A mechanistic model that describes events leading to in-channel fuel plateout following fuel pin failure under slow transient overpower accident conditions has been proposed. The thermal and hydraulic effects of the plated out fuel have also been investigated. Results based on this model indicate that during a slow transient overpower accident (2.4 cent/s), in-core fuel freezing and channel plugging can be expected to occur. The extent of fuel freezing and channel plugging is sensitive to fuel particle size, the amount of fuel injected, and the amount of fission gas injected into the coolant channel The results are also compared with experimental data from the TREAT H-4 experiment.