Radiation-induced segregation and precipitation in highly neutron-irradiated Be

This work presents a systematic analytical transmission electron microscopy (TEM) investigation of impurity particles and radiation-induced segregation (RIS) in neutron-irradiated beryllium (Be). Spherical Be pebbles (Ø 1 mm) were irradiated within the HIDOBE-02 experiment in the High Flux Reactor (HFR, Petten) at temperatures of 370, 440, 560, and 650 °C, reaching damage levels of 21, 29, 34, and 37 dpa, respectively. In the unirradiated state, nanoscale precipitates with a complex composition of Fe, Al, Mg, Mn, Si, and Cr are observed, appearing as chain-like or clustered distributions within the Be matrix. Under irradiation, these precipitates progressively dissolve above ∼500 °C, significantly altering impurity redistribution and segregation behavior at defect sinks. Scanning TEM with energy-dispersive X-ray spectroscopy (STEM-EDX) reveals a strong temperature dependence of bubble chemistry. At ≤500 °C, bubble surfaces exhibit predominantly Al segregation. At 560 °C, Si enrichment becomes pronounced, while at 650 °C, segregation layers consist of Al, Si, and Mg in approximately equal proportions. Mg and Si decorate both basal and pyramidal facets, whereas Al segregates preferentially to basal planes. ... mehrAdditionally, the concentration of dissolved impurity elements in the Be matrix was quantified. These findings demonstrate that impurity redistribution during neutron irradiation is highly temperature dependent and governed by the interplay of RIS and defect-mediated radiation-enhanced diffusion, ultimately controlling gas bubble chemistry in Be.