A nuclear fuel bundle may include a first end face and a second end face axially spaced apart from the first end face and a plurality of elongate nuclear fuel elements supported by at least one spacer. The plurality of fuel elements and spacer being sized to be removably received within the fuel channel assembly. A coolant tube passage may extend axially through the fuel bundle between a first aperture in the first end face and a second aperture in the second end face. The coolant tube passage sized to removably receive a coolant fluid downflow tube provided in the fuel channel assembly. The tube passage extending from the first end face to the second end face to enable the coolant fluid downflow tube to pass through the fuel bundle.