Mechanical behaviour of monosized and binary beryllium pebble beds

Uniaxial compression tests with monosized and binary beryllium pebble beds were performed in a temperature range between ambient temperature and 480 C and pressures up to 8 MPa. Empirical correlations for the moduli of deformation are given for the different bed types and first measurements for thermal creep are presented. Stress-strain relations depend sensitively on the initial state of the bed and with this on the filling procedure. This is of special importance for binary beds where it must be ensured that a homogeneous distribution of small pebbles in the bed is obtained. First results for triaxial compression tests for monosized and binary beds are reported. The internal friction of these beds is significantly larger than that of beds with particles with smooth surfaces. (orig.)