Abstract
The impact of the neutron-displacement damage on phase stability and microstructure of substoichiometric yttrium dihydrides (YHx, x <2) were investigated to assess their use as solid moderator in high-temperature nuclear reactors. YHx specimens were, thus, subjected to neutron irradiations in the range of 0.1–2 displacements per yttrium atom (dpa-Y) in the temperature range of 536–878°C at the Oak Ridge National Laboratory's (ORNL's) High Flux Isotope Reactor (HFIR). YHx specimens were initially prepared at stoichiometry (H/Y) ratios of 1.69 and 1.83. HFIR-irradiated specimens were characterized by variety of techniques to investigate H retention characteristics including dimensional analysis, optical microscopy, scanning electron microscopy electron back scatter diffraction (EBSD), transmission electron microscopy, thermal desorption spectroscopy (TDS), and high-energy x-ray diffraction (HE-XRD) characterizations. Overall, YHx exhibited notable structural and phase stability under short-term neutron-irradiation, except for the samples with significant silicon carbide (SiC) interaction at high doses and temperatures. Basic dimensional and mass measurements were misleading for accurate assessment of H retention, as confirmed by EBSD phase maps, XRD line profiles, and TDS signals. Thus, it was discussed that a robust H retention metric is needed to assess irradiated hydrides. Nanoscale cavities were observed as a result of the neutron irradiation in all samples. Although no clear impact of dose and irradiation temperature was determined, the initial H/Y ratio had an impact on the cavity number density where low H/Y specimens had high-resistance to cavity formation. The Y-vacancy cluster formation at the collision stage of the displacement cascade and their stabilization by H were considered to be the likely underlying mechanisms for the observed cavity microstructure.
| Original language | English |
|---|---|
| Article number | 155374 |
| Journal | Journal of Nuclear Materials |
| Volume | 603 |
| DOIs | |
| State | Published - Jan 2025 |
Funding
The assistance and technical insights of Hsin Wang, Stephanie Curlin, and Bill Comings, at Oak Ridge National Laboratory (ORNL) are gratefully acknowledged. Andrew Nelson and T.S. Byun performed thorough reviews of the manuscript. The efforts of ORNL's staff at the Irradiated Materials Examination and Testing (IMET) hot cell facility and the Low Activation Materials Design and Analysis Laboratory (LAMDA) are gratefully acknowledged. This work was supported by the Advanced Materials and Manufacturing Technologies of the US Department of Energy Office of Nuclear Energy, formerly the Transformational Challenge Reactor program. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by ORNL. XRD experiments and analysis (D. Sprouster) were supported by the DOE Office of Fusion Energy Sciences under grant DESC0018322 with the Research Foundation for the State University of New York at Stony Brook. This research used The Pair Distribution Function beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704 . *This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE 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).
Keywords
- Cavity formation
- Electron back scatter diffraction
- Irradiation-induced defects
- Metal hydrides
- Neutron irradiation
- Neutron-irradiation
- Post-irradiation examination
- Transmission electron microscopy
- Yttrium hydride