CANDU Fuel Performance in NPD

Over 1500 fuel bundles have been irradiated in NPD. Most of this fuel was sheathed with thin, collapsible sheathing. Burnups and residence times have exceeded 10 000 MWd/t Uranium and 850 days, respectively. The deuterium picked up by the Zircaloy-2 sheathing from the heavy-water coolant has not affected fuel performance. Dimensional changes varied from no change to < 0.05% and ≈ 0.5% on element lengths and diameters, respectively. Measured fission-gas release was < 0.1% of that generated. A defected bundle showed little or no deterioration after two and one-half years operation. For NPD, the first operating reactor of the CANDU-PHW type, the fuel performance is fully proven.