Production and thermal stability of beryllium with fine grain structure to improve tritium release during neutron irradiation

In order to improve the tritium release capability of beryllium in helium cooled ceramic breeder (HCPB) type blankets, beryllium tablets with small grain sizes ranging from 0.4 to 20 mu m and 15 mm diameter and a few millimetres height have been produced by a wet ball-milling process with subsequent hot pressing. Depending on process parameters, about 0.4-1.5 kg Be powder can be produced per day. X-ray investigations, SEM and EDX confirmed among others that the impurity concentrations could be kept very close to the raw material. As grain coarsening of Be is at a given temperature besides pressure and possible grain surface layers a sensitive function of grain size, Be tablets have been subjected to isochronal annealing for 2h between 500 and 1000 degrees C in high vacuum. While annealing up to 800 degrees C did not change the average grain size of about 5 mu m on the basis of the initial datasets, grain coarsening occurs clearly during 900 degrees C annealing. (c) 2005 Published by Elsevier B.V.