Rod-Inserted Sintering of Annular Pellets for Dual-Cooled Annular Fuel

A heat flux split is one of the important technical issues in dual-cooled annular fuel. The inner and outer diameters of an annular pellet should be carefully controlled because they determine the inner and outer gap sizes and thereby influence the balance in a heat flux split. The outer diameter of a sintered annular pellet can be controlled to a final uniform size by a centerless grinding. However, it is difficult and unproductive to grind the inner surface of all annular pellets. To obtain a uniform inner diameter among annular pellets and to minimize a diametric tolerance without inner surface grinding, we applied a rigid rod-inserted sintering process to the annular pellet fabrication. An annular compact was first compacted with a double-acting press and then sintered with a precisely machined rigid rod inserted. The rigid rod can prevent an inhomogeneous deformation of the inner surface during sintering, and thus it controls the inner diameter of the sintered annular pellets and reduces the inner diametric tolerance of a sintered annular pellet without inner surface grinding.