Status of fabrication of Li2TiO3 pebbles by the extrusion-spheronisation-sintering process

Li2TiO3 pebbles are a ceramic breeder material option for the Helium-Cooled Pebble Bed (HCPB) blanket being developed in the E.U. The extrusion-spheronisation-sintering process was selected in order to produce Li2TiO3 pebbles fulfilling the HCPB blanket requirements, and developed with the collaboration of the industrial firm CERAMIQUES TECBMQUES ET INDUSTRIELLES. Adjusting the fabrication process parameters allows varying the pebbles characteristics, i.e., pebbles diameter, pebbles open/closed porosity, pebbles grain size which, in turn, determine the behaviour of the pebbles. Current reference pebbles have a diameter of 1 mm, a density of 90% of the theoretical density, a grain size of 1-2 mum and an excellent purity. The feasibility of the fabrication by pre-industrial means is demonstrated at the 10 Kg scale which is sufficient to cover the present needs for the tests. A production of 150 Kg/year of Li2TiO3 pebbles is achievable with the current facility and no significant difficulty is to be expected for extrapolation of the production to the industrial scale. The advantage of this fabrication process to cover a wide range of characteristics (geometrical, microstructural, and mechanical) is shown. The overall results indicate both excellent prospects for the fabrication of Li2TiO3 pebbles and the attractiveness of their properties. In addition, in view of the necessary utilisation in the future of costly Li-6 enriched ceramic pebbles, focus is being placed on the minimisation of production losses as well as on the recycling process of the unburnt Li-6 in the Li2TiO3 pebbles after service in a reactor.