Presentation Recent progress of beryllides R&D as advanced neutron multipliers for DEMO fusion reactors

中道, 勝  ,  金, 宰煥

Since hydrogen generated via an oxidation reaction of beryllium (Be) with water vapor is explosive, this is major drawback of Be which is placed in high temperatures. Therefore, DEMO reactors require advanced neutron multipliers which have higher stability at high temperatures. Beryllium intermetallic compounds (beryllides) are the most promising material for this purpose. Development of beryllides has been started between Japan and the EU in the DEMO R&D of the International Fusion Energy Research Centre (IFERC) project as a part of the Broader Approach activities.The authors have developed a fabrication method of beryllide pebbles with Be12Ti, which it is a combination of a plasma sintering method and a rotating electrode method. However, Be12Ti pebbles have a critical problem, which an additional annealing treatment is inevitably necessary to homogenize the pebbles to a single Be12Ti phase, because composition was changed owing to a peritectic reaction caused by re-melting under granulation. Then, the homogenized Be12Ti pebbles showed larger reactivity than that without treatment, since the homogenization caused an increase of the specific surface area. To prevent increased surface area and reactivity, prototypic pebbles with Be12V composition which has no peritectic reaction were successfully fabricated without homogenization. Then, the Be12V prototypic pebbles indicated a good oxidation resistance.From the reactivity result, it was clarified that BeO layer on the surface of Be12V pebbles acts as a protective barrier against hydrogen generation reaction. As the next stage, surface-modified Be12V pebbles covered with BeO layer were prepared as specimen. The reactivity test depicted that hydrogen generation rate reduced to almost the same level as the background by the surface modification. From these results, surface-modified Be12V pebbles with no-hydrogen generation reaction were successfully fabricated.In this study, those recent progress on R&D of beryllides as the advanced neutron multipliers in Japan will be presented.
NuMat2016 (The Nuclear Materials Conference)

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