Thermal creep of Li4SiO4 pebble beds

The description of thermal creep in ceramic breeder pebble bed blankets is of large importance for the calculation of the bed-structure mechanical interaction (BSMI) which is important for the assessment of the blanket lifetime. Results of thermal creep experiments with Li4SiO4 pebble beds (pebble diameters between 0.25 and 0.63 mm) are reported, performed in an uniaxial test facility at temperatures up to 850 °C and pressures up to 9 MPa. A correlation has been developed which describes thermal creep strain as a function of temperature, pressure and time. The temperature influence is, as expected, quite pronounced, the stress influence, however, is very small compared with homogeneous materials. For future BSMI calculations the proposed correlation is recommended to be used together with a correlation for the modulus of deformation at ambient temperature.