Tritium Breeding Ceramics for Nuclear Fusion

Tritium and deuterium are widely considered as fuel for fusion power plants. While deuterium is quite abundant in nature, tritium needs to be “bred” from lithium in a neutron reaction. Hence, for the breeding blanket development of the International Thermonuclear Experimental Reactor (ITER) and the DEMOnstration power plant (DEMO), the development of an efficient tritium breeder material is essential. The Advanced Ceramic Breeder (ACB), consisting of lithium orthosilicate (Li4SiO4) and lithium metatitanate (Li2TiO3), is the European Union’s reference breeder material for solid breeder concepts.
The ACB material is produced in the form of pebbles using a melt-based process called KALOS (KArlsruhe Lithium OrthoSilicate). The synthesis powders are melted at about 1400 °C in a platinum alloy crucible. Then pressure is applied to the crucible to force the melt through a nozzle on the underside. The formed jet breaks up into droplets that are solidified in a cooling tower using liquid nitrogen. The obtained pebbles undergo a comprehensive quality control with regard to their chemical and phase composition, density, porosity, mechanical stability, and microstructure.
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Besides the standard characterisation of the material, further experiments are performed to study the material behaviour under the harsh conditions that it has to face in the blanket of a future fusion power plant. These studies comprise for example activation and reprocessing, long-term thermal stability, and radiation stability as well as tritium release behaviour.
The presented work will introduce the unique production process KALOS and demonstrate the development and qualification of the ACB pebbles as the EU reference tritium breeder material.