[en] Stacks of seven urania fuel pellets were subjected to direct Joulean heating via a voltage applied to electrodes emplaced at either end of the stack. Heat was removed by recirculating helium loop. The stacks were observed to crack upon attaining an equivalent in-reactor power below 7 kW/m. Cracks link up and the pellets separate into fragments above an equivalent power of 25 kW/m-h. The fragments move downward and outward driven by center temperature changes giving diameter increases equivalent to typical as-fabricated pellet-cladding gaps in commercial fuel rods. In tests with single crystal alumina cladding tubes the relocated pellet fragments were found to be noncompliant to radial pressure generated by pellet-cladding mechanical interaction. Experimental results include basic urania fracture mechanics data. Statistical analyses of the 13,000 event data base are presented