noun / verb
channel
CHAN-ul/ˈtʃænl/
A passage directing a flow from one place to another.
Water flows through the narrow channel between rocky banks.

Etymology
A canalis carried water along a defined passage. That physical image broadened into anything through which something passes or is transmitted, including information.
In context
each fuel assembly is positioned in its own vertical pressure tube 7 m long each channel is individually cooled by pressurized water