Speaker
Description
Julia Leys, Thomas Bergfeldt, Oliver Leys, Regina Knitter
Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM), Karlsruhe, Germany
Advanced Ceramic Breeder (ACB) pebbles represent the EU reference material for solid tritium breeders. Their application is foreseen in the ITER TBM and in DEMO. Therefore, comprehensive knowledge about their material properties are essential for the development of blanket concepts such as the Helium Cooled Pebble Bed (HCPB) or the Water cooled Lead Ceramic Breeder (WLCB) designs. The ACB material has been extensively evaluated in the past, also with regard to their long-term thermal stability, but this study presents results from the first thermal cycling test. Even if the pebbles will not experience such a thermal cycling in a future fusion power plant, the experiment was used to test the material under extreme thermal stress.
For the thermal cycling test, two batches of ACB pebbles consisting of nominal 70 mol% Li4SiO4 and 30 mol% Li2TiO3 were used. The samples experienced cycles with 12 h at 300 °C and 12 h at 800 °C. The ACB pebbles were retrieved after 2, 14 and 30 cycles. A gas atmosphere of He + 0.1 vol% H2 was applied during the experiment. The ACB pebbles underwent a comprehensive characterisation using ICP-OES, XRD, SEM, uniaxial crush load tests, He-pycnometry, Hg-porosimetry before and after the heat treatment.
The results of the first thermal cycling test on ACB pebbles will be presented. Furthermore, the outcomes will be compared to previous long-term annealing experiments. This study will contribute to the knowledge on thermal stability of these ceramic breeder pebbles.
