Evaluation of the feasibility of the powder injection moulding process for the fabrication of nuclear fuel and comparison of several formulations

• Powder injection moulding (PIM) was evaluated to manufacture nuclear fuel pellets.
• Six formulations were especially designed for actinide powders.
• Net-shaped pellets have been obtained directly after sintering.
• The different forming aid formulations lead to different microstructures.

Six forming aid formulations were used to assess the nuclear fuel elaboration by means of the powder injection moulding (PIM) process. These formulations were especially designed for actinide powders (UO2 and MOX) by taking into account the specificities of these powders, in particular any solutions to prevent radiolysis. Once the feedstocks with the UO2 powder had been prepared, the thermal studies showed no significant endothermic or exothermic reaction, which demonstrates the quasi-independent behaviour of the polymer system with respect to the uranium dioxide powder. The mass of the carbon residues – a key criterion in selecting a formulation – was below 150 ppm for all six formulations, which is still sufficient for obtaining net-shaped pellets following the sintering process. The formulations to be recommended for the nuclear fuel application are those containing polystyrene as they achieve satisfactory deagglomeration combined with an adequate level of injectability (low shear viscosity of the system). Moreover, they are theoretically resistant to radiolysis phenomena due to the benzene rings of the polystyrene.

UO2 pellets have been obtained by an approach of powder injection moulding at the laboratory scale. Several formulations potentially suitable for actinide powders have been tested.Figure optionsDownload as PowerPoint slide