Closure device for the handling vessel of a nuclear fuel assembly

A closure device is described for a handling vessel of a fast nuclear reactor cooled by a liquid metal, such as sodium, comprising a vertical vessel containing the core and a given volume of sodium contained in the vessel, marking above the core a free level capped by an inert gas cushion, a thick horizontal slab above the gas cushion and forming the upper closure of a protective casing around the vessel, a sloping ramp plunging into the down to a loading and unloading station, a second sloping ramp connecting the interior of the handling lock to a second loading and unloading station located inside the casing in a storage bin, a trolley carrying the handling vessel capable of moving along the ramps to transfer the vessel from a position where it is immersed in the sodium to one where it is introduced into the inert gas atmosphere above the sodium level. This handling vessel is open at its upper end so that when it is in a vertical position on its trolley at the loading/unloading station, the assembly to be handled can be introduced or withdrawn