Effect of CANDU Bundle-Geometry Variation on Dryout Power

Dryout powers have been evaluated at selected inlet-flow conditions for two proposed designs of Canada deuterium uranium, CANDU® (a registered trademark of Atomic Energy of Canada Limited (AECL)) bundles and compared with those of the 37-element and CANDU Flexible, CANFLEX® (a registered trademark of AECL and Korea Atomic Energy Research Institutes (KAERI)) bundles. These proposed designs consist of a large center element (18 mm for one design and 20 mm for the other) and three rings of elements of 11.5 mm in outer diameter. The critical heat flux for each bundle design has been predicted using the correlation derived with Freon data obtained from the corresponding full-scale bundle test. An improvement in dryout power has been shown for the proposed design having a 20 mm center element with a radial power profile corresponding to the natural-uranium fuel as compared with other bundles, particularly the natural-uranium 37-element bundle, with a symmetric-cosine axial power profile. The dryout power improvement is further enhanced for the upstream-skewed axial power profile.