Thermal cycling experiment of biphasic Li4SiO4-Li2TiO3 EU reference tritium breeder ceramics

• First thermal cycling experiments for Advanced Ceramic Breeder (ACB) pebbles. • ACB pebbles remain stable under thermal cycling between 300 and 800 °C. • Only the mean crush load values decrease slightly more than at constant 900 °C. The thermal cycling behaviour of Advanced Ceramic Breeder (ACB) pebbles was investigated in a temperature range from 300 to 800 °C in a He + 0.1 vol% H 2 gas atmosphere for up to 30 cycles. For the experiment, two batches of ACB pebbles, each with a nominal composition of 70 mol% Li 4 SiO 4 and 30 mol% Li 2 TiO 3 and comparable material properties, were selected. One cycle comprised 12 h at 300 °C and 12 h at 800 °C (heating rate: 10 K/min, cooling rate: ∼0.5 K/min). Different material properties were measured before the experiment and after 2, 14, and 30 cycles. Comparable to previous long-term thermal treatments, the ACB pebbles also show a good performance during thermal cycling. They remain stable with regard to their chemical and phase composition. No significant changes occur with regard to their microstructure and porosity. The mechanical stability is decreased after 2 cycles and remains stable afterwards.