Influence of pebble bed dimensions and filling factor on mechanical pebble bed properties

For the characterisation of thermal–mechanical properties of pebble beds for ceramic breeder blankets, uniaxial compression tests (UCTs) are used for the determination of the strain–stress dependence, respectively, the modulus of deformation E. Detailed UCTs have been performed with different cylindrical cavities (diameter D) and both Li4SiO4 pebbles (diameters 0.25≤d (mm) ≤0.6) and Li2TiO3 pebbles (0.8≤d (mm) ≤1.2). The dependence of E from H, D, d and the packing factor γ was investigated. A test section was used for the investigation of blanket relevant pebble bed geometries and filling techniques. Pebble stress distributions were visualised. The achievement of homogeneous distributions in blanket structures requires further R&D work.