ANALYTICAL MODEL FOR HEAT TRANSFER WITHIN A CANDU FUEL BUNDLE RESIDING IN AIR.

There are a number of different situations in a CANDU fuel cycle when the irradiated fuel resides in air. The typical examples include operating during fuel transfer, shipping, potential dry storage. In abnormal situations, dry fuel may be found in a reactor channel, end fitting, fueling machine, etc. As soon as a fuel bundle is withdrawn from its normal D//2O (or H//2O) environment, its sheath temperature starts to rise until it reaches the equilibrium (maximum) value. This fuel heat up is caused by decay power. UO//2, as well as Zircaloy-4 oxidation rates depend on the temperature. Hence, the knowledge of the fuel temperature is essential in assessing the behaviour of dry fuel.