Fission product migration in intact fuel rods

Temperature prediction for rods S176-6, 7, 8 and 9 have been made using the present modification of GAPCON-THERMAL-2. Due to availability of a large amount of data for these rods comparison can be made between experimental data and GAPCON predictions. In most cases the predictions are certainly within +-2000C and probably even better (+-1000C). In one specimen (S176-6 mid, 1005) grain growth indicates a much higher temperature than predicted. It was found that a cold gap size and densification for this rod at the tolerance limits could explain this. It is clear that the large amount of data for the S176 rods should be used further for control and improvement of GAPCON. (Auth.)