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

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.