Abstract: A nuclear fuel assembly including: a casing delimiting an inner space divided into a central part as a fissile zone, in which a bundle of nuclear fuel pins is located, an upper part, and a lower part; a lower end including a coolant supply inlet; an upper end including a coolant evacuation outlet; pins in a bundle of pins including an upper and/or a lower plenum; a mechanism creating a communication with the lower part of the inner space of the casing with the zone surrounding the assembly, as an inter-assembly zone, through the wall of the casing; and an upper neutron protection mechanism inside the casing.