Granulation of Be12V pebbles using the rotating electrode method

Abstract

Hydrogen generation via the oxidation of beryllium (Be) in the presence of water vapor at high temperatures needs to be minimized in fusion reactors because of safety concerns. Advanced neutron multipliers with increased stability at high temperatures are desirable in pebble bed blanket design with water coolant. Beryllium intermetallic compounds (e.g., vanadium beryllide Be12V) are a promising material that can be used as advance neutron multipliers. Granulation aims to produce beryllide pebbles that are a critical element in the development of advanced neutron multipliers.Based on previous trial granulations of beryllides, a rotating electrode method (REM) was selected [1–3]. Furthermore, its experimental dataset is broad, covering beryllium and metallic pebbles. Rod-shaped beryllide blocks are necessary to fabricate beryllide pebbles via the REM. Hot isostatic pressing and casting have been proposed to synthesize beryllides. However, pure beryllium-based intermetallic compounds have very limited plasticity at high rotational speeds. The use of Be–V rods containing pure beryllium phase was considered a reasonable solution to this problem. The microstructure of Be–V rods and pebbles confirmed that the REM produced single-phase Be12V pebbles from multiphase Be–V rods. Special emphasis has been placed on the yield properties, size distribution, and sphericity of vanadium beryllide pebbles fabricated under different granulation conditions. The effect of rotational speed and electric current on pebble fabrication with the REM is discussed in this study. Taking into account the high costs and restricted availability of beryllium products, the perspective of material re-use was also considered by the process development and appropriate granulation trials were performed.