[en] This report describes the results in the NSRR inpile loop experiments conducted to study the effects of coolant flow conditions on fuel behaviors under a reactivity initiated accident. As the preceding experiments, small scale forced flow tests were performed under atmospheric pressure and at the coolant velocity up to the maximum 3.2 m/s, by installing a small circulation rig in an atmospheric pressure capsule. These preliminary tests revealed a large influence of coolant flow on fuel behaviors. The present loop experiments have been planned based on the mentioned preliminary test results as the intermediate tests for the future high pressure, high temperature loop experiments to simulate actual PWR or BWR operating conditions. In the loop experiment, a single PWR type standard fuel rod with eight surrounding dummy rods constituting a 3 x 3 rod bundle was tested under system pressure of 1.1 MPa, coolant flow velocity of 3 to 6 m/s, and coolant subcooling of 30 to 80₀C. The experiment results exhibited that the increase of coolant pressure, velocity or subcooling enhances film boiling heat transfer largely, and affects to increase fuel failure thresholds by lowering the cladding temperature rise. (author)