Abstract: A fuel assembly for a fast-neutron reactor comprises a shroud having an upstream end and a downstream end. The shroud houses fuel elements having portions filled with fissionable and raw materials, corresponding fission-gas plenums to collect the gaseous products of fission and a shell. The fission-gas pleunums are divided into central and peripheral groups, and at least one of said groups is located downstream of the coolant before the portions of fuel elements filled with fissionable and raw materials. The shell is placed inside the shroud with a certain clearance with respect to its walls and is secured at one of its butt ends to the downstream end of said shroud.

Abstract: A fuel assembly for a nuclear fast neutron reactor comprises a shroud having an upstream head piece and a downstream tail piece. The shroud houses fuel elements having portions filled with fissionable and raw materials and plenums serving as accumulation reservoirs for fission gases evolved in the fuel. The fission-gas plenums are divided into a central and peripheral groups. At least one of these groups is positioned in the tail piece of the fuel assembly shroud downstream of the coolant inlet ports before the portions filled with fissionable and raw materials.