R&Ds on Vanadium Beryllides as an advanced neutron multipliers for DEMO Fusion applications

Beryllium intermetallic compounds (beryllides) such as Be12Ti, Be12V, and Be13Zr are the most promising advanced neutron multipliers for demonstration (DEMO) fusion reactors owing to low reactivity with water vapor and low swelling at elevated temperatures. By a novel process combined with a plasma sintering and a rotating electrode process for a rod fabrication and granulation, respectively, we have successfully fabricated the beryllides pebbles with 1 mm in diameter for the first time in the world and attempted the optimization of the granulation conditions to control the pebble size and improve the granulation yield.This presentation aimed to clarify the superiority of Be12V pebbles from viewpoints of easiness of fabrication process, excellent properties, low reactivity, low hydrogen retention, and verify the pebble packing fraction as well as the thermal conductivity for the pebble bed filled with Be12V pebbles.It was concluded that Be12V pebbles with single phase were successfully fabricated by two processes, a plasma sintering and rotating electrode process with high granulation yield (including improvement of the yield by a reuse process), which were advantageous to mass production while the Be12V pebbles indicated much lower reactivity with H2O as well as lower hydrogen isotope retention. Furthermore, the packing fractions of single-sized pebble with either 0.4 (0.3-0.5) or 2.5 (2.36-2.80) mm and binary-size Be12V pebbles with 0.4 (0.3-0.5) and 2.5 (2.36-2.80) mm in diameter reached at 65% and 81%, respectively, which are target packing fractions for the blanket designing. In addition, the effective thermal conductivity of the single-size packing of Be12V pebble bed with 1 (0.85-1.18) mm in diameter found out to be lower by 33 % than that of Be pebble bed at 873 K, which this value is within an allowable range for the blanket designing.アメリカ・カリフォルニアで開催される第14回ベリリウム技術国際ワークショップ(BeWS14