(FT/P5-10) Development of Advanced Tritium Breeders and Neutron Multipliers for DEMO Solid Breeder Blankets

K. Tsuchiya1), T. Hoshino1), H. Kawamura1), Y. Mishima2), N. Yoshida3), T. Terai4), S. Tanaka4), K. Munakata3), S. Kato5), M. Uchida6), M. Nakamichi1), H. Yamada1), D. Yamaki1), K. Hayashi1)
1) Japan Atomic Energy Agency, Ibaraki-ken, Japan
2) Tokyo Institute of Technology, Kanagawa-ken, Japan
3) Kyushu University, Fukuoka-ken, Japan
4) The University of Tokyo, Tokyo, Japan
5) Nuclear Fuel Industries, Ltd., Ibaraki-ken, Japan
6) NGK INSULATORS, LTD., Aichi-ken, Japan

Abstract.  With a target to realize attractive breeding blankets for DEMO reactors, advanced tritium breeders and neutron multipliers, operational at temperatures and neutron fluence higher than those of conventional materials, have been developed. As for tritium breeders, lithium titanate ( Li2TiO3) pebbles are one of the primary candidate breeding materials mainly from viewpoints of easy tritium release at lower temperatures and chemical stability at high temperatures. However, degradation of tritium release property caused by grain growth at higher temperatures is an issue for this material. Therefore, effects of additives to Li2TiO3 have been investigated, and a good prospect has been obtained by using oxide additives such as TiO2, CaO and Li2O. The influence of Li evaporation on the crystal structure was examined by adding CaO or Li2O to Li2TiO3, which indicated that the CaO and Li2O additives are able to control not only the growth of the grain size but also the amount of lithium defects. As for neutron multiplier, development of a real-size electrode fabrication technique and the characterization of beryllium based intermetallic compounds such as Be-Ti and Be-V have been performed. The growth rate of the reaction layer for the Be-Ti alloys decreased with increasing the Ti content up to 5at% in compatibility tests between Be-Ti alloys and structural materials such as SS316LN and F82H. Tritium inventory and irradiation effects of Be-Ti alloys have been evaluated and the properties of the Be-Ti alloys are better than those of beryllium metal. Furthermore, steam interaction of a Be-Ti alloy was about 1/1000 as small as those of beryllium metal. These results indicate a possibility to reduce a risk of a water or air ingress accident and to realize a blanket with high efficiency of electric power generation. These activities have given bright prospects to realize the water-cooled DEMO breeder blanket by the application of these advanced materials.

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