Microstructural understanding on the fouling behavior of crud on PWR fuel cladding surface

In the present paper, an accelerate crud creation experiment was conducted by a laboratory simulation facility. A TEM sample was prepared at the interface between the crud layer and pressurized water reactor (PWR) fuel cladding tube to investigate the fouling behavior of crud on the surface of cladding tubes at a microstructural level. The results show that the crud layer consisted mainly of NiFe₂O₄, as Fe³⁺ and Ni²⁺ serving as the primary sources. Heterogeneous growth of Fe₃O₄ was observed by HRTEM, which formed dislocations NiFe₂O₄ grains. Based on the microstructural characterization results, the growth mechanism of crud particles on cladding tube surface during subcooled nucleate boiling was discussed with a focus on mass and heat transfer.