Fabian Naab

experiment to a single set of irradiation parameters (e.g., dose, fluence, injection rate, temperature etc.). Despite being capable of achieving damage rates up to three orders of magnitude higher than neutron irradiation, its overall sample throughput remains low due to the need to conduct separate irradiations for each unique parameter set. To address these limitations, a novel capability has been developed at the Michigan Ion Beam Laboratory (MIBL), enabling for the creation of two-dimensional lateral ion implantation gradients using recently installed motorized-controlled ion beam shutters. This advancement can generate a wide scope of the two dimensional (H+, He2+) implantation parameter space within a single sample. Integration of this new capability enables dual- and triple-ion beam experiments to be performed with full user control over not only the ion implantation depth profile, but also over the lateral imposed concentration gradients, thus providing researchers with a high-throughput means for material testing under various irradiation conditions. Furthermore, the recent installation of a microbeam in the ion-beam analysis (IBA) target station now allows for probing these concentration gradients in irradiated alloys with unprecedently high spatial resolutions. These developments promise to significantly improve ion irradiation capabilities, offering researchers a robust and high-throughput method to efficiently investigate candidate alloys for both advanced fission and fusion reactor applications, in both a time- and cost-effective manner. This paper demonstrates all the above through showcasing detailed implantation profiling and swelling characterization conducted over the lateral gradients imposed on single crystal Si and the fusion candidate alloy F82H-IEA.

High moderation per unit volume solid moderator materials like yttrium hydride (YHx) are necessary for compact nuclear microreactors. However, the phase stability and hydrogen transport processes of YHx under high-temperature irradiation are largely unknown. Proton irradiation was conducted on YHx at 300 °C and 580 °C to 0.2 dpa using 1 MeV or 2 MeV protons in a high-vacuum environment. The hydrogen concentration was determined before and after irradiation using elastic recoil detection analysis, and microstructural evolution was examined via post-irradiation scanning transmission electron microscopy and Raman spectroscopy. Dislocation loops and cavities were observed in all conditions; their distribution was correlated with the bombarding proton energy and ion irradiation temperature. This work revealed that hydrogen retention is proportional to the formation of traps for hydrogen gas atoms and identified pathways for hydrogen release. The relative contributions of bulk or fast diffusion paths, such as grain boundaries, delamination boundaries, and stacking faults are discussed; the primary mechanisms of hydrogen loss are likely based on diffusion, ruling out artefacts of the experimental design. The study suggests proton irradiation may be a strong surrogate to study hydrogen transport in hydride moderator materials under irradiation.

An international collaboration was established as a Coordinated Research Project (CRP) under the IAEA and entitled Accelerator Simulation and Theoretical Modelling of Radiation Effects-II (SMoRE-II). It was created to determine, by way of a Round Robin process, the degree to which ion irradiations produced the same irradiated microstructure when conducted in different labs on the same alloy and provided with the same irradiation protocol. The Round Robin consisted of 13 participating organizations from 9 IAEA member states with ion irradiations conducted at all CRP partner sites on samples of a single alloy (T91) from a single billet with the same thermal-mechanical history, and with a specific protocol for conducting the irradiations. Of the 14 parameters specified for the ion irradiations, only 1 of 12 facilities was able to follow the protocol exactly. Major differences included vacuum pressure, temperature measurement and control, beam mode (raster-scanning vs. steady beam), and dosimetry. The microstructure features characterized were the sizes and number densities of cavities, dislocation loops, precipitates, and the radiation induced segregation. While loop size and number density appeared to correlate with carbon content, no such correlation was identified for cavities. The divergence from the irradiation protocol undoubtedly affected the irradiated microstructure with carbon contamination occurring in most cases. The cavity, dislocation loop and precipitate microstructures all fell within the range of that in the literature. Additionally, a T91 sample that was irradiated to 47 dpa at 376°C in the BOR-60 reactor was selected for comparison of the microstructure to those in the Round Robin study.