Fabrication and characterization of advanced neutron multipliers for DEMO blanket

Nakamichi, Masaru; Kim, Jae-Hwan; Miyamoto, Mitsutaka*

Hydrogen generated via an oxidation reaction of beryllium (Be) with water vapor is explosive, and BeO produced by this reaction is harmful to human bodies. Advanced neutron multipliers with high stability at high temperatures are desirable for a fusion reactor. Development of beryllides as the advanced neutron multipliers has been started in the Broader Approach activities. The authors have developed the fabrication methods of beryllide pebbles: a combination of a plasma sintering method and a rotating electrode method (REM). The beryllide demonstrated a lower reactivity than Be. However, in the case of BeTi, it is a serious problem that an annealing treatment is necessary to homogenize the pebbles to a single BeTi phase. On the other hand, the homogenized BeTi pebbles thus produced by the above methods showed larger reactivity than that with no treatment, since the homogenization caused an increase in the specific surface area of the treated pebbles. To prevent increased surface area and reactivity, prototypic pebbles with BeTi and BeV compositions that have no peritectic reaction during cooling process were successfully fabricated without homogenization. Then, the BeTi and BeV prototypic pebbles indicated to have a good oxidation resistance. In the present study, hydrogen retention property that will influence the used materials handling and the system safety as well as reactivity with water vapor are reported.