[en] As part of the NRC/EPRI/Westinghouse Full-Length Emergency Cooling Heat Transfer Separate Effects and Systems Effects Test (FLECHT SEASET) heat transfer and hydraulic program, a series of natural circulation tests were conducted on a test facility whose dimensions were scaled to those of current PWRs with a scale factor of 1/307 on a volume basis, in which full lengths and full heights were prototypical. The purpose of these tests was to identify hydraulic and heat transfer phenomena during natural circulation cooling modes. The resulting test data, evaluation, and analysis are to be used for PWR code and model assessment as well as to provide a comparison to similar experiments in other scaled systems. This report presents the test data; data reduction, analysis, and evaluation; and resulting model development and analysis. The models which have been developed include a reflux tube condensation model as well as a single- and two-phase model for the overall system