In one Ontario CANDU reactor unit, the horizontal feeders are interlinked with feeder spacer rods, which are installed to prevent the contact between adjacent feeders. In the normal operating conditions, spaces do not carry any loads. Therefore, the individual feeder model is used without spacers for the horizontal feeders. This reactor unit is under extensive fuel channel shifting in order to extend the life time. The axial shifting of channels is expected to put additional loads on spacers and may constrain feeder movement. In order to determine how the spacer affects the feeder stress and feeder movement due to the extensive fuel channel shifting, multifeeder models that include spacers are created for stress analysis. Multi-feeder modelling capability is not readily available in AUTOPIPE. A novel approach of inter connecting feeders with structural elements is developed for AUTOPIPE. A significant increase in feeder stress under the extensive fuel channel shift loading condition is found when the feeder spacers are included in the model. However, the feeder stresses for Design, Level A&B loading under fuel channel shift configuration meet the ASME B&PV Code NB-3600 stress limit requirements. The feeder spacer assessment results also show that the structural integrity of feeder spacers is not affected by the fuel channel shifting. In addition, this study confirmed that it is unnecessary to release the feeder spacers to prevent spacer break or feeder overstress during the post fuel channel sifting operation, thus saving significant outage time to achieve shifting configuration.

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