Thermal creep of beryllium pebble beds

Results from thermal creep experiments on beryllium pebble beds consisting of 1 mm NGK pebbles are presented. The experiments were performed in the uniaxial test facility HECOP II at temperatures ranging between 450 °C and 650 °C and under uniaxial stresses up to 3.6 MPa. A correlation of the type ε cr = A   exp − B T σ p t n was established. ed to ceramic breeder materials, beryllium pebble beds are characterised by larger creep strains (by a factor 5–10) for given creep parameter values. For blanket conditions, these differences are smaller because characteristic temperatures are lower for beryllium than for the breeder material. For relatively short creep time periods, this factor is about 2–3. hese results, a complete set of data exists, required as input for codes used for the description of the thermal–mechanical interaction of solid breeder and beryllium pebble beds with the structural material of blanket elements.