[en] To meet the CANDU 3 design targets for low occupational exposures and for load following operation, the reference 37-element fuel bundle must perform as well as or better in a CANDU 3 than in previous CANDU's. With single-ended refuelling, the entire fuel column must be temporarily removed from the channel and placed inside the fuelling machine located at the downstream end of the fuel channel. The power boosts on upstream bundles as they slide through the centre of the core are acceptable for low burnup fuel, but not for bundles at normal discharge burnup. To eliminate the concerns about fuel performance, symmetric refuelling schemes are now planned for the central region of the core. This flattens the power profile in the axial direction and reduces peak bundle powers from 920 kW to levels below about 800 kW. These low powers will ensure good performance. The new refuelling schemes will result in some burnup loss (7.5%) but will ensure that the design targets are met. They will also have favourable impacts on safety and licensing primarily because of lower fuel element and bundle powers. (Author) 7 refs., 7 figs., tab