Modeling crud attachment on fuel surfaces – Role of interaction forces

Crud deposition is one of the major cause of fuel failures in PWRs operating in U.S. and around the world. Various experimental and computational studies have tried to relate thickness or amount of crud deposits to evaporative flux maps [1, 2, 3, 4]. Macroscopic models relating evaporation rate to deposition rate and the total amount of deposit, do not take into account shape of deposition patterns, interaction mechanisms between the crud particles and interactions between crud particles and substrate (in this case fuel surface). However, experimentally it is observed that there is spatio-temporal variation in the porosity and structure of crud layer deposits. It is also important to note that the deposition kinetics and the amount of deposits is highly dependent upon local or global chemistry which impact the interactions between particles and surfaces, and eventually e ffect attachment probability. The focus of this summary will be to present a model to describe the crud attachment kinetics on a fuel surface.