixed-spectrum neutron irradiation and subsequent isochronal annealing at 400, 500, 650, 800, 1000, 1150, and 1300 °C. The results provide insights into microstructural and defect evolution, thus identifying the mechanisms of different annealing behavior. Following 1 h annealing, ex situ characterization of vacancy defects using positron lifetime spectroscopy and coincidence Doppler broadening was performed. The vacancy cluster size distributions indicated intense vacancy clustering at 400 °C with significant damage recovery around 1000 °C. Coincidence Doppler broadening measurements confirm the trend of the vacancy defect evolution, and the S–W plots indicate that only a single type of vacancy cluster is present. Furthermore, transmissionmore » electron microscopy observations at selected annealing conditions provide supplemental information on dislocation loop populations and visible void formation. This microstructural information is consistent with the measured irradiation-induced hardening at each annealing stage. This provides insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Tohoku Univ., Sendai (Japan)
  3. Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 470; Journal ID: ISSN 0022-3115
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
OSTI Identifier:
1234347
Alternate Identifier(s):
OSTI ID: 1252047

Hu, Xunxiang, Koyanagi, Takaaki, Fukuda, Makoto, Katoh, Yutai, Wirth, Brian D, and Snead, Lance Lewis. Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation. United States: N. p., Web. doi:10.1016/j.jnucmat.2015.12.040.
Hu, Xunxiang, Koyanagi, Takaaki, Fukuda, Makoto, Katoh, Yutai, Wirth, Brian D, & Snead, Lance Lewis. Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation. United States. doi:10.1016/j.jnucmat.2015.12.040.
Hu, Xunxiang, Koyanagi, Takaaki, Fukuda, Makoto, Katoh, Yutai, Wirth, Brian D, and Snead, Lance Lewis. 2016. "Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation". United States. doi:10.1016/j.jnucmat.2015.12.040. https://www.osti.gov/servlets/purl/1234347.
@article{osti_1234347,
title = {Defect evolution in single crystalline tungsten following low temperature and low dose neutron irradiation},
author = {Hu, Xunxiang and Koyanagi, Takaaki and Fukuda, Makoto and Katoh, Yutai and Wirth, Brian D and Snead, Lance Lewis},
abstractNote = {The tungsten plasma-facing components of fusion reactors will experience an extreme environment including high temperature, intense particle fluxes of gas atoms, high-energy neutron irradiation, and significant cyclic stress loading. Irradiation-induced defect accumulation resulting in severe thermo-mechanical property degradation is expected. For this reason, and because of the lack of relevant fusion neutron sources, the fundamentals of tungsten radiation damage must be understood through coordinated mixed-spectrum fission reactor irradiation experiments and modeling. In this study, high-purity (110) single-crystal tungsten was examined by positron annihilation spectroscopy and transmission electron microscopy following low-temperature (~90 °C) and low-dose (0.006 and 0.03 dpa) mixed-spectrum neutron irradiation and subsequent isochronal annealing at 400, 500, 650, 800, 1000, 1150, and 1300 °C. The results provide insights into microstructural and defect evolution, thus identifying the mechanisms of different annealing behavior. Following 1 h annealing, ex situ characterization of vacancy defects using positron lifetime spectroscopy and coincidence Doppler broadening was performed. The vacancy cluster size distributions indicated intense vacancy clustering at 400 °C with significant damage recovery around 1000 °C. Coincidence Doppler broadening measurements confirm the trend of the vacancy defect evolution, and the S–W plots indicate that only a single type of vacancy cluster is present. Furthermore, transmission electron microscopy observations at selected annealing conditions provide supplemental information on dislocation loop populations and visible void formation. This microstructural information is consistent with the measured irradiation-induced hardening at each annealing stage. This provides insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.},
doi = {10.1016/j.jnucmat.2015.12.040},
journal = {Journal of Nuclear Materials},
number = ,
volume = 470,
place = {United States},
year = {2016},
month = {1}
}