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Abstract
The CATHENA “slave” channel model is used for fuel channel analysis of a 30% reactor inlet header break in a Canada deuterium uranium (CANDU)-6 reactor loaded with 43-element bundles of advanced CANDU [CANDU flexible fueling (CANFLEX)] fuel. The predicted results are compared with those for the reactor loaded with standard 37-element bundles.
The maximum fuel centerline and sheath temperatures for the CANFLEX bundle are lower by 388 and 128°C, respectively, than those for the standard bundle because of the lower maximum linear power of the CANFLEX bundle. The pressure tube (PT)/calandria tube (CT) contact for the CANFLEX bundle occurs 2 s later than that for the standard bundle. The PT/CT contact temperature for the CANFLEX bundle is 7°C lower than that for the standard bundle. These provide the CANFLEX bundle with a slightly enhanced safety margin for fuel channel integrity in the CANDU-6 reactor, compared with the standard bundle.
The effect of bearing pad (BP)/PT contact on the PT temperature predictions is assessed. A BP/PT contact conductance of 3 kW/m2·K prior to the onset of PT ballooning creates ∼ 100° C of a local hot spot at the contacted PT sector. A BP/PT contact conductance of 0.5 kW/m2·K after PT ballooning does not create any hot spot because it gives the contacted PT sector approximately the same heat transfer as convective heating by the hot coolant for the adjacent sector. The assumed BP/PT contact conductance does not threaten the fuel channel integrity.