Effect of TiN Coating on the Fouling Behavior of Crud on Pressurized Water Reactor Fuel Cladding

Highlights: • Zr-Nb-Sn alloy fuel cladding surfaces were coated with TiN films to mitigate crud deposition. • TiN coating reduced crud thickness compared to uncoated Zr-Nb-Sn alloy after 1–2 weeks. • TiN coating also changed the crud chemical composition, increasing the Ni/Fe ratio. A titanium nitride film was applied to mitigate the deposition of fouling deposits (crud) on pressurized water reactor fuel cladding. Titanium nitride was chosen as it reduces the van der Waals force, believed to be the dominant surface force at pressurized water reactor conditions, between crud and the substrate. Crud deposition experiments were conducted in a heated, flowing pressurized water reactor-simulant loop with uncoated and titanium nitride-coated Zr-Nb-Sn alloy tubes for 1–2 weeks. Crud morphology and thickness were investigated using focused ion beam–scanning electron microscopy, and crud chemical composition was measured via energy-dispersive X-ray spectroscopy. Results demonstrate that the titanium nitride coating effectively reduced crud deposition thickness compared to uncoated Zr-Nb-Sn alloy in the 2-week experiment. In addition, the titanium nitride coating increased the Ni/Fe ratio of the crud, which may help mitigate crud-induced power shifts.