Heat transfer from fuel rod surface under reactivity-initiated accident conditions; NSRR experiments under varied cooling conditions

Udagawa, Yutaka  ; Sugiyama, Tomoyuki ; Amaya, Masaki  

In order to study the effects of cooling conditions on the boiling heat transfer from the fuel rod surface to the coolant water, RIA-simulating experiments with fresh fuels had been conducted in the nuclear safety research reactor (NSRR) under cooling conditions with subcoolings of 10 to 80 K, flow velocities of 0 to 3 m/s, pressures of 0.1 to 16 MPa. In addition, pre-irradiated fuels had been subjected to the NSRR experiments under cooling conditions with subcoolings of 80 K, stagnant water, and atmospheric pressure. Out of the NSRR experiments, this report presents the fuel specifications, the test conditions, and the transient records during the pulse operations for the cases that the cladding temperature had been successfully measured. Characteristic parameters such as cladding peak temperatures were extracted from the transient records for summarizing the effects of cooling conditions and pre-irradiation on the heat transfer from the cladding surface.