Abstract
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, providing insight into tungsten hardening and embrittlement due to irradiation-induced matrix defects.
Original language | English |
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Pages (from-to) | 278-289 |
Number of pages | 12 |
Journal | Journal of Nuclear Materials |
Volume | 470 |
DOIs | |
State | Published - Mar 2016 |
Funding
The aid and technical insight of Prof. Steven Zinkle and Prof. Donghua Xu at University of Tennessee–Knoxville and Drs. Lauren Garrison, Philip Edmondson, and Kiran Kumar Nimishakavi at ORNL are gratefully acknowledged. We thank Dr. Thak Sang Byun at Pacific Northwest National Laboratory for kindly providing the tensile test data. The work presented in this paper was partially supported by Laboratory Directed R&D funds at ORNL . The research was also sponsored by the US Department of Energy Office of Fusion Energy Science under grants DOE-DE-SC0006661 with University of Tennessee–Knoxville and DE-AC05-00OR22725 with UT-Battelle LLC , and by the US-Japan PHENIX project under contract NFE-13-04478 , with UT-Battelle LLC . This research was supported by the U.S. Department of Energy, Office of Science, Fusion Energy Sciences . This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).