Evaluation of circumferential temperature distribution of Zry-4 cladding based on oxide layer thickness in NSRR experiments

Maximum temperature distributions around circumference of the Zry-4 cladding of test fuel rods irradiated in the NSRR experiments were evaluated on the basis of measured oxide layer thickness. The relationship between maximum cladding surface temperature and oxide layer thickness obtained in the NSRR experiments was used to evaluate circumferential temperature distributions. Following are the results: (1) The depression of maximum temperature at thermocouple positions was estimated from the drop of oxide layer thickness. It was possibly caused by the fin cooling effect of thermocouples. (2) Large temperature differences 2000C-6000C around circumference of Zry-4 cladding where estimated in the temperature range of cladding over 12000C. Because maximum temperature distribution around the circumference was sinusoidal, the temperature differences were caused by the eccentricity of UO2 pellets. These phenomena would also be observed in other experiments than NSRR. (author)