Influence of Plasma-Sprayed Coating for the Crucible in Casting of U–Zr Fuel

To develop a re-usable crucible, the issues of thermal expansion mismatch between coatings and crucibles are very important. Here, we present a coating technology for the crucibles to prevent material interactions with the U–Zr/U–TRU–Zr fuels. Y₂O₃, TiC, and TaC coating materials were selected as promising coating. Various combinations of coating conditions such as the coating thickness and double layer coating methods were investigated to find the bonding effect in pursuit of more effective ways to withstand the thermal stresses. Among the six coating methods investigated, even though all coating methods maintained good coating integrity in U–Zr melt, most of the coating method samples did not maintain integrity in the U–Zr–RE melt because of the cracks or microcracks of the coating layer, presumably formed from the thermal expansion difference. Only double layer coating of TaC and Y₂O₃ survived the 2-cycle dipping test of U–Zr–RE melt, which is likely caused by the good adhesion of the TaC onto the niobium rod and the chemical inertness of Y₂O₃ in a U–Zr–RE melt.