The dryout-power improvement of CANFLEX SEU bundles in CANDU reactors

An assessment of the impact on dryout power has been completed for a string of CANFLEX bundles containing 0.9% slightly enriched uranium (SEU) fuel with either a 2-bundle-shift or 4-bundle-shift fuelling scheme. The effect of radial heat-flux distribution on dryout power for the CANFLEX bundles has been shown to be small (about a 0.5% difference) between natural uranium (NU) and 0.9% SEU fuel with the same axial heat-flux distribution (AFD). On the other hand, the variation in AFD for the SEU fuel has a large impact on the dryout power, compared to the NU fuel. Based on the calculated results, the introduction of CANFLEX 0.9% SEU fuel bundles and a 2-bundle-shift fuelling scheme in a CANDU fuel channel would lead to a dryout-power enhancement of 8% to 27% over the complete range of pressure-tube creep (having the downstream-skewed profile), compared to the current 37-element NU fuel bundles using the 8-bundle-shift fuelling scheme. The enhancement is slightly higher (10% to 29%) for a 4-bundle-shift fuelling scheme. (author)