Hydrogen and helium trapping in hcp beryllium.

Even though hydrogen-metal surface interactions play an important role in energy technologies and metal corrosion, a thorough understanding of these interactions at the nanoscale remains elusive due to obstructive detection limits in instrumentation and the volatility of pure hydrogen. In the present paper we use analytical spectroscopy in TEM to show that hydrogen adsorbs directly at the (0001) surfaces of hexagonal helium bubbles within neutron irradiated beryllium. In addition to hydrogen, we also found Al, Si and Mg at the beryllium-bubble interfaces.

Author Correction: New insights into microstructure of irradiated beryllium based on experiments and computer simulations.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

New insights into microstructure of irradiated beryllium based on experiments and computer simulations.

The microstructural response of beryllium after neutron irradiation at various temperatures (643-923 K) was systematically studied using analytical transmission electron microscope that together with outcomes from advanced atomistic modelling provides new insights in the mechanisms of microstructural changes in this material. The most prominent feature of microstructural modification is the formation of gas bubbles, which is revealed at all studied irradiation temperatures. Except for the lowest irradiation temperature, gas bubbles have the shape of thin hexagonal prisms with average height and diameter increasing with temperature.

First simultaneous detection of helium and tritium inside bubbles in beryllium.

Electron energy loss spectroscopy (EELS) was applied to detect and analyze quantitatively helium (He) and tritium (H) enclosed inside bubbles in irradiated beryllium. Both gases were formed in beryllium under neutron irradiation as a consequence of neutron-induced transmutation reactions. They were detected for the first time as pronounced peaks at 13.

Vacancies and interstitials in yttrium.

The paper deals with the first principles simulation of formation energies and migration barriers of self point defects, including vacancies, di-vacancies and single interstitial atoms, in metallic yttrium. The vacancy formation energy in yttrium is shown to be relatively high (~1.8 eV), whereas the migration barriers are very similar for the jumps inside the basal planes and between basal planes, being equal to ~0.