Preparation of UO2 fragments for fuel-debris experiments

A unique process was developed for preparing multi-kilogram quantities of > 90% dense fragments of enriched and depleted UO2 sized 20 mm to 0.038 mm for fuel debris experiments. Precipitates of UO4 . xH2O were treated to obtain UO2 powders that would yield large cohesive green pieces when isostatically pressed to 206 MPa. The pressed pieces were crushed into fragments that were about 30% oversized, and heated to 18000C for 24 h in H2. Oversizing compensates for shrinkage during densification. Effort was dramatically reduced by working on a large scale and by presizing the green UO2 instead of directly crushing densified pellets