Electrical and metallographic characterization of beryllium pebbles

To confirm the conservative assumptions about the electrical resistivity of the beryllium pebble bed in the course of the electromagnetic analyses for the Reference ITER Breeding Blanket, this property has been actually measured. In case of a single size 2 mm pebble bed, the resistivity of the bed decreases drastically to about 10-4 Ωm by applying an external pressure. After this first drop, the resistivity shows an almost linear decrease with the applied pressure. The same trend appears for a single size 0.1-0.2 mm pebble bed, but the resistivity values are about one order of magnitude higher than in the case of 2 mm pebbles. At room temperature, the lowest resistivity values were found for the case of a binary pebble bed. Results from the pebbles metallographic structure analyses by means of optical microscopy as well as BeO measurements using, the Rutherford backscattering technique are also presented. (authors)