A GENERALIZED PREDICTION METHOD FOR CRITICAL HEAT FLUX IN CANDU FUEL-BUNDLE STRINGS

A generalized prediction method has been derived for critical heat flux (CHF) in CANDU® fuel-bundle strings. It is set up in the form of a look-up table (referred to as the bundle CHF table) and is primarily based on the tube CHF table of Groeneveld et al. (1996). Three correction factors have been introduced to account for (1) the enthalpy imbalance within the bundle, (2) the difference in characteristic diameter of the CANDU bundles from a 8-mm tube, and (3) the orientation effect from vertical to horizontal flow. The capability of the bundle CHF table in the prediction of bundle dryout power has been assessed with data of horizontal light-water flow and both vertical and horizontal Freon-12 flow. These data were obtained with 37-element bundle simulators having either uniform or non-uniform (primarily a downstream skewed-cosine flux shape) axial-flux distributions. Using the bundle CHF table in the calculations, the measured CANDU bundle dryout power was predicted with good accuracy.