Development of Advanced Neutron Multipliers for DEMO Blankets

Advanced neutron multipliers with low swelling and high stability at high temperatures are desired for the pebble bed blankets of demonstration fusion power (DEMO) reactors. Beryllium intermetallic compounds (beryllides) such as Be₁₂Ti are the most promising material for this purpose. To fabricate the beryllide pebbles, a new granulation process has been established that combines a plasma sintering method for beryllide synthesis and a rotating electrode method using a plasma-sintered electrode for granulation. In trial granulation examinations, prototypic beryllide pebbles 1 mm in diameter were successfully fabricated. This study describes the results of a crush test and the characterization of the oxidation properties of the prototypic beryllide pebbles compared with those of Be pebbles. The crush test revealed that the prototypic beryllide pebble was more brittle than a Be pebble, and its crush load is one-third that of a Be pebble. The oxidation experiment showed that the weight gain ratios of the prototypic beryllide pebbles were significantly smaller than those of pure Be pebbles. The results confirmed that the prototypic beryllide pebbles have better oxidation resistance than pure Be pebbles.