Effect of aluminum oxide coated on fuel cladding surface on crud deposition in simulated PWR primary water

Highlights: • Effect of aluminum oxide coated on fuel cladding on crud deposition was investigated. • Crud deposition tests were performed in simulated PWR primary water at 328 °C. • The crud mass decreased by 23% by the Al₂O₃-coating. • Repulsive force between magnetite particle and cladding increased by the Al₂O₃-coating. - Abstract: Deposits on fuel assemblies (crud) have been the main cause of local power shift, increased fuel cladding temperature, accelerated fuel cladding corrosion, and radiation buildup in nuclear power plants. We report the experimental results on aluminum oxide (Al₂O₃) as a fuel cladding coating for crud mitigation. Crud deposition tests were performed under a sub-cooled nucleate flow boiling condition in simulated primary water of pressurized water reactors at 328 °C. The amount of deposits on the Al₂O₃-coated cladding tube decreased by 23% compared with that on the uncoated cladding tube. The difference of zeta potentials between magnetite particle and cladding surface increased from 7.5 mV to 16.1 mV, when the cladding surface was coated with Al₂O₃. Therefore, the reduction of crud deposition can be attributed to the increased repulsive force between the magnetite particle and Al₂O₃-coated cladding surface. The effect of the Al₂O₃ layer is discussed from the view point of zeta potential, wettability, and thermodynamic stability.